Re: [time-nuts] Test equipment / work benches...

[Bob Camp]

Hi

 rent a bigger storage locker  guilty 

Bob


On Jan 24, 2010, at 6:48 PM, Lux, Jim (337C) wrote:

> 
> 
> 
> On 1/24/10 2:06 PM, "Bob Camp"  wrote:
> 
>> Hi
>> 
>> Complete something !! Yikes what a terrible idea. That would involve actually
>> doing all the un-fun things that I've been putting off once the fun stuff was
>> all done.
>> 
>> Bob
>> 
> 
> Well, even though we had a fair amount of time to tinker with "ideas that
> might pan out", most of the work was actually for a client and had a defined
> delivery date (usually in a couple weeks from starting the job).
> 
> And, of course, it's just like running out of room in the garage.  Do you
> just buy a bigger garage?
> 
> 
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[time-nuts] OT: DMTD Question

[Bob Camp]

Hi

I realize that this is a bit off topic from the flow of the last few days. I 
can only claim temporary insanity. Any comments about the temporary modifier in 
that sentence being unneeded will of course be ignored...

Assuming that:

1) I have a DMTD setup of the "basement engineering" variety.
2) The beat note is > 5 Hz and < 10 Hz
3) The DUT's are all worse than 1x10^-12 at one second tau (no hydrogen masers 
in the basement)
4) The offset oscillator is at least 2x10^-11 at one second tau.
5) The DUT's all put out 10 MHz
6) My counter will resolve 10 ns (= I could do better)
7) The limiters are good enough to not be an issue relative to the counter's 10 
ns.
8) The zero crossings are phase shifted to be close, but not so close I arm 
after I start during a run. 
9) Regardless of the tau involved, nothing I'm looking at will be better than 
1x10-14

My down conversion from 10 MHz to 10 Hz gives me a 10^6 multiplication.
10 ns is a part in 10^8 at one second. It's a part in 10^7at 0.1 second (10 Hz).
First order, I should be able to hit (7+6 = 13) a part in 10^13 at less than 1 
second. That's significantly better than the DUT's. I don't need anything 
better in the counter or limiters to measure what I'm looking at. Even if the 
limiters are 2X worse than the counter, I'm still at the don't need better 
level in terms of counter and limiters. The offset oscillator is going to cause 
some second order issues regardless of the limiters and counter, but it still 
should be "ok". 

Next up:

If I phase shift one of the DUT's by 360 degrees, the beat note does the same. 
All I need is 100 ns of phase shift to get everything lined up. I could do it 
with 180 degrees of shift and an phase inversion switch. 

I'm assuming (phase shifter and DMTD stuff)  can fit it all in a 2x4x8" box - I 
don't need a new bench to hold it all ...

So what did I miss? 


Bob 



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Re: [time-nuts] OT: DMTD Question

[Bob Camp]

Hi

I agree that the limiters may not actually be "20 ns good". It's certainly well 
worth checking. I'm also thinking that there may be a compromise in the limiter 
chain to reduce the phase noise issue. What I'm trying to do here is come up 
with a "noise floor" number that's adequate before I start. 

The isolation amp, mixer, and  phase shifter all operate at RF, so a picosecond 
change does indeed get me a 1x10^-12 at the output. The limiter operates at 
audio, so I've already got the down conversion so a picosecond there is less of 
an issue. Of course the first limiter is going to be a whole lot more time 
unstable than the RF stuff.

What I'm getting around to is that the counter really does not have to be a 
SR-620, or even a 5335 to do the job. The problems lie elsewhere. A time 
tagging FPGA with a 100 MHz clock would do the counting job quite nicely. It 
also would not be terribly hard to build. I'll grant a 10 or 100 ps/C delay 
variation with such a gizmo, but it runs at audio, so it's after the 1x10^6 
downconversion gain. Running time tags also takes care of issues like measuring 
the actual beat note frequency. 

Here's my guess for temperature stability of the setup;

1-10 seconds < 0.1 C
>10-1000 seconds < 0.2 C
>1000-10,000 seconds < 0.4 C (that may be a stretch)
> 10,000 - 100,000 seconds < 1 C

That would give me: 

Mixer : 1ps to 10 sec, 2 ps at 1000 sec.
Phase shifter: half the mixer if I use a switch on the transformer for 
inversion. 
Isolation amps: something to look at

That would give me a limit from mixer and phase shifter of:

1.4x10^-12 at 1 sec
1.4x10^-13 at 10 sec
2.8x10^-14 at 100 sec
better than 1x10^-14 at 1000 sec and beyond

I suppose that if those numbers were 10X worse than that once the rest of it 
shows up, I would stabilize the temperature of the setup.

So what's still missing?

Bob


On Jan 24, 2010, at 8:43 PM, Bruce Griffiths wrote:

> Bob Camp wrote:
>> Hi
>> 
>> I realize that this is a bit off topic from the flow of the last few days. I 
>> can only claim temporary insanity. Any comments about the temporary modifier 
>> in that sentence being unneeded will of course be ignored...
>> 
>> Assuming that:
>> 
>> 1) I have a DMTD setup of the "basement engineering" variety.
>> 2) The beat note is>  5 Hz and<  10 Hz
>> 3) The DUT's are all worse than 1x10^-12 at one second tau (no hydrogen 
>> masers in the basement)
>> 4) The offset oscillator is at least 2x10^-11 at one second tau.
>> 5) The DUT's all put out 10 MHz
>> 6) My counter will resolve 10 ns (= I could do better)
>> 7) The limiters are good enough to not be an issue relative to the counter's 
>> 10 ns.
>> 8) The zero crossings are phase shifted to be close, but not so close I arm 
>> after I start during a run.
>> 9) Regardless of the tau involved, nothing I'm looking at will be better 
>> than 1x10-14
>> 
>> My down conversion from 10 MHz to 10 Hz gives me a 10^6 multiplication.
>> 10 ns is a part in 10^8 at one second. It's a part in 10^7at 0.1 second (10 
>> Hz).
>> First order, I should be able to hit (7+6 = 13) a part in 10^13 at less than 
>> 1 second. That's significantly better than the DUT's. I don't need anything 
>> better in the counter or limiters to measure what I'm looking at. Even if 
>> the limiters are 2X worse than the counter, I'm still at the don't need 
>> better level in terms of counter and limiters. The offset oscillator is 
>> going to cause some second order issues regardless of the limiters and 
>> counter, but it still should be "ok".
>> 
>> Next up:
>> 
>> If I phase shift one of the DUT's by 360 degrees, the beat note does the 
>> same. All I need is 100 ns of phase shift to get everything lined up. I 
>> could do it with 180 degrees of shift and an phase inversion switch.
>> 
>> I'm assuming (phase shifter and DMTD stuff)  can fit it all in a 2x4x8" box 
>> - I don't need a new bench to hold it all ...
>> 
>> So what did I miss?
>> 
>> 
>> Bob
>> 
>> 
>>   
> Once you have built the DMTD you need to measure its noise floor.
> 
> How do you ensure that the limiters actually achieve a jitter better than 
> 10ns?
> With a < 10Hz beat frequency this is actually quite difficult to do given, 
> typical mixer and amplifier noise.
> Low frequency ground loop noise can be a major problem with low frequency 
> beat signals.
> 
> Some limiting factors for long tau:
> 
> 1) Mixer phase shift tempco (can be as large as 10ps/C)
> 
> 2) Limiter phase shif

Re: [time-nuts] OT: DMTD Question

[Bob Camp]

Hi

More or less in order:

The beat frequency is coming out of a rubidium. Hopefully it's fairly stable. 
It won't be super quiet for 1 or .1 second tau. It looks like the counter will 
be a FPGA time tagger, so the beat note frequency will drop out for free. 

The isolation amps are common base buffers. Not much gain, but quite a bit of 
isolation. Phase shift / C - need to look into that.

Mixer loading likely would be as I've done it before. Resistive termination at 
RF and fairly high impedance at audio. Resistor here and there to improve the 
match at RF. LC filtering adequate to suppress the RF stuff on the output of 
the mixer.  Single pole R-C for audio bandwidth control. Big capacitors and 
small resistors for low noise. 

Until I've measured them I'm not sure of the floor of the limiters. Before I 
get into that I want to be fairly sure I'm not over spec'ing them. If 100 ns is 
as good as 3 ns it's not as hard a problem. 

The issue of the group delay is an interesting one. I believe that people have 
been getting good results with coax line for the phase shift. I'm a bit 
conflicted on the  coax. 15 meters of small diameter stuff will fit in the box 
(maybe), but it's not super stable.. If I go foam coax then the phase shifter 
gets pretty big. If I go with some kind of LC setup, temperature stability 
would likely be an issue. 

Crazy Stuff 

So what did I miss that time?

Bob



 
On Jan 24, 2010, at 9:01 PM, Magnus Danielson wrote:

> Bob Camp wrote:
>> Hi
>> I realize that this is a bit off topic from the flow of the last few days. I 
>> can only claim temporary insanity. Any comments about the temporary modifier 
>> in that sentence being unneeded will of course be ignored...
>> Assuming that:
>> 1) I have a DMTD setup of the "basement engineering" variety.
>> 2) The beat note is > 5 Hz and < 10 Hz
>> 3) The DUT's are all worse than 1x10^-12 at one second tau (no hydrogen 
>> masers in the basement)
>> 4) The offset oscillator is at least 2x10^-11 at one second tau.
>> 5) The DUT's all put out 10 MHz
>> 6) My counter will resolve 10 ns (= I could do better)
>> 7) The limiters are good enough to not be an issue relative to the counter's 
>> 10 ns.
>> 8) The zero crossings are phase shifted to be close, but not so close I arm 
>> after I start during a run. 9) Regardless of the tau involved, nothing I'm 
>> looking at will be better than 1x10-14
>> My down conversion from 10 MHz to 10 Hz gives me a 10^6 multiplication.
>> 10 ns is a part in 10^8 at one second. It's a part in 10^7at 0.1 second (10 
>> Hz).
>> First order, I should be able to hit (7+6 = 13) a part in 10^13 at less than 
>> 1 second. That's significantly better than the DUT's. I don't need anything 
>> better in the counter or limiters to measure what I'm looking at. Even if 
>> the limiters are 2X worse than the counter, I'm still at the don't need 
>> better level in terms of counter and limiters. The offset oscillator is 
>> going to cause some second order issues regardless of the limiters and 
>> counter, but it still should be "ok". Next up:
>> If I phase shift one of the DUT's by 360 degrees, the beat note does the 
>> same. All I need is 100 ns of phase shift to get everything lined up. I 
>> could do it with 180 degrees of shift and an phase inversion switch. I'm 
>> assuming (phase shifter and DMTD stuff)  can fit it all in a 2x4x8" box - I 
>> don't need a new bench to hold it all ...
>> So what did I miss? 
> 
> Remember that you *must* measure the actual beat frequency, since you will 
> need that to calculate the beat-gain. If it is between 5 and 10 Hz
> the for a 10 MHz source your gain is 2E6 and 1E6 respectively, which is a 
> factor of 2 difference or 6 dB. So, your measurements will be inprecise from 
> that factor alone by +/- 3 dB. The remedy is fairly easy to come up with, 
> measure the input frequency and beat frequency for each arm. The best thing 
> is naturally to ensure that the beat frequencies of both arms is fairly 
> close. EFC steering of either source may work well enought in open-loop mode 
> during measurement (with the added benefit of not do spectral interference 
> with the phase noise which locked loop does).
> 
> How do you control the input levels to the mixers?
> 
> Do you have any isolational amplifiers?
> 
> How do you load and pre-filter the mixer outputs?
> 
> You haven't convinced me of the expected performance of the limiters.
> 
> I'm not sure it will be your biggest problem, but the way you phase-shift can 
> be of importance for the decorrelation los

Re: [time-nuts] OT: DMTD Question

[Bob Camp]

Hi

Again more or less in order:

I'm trying to keep things as simple as I can at least to start. That rules out 
the clean up loop oscillator at least in the beginning. It is a good idea, and 
eventually I'll probably put one in.

I guess I'm going to need to do some looking on transformer feedback high 
isolation amps. Everything I've seen so far on hight isolation has been 
straight / no feedback stuff.

The loading at RF on the mixer does reduce the audio output, but it improves 
the isolation / match on the mixer. You trade one for the other.

Looks like some kind of local temperature stabilization might be a good idea 
for the audio band limiting stuff. It's after the down convert, but some of the 
time constants are indeed very long. 

I suspect that silica dielectric cable is outside the budget constraints on 
this project. Cheap foam coax in a spool on the floor or tiny stuff in the box, 
possibly with better temperature control are about the only two choices. 

-

Another very real choice is to simply move the goal post a bit. Pushing the 
1x10*-12 point to 10 seconds from 1 second could turn out to be the only 
economical basement alternative.

Off to bed 

Bob

On Jan 24, 2010, at 10:26 PM, Bruce Griffiths wrote:

> Bob Camp wrote:
>> Hi
>> 
>> More or less in order:
>> 
>> The beat frequency is coming out of a rubidium. Hopefully it's fairly 
>> stable. It won't be super quiet for 1 or .1 second tau. It looks like the 
>> counter will be a FPGA time tagger, so the beat note frequency will drop out 
>> for free.
>> 
>>   
> A cleanup loop may be useful to improve the offset source short term 
> stability.
> The cancellation of offset oscillator noise in a DMTD is imperfect.
>> The isolation amps are common base buffers. Not much gain, but quite a bit 
>> of isolation. Phase shift / C - need to look into that.
>>   
> You can achieve similar isolation together with lower noise and distortion 
> with a transformer feedback CE stage.
> Transformer feedback CB stages have even lower noise coupled with low 
> isolation, however they can be useful for amplifying low level signals ahead 
> of a high isolation amplifier.
>> Mixer loading likely would be as I've done it before. Resistive termination 
>> at RF and fairly high impedance at audio. Resistor here and there to improve 
>> the match at RF. LC filtering adequate to suppress the RF stuff on the 
>> output of the mixer.  Single pole R-C for audio bandwidth control. Big 
>> capacitors and small resistors for low noise.
>> 
>>   
> That's one of the worst terminations possible from the noise perspective.
> To lower the noise its essential to reflect the sum frequency back into the 
> mixer.
> Resistors in series with the mixer LO and RF inputs will then be required to 
> improve the mixer input VSWR.
>> Until I've measured them I'm not sure of the floor of the limiters. Before I 
>> get into that I want to be fairly sure I'm not over spec'ing them. If 100 ns 
>> is as good as 3 ns it's not as hard a problem.
>> 
>>   
> You can take the published phase noise for unspecified mixers as a lower 
> limit.
> The noise in the flicker region for the mixers (eg those from minicircuits) 
> that use integrated diode quads may be somewhat higher.
> Initial measurements on a HP10534B (uses discrete diodes) appear consistent 
> with the typical noise specs for a low level mixer.
>> The issue of the group delay is an interesting one. I believe that people 
>> have been getting good results with coax line for the phase shift. I'm a bit 
>> conflicted on the  coax. 15 meters of small diameter stuff will fit in the 
>> box (maybe), but it's not super stable.. If I go foam coax then the phase 
>> shifter gets pretty big. If I go with some kind of LC setup, temperature 
>> stability would likely be an issue.
>> 
>>   
> NIST's measurements indicate that lowest delay tempco is achieved with a 
> powdered silica dielectric.
> Specialised fibres can have very low delay tempcos.
>> Crazy Stuff 
>> 
>> So what did I miss that time?
>> 
>> Bob
>> 
>>   
> Bruce
>> 
>> 
>> On Jan 24, 2010, at 9:01 PM, Magnus Danielson wrote:
>> 
>>   
>>> Bob Camp wrote:
>>> 
>>>> Hi
>>>> I realize that this is a bit off topic from the flow of the last few days. 
>>>> I can only claim temporary insanity. Any comments about the temporary 
>>>> modifier in that sentence being unneeded will of course be ignored...
>>>> Assuming that:
>>>> 1) I have a DMTD setup of 

Re: [time-nuts] OT: DMTD Question

[Bob Camp]

Hi

I will be running with both of the input ports on the mixer saturated. In that 
case, it's not clear that I'm worried about harmonic distortion in the 
isolation amplifiers. I get plenty of that when I saturate the mixer ports. 
There are indeed other kinds of distortion in an amplifier and they may be an 
issue. 

The mixers will be RPD-1's or the SMT equivalent. They have done sub 1x10^-12 
under the same conditions in the past. They are cheap and easy to get ahold of.

There is a pretty old model for the 5109, I don't know of one for the 5943. 
Last time I used the 5109 model it was not very useful for sub 200 MHz work. I 
wound up tossing one on a network analyzer to get some better data.

I've used 0.1 uf NPO's for some stuff in the past. They are out there. They 
aren't cheap. Of course they may be cheaper than ovenizing an active filter 
that uses four inch long plastic capacitors. 

To get back to the original question - what's good enough? The objective is not 
 state of the art. I'm quite happy with 1x10^-12 at 1 second. I'll probably be 
willing to accept that at 10 seconds if that's what makes more economic sense.  
If I hit anything at or below 1x10^-13 it will be out beyond 1,000 seconds. I'm 
guessing that anything that does the 1 or 10 second number will also be quite 
adequate from there on out. 

So many things to consider 

Bob



On Jan 24, 2010, at 11:30 PM, Bruce Griffiths wrote:

> Bob Camp wrote:
>> Hi
>> 
>> Again more or less in order:
>> 
>> I'm trying to keep things as simple as I can at least to start. That rules 
>> out the clean up loop oscillator at least in the beginning. It is a good 
>> idea, and eventually I'll probably put one in.
>> 
>> I guess I'm going to need to do some looking on transformer feedback high 
>> isolation amps. Everything I've seen so far on hight isolation has been 
>> straight / no feedback stuff.
>>   
> John Miles did some phase noise measurements 
> (http://www.thegleam.com/ke5fx/norton.htm) on designs like those at:
> 
> http://www.ko4bb.com/~bruce/CE_TransformerFeedback_BufferAmplifier.html 
> <http://www.ko4bb.com/%7Ebruce/CE_TransformerFeedback_BufferAmplifier.html>
> 
> John and I actually used 2N5109s and 2N5943's respectively.
> I have LTSpice simulation files for some of these designs (however I don't 
> have a spice model for either transistor).
> If you need more isolation just cascade a few such stages.
> Simulation indicates that such stages can easily produce an output of +23dBm 
> or more should you need it.
> The reverse isolation of a single stage is about 40dB which is easily 
> measured with a scope.
> The collector current of such a CE stage is significantly lower than that of 
> a CB stage with similar output and distortion.
> 
> The input distortion of a CB stage limits the distortion performance unless 
> one augments the circuit with another transistor or a transformer.
> Then collector output capacitance modulation limits the distortion 
> performance especially with high collector impedances.
> 
>> The loading at RF on the mixer does reduce the audio output, but it improves 
>> the isolation / match on the mixer. You trade one for the other.
>> 
>>   
> The matching requirement is a red herring (there are various HP/Agilent and 
> Watkins-Johnson application notes on reducing mixer noise and loss by 
> reflecting all the unwanted mixer products back into the mixer). NIST also 
> did some work on the advantages of a capacitive mixer IF port termination.
> Resistors in series with the input will largely fix the matching and locating 
> the output stage of the isolation amplifier close to the mixer also helps.
> One way of reducing the mixer phase shift tempco (NIST claim a factor of 
> about 10) is to use it with the RF port unsaturated, however this increases 
> the noise.
> The noise disadvantage can be offset by using a high level mixer.
> Choose a mixer with high isolation as this usually indicates good diode match 
> and low transformer imbalance.
> Usually DMTDs saturate both the IF and RF mixer ports.
>> Looks like some kind of local temperature stabilization might be a good idea 
>> for the audio band limiting stuff. It's after the down convert, but some of 
>> the time constants are indeed very long.
>> 
>>   
> One can easily obtain 0.22uF NPO/C0G caps so one could parallel a few of 
> these and use low tempco resistors.
>> I suspect that silica dielectric cable is outside the budget constraints on 
>> this project. Cheap foam coax in a spool on the floor or tiny stuff in the 
>> box, possibly with better temperature control are about the only two choi

Re: [time-nuts] DMTD Question

[Bob Camp]

Hi

I think you will find that the SYPD-1 (or RPD-1) is the better choice compared 
to the SRA-1.

Are the schematics out there for the curious to look at?

Thanks!

Bob


On Jan 25, 2010, at 7:01 AM, ewkeh...@aol.com wrote:

> Allow me to add some comments to this subject.
> Five month ago I set out to make a DMTD that would be $ 200 max and be such 
> that any one can build it with readily available parts. The unit also 
> includes  five counters yielding a resolution of 1 E-15. Using five counters 
> not 
> only  gives Allan Variance but also frequency difference. The counter is 
> powered by  the computer through USB and also transfers the data to the PC. 
> The counter  section is less than $30 of the total cost. The cost goal has 
> been  reached. The counter does not have to be used if one wants to use his 
> present  counter. The DM board does have high speed opto couplers that allow 
> other  counters. Corby is presently using that approach. Cost does not 
> include 
> the  offset Osc. but a low cost solution is in the works, subject to  
> evaluation.
> Corby Dawson and Richard McCorkle have been major contributors.
> The goal is 1 E-13 and present tests show 3 E-13 right out of the box. 
> Having Cesiums, Rubidiums and Xtal Osc. the best I have is a FTS 1000  
> A-100 with 3.11 E-13 at one second. I also think I will never have any  thing 
> better than the FTS unit. That is why my goal is 1 E-13.
> The present unit uses SYPD-1 as mixers but Corby will test the unit  with a 
> couple of HP10514A's to evaluate the Mixer contribution.
> I realize I am offending some of the purists on this site but I wanted to  
> keep cost down so I squeezed both channels on a very compact board  
> (4.3X2.9) and the counter is on a 4.3X2.3 board. How ever if we will  not 
> reach 1 
> E-13 with this approach I have a fallback using individual  boards for each 
> channel still meeting the cost goal. Other Mixers will also be  evaluated, 
> like the SRA1 since price and availability of the HP10514A/B will not  help 
> the 
> cost goal.
> 1 E-13 should satisfy 95% of time-nuts and at $200 including PC  boards. 
> The second board with some changes hopefully will be assembled this week  for 
> testing and based on its results a third board will go  to ExpressPCB. 
> It is moving slower than what I had hoped for, but 3 E-13 right out of the  
> box with no special magnetic shielding or power supply decoupling gives me  
> hope.
> PC boards will be the major cost factor, for my calculations I assume in my 
> calculations that ten boards will be ordered at a time.
> 
> Bert Kehren   Miami
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Re: [time-nuts] Low temperature coefficient capacitors for DMTD

[Bob Camp]

Hi

The plastic capacitors I have sitting in stock last saw service with the
Soviet era navy. They probably are rated to survive a direct torpedo hit on
the submarine. Small and compact did not seem to figure into their design.

Bob

-Original Message-
From: time-nuts-boun...@febo.com [mailto:time-nuts-boun...@febo.com] On
Behalf Of Corby Dawson
Sent: Monday, January 25, 2010 12:54 PM
To: time-nuts@febo.com
Subject: [time-nuts] Low temperature coefficient capacitors for DMTD

Almost forgot!

The reason I posted the original message was the reference to "four inch
long plastic capacitors"

The PPS capacitors are quite compact and available in surface mount too.

Corby

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Re: [time-nuts] Low temperature coefficient capacitors for DMTD

[Bob Camp]

Hi

My understanding is that it was part of a several decades long multi-billion 
dollar Coast Guard program to enhance the long term reliability of the Loran-C 
transmitter chains .

Bob


On Jan 25, 2010, at 5:47 PM, Poul-Henning Kamp wrote:

> In message 
>  PL>, "Lux, Jim (337C)" writes:
> 
>> Seems that boutique item and time-nut might go together, if there
>> was an actual performance advantage.  Besides, think of the bragging
>> rights from some of this stuff.  It could be worse than audiophile
>> craziness: [...]
> 
> Thanks for pointing that little shop out.
> 
> Did you notice this in their whitepaper:
> 
>   From 1960s to 1980s, Electronic Concepts used Peter Schweitzer
>   (a Division of Kimberly Clark) manufactured film, the only
>   United States supplier of material, by license agreement
>   with Bayer. In 1984, Electronic Concepts acquired the Peter
>   Schweitzer film division, terminating the license, allowing
>   Bayer to market the film in the United States. For economic
>   considerations, Electronic Concepts started manufacturing
>   capacitors using a balance of Bayer and Electronic Concepts
>   film.
> 
> Does that sound like a run-of-the-mill business decisions made by
> a small company which produces capacitors ?
> 
> No ?
> 
> Then how about this:
> 
>   In 1990, the conclusion of a polycarbonate film capacitor
>   paper[1] stated, "both the orientation and crystal structure
>   of PC (polycarbonate) film affects its mechanical properties
>   and electrical dissipation factor". The paper was a cooperative
>   investigation by the Jet Propulsion Laboratory and Electronic
>   Concepts' film manufacturing division,
> 
> Why would JPL study obscure production details of polycarbonate
> film capacitors in 1990, if they fell of the market six years earlier ?
> 
> Sounds fishy ?
> 
> Anybody know what this means ?
> 
>   Electronic Concepts accumulated almost five hundred million
>   hours of testing military grade Polycarbonate capacitors;
>   and, currently meet established reliability failure rate
>   level "R."
> 
> Have you connected the dots yet ?
> 
> A fair number of the in-stockpile nuclear weapon designs are qualified
> using polycarbonate capacitors and can't be retested, redesigned
> or requalified...
> 
> Poul-Henning
> 
> -- 
> Poul-Henning Kamp   | UNIX since Zilog Zeus 3.20
> p...@freebsd.org | TCP/IP since RFC 956
> FreeBSD committer   | BSD since 4.3-tahoe
> Never attribute to malice what can adequately be explained by incompetence.
> 
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[time-nuts] Rb Mag sensitivity

[Bob Camp]

Hi

I finally found a number listed for the external magnetic field sensitivity of 
a fairly small Efratom rubidium. It's specified as 3 x10^-11 per 0.1 mili 
tesla.  I did *not* make up those units, that's the way they stated it. If 
that's correct *and* my very rusty physics is also right:

A 1 A change in a wire one inch away will produce  0.08 mili tesla of field 
change. That should produce  2.36x10^-11 frequency change. Obviously it's not 
quite that simple since the wire is a lot closer to the device than the device 
is large. I suppose a more proper measure would be 1" away from the physics 
package. Even then the field is not uniform over the entire physics package. 

The reasonable conclusion would seem be that amp or multi amp conductors at an 
inch or more from the package might indeed be an issue at the 1x10^-11 level. 
At the very least twisted paris for DC in the area sound like a good idea as 
opposed to random wire routing. It also sounds like a good idea to simply not 
have that sort of current running right by the physics package. 

Ok, what did I miss that time. Hand calculating DC fields is something I 
haven't done in ... ummm,... errr ... let's leave it at "quite a while".

Bob
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Re: [time-nuts] Conducting Bench Top Material

[Bob Camp]

Hi

If you are manually loading up a wire bonder with conventional CMOS chips, ESD 
damage is a very real thing. You can haul the chip over to a SEM and actually 
take pictures of he craters you blast in it. Very cool pictures. No cat's, 
carpets, or Windhurst machines needed.  Just normal operators with missing 
wrist straps will do the trick quite nicely. 

Bob


On Jan 26, 2010, at 2:21 AM, d.sei...@comcast.net wrote:

> Back about 1981, we had piles of 6502s, etc and decide to some "antistatic 
> testing". We put a 40pin ZIF socket into a VIC-20, and then set about trying 
> to fry the uP using carpet, a cat, car seats, etc. The DUT was then put back 
> into the VIC and series of tests run to verify operation. I don't think we 
> ever had a failure. Of course, there may have been some hiding that we 
> missed, but all the static damage I've seen has been pretty severe. 
> 
> That said, I always use a wrist strap and mat if I'm working on something I 
> don't want to break further. 
> 
> -Dave 
> - Original Message - 
> From: "Charles P. Steinmetz"  
> To: "Discussion of precise time and frequency measurement" 
>  
> Sent: Monday, January 25, 2010 11:27:11 AM GMT -07:00 US/Canada Mountain 
> Subject: Re: [time-nuts] Conducting Bench Top Material 
> 
> Bruce wrote: 
> 
>> Although over the years the non-conductive top has been an asset in 
>> avoiding short circuits, etc., I am concerned about static discharges when 
>> handling modern semiconductors. Would it make sense to spray the Masonite 
>> with a weak copper sulphate or similar solution so as to make the masonite 
>> slightly conductive, but not so conductive that 155 VAC connections 
>> could not 
>> safely rest upon it? Is there a better-suited material that could be used 
>> to replace the Masonite? 
> 
> I notice that many folks who have contributed on this thread use 
> anti-static benchtops, but I have never found it necessary (and I try 
> to keep the RH in my house under 45% -- it is generally 20% or less 
> in the winter). I've been fooling with static-sensitive parts for 35 
> years and haven't lost one to static yet. With that perspective, my 
> preferred benchtop is white Formica with a very, very slightly 
> pebbled surface. Very durable, including to molten solder, and small 
> parts show up well. I use rubberized "gunsmith" mats for preventing 
> scratches to delicate workpieces (these happen to be anti-static, but 
> that is not why I have them). 
> 
> Other bench thoughts: 
> 
> Bench depth is very important. I sometimes work on equipment that is 
> more than 24" deep, so I want at least 30" of clear space in front of 
> any obstructions (power strips, Variac, test equipment, 
> whatever). In the past, I used a "flying bridge" over the rear 18" 
> of a 48"-deep bench to elevate the test equipment, which worked very 
> well. Now I use 24" deep adjustable wire-rack shelving units behind 
> a 30" benchtop (As others have pointed out, you can do the same with 
> equipment racks -- I'm not a fan of rack-mounting test equipment 
> unless the racks are anchored and everything is on slides, which I 
> was not prepared to do). I don't have enough shop real estate to 
> have a permanent access aisle behind the test equipment, so the bench 
> and racks have large (5") locking polyurethane wheels and can be 
> pulled out relatively easily for reconfiguration. This provides 
> plenty of stability for electronic projects, but you wouldn't want to 
> mount a big vise on the bench and try to bend 1" rebar. For that, I 
> have a separate metalworking shop. 
> 
> Bench height is also important. I prefer a tall bench, suited to 
> working standing or sitting on an ergonomic stool, so my bench top is 
> 44" above the floor -- a bit below my standing elbow height. 
> 
> Finally, one can never have too many power outlets, or too much 
> light, in a workshop. Lighting should be arranged so that it doesn't 
> cause specular reflections from the workpiece or the faces of test equipment. 
> 
> Best regards, 
> 
> Charles 
> 
> 
> 
> 
> 
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Re: [time-nuts] ko4bb monitor

[Bob Camp]

Hi

Now I don't feel so bad. 

70 useful displays for $1000 is something I won't worry about missing out
on. 1800 displays at 63 cents each, that would have been a shame

They are out there though. If we could just find the right auction at the
right time !!!

Bob

-Original Message-
From: time-nuts-boun...@febo.com [mailto:time-nuts-boun...@febo.com] On
Behalf Of Arthur Dent
Sent: Tuesday, January 26, 2010 12:40 PM
To: time-nuts@febo.com
Subject: [time-nuts] ko4bb monitor

"Hi

I found that warehouse! 
http://www.liquidation.com/auction/view?id=2954816
I don't know what should be the next step.

Ignacio"


That auction ended 01-17-2010. If you check the manifest there apparently
were only 
70 of the LCD display units in the lot and the rest was cables and other
parts of the 
system. The final price seemed to be $1100. 



  
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Re: [time-nuts] HP 58516A GPS distribution amplifier information

[Bob Camp]

Hi

The one on mine does indeed properly mate with a SMC connector.

Bob


On Jan 26, 2010, at 9:35 PM, Bruce Griffiths wrote:

> Claude Houde wrote:
>> Hello !
>> 
>> I'm using an HP 58516A GPS distribution amplifier to share my GPS antenna 
>> between my receivers.
>> 
>> What is the proper part number or connector "name"  for the power supply 
>> connector ?
>> 
>> Thanks for your help !
>> 
>> Claude
>> 
>> 
> According to the datasheet option 05 uses an SMC connector for the power.
> 
> Bruce
> 
> 
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Re: [time-nuts] HP 58516A GPS distribution amplifier information

[Bob Camp]

Hi

I found a SMC-BNC adapter of the correct orientation in the bottom of my junk 
box. Somehow I doubt I'll ever use it for anything else. BNC cables and jacks 
are something I can find easily. 

The top of the unit is held on with screws so getting inside it should not be 
very hard. You could swap the SMC out to something that's more common for power 
distribution. Maybe an APC-7 ...

My guess is they used the SMC because it's unusual. That way you don't get a 
cable with 30 VDC on it hooked where it shouldn't go. If you did run a 30 volt 
supply the dc could do some damage. Of course 30 volts on that unit connected 
to a "normal" antenna would do some damage as well. 

Bob


On Jan 27, 2010, at 1:14 AM, saidj...@aol.com wrote:

> I recommend un-screwing that SMC since it is almost impossible to find the  
> mate, and feeding two wires from a 5V supply into the unit through the 
> hole, and  soldering the wires to the PCB. Works well for me.
> 
> bye,
> Said
> 
> 
> In a message dated 1/26/2010 18:36:18 Pacific Standard Time,  
> bruce.griffi...@xtra.co.nz writes:
> 
>> I'm  using an HP 58516A GPS distribution amplifier to share my GPS 
>> antenna  between my receivers.
>> 
>> What is the proper part number or  connector "name"  for the power 
>> supply connector  ?
>> 
>> Thanks for your help !
>> 
>> Claude
>> 
>> 
> According to the datasheet option 05 uses an SMC  connector for the  power.
> 
> Bruce
> 
> 
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Re: [time-nuts] HP 58516A GPS distribution amplifier information

[Bob Camp]

Hi

Has anybody torn into one to see how easy/hard that would be? Sometimes HP's
construction techniques are not very "hacker friendly"..

Since you probably will have multiple GPS's on the gizmo (why have it
otherwise...) Leaving the 200 ohm DC resistors in place does not sound like
a problem. Maybe you short out two of the DC blocks rather than just one.

Bob 

-Original Message-
From: time-nuts-boun...@febo.com [mailto:time-nuts-boun...@febo.com] On
Behalf Of b...@lysator.liu.se
Sent: Wednesday, January 27, 2010 9:41 AM
To: Discussion of precise time and frequency measurement
Subject: Re: [time-nuts] HP 58516A GPS distribution amplifier information

Hi,

Another option is to remove the DC-block cap on port 1. Then let your
primary GPS power the splitter and upstream antenna.

http://www.to-way.com/tf/hp58516a.pdf

--

   Björn

> Hi
>
> I found a SMC-BNC adapter of the correct orientation in the bottom of my
> junk box. Somehow I doubt I'll ever use it for anything else. BNC cables
> and jacks are something I can find easily.
>
> The top of the unit is held on with screws so getting inside it should not
> be very hard. You could swap the SMC out to something that's more common
> for power distribution. Maybe an APC-7 ...
>
> My guess is they used the SMC because it's unusual. That way you don't get
> a cable with 30 VDC on it hooked where it shouldn't go. If you did run a
> 30 volt supply the dc could do some damage. Of course 30 volts on that
> unit connected to a "normal" antenna would do some damage as well.
>
> Bob
>
>
> On Jan 27, 2010, at 1:14 AM, saidj...@aol.com wrote:
>
>> I recommend un-screwing that SMC since it is almost impossible to find
>> the
>> mate, and feeding two wires from a 5V supply into the unit through the
>> hole, and  soldering the wires to the PCB. Works well for me.
>>
>> bye,
>> Said
>>
>>
>> In a message dated 1/26/2010 18:36:18 Pacific Standard Time,
>> bruce.griffi...@xtra.co.nz writes:
>>
>>> I'm  using an HP 58516A GPS distribution amplifier to share my GPS
>>> antenna  between my receivers.
>>>
>>> What is the proper part number or  connector "name"  for the power
>>> supply connector  ?
>>>
>>> Thanks for your help !
>>>
>>> Claude
>>>
>>>
>> According to the datasheet option 05 uses an SMC  connector for the
>> power.
>>
>> Bruce
>>
>>
>> ___
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>> https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts
>> and follow the instructions there.
>>
>
>
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Re: [time-nuts] HP 58516A GPS distribution amplifier information

[Bob Camp]

Hi

I'm sitting here looking at the spec sheet for the splitter:

A normal four way splitter should have a loss of a bit over 6 db. 

The reason that's bad is that it may degrade the noise figure at your
otherwise perfect receiver (and sub 1 db noise figure antenna) by 6 db. (it
may also do absolutely nothing bad at all)

The splitter has a rated noise figure of 7 db max / 5 db typical.

It has a gain that may be a loss of 3 db or a gain of 3 db.

Worst case, it's got a -3db gain and a 7 db noise figure. It may degrade the
noise figure at the receiver by 10 db. Best case it's got 3 db of gain and a
5 db noise figure. That's still a noise figure hit of 5 db. 

All of that is pretty easy to blow holes in as far as a real / normally
operating system is concerned. I *think* it's pretty close in the limit case
though. 

If it is close, then the part (yes I bought one to) might improve things by
1 db. It also might degrade things by 4 db under the worst case conditions
where it likely matters.

Am I missing something here? Obviously it does more than split. It may have
better isolation than a conventional splitter. It also has the cute little
DC loads in it. 

Seems like a little bit more RF gain might have been a good idea.

Bob



-Original Message-
From: time-nuts-boun...@febo.com [mailto:time-nuts-boun...@febo.com] On
Behalf Of b...@lysator.liu.se
Sent: Wednesday, January 27, 2010 9:41 AM
To: Discussion of precise time and frequency measurement
Subject: Re: [time-nuts] HP 58516A GPS distribution amplifier information

Hi,

Another option is to remove the DC-block cap on port 1. Then let your
primary GPS power the splitter and upstream antenna.

http://www.to-way.com/tf/hp58516a.pdf

--

   Björn

> Hi
>
> I found a SMC-BNC adapter of the correct orientation in the bottom of my
> junk box. Somehow I doubt I'll ever use it for anything else. BNC cables
> and jacks are something I can find easily.
>
> The top of the unit is held on with screws so getting inside it should not
> be very hard. You could swap the SMC out to something that's more common
> for power distribution. Maybe an APC-7 ...
>
> My guess is they used the SMC because it's unusual. That way you don't get
> a cable with 30 VDC on it hooked where it shouldn't go. If you did run a
> 30 volt supply the dc could do some damage. Of course 30 volts on that
> unit connected to a "normal" antenna would do some damage as well.
>
> Bob
>
>
> On Jan 27, 2010, at 1:14 AM, saidj...@aol.com wrote:
>
>> I recommend un-screwing that SMC since it is almost impossible to find
>> the
>> mate, and feeding two wires from a 5V supply into the unit through the
>> hole, and  soldering the wires to the PCB. Works well for me.
>>
>> bye,
>> Said
>>
>>
>> In a message dated 1/26/2010 18:36:18 Pacific Standard Time,
>> bruce.griffi...@xtra.co.nz writes:
>>
>>> I'm  using an HP 58516A GPS distribution amplifier to share my GPS
>>> antenna  between my receivers.
>>>
>>> What is the proper part number or  connector "name"  for the power
>>> supply connector  ?
>>>
>>> Thanks for your help !
>>>
>>> Claude
>>>
>>>
>> According to the datasheet option 05 uses an SMC  connector for the
>> power.
>>
>> Bruce
>>
>>
>> ___
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>> To unsubscribe, go to
>> https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts
>> and follow the instructions there.
>>
>
>
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Re: [time-nuts] HP 58516A GPS distribution amplifier information

[Bob Camp]

Hi

I think the big issue with two receivers is if one of them powers down and
the other stays up. Then you try to back feed the one that's power down.
That may or may not be good for it's health. I'd hope there's a diode or
something like a diode in the DC path to protect it. It would be pretty easy
to double check.

Bob

-Original Message-
From: time-nuts-boun...@febo.com [mailto:time-nuts-boun...@febo.com] On
Behalf Of Dan Rae
Sent: Wednesday, January 27, 2010 12:28 PM
To: Discussion of precise time and frequency measurement
Subject: Re: [time-nuts] HP 58516A GPS distribution amplifier information

Bob Camp wrote:
> Hi
>
> Has anybody torn into one to see how easy/hard that would be? Sometimes
HP's
> construction techniques are not very "hacker friendly"..
>   


Bob, I had to do that because my 8 way version came from the swap meet 
fried ( it was only $5).  The circuitry inside is very obvious since it 
is all surface mount. 
> Since you probably will have multiple GPS's on the gizmo (why have it
> otherwise...) Leaving the 200 ohm DC resistors in place does not sound
like
> a problem. Maybe you short out two of the DC blocks rather than just one.
>
>   
  Converting it to be powered from the No 1 output is easy, but you do 
NOT want to try to power the antenna from two outputs. Unless you want a 
schizoid divider.

Dan


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Re: [time-nuts] HP 58516A GPS distribution amplifier information

[Bob Camp]

Hi

I agree that in a normal system there likely will be no observable hit at
all. That would be true with both the active splitter and with the passive
splitter. 

My assumption was that in the absolute worst case, you have used up all of
the antenna's gain with cable loss. It's only a useful case because that's
where the splitter is likely to have it's maximum impact. It's likely a case
where the receiver has given up already 

The basic question is still "what did I get for my money?".

Bob

-Original Message-
From: time-nuts-boun...@febo.com [mailto:time-nuts-boun...@febo.com] On
Behalf Of jmfranke
Sent: Wednesday, January 27, 2010 12:59 PM
To: 'Discussion of precise time and frequency measurement'
Subject: Re: [time-nuts] HP 58516A GPS distribution amplifier information

The noise figure hit may be nowhere as bad as 5dB because it depends on the 
noise figure and gain of the antenna preamplifier, not just the noise 
figure.

John WA4WDL

------
From: "Bob Camp" 
Sent: Wednesday, January 27, 2010 12:34 PM
To: "'Discussion of precise time and frequency measurement'" 

Subject: Re: [time-nuts] HP 58516A GPS distribution amplifier information

> Hi
>
> I'm sitting here looking at the spec sheet for the splitter:
>
> A normal four way splitter should have a loss of a bit over 6 db.
>
> The reason that's bad is that it may degrade the noise figure at your
> otherwise perfect receiver (and sub 1 db noise figure antenna) by 6 db. 
> (it
> may also do absolutely nothing bad at all)
>
> The splitter has a rated noise figure of 7 db max / 5 db typical.
>
> It has a gain that may be a loss of 3 db or a gain of 3 db.
>
> Worst case, it's got a -3db gain and a 7 db noise figure. It may degrade 
> the
> noise figure at the receiver by 10 db. Best case it's got 3 db of gain and

> a
> 5 db noise figure. That's still a noise figure hit of 5 db.
>
> All of that is pretty easy to blow holes in as far as a real / normally
> operating system is concerned. I *think* it's pretty close in the limit 
> case
> though.
>
> If it is close, then the part (yes I bought one to) might improve things 
> by
> 1 db. It also might degrade things by 4 db under the worst case conditions
> where it likely matters.
>
> Am I missing something here? Obviously it does more than split. It may 
> have
> better isolation than a conventional splitter. It also has the cute little
> DC loads in it.
>
> Seems like a little bit more RF gain might have been a good idea.
>
> Bob
>
>
>
> -Original Message-
> From: time-nuts-boun...@febo.com [mailto:time-nuts-boun...@febo.com] On
> Behalf Of b...@lysator.liu.se
> Sent: Wednesday, January 27, 2010 9:41 AM
> To: Discussion of precise time and frequency measurement
> Subject: Re: [time-nuts] HP 58516A GPS distribution amplifier information
>
> Hi,
>
> Another option is to remove the DC-block cap on port 1. Then let your
> primary GPS power the splitter and upstream antenna.
>
>http://www.to-way.com/tf/hp58516a.pdf
>
> --
>
>   Björn
>
>> Hi
>>
>> I found a SMC-BNC adapter of the correct orientation in the bottom of my
>> junk box. Somehow I doubt I'll ever use it for anything else. BNC cables
>> and jacks are something I can find easily.
>>
>> The top of the unit is held on with screws so getting inside it should 
>> not
>> be very hard. You could swap the SMC out to something that's more common
>> for power distribution. Maybe an APC-7 ...
>>
>> My guess is they used the SMC because it's unusual. That way you don't 
>> get
>> a cable with 30 VDC on it hooked where it shouldn't go. If you did run a
>> 30 volt supply the dc could do some damage. Of course 30 volts on that
>> unit connected to a "normal" antenna would do some damage as well.
>>
>> Bob
>>
>>
>> On Jan 27, 2010, at 1:14 AM, saidj...@aol.com wrote:
>>
>>> I recommend un-screwing that SMC since it is almost impossible to find
>>> the
>>> mate, and feeding two wires from a 5V supply into the unit through the
>>> hole, and  soldering the wires to the PCB. Works well for me.
>>>
>>> bye,
>>> Said
>>>
>>>
>>> In a message dated 1/26/2010 18:36:18 Pacific Standard Time,
>>> bruce.griffi...@xtra.co.nz writes:
>>>
>>>> I'm  using an HP 58516A GPS distribution amplifier to share my GPS
>>>> antenna  between my receivers.
>>>>
>>>> What is the proper part number or  connector "n

Re: [time-nuts] Conducting Bench Top Material

[Bob Camp]

Hi

If we ever go back to tubes we're going to have a bunch of tech's knocked out 
on the floor. Nobody has a clue about high voltage any more. You had to have a 
good respect for it on a tube circuit or you got in big trouble. 

Bob


On Jan 27, 2010, at 9:23 PM, Steve Rooke wrote:

> Wasn't life so much easier with valves (tubes)...
> 
> :-)
> 
> Steve
> 
> 2010/1/27 Bob Camp :
>> Hi
>> 
>> If you are manually loading up a wire bonder with conventional CMOS chips, 
>> ESD damage is a very real thing. You can haul the chip over to a SEM and 
>> actually take pictures of he craters you blast in it. Very cool pictures. No 
>> cat's, carpets, or Windhurst machines needed.  Just normal operators with 
>> missing wrist straps will do the trick quite nicely.
>> 
>> Bob
>> 
>> 
>> On Jan 26, 2010, at 2:21 AM, d.sei...@comcast.net wrote:
>> 
>>> Back about 1981, we had piles of 6502s, etc and decide to some "antistatic 
>>> testing". We put a 40pin ZIF socket into a VIC-20, and then set about 
>>> trying to fry the uP using carpet, a cat, car seats, etc. The DUT was then 
>>> put back into the VIC and series of tests run to verify operation. I don't 
>>> think we ever had a failure. Of course, there may have been some hiding 
>>> that we missed, but all the static damage I've seen has been pretty severe.
>>> 
>>> That said, I always use a wrist strap and mat if I'm working on something I 
>>> don't want to break further.
>>> 
>>> -Dave
>>> - Original Message -
>>> From: "Charles P. Steinmetz" 
>>> To: "Discussion of precise time and frequency measurement" 
>>> 
>>> Sent: Monday, January 25, 2010 11:27:11 AM GMT -07:00 US/Canada Mountain
>>> Subject: Re: [time-nuts] Conducting Bench Top Material
>>> 
>>> Bruce wrote:
>>> 
>>>> Although over the years the non-conductive top has been an asset in
>>>> avoiding short circuits, etc., I am concerned about static discharges when
>>>> handling modern semiconductors. Would it make sense to spray the Masonite
>>>> with a weak copper sulphate or similar solution so as to make the masonite
>>>> slightly conductive, but not so conductive that 155 VAC connections
>>>> could not
>>>> safely rest upon it? Is there a better-suited material that could be used
>>>> to replace the Masonite?
>>> 
>>> I notice that many folks who have contributed on this thread use
>>> anti-static benchtops, but I have never found it necessary (and I try
>>> to keep the RH in my house under 45% -- it is generally 20% or less
>>> in the winter). I've been fooling with static-sensitive parts for 35
>>> years and haven't lost one to static yet. With that perspective, my
>>> preferred benchtop is white Formica with a very, very slightly
>>> pebbled surface. Very durable, including to molten solder, and small
>>> parts show up well. I use rubberized "gunsmith" mats for preventing
>>> scratches to delicate workpieces (these happen to be anti-static, but
>>> that is not why I have them).
>>> 
>>> Other bench thoughts:
>>> 
>>> Bench depth is very important. I sometimes work on equipment that is
>>> more than 24" deep, so I want at least 30" of clear space in front of
>>> any obstructions (power strips, Variac, test equipment,
>>> whatever). In the past, I used a "flying bridge" over the rear 18"
>>> of a 48"-deep bench to elevate the test equipment, which worked very
>>> well. Now I use 24" deep adjustable wire-rack shelving units behind
>>> a 30" benchtop (As others have pointed out, you can do the same with
>>> equipment racks -- I'm not a fan of rack-mounting test equipment
>>> unless the racks are anchored and everything is on slides, which I
>>> was not prepared to do). I don't have enough shop real estate to
>>> have a permanent access aisle behind the test equipment, so the bench
>>> and racks have large (5") locking polyurethane wheels and can be
>>> pulled out relatively easily for reconfiguration. This provides
>>> plenty of stability for electronic projects, but you wouldn't want to
>>> mount a big vise on the bench and try to bend 1" rebar. For that, I
>>> have a separate metalworking shop.
>>> 
>>> Bench height is also important. I prefer a tall bench, suited to
>>> working st

Re: [time-nuts] Conducting Bench Top Material

[Bob Camp]

Hi

At least down here the CF lamps seem to run at least 2X and probably more than 
that compared to the old style bulbs. There are 20 of them in this room so 
that's a pretty good sample. 

The big thing I notice is that the room does not self heat as much with 1/10th 
the power going into it. Right now a little self heating might be nice. Not so 
much so in the summer 

The only issue I've seen is that they don't seem to like tightly enclosed 
fixtures very much. They seem to need a much lower temperature at the base than 
an old style bulb. In a can light, or most open fixtures that's not an problem. 
In some covered / enclosed celling fixtures they don't seem to get the cooling 
they need. 

Bob


On Jan 29, 2010, at 2:32 AM, d.sei...@comcast.net wrote:

> And now "they" are trying to do away with edison bulbs. I hope the LED 
> equivalents are better, because the CF bulbs seem to last less in most home 
> apps. (I have "standard" bulbs that have outlasted multiple CF bulbs in 
> similar applications) In particular, I have a 75W desk lamp bulb which has 
> been in use since '97 and gets more hours than the ceiling CFs in the same 
> room, which have been replaced at least 3 times... 
> 
> They are not enclosed or abused. I was really PO'd at the short life of my 
> first set of CF lamps. They seem to be doing better now, but still there is 
> no great enhanced life span. 
> 
> Dave 
> - Original Message - 
> From: "Bill Hawkins"  
> To: "Discussion of precise time and frequency measurement" 
>  
> Sent: Thursday, January 28, 2010 2:28:31 AM GMT -07:00 US/Canada Mountain 
> Subject: Re: [time-nuts] Conducting Bench Top Material 
> 
> Warning: Way OT 
> 
> When the vacuum tube was born, there were half as many people on 
> this planet, and global climate change wasn't a problem. Very few 
> people will talk about populution. It's as if there was a blind 
> spot in the brain. Maybe there's no intelligent life in the 
> Universe because all life evolves with similar selection pressures. 
> Once technology removes natural predators (or stops world wars with 
> the atomic bomb), population heads for the sky until the big die-off. 
> 
> If other people don't have a problem with having four kids, I have 
> no problem with using vacuum tubes and Edison bulbs. 
> 
> All in my humble opinion, of course. 
> 
> Bill Hawkins 
> 
> -Original Message- 
> From: Rex 
> Sent: Wednesday, January 27, 2010 11:50 PM 
> 
> Steve Rooke wrote: 
>> Wasn't life so much easier with valves (tubes)... 
> Nostalgia? 
> 
> Valves (tubes) warmer in close proximity, yes. Global warming should 
> make that, on average, less helpful. 
>  
> glowing bulbs 
> Other than that memory, and certain trade-offs at big Rf power, I'll say 
> I no longer encourage the glowing bulbs for most things. 
> 
> 
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Re: [time-nuts] [OT] Ikea Lamp

[Bob Camp]

Hi

But wouldn't cutting and splicing the wire void the warranty and possibly
thus lead to the end of civilization as we know it

Where is the AC to DC conversion done? In a lot of these it's in the base.

Bob

-Original Message-
From: time-nuts-boun...@febo.com [mailto:time-nuts-boun...@febo.com] On
Behalf Of Poul-Henning Kamp
Sent: Friday, January 29, 2010 12:07 PM
To: Discussion of precise time and frequency measurement
Subject: Re: [time-nuts] [OT] Ikea Lamp

In message <4b631407.9090...@pacific.net>, Brooke Clarke writes:
>Hi Poul:
>
>Can the base be hung on a wall?
>http://www.ikea.com/us/en/catalog/products/10128734

The base is a lump of metal

But the swan-neck is just screwed into the base (some assembly :-)
so if you are comfortable with cutting the wire and splicing it
again, you can mount it on anything you can drill a 10mm hole in...


-- 
Poul-Henning Kamp   | UNIX since Zilog Zeus 3.20
p...@freebsd.org | TCP/IP since RFC 956
FreeBSD committer   | BSD since 4.3-tahoe
Never attribute to malice what can adequately be explained by incompetence.

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Re: [time-nuts] Conducting Bench Top Material

[Bob Camp]

Hi

At the cost target on those bulb's it's always a race to see who dies first. 

The same can be said of conventional fluorescent fixtures. I have some big ones 
in the shop downstairs. The no name electronic ballasts that came with them all 
died in the first two years. I replaced them with name brand parts and they 
have run fine ever since (at least 3 years so far). All the fixtures are on 
their first set of bulbs. 

Bob


On Jan 30, 2010, at 8:26 AM, Magnus Danielson wrote:

> d.sei...@comcast.net wrote:
>> I took apart the last dead one just for that purpose. I initially eyed the 
>> 105deg Al cap, but it was dead, along with one of the xstrs (hole in 
>> package). The film caps, diodes and fuse are still good too. As is the tube- 
>> don't know what I'll do with that. 
> 
> Sounds to me that the electronics died... rather than the bulb.
> 
> Cheers,
> Magnus
> 
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Re: [time-nuts] Austron 1150

[Bob Camp]

Hi

I haven't tested one in about 20 years. I don't remember exact numbers.

It's a good low phase noise oscillator ( similar to the 10811). It's not 
optimized for short term stability past about 10 seconds. They had other 
products in the line up that did better in that respect.


Bob

--
From: 
Sent: Sunday, January 31, 2010 10:53 AM
To: 
Subject: [time-nuts] Austron 1150


Has any one done testing on the Austron 1150 oscillator module,
specifically Allan Variance.
Thank you   Bert KehrenMiami
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Re: [time-nuts] help from Electronic Vibration Compensation

[Bob Camp]

Hi

Are you interested in simple tip over compensation or are you really after 
vibration compensation?  If so, to how high a frequency? To what levels of 
vibration? On what sort of oscillator?

A fairly simple 2G 3 axis accelerometer can compensate just about any 
oscillator for tip over. There are some fairly cheap digital ones out there 
from several semiconductor outfits. The question would be - how fast can I tip 
it? Some oscillators respond to temperature effects of a tip as well as 
gravity. That's going to slow things down a *lot*. The simple approach wold be 
to pick another oscillator, that may not be an option in your case. 

Lots of options / questions / routes to run down. Lots of answers that all 
start out with "that depends ...".

Pretty much the best case hardware for vibration:

1) Military ruggedized OCXO designed specifically for good G sensitivity
2) Accelerometer with a G level adequate to read out your G level with good 
signal to noise 
3) Accelerometer and DSP adequate to handle the upper frequency you want to 
compensate
4) Good equipment to measure  phase noise under vibration

Even with all that stuff, you need to ask, how far down do you want to 
compensate, and at what frequency? 

Bob


On Feb 1, 2010, at 2:55 AM, weijiaz...@sina.com wrote:

> Now I am interested in low-g oscillators.
> http://www.freqelec.com/oscillators/g-comp_qz_brfg_04-07.pdf
> 
> Which accelerometer is selected in the low-g oscillator? 
> How to hack my normal oscillator to low-g one ?
> Any other suggestion?
> 
> 
> 
> wei
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Re: [time-nuts] More IKEA hardware...

[Bob Camp]

Hi

They are available for order on the internet in the USA. I just ordered a
couple for putting the Symmetricom boxes into. 

Bob

-Original Message-
From: time-nuts-boun...@febo.com [mailto:time-nuts-boun...@febo.com] On
Behalf Of Tom Holmes, N8ZM
Sent: Monday, February 01, 2010 10:57 AM
To: 'Discussion of precise time and frequency measurement'
Subject: Re: [time-nuts] More IKEA hardware...

While we are briefly back on the subject of IKEA, I recall someone
commenting that IKEA does not do web sales. According to the catalog my
better half received a couple of weeks ago, in the States it is
www.ikea-usa.com for web sales. But I admit I haven't tried it out, yet.

Regards,

Tom Holmes, N8ZM
Tipp City, OH
EM79xx

-Original Message-
From: time-nuts-boun...@febo.com [mailto:time-nuts-boun...@febo.com] On
Behalf Of Poul-Henning Kamp
Sent: Monday, February 01, 2010 7:17 AM
To: Discussion of precise time and frequency measurement
Subject: [time-nuts] More IKEA hardware...


http://wiki.eth-0.nl/index.php/LackRack

(Please try to avoid a long wandering thread on this one...)

-- 
Poul-Henning Kamp   | UNIX since Zilog Zeus 3.20
p...@freebsd.org | TCP/IP since RFC 956
FreeBSD committer   | BSD since 4.3-tahoe
Never attribute to malice what can adequately be explained by incompetence.

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Re: [time-nuts] Info Needed on MOT KX1516AA VC-TCXO

[Bob Camp]

Hi

>From what little I can find, the oscillator is specified as a sine wave
output into a 1K ohm resistive load. The supply voltage shows up as 8 volts
and as 9.6 volts. I have seen other oscillators specified as high as 10K ohm
resistive load, so 1K isn't as crazy as it might first sound. 

Back 30 years ago (Motorola was a while back) the intention was that the
oscillator would be run into a tuned tank. They all went into radios, and
things like radio spurs from oscillator harmonics were a concern. 

Bob

-Original Message-
From: time-nuts-boun...@febo.com [mailto:time-nuts-boun...@febo.com] On
Behalf Of Joe McElvenney
Sent: Monday, February 01, 2010 9:09 AM
To: Time Nuts Digest
Subject: [time-nuts] Info Needed on MOT KX1516AA VC-TCXO

Hi,

I have some Motorola K1516AA, 10MHz, VC-TXCO devices (date-coded 1988)
but with only a basic pin-out diagram to their name and am wondering if
anyone knows a little more about them. Specifically I'm concerned with
the apparent high output-Z which means that a sniff of 'C' or a tad of
loading drags down the output to a fraction of the off-load value.
Unless they were made for a very specific purpose, this characteristic
would seem to me as pointless. Also, by measurement and experimentation,
I'm fairly sure that they don't use an open collector or emitter
follower output port. They may work as a current source but I haven't
gone that route as yet.


TIA - Joe G3LLV

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Re: [time-nuts] Test Equipment

[Bob Camp]

Hi

I do believe the last (or maybe next to last) of the Amtronix E8285A's is
now on it's way to a basement in Pennsylvania. If anybody else here is
looking for one, I'd sure call Rick pretty quick.

Bob

-Original Message-
From: time-nuts-boun...@febo.com [mailto:time-nuts-boun...@febo.com] On
Behalf Of John Ackermann N8UR
Sent: Thursday, January 21, 2010 4:14 PM
To: john.fo...@gmail.com; Discussion of precise time and frequency
measurement
Subject: Re: [time-nuts] Test Equipment

If RF measurement is your bag, and you're able to spend a couple of $K 
(actually, <$2K if what I've seen recently holds), consider a 
communications service monitor like the HP 
8920A/8920B/8921/8924/8935/E8285 (all pretty much the same thing).

You get an RF generator, RF power meter, RX frequency meter and 
modulation analyzer, audio generator, audio analyzer, digital o'scope, 
and in most units a spectrum analyzer (many have a tracking generator, 
too) in one box.  And I've probably forgotten a few things.  If you get 
one with spec analyzer and tracking generator, there's software that 
lets you do swept insertion/return loss and cable fault finding.

None of its capabilities are as good as those of a dedicated box 
performing a single function, but they're good enough for the vast 
majority of uses.  An 8920 was the first significant piece of test gear 
I bought, and if I ever have to sell out, it'll be the last one to go.

The prices came down a lot when Lucent surplused hundreds (thousands?) 
of them from their portable and cell phone production lines.  I saw an 
8935 with spec an, fully functional (as far as I could tell) for about 
$1500 this summer.

A guy who sells and services a lot of these boxes is Rick at 
http://www.amtronix.com -- that web site will give you lots of info 
about the various versions and options.  (I just noticed he has some 
Agilent 8285As as a "hobbyist special" with spec an and tracking 
generator for $650.  That looks like a deal.)

John

john.fo...@gmail.com said the following on 01/21/2010 03:43 PM:
> Just that John, I'm looking to setup a general purpose lab. I'd lean
towards RF type stuff since I'm a HAM. 
> Sent via BlackBerry by AT&T
> 
> -Original Message-
> From: "J. Forster" 
> Date: Thu, 21 Jan 2010 12:22:11 
> To: ; Discussion of precise time and frequency
measurement
> Subject: Re: [time-nuts] Test Equipment
> 
> I made the mistake of setting up a purpose-built lab once, and soon
> discovered to do most things, you really need at least a basic general
> purpose lab.
> 
> The only exception is, I suppose, if you are going to repair a specific
> instrument and do nothing else.
> 
> Also, as others have pointed out, you really need to define what are your
> area(s) of interest. Specialized gear gets $$$ pretty quickly.
> 
> -John
> 
> 
> 
>> John,
>>
>> That sounds like asking what is the best vehicle for you to buy. If you
do
>> not know what you want to do with it, I am not sure we can help you all
>> that much. However, if you have a specific objective, I am sure you will
>> get a lot of valuable information here.
>>
>> You have a (good) analog scope, you may want a power supply or two, a
>> soldering iron and maybe a desoldering station if you do surface mount.
>> You also want a good hand-held multimeter. Some sort of signal or
function
>> generator may be useful too. These vary widely depending on frequency
>> range and features. There is no good single answer to any of these
>> questions without knowing more about what you do with it.
>>
>> Many of us on this list have more than one of pretty much everything (I
am
>> guilty of that too) to reflect the fact that no single instrument is
>> universal, with possibly one exception: my favorite hand held DMM is a
>> Fluke 8060A, but I am sure some people will have another favorite :)
>>
>> Don't start spending what little money you have until you know what you
>> need. If you just need to spend money, may I interest you in a wonderful
>> business opportunity in Nigeria?
>>
>> Didier KO4BB
>>
>>
>>  Sent from my BlackBerry Wireless thingy while I
>> do other things...
>>
>> -Original Message-
>> From: John Foege 
>> Date: Thu, 21 Jan 2010 13:35:22
>> To: Discussion of precise time and frequency
>> measurement
>> Subject: [time-nuts] Test Equipment
>>
>> I realize that this e-mail is somewhat off topic, however, I also
>> believe that I will get some of the best answers from the members of
>> this list:
>>
>> I have recently started to build an electronics lab, and am currently
>> trying to acquire test and general equipment for my little basement
>> workshop of horrors. So far, being on a limited budget, I have
>> acquired a Tek 2465A in good working order, a Fluke 1953A counter, and
>> my little gem (ok not quite so little) HP5345A with the 4-ghz freq
>> converter plugin w/ opt 11 & 12.
>>
>> I'd just like to ask everyone what they would be, if they were in my
>

Re: [time-nuts] Test Equipment

[Bob Camp]

Hi

I *suspect* that any size that was common in 2003 will be ok. I have no basis 
for that claim. That likely will limit you to 2 gig and down. 

Each time I called Amtronix, Rick answered on the first ring. It's definitely 
someplace I would recommend dealing with.

How's the display on your unit? That sees to be the weakness of a lot of test 
gear these days.

Can't wait to measure -100 dbc/Hz phase noise with mine :) 

Bob


On Feb 1, 2010, at 5:34 PM, Don Latham wrote:

> Just bought one last week. As advertised, came with a cal and checkout
> sheet.  BTW, cost another $150 to have manuals printed out. But, I'm old
> fashioned and have a hard time using manuals onscreen...
> I also got the feeling (phone order) that I can call Amtronix and at least
> reach a Real Person who will talk to me.
> I think the E8285A will replace at least three present instruments with
> better, once I master Instrument Basic :-).
> Does anyone know which low-cost PCMCIA memory card will work? They're on
> Epay for as little as $10
> Don
> 
> Bob Camp
>> Hi
>> 
>> I do believe the last (or maybe next to last) of the Amtronix E8285A's is
>> now on it's way to a basement in Pennsylvania. If anybody else here is
>> looking for one, I'd sure call Rick pretty quick.
>> 
>> Bob
>> 
>> -Original Message-
>> From: time-nuts-boun...@febo.com [mailto:time-nuts-boun...@febo.com] On
>> Behalf Of John Ackermann N8UR
>> Sent: Thursday, January 21, 2010 4:14 PM
>> To: john.fo...@gmail.com; Discussion of precise time and frequency
>> measurement
>> Subject: Re: [time-nuts] Test Equipment
>> 
>> If RF measurement is your bag, and you're able to spend a couple of $K
>> (actually, <$2K if what I've seen recently holds), consider a
>> communications service monitor like the HP
>> 8920A/8920B/8921/8924/8935/E8285 (all pretty much the same thing).
>> 
>> You get an RF generator, RF power meter, RX frequency meter and
>> modulation analyzer, audio generator, audio analyzer, digital o'scope,
>> and in most units a spectrum analyzer (many have a tracking generator,
>> too) in one box.  And I've probably forgotten a few things.  If you get
>> one with spec analyzer and tracking generator, there's software that
>> lets you do swept insertion/return loss and cable fault finding.
>> 
>> None of its capabilities are as good as those of a dedicated box
>> performing a single function, but they're good enough for the vast
>> majority of uses.  An 8920 was the first significant piece of test gear
>> I bought, and if I ever have to sell out, it'll be the last one to go.
>> 
>> The prices came down a lot when Lucent surplused hundreds (thousands?)
>> of them from their portable and cell phone production lines.  I saw an
>> 8935 with spec an, fully functional (as far as I could tell) for about
>> $1500 this summer.
>> 
>> A guy who sells and services a lot of these boxes is Rick at
>> http://www.amtronix.com -- that web site will give you lots of info
>> about the various versions and options.  (I just noticed he has some
>> Agilent 8285As as a "hobbyist special" with spec an and tracking
>> generator for $650.  That looks like a deal.)
>> 
>> John
>> 
>> john.fo...@gmail.com said the following on 01/21/2010 03:43 PM:
>>> Just that John, I'm looking to setup a general purpose lab. I'd lean
>> towards RF type stuff since I'm a HAM.
>>> Sent via BlackBerry by AT&T
>>> 
>>> -Original Message-
>>> From: "J. Forster" 
>>> Date: Thu, 21 Jan 2010 12:22:11
>>> To: ; Discussion of precise time and frequency
>> measurement
>>> Subject: Re: [time-nuts] Test Equipment
>>> 
>>> I made the mistake of setting up a purpose-built lab once, and soon
>>> discovered to do most things, you really need at least a basic general
>>> purpose lab.
>>> 
>>> The only exception is, I suppose, if you are going to repair a specific
>>> instrument and do nothing else.
>>> 
>>> Also, as others have pointed out, you really need to define what are
>>> your
>>> area(s) of interest. Specialized gear gets $$$ pretty quickly.
>>> 
>>> -John
>>> 
>>> 
>>> 
>>>> John,
>>>> 
>>>> That sounds like asking what is the best vehicle for you to buy. If you
>> do
>>>> not know what you want to do with it, I am not sure we can help you all
>>>> that

Re: [time-nuts] Standard Resistor oil

[Bob Camp]

Hi

Some drug store mineral oil has extra "stuff" in it. This is one case where you 
want the cheap generic version rather than the "improved" name brand.

Bob


On Feb 1, 2010, at 5:56 PM, Chuck Harris wrote:

> Plain old mineral oil, also known as paraffin oil, as can be found in any
> drugstore.
> 
> They should be filled above the element, but not quite full.  Maybe 3/4 to 7/8
> full.  It isn't really important.
> 
> -Chuck Harris
> 
> Chris Erickson wrote:
>> I bought some old Leeds & Northrup standard resistors on ebay and and seller
>> dumped the oil out before sending them. Does anyone know what the correct
>> kind of oil to put back in these? How full should they be?
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Re: [time-nuts] Test Equipment

[Bob Camp]

Hi

The big question in my mind about these is how well they do below 30 MHz. Until 
I know I can trust them it down there, I'm not selling very much stuff. 

I have yet to find a data sheet from before 2000 when they shipped with the 
sub-800 MHz stuff enabled. I get the impression that the E8285's never quite 
did as well below 30 MHz as the 8920's do.  

Bob


On Feb 1, 2010, at 7:29 PM, Don Latham wrote:

> Hi Bob. Display shows use, definitely, but I can see info over the whole
> tube. I have a couple of things to do before I can start the learning
> curve, but am looking forward to using it.
> I'll have a bunch of test stuff for sale if this thing works out ;-)
> Don
> 
> Bob Camp
>> Hi
>> 
>> I *suspect* that any size that was common in 2003 will be ok. I have no
>> basis for that claim. That likely will limit you to 2 gig and down.
>> 
>> Each time I called Amtronix, Rick answered on the first ring. It's
>> definitely someplace I would recommend dealing with.
>> 
>> How's the display on your unit? That sees to be the weakness of a lot of
>> test gear these days.
>> 
>> Can't wait to measure -100 dbc/Hz phase noise with mine :) 
>> 
>> Bob
>> 
>> 
>> On Feb 1, 2010, at 5:34 PM, Don Latham wrote:
>> 
>>> Just bought one last week. As advertised, came with a cal and checkout
>>> sheet.  BTW, cost another $150 to have manuals printed out. But, I'm old
>>> fashioned and have a hard time using manuals onscreen...
>>> I also got the feeling (phone order) that I can call Amtronix and at
>>> least
>>> reach a Real Person who will talk to me.
>>> I think the E8285A will replace at least three present instruments with
>>> better, once I master Instrument Basic :-).
>>> Does anyone know which low-cost PCMCIA memory card will work? They're on
>>> Epay for as little as $10
>>> Don
>>> 
>>> Bob Camp
>>>> Hi
>>>> 
>>>> I do believe the last (or maybe next to last) of the Amtronix E8285A's
>>>> is
>>>> now on it's way to a basement in Pennsylvania. If anybody else here is
>>>> looking for one, I'd sure call Rick pretty quick.
>>>> 
>>>> Bob
>>>> 
>>>> -Original Message-
>>>> From: time-nuts-boun...@febo.com [mailto:time-nuts-boun...@febo.com] On
>>>> Behalf Of John Ackermann N8UR
>>>> Sent: Thursday, January 21, 2010 4:14 PM
>>>> To: john.fo...@gmail.com; Discussion of precise time and frequency
>>>> measurement
>>>> Subject: Re: [time-nuts] Test Equipment
>>>> 
>>>> If RF measurement is your bag, and you're able to spend a couple of $K
>>>> (actually, <$2K if what I've seen recently holds), consider a
>>>> communications service monitor like the HP
>>>> 8920A/8920B/8921/8924/8935/E8285 (all pretty much the same thing).
>>>> 
>>>> You get an RF generator, RF power meter, RX frequency meter and
>>>> modulation analyzer, audio generator, audio analyzer, digital o'scope,
>>>> and in most units a spectrum analyzer (many have a tracking generator,
>>>> too) in one box.  And I've probably forgotten a few things.  If you get
>>>> one with spec analyzer and tracking generator, there's software that
>>>> lets you do swept insertion/return loss and cable fault finding.
>>>> 
>>>> None of its capabilities are as good as those of a dedicated box
>>>> performing a single function, but they're good enough for the vast
>>>> majority of uses.  An 8920 was the first significant piece of test gear
>>>> I bought, and if I ever have to sell out, it'll be the last one to go.
>>>> 
>>>> The prices came down a lot when Lucent surplused hundreds (thousands?)
>>>> of them from their portable and cell phone production lines.  I saw an
>>>> 8935 with spec an, fully functional (as far as I could tell) for about
>>>> $1500 this summer.
>>>> 
>>>> A guy who sells and services a lot of these boxes is Rick at
>>>> http://www.amtronix.com -- that web site will give you lots of info
>>>> about the various versions and options.  (I just noticed he has some
>>>> Agilent 8285As as a "hobbyist special" with spec an and tracking
>>>> generator for $650.  That looks like a deal.)
>>>> 
>>>> John
>>>> 
>>&g

[time-nuts] Triangle Waves

[Bob Camp]

Hi

Ok, next up on the dual mixer stuff is checking the limiter chain. To do that 
with any chance of the results meaning anything you need a good triangle wave. 
You certainly can build some pretty complex gizmos to make them. There also 
appears to be a fairly simple approach. 

If I take a fairly good 16 bit DAC that will accept a clock a bit above 1 MHz, 
I can feed a simple count up / count down into it. That should give me a 
triangle wave at (clock rate) / 2^32. Simply put, 1.3 MHz data gives me a 10 Hz 
triangle wave. The digital crud should be almost entirely up around the clock 
rate or higher and > 90 db down. That assumes that the DAC is a low clock feed 
through version and that it's got good linearity. 

A reasonable dual mixer or heterodyne system should have some kind of low pass 
filter built into it. Even a 150 Hz lowpass should knock the digital stuff down 
into a -160 noise floor. 

The gotcha seems to be flicker noise out of the DAC. There's no guarantee that 
the gizmo will have a 1nV/Hz class noise floor. The same sort of audio spectrum 
analyzers used for phase noise should be able to measure the noise coming out 
under various conditions. 

The nice thing about this gizmo is that it does not have to *only* put out a 
triangle wave. If you drive it with a micro, you can tell it to do all sorts of 
things. You might try a number of DC levels as you check for noise. You might 
also try various triangle wave levels to see how everything matches up. Slew 
rate limited square waves also sound interesting. 

There are a couple of other details like DC level shifting and driving it all 
with a decent clock. Both need to be done properly, but they don't appear to be 
the limiting factors in this kind of setup. 

I suspect this approach has been tried before. Any record of it out there?

Bob
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Re: [time-nuts] Triangle Waves

[Bob Camp]

Hi

At least from the last time I tried it:

If you use a sine wave input source, it's got to be an amazingly good 10 Hz 
sine wave. A normal audio generator will not produce a 10 Hz output with good 
enough short term stability / noise to give you useful data. Audio generators 
may be out there that will do the job, but I certainly don't have one, and have 
never come across one. 

Since the output of the mixer is basically a triangle wave, it makes sense to 
use that as your test source. A triangle wave also has the nice property that 
it's easy on the math. You don't have any approximation issues with the 
integers going into the DAC. That shoves the inevitable digital crud higher in 
frequency. 

Another nice thing about a pure digital approach is that it provides a clean 
trigger for the "start" channel of the counter you are testing things with. You 
can even set up the DAC to put out square waves to see just how good various 
bits of the chain are. Tough to do that with anything other than another 
arbitrary function generator. 

I agree that the reference is going to be an issue and that a LED stack may be 
the way to go. No matter how you generate the test tone, power supply noise 
will be an issue. 

The output amplifier on the DAC is my biggest worry. I could go with a current 
out DAC and something like an OP-27.  That won't give me 1nV/Hz either, but it 
will at least be within shouting distance of it.  Sigma deltas might be a third 
option. I have no idea what their low frequency flicker noise looks like. 

So, other than the noise issue (which obviously needs to be analyzed / tested / 
pounded on) any other issues with the approach?



At least from what I have seen in the past, level sensitivity on the inputs 
shows up pretty fast in the output "beat note" as you vary the input signals 
that are supposed to be saturating the mixer. If they are doing their job, a 2 
db level change produces a very small change in the output. If you have 
something amiss in that department, you will see it pretty fast. On that I'm 
pretty much in agreement with Rubiola's stuff. 

Since I intend to mate the isolation amps up directly on the same board as the 
mixer, there is no real need for a 50 ohm interface between them. If the mixer 
looks like 18.26 ohms,  the amp output can be transformed to that level rather 
than 50 ohms. Everything is matched (over a 1/8" trace) and you don't burn up 
power in a bunch of resistors. How well that idea works - time will tell. It's 
easy to put the resistors in if it flunks out. 

So many things to try ....

Bob



On Feb 1, 2010, at 9:48 PM, Bruce Griffiths wrote:

> Bob Camp wrote:
>> Hi
>> 
>> Ok, next up on the dual mixer stuff is checking the limiter chain. To do 
>> that with any chance of the results meaning anything you need a good 
>> triangle wave. You certainly can build some pretty complex gizmos to make 
>> them. There also appears to be a fairly simple approach.
>> 
>> If I take a fairly good 16 bit DAC that will accept a clock a bit above 1 
>> MHz, I can feed a simple count up / count down into it. That should give me 
>> a triangle wave at (clock rate) / 2^32. Simply put, 1.3 MHz data gives me a 
>> 10 Hz triangle wave. The digital crud should be almost entirely up around 
>> the clock rate or higher and>  90 db down. That assumes that the DAC is a 
>> low clock feed through version and that it's got good linearity.
>> 
>> A reasonable dual mixer or heterodyne system should have some kind of low 
>> pass filter built into it. Even a 150 Hz lowpass should knock the digital 
>> stuff down into a -160 noise floor.
>> 
>> The gotcha seems to be flicker noise out of the DAC. There's no guarantee 
>> that the gizmo will have a 1nV/Hz class noise floor. The same sort of audio 
>> spectrum analyzers used for phase noise should be able to measure the noise 
>> coming out under various conditions.
>> 
>> The nice thing about this gizmo is that it does not have to *only* put out a 
>> triangle wave. If you drive it with a micro, you can tell it to do all sorts 
>> of things. You might try a number of DC levels as you check for noise. You 
>> might also try various triangle wave levels to see how everything matches 
>> up. Slew rate limited square waves also sound interesting.
>> 
>> There are a couple of other details like DC level shifting and driving it 
>> all with a decent clock. Both need to be done properly, but they don't 
>> appear to be the limiting factors in this kind of setup.
>> 
>> I suspect this approach has been tried before. Any record of it out there?
>> 
>> Bob
>> ___
>>   
>

Re: [time-nuts] Test Equipment

[Bob Camp]

HI

I agree. The 800 MHz spec was all I could find. That's the only spec that 
Google seems to know about. 

Back before some point like mid 2001, there was a different spec on these 
boxes. They went down to much lower frequencies. That information is still 
preserved in the repair manual. Unfortunately, it does not give a full detail 
set of specifications for the earlier box. The boxes Amtronix is / was selling 
have the "old" firmware and modules in them. They will go to the old wider 
frequency range. 

Bob


On Feb 1, 2010, at 10:18 PM, k3...@aol.com wrote:

> If goggle HP 8285a spec, you will get HP spec which say this unit is 800  
> Mhz up.  The 8920, 8921, 8025 will go down to ham freq.
> 
> Regards,
> 
> Dr. Joseph G. Palsa P.E.
> Director, Sales &  Marketing
> Clary Corporation
> Phone: 888-442-5279
> Phone:  804-674-0364
> Fax: 804-674-0714
> Cell:  804-350-2665
> jpa...@clary.com
> djpa...@yahoo.com  
> k3...@aol.com
> k3...@arrl.net
> 
> This e-mail (including any  attachments) is intended only for the use of 
> the 
> individual or entity named  above and may contain privileged, proprietary, 
> or 
> confidential  information.  The information may also contain technical data 
> subject  to export control laws.  
> 
> 
> In a message dated 2/1/2010 8:42:56 P.M. Eastern Standard Time, li...@cq.nu 
> writes:
> 
> Hi
> 
> The big question in my mind about these is how well they do  below 30 MHz. 
> Until I know I can trust them it down there, I'm not selling  very much 
> stuff. 
> 
> I have yet to find a data sheet from before 2000 when  they shipped with 
> the sub-800 MHz stuff enabled. I get the impression that the  E8285's never 
> quite did as well below 30 MHz as the 8920's do.   
> 
> Bob
> 
> 
> On Feb 1, 2010, at 7:29 PM, Don Latham  wrote:
> 
>> Hi Bob. Display shows use, definitely, but I can see info  over the whole
>> tube. I have a couple of things to do before I can  start the learning
>> curve, but am looking forward to using it.
>> I'll have a bunch of test stuff for sale if this thing works out ;-)
>> Don
>> 
>> Bob Camp
>>> Hi
>>> 
>>> I  *suspect* that any size that was common in 2003 will be ok. I have  no
>>> basis for that claim. That likely will limit you to 2 gig and  down.
>>> 
>>> Each time I called Amtronix, Rick answered on  the first ring. It's
>>> definitely someplace I would recommend  dealing with.
>>> 
>>> How's the display on your unit? That  sees to be the weakness of a lot of
>>> test gear these  days.
>>> 
>>> Can't wait to measure -100 dbc/Hz phase noise  with mine :) 
>>> 
>>> Bob
>>> 
>>> 
>>> On Feb 1, 2010, at 5:34 PM, Don Latham wrote:
>>> 
>>>> Just bought one last week. As advertised, came with a cal and  checkout
>>>> sheet.  BTW, cost another $150 to have manuals  printed out. But, I'm 
> old
>>>> fashioned and have a hard time using  manuals onscreen...
>>>> I also got the feeling (phone order) that  I can call Amtronix and at
>>>> least
>>>> reach a Real  Person who will talk to me.
>>>> I think the E8285A will replace at  least three present instruments with
>>>> better, once I master  Instrument Basic :-).
>>>> Does anyone know which low-cost PCMCIA  memory card will work? They're 
> on
>>>> Epay for as little as  $10
>>>> Don
>>>> 
>>>> Bob  Camp
>>>>> Hi
>>>>> 
>>>>> I do  believe the last (or maybe next to last) of the Amtronix  
> E8285A's
>>>>> is
>>>>> now on it's way to a  basement in Pennsylvania. If anybody else here is
>>>>> looking  for one, I'd sure call Rick pretty quick.
>>>>> 
>>>>> Bob
>>>>> 
>>>>> -Original Message-
>>>>> From:  time-nuts-boun...@febo.com [mailto:time-nuts-boun...@febo.com]  
> On
>>>>> Behalf Of John Ackermann N8UR
>>>>> Sent:  Thursday, January 21, 2010 4:14 PM
>>>>> To:  john.fo...@gmail.com; Discussion of precise time and  frequency
>>>>> measurement
>>>>> Subject: Re:  [time-nuts] Test Equipment
>>>>> 
>>>>> If RF  measurement is your bag, and you're able to spend a couple of  
> $K
>>>>> (actually, <$2K if what I've seen recently holds),  consider a
>>>>> communications service monitor like the  HP
>>>

Re: [time-nuts] Triangle Waves

[Bob Camp]

Hi

The DAC will quite nicely produce a trapezoid (or clipped triangle wave). It's 
certainly on the list. 

---

I've had a lot of lunch time discussions with the NIST guys about their 
"obsession" with input levels. About all I can say is that I don't see the same 
sensitivities they do. I suspect a lot of the issue is that we're not using the 
exact same circuits / components. 

-

Matching the isolation amplifier to the mixer for efficient power transfer is 
something I do plan to look at. I suspect it's only good up to a certain point 
and then you get into trouble. 

-

Lots of things to check ...

Bob


On Feb 2, 2010, at 12:06 AM, Bruce Griffiths wrote:

> Bob Camp wrote:
>> Hi
>> 
>> At least from the last time I tried it:
>> 
>> If you use a sine wave input source, it's got to be an amazingly good 10 Hz 
>> sine wave. A normal audio generator will not produce a 10 Hz output with 
>> good enough short term stability / noise to give you useful data. Audio 
>> generators may be out there that will do the job, but I certainly don't have 
>> one, and have never come across one.
>> 
>> Since the output of the mixer is basically a triangle wave, it makes sense 
>> to use that as your test source. A triangle wave also has the nice property 
>> that it's easy on the math. You don't have any approximation issues with the 
>> integers going into the DAC. That shoves the inevitable digital crud higher 
>> in frequency.
>> 
>>   
> When both the RF and LO ports are saturated, the mixer output waveform 
> depends on how the IF port is terminated.
> The output is indeed approximately triangular with your IF port termination 
> method when both the RF and LO ports are saturated.
> With the IF port terminated in a capacitor when both RF and LO ports are 
> saturated the output waveform is quasi trapezoidal.
> When only the LO port is saturated the IF output is sinusoidal.
>> Another nice thing about a pure digital approach is that it provides a clean 
>> trigger for the "start" channel of the counter you are testing things with. 
>> You can even set up the DAC to put out square waves to see just how good 
>> various bits of the chain are. Tough to do that with anything other than 
>> another arbitrary function generator.
>> 
>> I agree that the reference is going to be an issue and that a LED stack may 
>> be the way to go. No matter how you generate the test tone, power supply 
>> noise will be an issue.
>> 
>> The output amplifier on the DAC is my biggest worry. I could go with a 
>> current out DAC and something like an OP-27.  That won't give me 1nV/Hz 
>> either, but it will at least be within shouting distance of it.  Sigma 
>> deltas might be a third option. I have no idea what their low frequency 
>> flicker noise looks like.
>>   
> Producing a high amplitude (eg 20V pp) output and attenuating it down to say 
> 2V pp or so typical of a mixer will significantly reduce the noise due to the 
> output amplifier.
>> So, other than the noise issue (which obviously needs to be analyzed / 
>> tested / pounded on) any other issues with the approach?
>> 
>> 
>> 
>> At least from what I have seen in the past, level sensitivity on the inputs 
>> shows up pretty fast in the output "beat note" as you vary the input signals 
>> that are supposed to be saturating the mixer. If they are doing their job, a 
>> 2 db level change produces a very small change in the output. If you have 
>> something amiss in that department, you will see it pretty fast. On that I'm 
>> pretty much in agreement with Rubiola's stuff.
>> 
>>   
> Yes but NIST used a saturated mixer and still found that the mixer phase 
> shift depended on how hard you drive the diodes.
> Long term variations in isolation amplifier output due to temperature 
> variations may be significant.
>> Since I intend to mate the isolation amps up directly on the same board as 
>> the mixer, there is no real need for a 50 ohm interface between them. If the 
>> mixer looks like 18.26 ohms,  the amp output can be transformed to that 
>> level rather than 50 ohms. Everything is matched (over a 1/8" trace) and you 
>> don't burn up power in a bunch of resistors. How well that idea works - time 
>> will tell. It's easy to put the resistors in if it flunks out.
>> 
>> So many things to try 
>> 
>> Bob
>> 
>>   
> You could also try driving the mixer ports from a highe impedance source (eg 
> transistor collector).
> One early NIST paper advocated this.
> 

Re: [time-nuts] Test Equipment

[Bob Camp]

Hi

The 2.x firmware is the magic that lets it run down to HF type frequencies. You 
really do not want to "upgrade" the firmware.

It would be very nice to find a back shelf somewhere with a set of original 
manuals for the 2.x version. 

Now if it just had a SR-620 counter built into it 

Bob


On Feb 2, 2010, at 1:20 AM, Don Latham wrote:

> Oh, forgot. My firmware appears to be something like A.02.4 or something like 
> that, and the manuals are A.05.0 or so. another possible problem.
> Don
> 
> - Original Message - From: "Bob Camp" 
> To: "Discussion of precise time and frequency measurement" 
> 
> Sent: Monday, February 01, 2010 6:42 PM
> Subject: Re: [time-nuts] Test Equipment
> 
> 
>> Hi
>> 
>> The big question in my mind about these is how well they do below 30 MHz. 
>> Until I know I can trust them it down there, I'm not selling very much stuff.
>> 
>> I have yet to find a data sheet from before 2000 when they shipped with the 
>> sub-800 MHz stuff enabled. I get the impression that the E8285's never quite 
>> did as well below 30 MHz as the 8920's do.
>> 
>> Bob
>> 
>> 
>> On Feb 1, 2010, at 7:29 PM, Don Latham wrote:
>> 
>>> Hi Bob. Display shows use, definitely, but I can see info over the whole
>>> tube. I have a couple of things to do before I can start the learning
>>> curve, but am looking forward to using it.
>>> I'll have a bunch of test stuff for sale if this thing works out ;-)
>>> Don
>>> 
>>> Bob Camp
>>>> Hi
>>>> 
>>>> I *suspect* that any size that was common in 2003 will be ok. I have no
>>>> basis for that claim. That likely will limit you to 2 gig and down.
>>>> 
>>>> Each time I called Amtronix, Rick answered on the first ring. It's
>>>> definitely someplace I would recommend dealing with.
>>>> 
>>>> How's the display on your unit? That sees to be the weakness of a lot of
>>>> test gear these days.
>>>> 
>>>> Can't wait to measure -100 dbc/Hz phase noise with mine :) 
>>>> 
>>>> Bob
>>>> 
>>>> 
>>>> On Feb 1, 2010, at 5:34 PM, Don Latham wrote:
>>>> 
>>>>> Just bought one last week. As advertised, came with a cal and checkout
>>>>> sheet.  BTW, cost another $150 to have manuals printed out. But, I'm old
>>>>> fashioned and have a hard time using manuals onscreen...
>>>>> I also got the feeling (phone order) that I can call Amtronix and at
>>>>> least
>>>>> reach a Real Person who will talk to me.
>>>>> I think the E8285A will replace at least three present instruments with
>>>>> better, once I master Instrument Basic :-).
>>>>> Does anyone know which low-cost PCMCIA memory card will work? They're on
>>>>> Epay for as little as $10
>>>>> Don
>>>>> 
>>>>> Bob Camp
>>>>>> Hi
>>>>>> 
>>>>>> I do believe the last (or maybe next to last) of the Amtronix E8285A's
>>>>>> is
>>>>>> now on it's way to a basement in Pennsylvania. If anybody else here is
>>>>>> looking for one, I'd sure call Rick pretty quick.
>>>>>> 
>>>>>> Bob
>>>>>> 
>>>>>> -Original Message-
>>>>>> From: time-nuts-boun...@febo.com [mailto:time-nuts-boun...@febo.com] On
>>>>>> Behalf Of John Ackermann N8UR
>>>>>> Sent: Thursday, January 21, 2010 4:14 PM
>>>>>> To: john.fo...@gmail.com; Discussion of precise time and frequency
>>>>>> measurement
>>>>>> Subject: Re: [time-nuts] Test Equipment
>>>>>> 
>>>>>> If RF measurement is your bag, and you're able to spend a couple of $K
>>>>>> (actually, <$2K if what I've seen recently holds), consider a
>>>>>> communications service monitor like the HP
>>>>>> 8920A/8920B/8921/8924/8935/E8285 (all pretty much the same thing).
>>>>>> 
>>>>>> You get an RF generator, RF power meter, RX frequency meter and
>>>>>> modulation analyzer, audio generator, audio analyzer, digital o'scope,
>>>>>> and in most units a spectrum analyzer (many have a tracking generator,
>>>>>> too) in one box.  And I've probably forgott

Re: [time-nuts] OT: Practical PLL low noise?

[Bob Camp]

Hi

The first issue - your oscillator may be drifting quite a lot. If so, that's
the first thing to check and possibly fix. A reasonable oscillator should be
able to hold less than 100 Hz at 42 MHz under normal room conditions. Fixes
range from circuit improvements, to a better crystal, to simply eliminating
a draft that blows on the oscillator. 

If the oscillator is reasonably stable, it will need to be turned into a
VCXO in order to lock it. If both oscillators use fundamental crystals, that
should not be very hard. If they use higher overtone crystals it may be more
of a challenge. Often you will find a tradeoff between good oscillator
performance and wide tuning range. 

What ever chip you use to do the lock, keep the loop bandwidth small. The
GPSDO will be noisy and it will not help you for phase noise. I would start
the bandwidth at 100 Hz to be sure everything works ok and then start
narrowing it to 10 Hz or less. At some point the loop will be to narrow to
"keep up" with the changes and you will not be able to maintain phase lock.

What ever loop bandwidth you use, keep the phase margin large. You do not
need a fast locking loop. Instead you need one that has less tendency to
peak. Phase margins should be above 70 degrees.

The nice thing about doing this with a chip is that most of the
manufacturers have cute little web applications / free downloads to design
the loop filters for you. No digging out crazy formulas and wondering if you
got it all right. 

Have fun !

Bob
KB8TQ



-Original Message-
From: time-nuts-boun...@febo.com [mailto:time-nuts-boun...@febo.com] On
Behalf Of francesco messineo
Sent: Tuesday, February 02, 2010 10:50 AM
To: Discussion of precise time and frequency measurement
Subject: [time-nuts] OT: Practical PLL low noise?

Hello all,
sorry for the OT, but I know there're many real electronic artists here.

As an amateur radio operator I often use transverters, some home made.
They usually can be made sigthly better (RF and noise-wise) than
japanese transceivers. However often the LO xtal oscillator drifts too
much for comfortable digital and weak signal work.
Now the big question: is there any PLL design that can lock 22 MHz and
42 MHz xtal oscillator to a 10 MHz reference (typically from a GPSDO)
without adding significant noise to the oscillators? The LOs usually
go to a single or doube balanced diode mixer like the famous
minicircuit ones, and at that point the RF signal has been already
amplified by 10 or 20 dB stage(s).
Other options would be "ovenizing" the LOs or making a DDS sinth.
Now, what would be more practical approach from the home construction point?
Thanks
Frank IZ8DWF

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Re: [time-nuts] Test Equipment -Memory cards

[Bob Camp]

Hi

The memory in the E8285A has a lithium cell associated with it. One of my
big questions is weather the firmware goes away when the coin cell dies
(battery backed SRAM) or if the firmware is in something a bit more robust.

Hopefully it's sitting on the porch when I get home tonight

--

141T ... how many do you need in addition to an E8285 ... all sorts of
questions to be answered.

Bob

-Original Message-
From: time-nuts-boun...@febo.com [mailto:time-nuts-boun...@febo.com] On
Behalf Of Robert Atkinson
Sent: Tuesday, February 02, 2010 8:42 AM
To: Discussion of precise time and frequency measurement
Subject: Re: [time-nuts] Test Equipment -Memory cards

Hi Don,
Congratulations on the E8285A. I've an 8924C that does me nicely  and came
with a bunch of other stuff including two 10811A's and a crystal impedance
meter (gotta keep on-topic) for £300 (~$500). Another useful instrument in
the range that can sometimes be picked up cheaply is the 8922X if you get
the 06 or 106 option you get a nice 1GHz digital SA with TG, a CW RF
generator and low frequency scope. The GSM test stuff is an unwanted extra.
A bit big, but better than a 141T setup.  I think you will find that the
E8285A is the same as the 8924C and uses non-volatile RAM cards, not flash.
These cards are rare now and have CMOS ram and a lithium coin cell. You
MIGHT be able to read a flash card, but I'm pretty certain you can't write
to them.
 
Robert G8RPI.

--- On Mon, 1/2/10, Don Latham  wrote:


From: Don Latham 
Subject: Re: [time-nuts] Test Equipment
To: "Discussion of precise time and frequency measurement"

Date: Monday, 1 February, 2010, 22:34


Just bought one last week. As advertised, came with a cal and checkout
sheet.  BTW, cost another $150 to have manuals printed out. But, I'm old
fashioned and have a hard time using manuals onscreen...
I also got the feeling (phone order) that I can call Amtronix and at least
reach a Real Person who will talk to me.
I think the E8285A will replace at least three present instruments with
better, once I master Instrument Basic :-).
Does anyone know which low-cost PCMCIA memory card will work? They're on
Epay for as little as $10
Don

Bob Camp
> Hi
>
> I do believe the last (or maybe next to last) of the Amtronix E8285A's is
> now on it's way to a basement in Pennsylvania. If anybody else here is
> looking for one, I'd sure call Rick pretty quick.
>
> Bob
>
> -Original Message-
> From: time-nuts-boun...@febo.com [mailto:time-nuts-boun...@febo.com] On
> Behalf Of John Ackermann N8UR
> Sent: Thursday, January 21, 2010 4:14 PM
> To: john.fo...@gmail.com; Discussion of precise time and frequency
> measurement
> Subject: Re: [time-nuts] Test Equipment
>
> If RF measurement is your bag, and you're able to spend a couple of $K
> (actually, <$2K if what I've seen recently holds), consider a
> communications service monitor like the HP
> 8920A/8920B/8921/8924/8935/E8285 (all pretty much the same thing).
>
> You get an RF generator, RF power meter, RX frequency meter and
> modulation analyzer, audio generator, audio analyzer, digital o'scope,
> and in most units a spectrum analyzer (many have a tracking generator,
> too) in one box.  And I've probably forgotten a few things.  If you get
> one with spec analyzer and tracking generator, there's software that
> lets you do swept insertion/return loss and cable fault finding.
>
> None of its capabilities are as good as those of a dedicated box
> performing a single function, but they're good enough for the vast
> majority of uses.  An 8920 was the first significant piece of test gear
> I bought, and if I ever have to sell out, it'll be the last one to go.
>
> The prices came down a lot when Lucent surplused hundreds (thousands?)
> of them from their portable and cell phone production lines.  I saw an
> 8935 with spec an, fully functional (as far as I could tell) for about
> $1500 this summer.
>
> A guy who sells and services a lot of these boxes is Rick at
> http://www.amtronix.com -- that web site will give you lots of info
> about the various versions and options.  (I just noticed he has some
> Agilent 8285As as a "hobbyist special" with spec an and tracking
> generator for $650.  That looks like a deal.)
>
> John
> 
> john.fo...@gmail.com said the following on 01/21/2010 03:43 PM:
>> Just that John, I'm looking to setup a general purpose lab. I'd lean
> towards RF type stuff since I'm a HAM.
>> Sent via BlackBerry by AT&T
>>
>> -Original Message-
>> From: "J. Forster" 
>> Date: Thu, 21 Jan 2010 12:22:11
>> To: ; Discussion of precise time and frequency
> measurement
>> Subject: Re: [time-nuts] Tes

Re: [time-nuts] Lady Heather Daemon for FreeBSD

[Bob Camp]

Hi

Sounds *very* useful. 

Which version(s) of FreeBSD have you tried it on? 

Thanks!

Bob

-Original Message-
From: time-nuts-boun...@febo.com [mailto:time-nuts-boun...@febo.com] On
Behalf Of Ralph Smith
Sent: Tuesday, February 02, 2010 12:41 PM
To: time-nuts@febo.com
Subject: [time-nuts] Lady Heather Daemon for FreeBSD

I have written a small daemon that attaches to a Thunderbolt and acts as a
client for Lady Heather. In addition, if specified it will provide data to
NTP through the shared memory driver. It currently compiles on FreeBSD,
and OS X.

Available at 

It is in a very early, rough stage at the moment, but I thought I would
provide it for anyone that is interested. There are two programs: tboltd,
and gpsdclient.

First tboltd:
Usage: tboltd [-t ] [-v] [-p ] [-u ] [-d]
  -t :  Specify Thunderbolt serial port. Default 'cuau1'.
  -v:Increase verbosity level.
  -p : UDP port to listen for client connections. Default 45000.
  -u : Unit number for NTP shared memory driver. Default to none
  -d:Do not detach and run in daemon mode.

Some notes:
- tboltd will currently accept as many clients as memory allows.
- tboltd currently does not buffer requests from clients. Multiple clients
risk having commands interleaved.
- Logging needs to be implemented properly
- tboltd blocks when there is no activity on the thunderbolt or client. On
a Net4501 (133 MHz 486 equivalent), with 3 clients (1 Heather + 2
gpsdclient) it takes less than 1% CPU.
- Likely to be bugs.
- I invoke it on my Net4501 as "tboltd -p 45000 -t cuau1 -u 0"
- Corresponding ntp.conf entry
  # Use shared memory
  tos mindist 0.030
  server 127.127.28.0 minpoll 4 maxpoll 4 prefer
  fudge 127.127.28.0 time1 0.0275 refid GPS

Second: gpsdclient.
gpsdclient will attach to tboltd or gpsd, receive Thunderbold TSIP
packets, and drive an NTP shared memory segment.
Usage: ./gpsdclient [-g] [-u ] [-p ] host
- The -g flag will sent the command to gpsd to put it in super-raw mode to
deliver TSIP
- Currently not configured to detach and run as a daemon, will fix that
when I get around to it.

This needs some cleanup and reorganization, but I thought some of you
might be interested. Any comments or suggestions please let me know.
--
Ralph Smith (AB4RS)



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Re: [time-nuts] Lady Heather Daemon for FreeBSD

[Bob Camp]

Hi

I'm running 8 on most of my stuff now, so that should not be an issue. If
you had come back with 6.1 that might have been reason to stop and think a
bit. 

Does the program take care of all the serial line setup stuff, or are there
links and stuff that need to be done to get it to talk right? Some of the
NTP serial drivers seem to require a bit of a massage on the serial settings
to make them happy. 

Bob

-Original Message-
From: time-nuts-boun...@febo.com [mailto:time-nuts-boun...@febo.com] On
Behalf Of Ralph Smith
Sent: Tuesday, February 02, 2010 12:54 PM
To: Discussion of precise time and frequency measurement
Subject: Re: [time-nuts] Lady Heather Daemon for FreeBSD

On Tue, February 2, 2010 12:47 pm, Bob Camp wrote:
> Hi
>
> Sounds *very* useful.
>
> Which version(s) of FreeBSD have you tried it on?

8.0-STABLE, but it should be good for earlier versions.

Ralph (AB4RS)

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Re: [time-nuts] OT: Practical PLL low noise?

[Bob Camp]

Hi

I happen to like the Analog Devices ADF4001 for this sort of thing. You
would need two of them, one for each oscillator.  The National chip
mentioned earlier will also work. The 2306 it's self is obsolete, but I'm
sure there are other National parts that will drop into the same socket. 

Either way you will need something like a PIC to "shoot" the settings into
the chip. It looks like all that is taken care of on the board in the
earlier post. The code on the PIC would need to be re-written to match up
with what ever chip you decide to use. 

Bob

-Original Message-
From: time-nuts-boun...@febo.com [mailto:time-nuts-boun...@febo.com] On
Behalf Of francesco messineo
Sent: Tuesday, February 02, 2010 12:58 PM
To: Discussion of precise time and frequency measurement
Subject: Re: [time-nuts] OT: Practical PLL low noise?

Hi Bob,

On 2/2/10, Bob Camp  wrote:
> Hi
>
>  The first issue - your oscillator may be drifting quite a lot. If so,
that's
>  the first thing to check and possibly fix. A reasonable oscillator should
be
>  able to hold less than 100 Hz at 42 MHz under normal room conditions.
Fixes
>  range from circuit improvements, to a better crystal, to simply
eliminating
>  a draft that blows on the oscillator.

it is drifting about 50 Hz during warm up, but the problem is thermal
drift internally as season changes, as tx/rx periods change, and so
on.

>  If the oscillator is reasonably stable, it will need to be turned into a
>  VCXO in order to lock it. If both oscillators use fundamental crystals,
that
>  should not be very hard. If they use higher overtone crystals it may be
more
>  of a challenge. Often you will find a tradeoff between good oscillator
>  performance and wide tuning range.

22 MHz can be fundamental, 42 MHz is third overtone for sure.

>
>  What ever chip you use to do the lock, keep the loop bandwidth small. The
>  GPSDO will be noisy and it will not help you for phase noise. I would
start
>  the bandwidth at 100 Hz to be sure everything works ok and then start
>  narrowing it to 10 Hz or less. At some point the loop will be to narrow
to
>  "keep up" with the changes and you will not be able to maintain phase
lock.
>
>  What ever loop bandwidth you use, keep the phase margin large. You do not
>  need a fast locking loop. Instead you need one that has less tendency to
>  peak. Phase margins should be above 70 degrees.
>
>  The nice thing about doing this with a chip is that most of the
>  manufacturers have cute little web applications / free downloads to
design
>  the loop filters for you. No digging out crazy formulas and wondering if
you
>  got it all right.


thanks for the suggestions, any good candidate as a chip?

73
Frank IZ8DWF

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Re: [time-nuts] FW: Injection locking

[Bob Camp]

Hi

If you do go the injection locking route check a couple of things:

1) Be sure to do the math and keep the 3db bandwidth down to the ~20 Hz
range. Otherwise you will be getting more phase noise than you probably
should. Generally this means having some kind of control on how much power
you are injecting. 

2) Consider what impact (if any) the extra signals running around in your
radio will have. The harmonics of what ever you inject are one issue. The
intermodulation products between the injection and the oscillator in some
cases can be another.

None of this is to say it does not work. Only that there are a few things
that may (or may not) be issues.

Bob


-Original Message-
From: time-nuts-boun...@febo.com [mailto:time-nuts-boun...@febo.com] On
Behalf Of francesco messineo
Sent: Tuesday, February 02, 2010 4:14 PM
To: Discussion of precise time and frequency measurement
Subject: Re: [time-nuts] FW: Injection locking

On 2/2/10, Bruce Griffiths  wrote:
> However injection locking also works when the frequencies ratios involved
> are rational numbers.
>  For 22MHz and 10MHz, the corresponding ratio is 11/5 a rational number.
>  For 42MHz and 10MHz, the frequency ratio is 21/5 a rational number

Then 2 MHz would work for both, obtaining 2 MHz from 10 MHz is quite
easy, HP AN-301-1
plus a 74LS193 would do it.
If I can make it work with the current oscillator design I'm using, I
can easily adapt it also to already made transverters, very tempting.

Frank

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Re: [time-nuts] LORAN C update

[Bob Camp]

Hi

At least when they were brand new, the Austron's had no problem at all locking 
to chains in Iceland and Europe from the central US. That was with the US 
chains going full bore

Bob


On Feb 2, 2010, at 5:37 PM, paul swed wrote:

> American LORAN C will shut down at 2000z Feb 8
> Dual rated chains that serve Canada will operate till 1 Oct.
> As an example North East 9960 will be off but Canadian 5930 will operate
> till Oct.
> Have used 5930 for years from Boston as a reference.
> 
> North American LORAN will be completely quite by Oct 1.
> Time to see if the Austrons will sync to Europe then.
> Have locked 1 time already at night.
> Regards
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Re: [time-nuts] Triangle Waves

[Bob Camp]

Hi

The NIST guys at least at lunch would come back with "We only put enough in to 
get the paper published. The rest of he details will appear in another paper 
down the road". Some of the stuff has been coming out a piece at a time for 30 
years now .

Bob

On Feb 2, 2010, at 2:32 PM, Bruce Griffiths wrote:

> Bob Camp wrote:
>> Hi
>> 
>> The DAC will quite nicely produce a trapezoid (or clipped triangle wave). 
>> It's certainly on the list.
>> 
>> ---
>> 
>> I've had a lot of lunch time discussions with the NIST guys about their 
>> "obsession" with input levels. About all I can say is that I don't see the 
>> same sensitivities they do. I suspect a lot of the issue is that we're not 
>> using the exact same circuits / components.
>> 
>> -
>>   
> Some of their papers are annoyingly incomplete, in that the measurement 
> setups used were incompletely specified.
>> Matching the isolation amplifier to the mixer for efficient power transfer 
>> is something I do plan to look at. I suspect it's only good up to a certain 
>> point and then you get into trouble.
>> 
>> -
>> 
>> Lots of things to check ...
>> 
>> Bob
>> 
>> 
>>   
> Bruce
> 
> 
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Re: [time-nuts] Triangle Waves

[Bob Camp]

Hi

At least the last time I tried it, the filter a square wave / integrate based 
on a square wave approach both appeared to give performance that was 
inadequate. Simply put, the triangle wave should give *better* performance than 
a similar wave generated off of a pair of good oscillators. That was not the 
case. Could there have been errors made - sure. Exactly what did I do - long 
time ago, details are in a log book that probably doesn't even exist any more. 

Ideally the signal source would be much better than the limiter I'm trying to 
test. If I want to verify a 10 ns limiter, a triangle wave good to a ns or so 
would be a nice thing to have. It would also be nice to easily verify that 
device. The objective is a quick test of a limiter rather than the world's best 
low frequency R-C oscillator. That of course assumes I can womp up the DAC 
gizmo easily.

Bob


On Feb 2, 2010, at 7:58 PM, Joseph M Gwinn wrote:

> time-nuts-boun...@febo.com wrote on 02/02/2010 07:20:24 PM:
> 
>> From:
>> 
>> Bruce Griffiths 
>> 
>> To:
>> 
>> Discussion of precise time and frequency measurement 
> 
>> 
>> Date:
>> 
>> 02/02/2010 07:27 PM
>> 
>> Subject:
>> 
>> Re: [time-nuts] Triangle Waves
>> 
>> Sent by:
>> 
>> time-nuts-boun...@febo.com
>> 
>> Magnus Danielson wrote:
> [snip]
>>> Just a reality check question here... a simple triangle oscillator is 
>>> very easily created by two op-amps, one for an integrator and one for 
>>> Schmitt trigger operation. If you want better long-term stability open 
> 
>>> the loop and insert a 10 Hz from your favourite divider chain of a 
>>> trusted 10 MHz or so. Would such a design be limiting your measurement 
> 
>>> goals considerable, and would any flaws be reasonably to overcome by 
>>> better design?
>>> 
>>> Cheers,
>>> Magnus
>>> 
>> For beat frequencies in the 1-100Hz range one only need verify the ZCD 
>> jitter and delay variations etc., to within a few nanosec.
>> In the short term such jitter tantalisingly close to what a well 
>> designed audio oscillator is capable of.
>> Unfortunately the trigger jitter in most counters is very large for 
>> frequencies in this range so verifying the low jitter of an audio 
>> oscillator requires using a ZCD or equivalent.
> 
> Would integration of a 50% duty cycle square wave generate an adequate 
> triangle wave?  Modern opamps make pretty good low-noise integrators, 
> although one would need to use a good integration capacitor to ensure 
> linear ramps.
> 
> The square wave would come from a simple binary divider chain, which will 
> clean many things up and ensure a stable duty cycle, whatever the nature 
> of the original signal source.
> 
> Joe Gwinn
> 
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Re: [time-nuts] Triangle Waves

[Bob Camp]

On Feb 2, 2010, at 9:29 PM, Joseph M Gwinn wrote:

> time-nuts-boun...@febo.com wrote on 02/02/2010 09:13:26 PM:
> 
>> From:
>> 
>> Bruce Griffiths 
>> 
>> To:
>> 
>> Discussion of precise time and frequency measurement 
> 
>> 
>> Date:
>> 
>> 02/02/2010 09:16 PM
>> 
>> Subject:
>> 
>> Re: [time-nuts] Triangle Waves
>> 
>> Sent by:
>> 
>> time-nuts-boun...@febo.com
>> 
>> Joseph M Gwinn wrote:
>>> time-nuts-boun...@febo.com wrote on 02/02/2010 08:19:26 PM:
>>> 
>>> 
 From:
 
 Bruce Griffiths
 
 To:
 
 Discussion of precise time and frequency measurement
 
>>> 
>>> 
 Date:
 
 02/02/2010 08:20 PM
 
 Subject:
 
 Re: [time-nuts] Triangle Waves
 
 Sent by:
 
 time-nuts-boun...@febo.com
 
 Joseph M Gwinn wrote:
 
> time-nuts-boun...@febo.com wrote on 02/02/2010 07:20:24 PM:
> 
> 
> 
>> From:
>> 
>> Bruce Griffiths
>> 
>> To:
>> 
>> Discussion of precise time and frequency measurement
>> 
>> 
> 
> 
> 
>> Date:
>> 
>> 02/02/2010 07:27 PM
>> 
>> Subject:
>> 
>> Re: [time-nuts] Triangle Waves
>> 
>> Sent by:
>> 
>> time-nuts-boun...@febo.com
>> 
>> Magnus Danielson wrote:
>> 
>> 
> [snip]
> 
> 
>>> Just a reality check question here... a simple triangle oscillator
>>> 
>>> is
>>> 
>>> very easily created by two op-amps, one for an integrator and one
>>> 
>>> for
>>> 
>>> Schmitt trigger operation. If you want better long-term
>>> 
 stability open
 
>>> 
> 
>>> the loop and insert a 10 Hz from your favourite divider chain of a
>>> trusted 10 MHz or so. Would such a design be limiting your
>>> 
 measurement
 
>>> 
> 
>>> goals considerable, and would any flaws be reasonably to 
>> overcome by
>>> better design?
>>> 
>>> Cheers,
>>> Magnus
>>> 
>>> 
>>> 
>> For beat frequencies in the 1-100Hz range one only need verify the
>> 
>>> ZCD
>>> 
>> jitter and delay variations etc., to within a few nanosec.
>> In the short term such jitter tantalisingly close to what a well
>> designed audio oscillator is capable of.
>> Unfortunately the trigger jitter in most counters is very large for
>> frequencies in this range so verifying the low jitter of an audio
>> oscillator requires using a ZCD or equivalent.
>> 
>> 
> Would integration of a 50% duty cycle square wave generate 
>> an adequate
> triangle wave?  Modern opamps make pretty good low-noise 
> integrators,
> although one would need to use a good integration capacitorto ensure
> linear ramps.
> 
> The square wave would come from a simple binary divider
> 
 chain, which will
 
> clean many things up and ensure a stable duty cycle, whateverthe
> 
>>> nature
>>> 
> of the original signal source.
> 
> Joe Gwinn
> 
> 
> 
 The integration function requires a low frequency cutoff (either a
 servoloop or a resistor shunting the integration capacitor) to avoid
 integrator saturation.
 This inevitably distorts the triangle wave, however it should be
 possible to reduce the triangular wave distortion by predistorting 
> the
 integrator input current.
 
>>> Yes, there would need to be some kind of drift compensation (I favor a
>>> opamp servoloop), but given that we are trying to measure ZCD jitter
>>> (versus long-term wander), isn't this good enough?  The 
>> distortion will be
>>> small and stable, and so will not cause jitter.
>>> 
>>> Joe Gwinn
>>> 
>> Yes one shouldn't lose sight of the goal which isnt a perfect triangular 
> 
>> wave, but merely a low jitter one.
>> The major problem is the Johnson noise of the resistors used in the 
>> integrator.
>> 
>> If for example one uses a simple RC filter using 25k plus 10uF and 
>> drives it with a 10Hz square wave the output noise at dc is 
>> about 20nv/rtHz.
>> The output slew rate with say a 5V amplitude square wave is about 1V pp 
>> and the zero crossing jitter due to Johnson noise is on the order of 
> 3ns.
> 
> I've lost track of our jitter objective, and why we need to achieve it.
> 
> Also, if the intent is to measure the inherent jitter of a ZCD circuit, we 
> may be better off using a really clean sinewave, as it will be easier to 
> generate a clean enough sinewave than trianglewave.
> 
> The fact that we will use a triangle or trapezoid in practice will change 
> the numbers somewhat, but the ranking of proposed circuits by their 
> sinewave jitter should carry over correctly, so long as the same 
> fundamental frequency is used.
> 
> Joe Gwinn
> 

The objective is to check out a limiter that will have performance at better 
than 10 ns level when driven with a beat note in the 5 to 10 Hz range. A signal 
5 to 10X better than the limiter target performance would be adeq

Re: [time-nuts] Triangle Waves

[Bob Camp]

On Feb 2, 2010, at 9:57 PM, Bruce Griffiths wrote:

> Joseph M Gwinn wrote:
>> 
> Figure 8 (attached) from Collin's paper indicates that the jitter of a 100Hz 
> wien bridge oscillator is of the order of a few hundred nanosec or so.
> This was taken using a 3 stage limiter and a 1 sec counter gate time.
> It may be feasible to do better.
> 
> It would also appear to be feasible to produce a 10Hz sinewave with ns jitter 
> by low pass filtering a square wave using a combination of active and passive 
> RC filtering.
> 

That figure pretty clearly shows the issue of getting a good trigger on a low 
frequency signal. 

It's a pretty big guess to figure out what the 100 Hz oscillator is doing. At 
least to my eye it's pretty far from the 1 ppb / second level. 

As long as we're on the Collins paper - has anybody dug up the final paper 
referenced? I believe it's titled something like "Hard Limiter Experimental 
Results"?

Bob

> Bruce
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Re: [time-nuts] EFRATOM LPRO-101

[Bob Camp]

Hi

A little more data from a group of recent units:

The XTAL pin is looking at the VCXO control voltage, It should move around 
(sweep) at turn on. It will settle in the vicinity of 6 volts. I have seen 
units anywhere from 5.5 to 7.2 volts on this pin.

The BITE is a logic level pin, it's either high or low. 

The lamp voltage on "early" units runs around 6 volts. On "later" units it's up 
around 9 volts. This may be a better bulb, or it just may be a different photo 
detector. Every time I've asked about lamp voltage, the answer has been "in 
range is ok". Trying to predict life from lamp voltage apparently is more 
complex than it might seem.  I would not throw out a 6 volt unit simply because 
it's not a 9 volt 

Bob


On Feb 3, 2010, at 7:08 AM, Roy Phillips wrote:

> Hi Jim
> This would appear to be a faulty unit, I also purchased the same unit from 
> Bob Mokia two weeks ago and its performing very well.  It gives a frequency 
> of 10.000,000,005 Mhz.
> One very obvious fault is the BITE voltage - - this should initially be 4.5 
> volts, which falls to less than 30 mV. within a few minutes. The XTAL Control 
> Volts, after a short while falls to 6.145 V., so yours, at 14.67 V, would 
> seem to be wrong ! The Lamp volts settle to 6.736 V, and the Ext  C Field is 
> 2.426 V. , which checks with your result.
> I'm  sure you will get a replacement.
> Roy
> 
> --
> From: "Jim" 
> Sent: Tuesday, February 02, 2010 9:08 PM
> To: 
> Subject: [time-nuts] EFRATOM LPRO-101
> 
>> Hello all.
>> 
>> I received an EFRATOM LPRO-101 last week from eBay Fluke 1, and wired it up 
>> last night. The results are not good.
>> 
>> Using a HP 5370B counter with calibration less than one year old, the 
>> frequency reads = 10,000,146,012.9
>> Power Applied = 24.9Vdc @ 0.30 amps after warm up
>> Lamp Voltage = 5.9 Vdc
>> Ext C Field = 2.437
>> XTL V Mon = 14.67
>> Bite = 4.57
>> 
>> Bite never goes low.
>> 
>> I just sent an email to the outfit I purchased it from, but would like to 
>> get this working instead of waiting a month or so.
>> 
>> Is it dead?  Any thing I can do to revive it?
>> 
>> Any suggestions?
>> 
>> Thanks to all.
>> 
>> Jim N0OBG
>> 
>> 
>> -- 
>> 
>> 
>> 
>> The heart of the wise inclines to the right, but the heart of the fool to 
>> the left. Eccl 10:2 (NIV)
>> 
>> 
>> 
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> 
> 
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Re: [time-nuts] EFRATOM LPRO-101

[Bob Camp]

Hi

I would second that as well. 

I got an LPRO in that had a "rattle" when it arrived. After some thought, I
popped the can and figured out what the issue was. Since it might have been
gong back, I kept Bob in the loop during the entire process. He was very
supportive through it all. Definitely a first class guy. 

Bob

-Original Message-
From: time-nuts-boun...@febo.com [mailto:time-nuts-boun...@febo.com] On
Behalf Of Doug Parker
Sent: Wednesday, February 03, 2010 9:23 AM
To: Discussion of precise time and frequency measurement
Subject: Re: [time-nuts] EFRATOM LPRO-101

Hi,
 
I'd like to confirm that Bob is a very good seller and been great with the
things I've had off him. 
 
He's also a member of this group
 
Doug
G4DZU

--- On Wed, 3/2/10, EB4APL  wrote:


From: EB4APL 
Subject: Re: [time-nuts] EFRATOM LPRO-101
To: "Discussion of precise time and frequency measurement"

Date: Wednesday, 3 February, 2010, 13:20


Hi,

Bob Mokia is a very good seller and you'll not have problems with him.  
In  order to avoid paying the return shipping and the delays I would ask 
him to let you open the unit and try to find an obvious fault such a 
loose connection.  When I bought my Rb (from another source) I opened it 
even it was working ok, and I found one of the connector pins touching 
its PCB pad without any trace of solder on it; nevertheless it worked 
perfectly but it was just a question of time before the unit will begin 
to act intermittently so I fixed it.  Thinking about I realized that 
maybe this unit showed problems and it was retired from active service 
and maybe it has very low hours on it.
Do your unit sweeps its frequency above and bellow 10 MHz when warming 
up the first minutes? it is the normal operation before a lock is 
obtained and if it is not done it will never lock the oscillator to the 
Rb frequency.

Good luck,
Ignacio, EB4APL

-------
Bob Camp wrote:
> Hi
>
> A little more data from a group of recent units:
>
> The XTAL pin is looking at the VCXO control voltage, It should move around
(sweep) at turn on. It will settle in the vicinity of 6 volts. I have seen
units anywhere from 5.5 to 7.2 volts on this pin.
>
> The BITE is a logic level pin, it's either high or low. 
>
> The lamp voltage on "early" units runs around 6 volts. On "later" units
it's up around 9 volts. This may be a better bulb, or it just may be a
different photo detector. Every time I've asked about lamp voltage, the
answer has been "in range is ok". Trying to predict life from lamp voltage
apparently is more complex than it might seem.  I would not throw out a 6
volt unit simply because it's not a 9 volt 
>
> Bob
>
>
> On Feb 3, 2010, at 7:08 AM, Roy Phillips wrote:
>
>   
>> Hi Jim
>> This would appear to be a faulty unit, I also purchased the same unit
from Bob Mokia two weeks ago and its performing very well.  It gives a
frequency of 10.000,000,005 Mhz.
>> One very obvious fault is the BITE voltage - - this should initially be
4.5 volts, which falls to less than 30 mV. within a few minutes. The XTAL
Control Volts, after a short while falls to 6.145 V., so yours, at 14.67 V,
would seem to be wrong ! The Lamp volts settle to 6.736 V, and the Ext  C
Field is 2.426 V. , which checks with your result.
>> I'm  sure you will get a replacement.
>> Roy
>>
>> --
>> From: "Jim" 
>> Sent: Tuesday, February 02, 2010 9:08 PM
>> To: 
>> Subject: [time-nuts] EFRATOM LPRO-101
>>
>>     
>>> Hello all.
>>>
>>> I received an EFRATOM LPRO-101 last week from eBay Fluke 1, and wired it
up last night. The results are not good.
>>>
>>> Using a HP 5370B counter with calibration less than one year old, the
frequency reads = 10,000,146,012.9
>>> Power Applied = 24.9Vdc @ 0.30 amps after warm up
>>> Lamp Voltage = 5.9 Vdc
>>> Ext C Field = 2.437
>>> XTL V Mon = 14.67
>>> Bite = 4.57
>>>
>>> Bite never goes low.
>>>
>>> I just sent an email to the outfit I purchased it from, but would like
to get this working instead of waiting a month or so.
>>>
>>> Is it dead?  Any thing I can do to revive it?
>>>
>>> Any suggestions?
>>>
>>> Thanks to all.
>>>
>>> Jim N0OBG
>>>
>>>
>>> -- 
>>>
>>>
>>>
>>> The heart of the wise inclines to the right, but the heart of the fool
to the left. Eccl 10:2 (NIV)
>>>
>>>
>>>
>>> ___
>>> time-nuts mailing list -- time-nuts@feb

Re: [time-nuts] Triangle Waves

[Bob Camp]

Hi

My *guess* would be that magnetic pickup (power lines etc) in the L of the
L/R (or LC or even RLC) network would be a difficult problem to address. Big
toroidal coils might be one solution to that. 

Cost wise the DAC is looking better and better

Bob

-Original Message-
From: time-nuts-boun...@febo.com [mailto:time-nuts-boun...@febo.com] On
Behalf Of Magnus Danielson
Sent: Wednesday, February 03, 2010 4:02 PM
To: Discussion of precise time and frequency measurement
Subject: Re: [time-nuts] Triangle Waves

Bruce Griffiths wrote:
> Joseph M Gwinn wrote:
>>> The integration function requires a low frequency cutoff (either a
>>> servoloop or a resistor shunting the integration capacitor) to avoid
>>> integrator saturation.
>>> This inevitably distorts the triangle wave, however it should be
>>> possible to reduce the triangular wave distortion by predistorting the
>>> integrator input current.
>>>  
>> Yes, there would need to be some kind of drift compensation (I favor a
>> opamp servoloop), but given that we are trying to measure ZCD jitter
>> (versus long-term wander), isn't this good enough?  The distortion 
>> will be
>> small and stable, and so will not cause jitter.
>>
>> Joe Gwinn
>>
> Yes one shouldn't lose sight of the goal which isnt a perfect triangular 
> wave, but merely a low jitter one.

Indeed.

> The major problem is the Johnson noise of the resistors used in the 
> integrator.
> 
> If for example one uses a simple RC filter using 25k plus 10uF and 
> drives it with a 10Hz square wave the output noise at dc is about 
> 20nv/rtHz.
> The output slew rate with say a 5V amplitude square wave is about 1V pp 
> and the zero crossing jitter due to Johnson noise is on the order of 3ns.

Hmm... what about an LR replacement of the RC chain over the op-amp?

Just a thought. It is a bit uncommon, but is essentially the same in 
function. Could prove interesting since the LR balance could possibly 
allow for lower noise selections.

Cheers,
Magnus

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Re: [time-nuts] CPLDs for clock dividers

[Bob Camp]

Hi

Discrete logic is a good thing for low jitter.

CPLD's (and FPGA's) can have all sorts of interesting stuff running inside 
them. Some versions even have exciting stuff like charge pump bias generators 
that turn on and off at random times. 

Simple check - if it's logic and it pulls many ma of current with no clock 
input = not a good thing 

Bob


On Feb 3, 2010, at 6:14 PM, Pete Rawson wrote:

> On the subject of dividers, the 74HC4059 is a synchronous CMOS part
> with a really easy to use divide by 10K function & favorable jitter
> performance. It's cheap & available from distributors.  With a 10MHZ
> sinewave input, jitter measures less than 4ps rms & 27ps p-p on 2 
> samples I checked.
> 
> Pete Rawson
> 
> On Feb 3, 2010, at 12:42 PM, paul swed wrote:
> 
>> They are indeed cheap and it would be handy to have low noise divider
>> chains.
>> 6 decades worth. 74ls90s get really boring to wire.
>> Unfortunately I am unfamiliar with using the device. But I do seem them
>> used.
>> 
>> On Wed, Feb 3, 2010 at 1:59 PM, Matt Ettus  wrote:
>> 
>>> Does anyone have any experience using CPLDs for very low phase noise
>>> dividers?  You can get an XC9536XL from Xilinx for around $1, and I
>>> thought it would make a good divide by 2 through 10 device.
>>> 
>>> Matt
>>> 
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Re: [time-nuts] CPLDs for clock dividers

[Bob Camp]

Hi

One trick is indeed to turn all of the unused output pins into grounds. 

That does not help the power much. There you need good solid bypassing on all 
of the power pins. With a little CPLD you don't have many pins. WIth even a 
small FPGA there are a lot of them to bypass.  I've seen a number of boards 
where people have given up after fully bypassing most but not all of the power 
pins.

Bob


On Feb 4, 2010, at 2:58 AM, Gerhard Hoffmann wrote:

> Luis Cupido wrote:
>> That is not by any means a CPLD. it is a big FPGA and I bet it would
>> be doing a bazilon things besides the divider.
> It shares the CPLD's problems of ground and VCC bounce. The Virtex
> was completely empty otherwise and the counter was stoppable, so
> it was easy to see the culprit.
> 
> Having a hundred ground  pins  should  be more of an advantage and
> wether the innards are fine-grained (FPGA) or sum-of-products-cells (CPLD)
> really does not matter.
> 
> 
> 73s, Gerhard, DK4XP
> 
> 
> 
> 
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Re: [time-nuts] CPLDs for clock dividers

[Bob Camp]

Hi

>From the Altera doc's on the Max II:

There's an oscillator in there to clock the flash (page 2-20). It runs at
around 5 MHz. Need to turn that off. Since standby current is rated at 25ua
it's something that can be done. Low standby also suggests there isn't
anything else nasty sneaking around in there. 

They have four global clocks (page 2-16). Normally they are pretty stable
and free from "stuff".

They have 2 to 4 independently powered output banks (page 2-31). The
isolation between banks is pretty good. Isolation between adjacent cells in
a bank - not so good.  

They will only do single ended I/O (page 2-26). No PECL or LVDS. To get that
you would have to cross over to a Cyclone III FPGA and all of it's issues.

Bob



-Original Message-
From: time-nuts-boun...@febo.com [mailto:time-nuts-boun...@febo.com] On
Behalf Of Ulrich Bangert
Sent: Thursday, February 04, 2010 11:34 AM
To: 'Discussion of precise time and frequency measurement'
Subject: Re: [time-nuts] CPLDs for clock dividers

Luis,

with the help of Bruce I have been trying to put the digital part of a
linear phase comparator (for oscillator characterization) into some
different Xilinx CPLDs. Only to find out that there must be a lot of
"analogue kind" interactions between blocks within the CPLD that had
originally been understood as being purely digital circuitry. I have the
tool chain for ALTERA available as well and I find it highly interesting
that your experience with the MAXII is that good. I will give them a try!
Can you explain a bit what measurement possibilities for jitter you have
available to make these conclusions from?

Best regards
Ulrich, DF6JB

> -Ursprungliche Nachricht-
> Von: time-nuts-boun...@febo.com 
> [mailto:time-nuts-boun...@febo.com] Im Auftrag von Luis Cupido
> Gesendet: Donnerstag, 4. Februar 2010 15:21
> An: Discussion of precise time and frequency measurement
> Betreff: Re: [time-nuts] CPLDs for clock dividers
> 
> 
> I understand your arguments...
> 
> I just wonder why reality differs.
> I had a design (GPSDO) that I tested on a FPGA
> (Cyclone) and the same on MAXII and the difference
> was abyssal !!!
> 
> Whatever... the MAXII family has a unbeatable jitter 
> performance compared to discrete logic... That I can tell by 
> direct observation. Other CPLD's I can't tell much only 
> MAX3000 that was slightly worst and MAX7000 that was the same 
> as TTL +/-. Know nothing about Xilinx or others...
> 
> There are so many devices nowadays that I do accept that we
> may no longer set a guideline of what is good or bad in
> general terms anymore.
> 
> Luis Cupido.
> ct1dmk.
> 
> 
> Gerhard Hoffmann wrote:
> > Luis Cupido wrote:
> >> That is not by any means a CPLD. it is a big FPGA and I 
> bet it would 
> >> be doing a bazilon things besides the divider.
> > It shares the CPLD's problems of ground and VCC bounce. The 
> Virtex was 
> > completely empty otherwise and the counter was stoppable, so it was 
> > easy to see the culprit.
> > 
> > Having a hundred ground  pins  should  be more of an advantage and 
> > wether the innards are fine-grained (FPGA) or sum-of-products-cells 
> > (CPLD) really does not matter.
> > 
> > 
> > 73s, Gerhard, DK4XP
> > 
> > 
> > 
> > 
> > ___
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> > 
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Re: [time-nuts] CPLDs for clock dividers

[Bob Camp]

HI

Takes maybe an hour to download. Everything you need for simple logic design is 
right there.

Bob


On Feb 4, 2010, at 8:31 PM, Luis Cupido wrote:

> You may try Altera. Quatus web 9.1 is 1.5Gb and painless to setup.
> https://www.altera.com/support/software/download/altera_design/quartus_we/dnl-quartus_we.jsp
> 
> lc.
> ct1dmk.
> 
> 
> paul swed wrote:
>> I also did the web install and need to go back and add more options.
>> How painful. Enough to drive me away from this project
>> On Thu, Feb 4, 2010 at 6:26 PM, Gerhard Hoffmann  wrote:
>>> paul swed wrote:
>>> 
 Well not having a lot of luck with the xilinx wise application.
 Its a 6.5 GB tar and after a good 5 hr plus download the tar doesn't open
 with zipgenious
 But 6.5 GB to work a cpld. Seems crazy to me.
 
 
>>> I also had no luck two weeks ago with the single file download.
>>> The web install worked ok, however. It downloads many smaller
>>> files. I think my very slow DSL connection is to blame here.  :-(
>>> 
>>> Two years ago, when I still lived in Berlin, Xilinx used to have one of the
>>> few servers that were capable to max out my (then) 16 MBit/s link.
>>> 
>>> 
>>> @ Ulrich:
>>> Did you see a show stopper with the Xilinx Coolrunners?
>>> I have used them before and liked them. Really fast and they
>>> consume close to no power. I'd like to deploy them for something
>>> jitter-critical very soon.
>>> 
>>> regards, Gerhard dk4xp
>>> 
>>> 
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Re: [time-nuts] CPLDs for clock dividers

[Bob Camp]

Hi

All of these packages have a *lot* of crazy optimizations you can do. The 
defaults work pretty well in Quartus with one exception.

They are in the process of moving from their "classic timing analyzer" to 
another timing analyzer (TimeQuest?). Right now the classic analyzer is 
disabled by default, but it still sets it's self up ok for simple stuff. By 
default you will get error messages about "timing driven synthesis" unless you 
do a timing constraints file. If you just go to the timing analyzer section and 
flip over to the classic analyzer,  the messages will go away. You can go back 
and fiddle with timing files after you have the basic design in and running.

The other alternative is of course to do the timing file first and then put in 
the design. Nothing wrong with that, if its the work flow you prefer.

Bob

On Feb 4, 2010, at 11:12 PM, paul swed wrote:

> I used the link and the file downloaded reasonably
> Install tomorrow
> Thanks
> 
> On Thu, Feb 4, 2010 at 8:31 PM, Luis Cupido  wrote:
> 
>> You may try Altera. Quatus web 9.1 is 1.5Gb and painless to setup.
>> 
>> https://www.altera.com/support/software/download/altera_design/quartus_we/dnl-quartus_we.jsp
>> 
>> lc.
>> ct1dmk.
>> 
>> 
>> paul swed wrote:
>> 
>>> I also did the web install and need to go back and add more options.
>>> How painful. Enough to drive me away from this project
>>> 
>>> On Thu, Feb 4, 2010 at 6:26 PM, Gerhard Hoffmann  wrote:
>>> 
>>> paul swed wrote:
 
 Well not having a lot of luck with the xilinx wise application.
> Its a 6.5 GB tar and after a good 5 hr plus download the tar doesn't
> open
> with zipgenious
> But 6.5 GB to work a cpld. Seems crazy to me.
> 
> 
> I also had no luck two weeks ago with the single file download.
 The web install worked ok, however. It downloads many smaller
 files. I think my very slow DSL connection is to blame here.  :-(
 
 Two years ago, when I still lived in Berlin, Xilinx used to have one of
 the
 few servers that were capable to max out my (then) 16 MBit/s link.
 
 
 @ Ulrich:
 Did you see a show stopper with the Xilinx Coolrunners?
 I have used them before and liked them. Really fast and they
 consume close to no power. I'd like to deploy them for something
 jitter-critical very soon.
 
 regards, Gerhard dk4xp
 
 
 ___
 time-nuts mailing list -- time-nuts@febo.com
 To unsubscribe, go to
 https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts
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 ___
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Re: [time-nuts] Small CPLD/FPGA for microcontroller replacement

[Bob Camp]

Hi

The Max II is the current Altera CPLD family.

http://www.altera.com/products/devices/cpld/max2/mx2-index.jsp

There are some older families like the MAX3000 still running around at some
level of production. For a new design of the complexity you are looking at,
go with the latest and greatest. 

You are going to use a lot of gates, and the newer parts have much larger
gate populations than the older ones. The biggest part in the series has
2210 LE's or 1700 Macro cells. Think of them both as a couple of super gates
+ flip flop(s) that can do a useful function. Done the easy way, a 24 bit
modulo N counter will use 24 LE's. 

It's likely you will run out of gates before you run out of pins. The bigger
parts come in 256 / 324 pin packages. You may be able to implement crude
D/A's with unused pins and R/2R resistor arrays. Maybe not cheap, but it
might help you on reliability. 

The MAX II's all have 8K bits (1K bytes) of user accessible flash memory.
It's a nice for things like calibration data and embedded serial numbers. 

For the master clock, the first thing to check would be a system clock
signal that's already running around. Just about anything in the 1 to 200
MHz range could be useful. If the application is simple enough, the chips do
have an accessible onboard R/C oscillator. It's spec'd as 3.5 to 5.5 MHz and
you can't tune it. Better than nothing though.

You should be able to do everything you need to do with the web download
tools. There are a few small things they leave out. Altera support is pretty
good. We are out in the middle of nowhere and they drop by every few months.


I'm absolutely certain that Xilinx has similar parts that also work well. We
are an Altera shop, so I'll let somebody else chime in there. 

Bob



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Re: [time-nuts] new Al atomic clock publication

[Bob Camp]

Hi

All that work and the biggest chunk of uncertainty contains "fluctuations
caused by periodic line noise (50 to 60 Hz)".

I guess even NIST can't afford good shielding

Bob 

-Original Message-
From: time-nuts-boun...@febo.com [mailto:time-nuts-boun...@febo.com] On
Behalf Of Chris Caudle
Sent: Friday, February 05, 2010 3:22 PM
To: time-nuts@febo.com
Subject: [time-nuts] new Al atomic clock publication

No discussion on the new Al based atomic clock paper from NIST?

http://arxiv.org/PS_cache/arxiv/pdf/0911/0911.4527v2.pdf

"Here we describe an Al+ ion clock with an inaccuracy of 8.6×10−18."

Doesn't get more nutty than that.

-- 
Chris Caudle







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Re: [time-nuts] Small CPLD/FPGA for microcontroller replacement

[Bob Camp]

Hi

I believe you will find a state machine compiler in the web version of Quartus. 
I know it's there in the full version. It has some nice features if you are 
after a provably "fail safe" machine.  

There is also a simple version of the NIOS processor available that may fit 
into the larger CPLD's. It and a reasonable set of peripherals would definitely 
fit into a set of chips.  I'm not sure exactly what the authorities wold make 
of a micro controller made within a CPLD. I know what I would think, but 
their's is indeed the only opinion that matters.  

Bob

 
On Feb 5, 2010, at 5:18 PM, Didier Juges wrote:

> I am not trying to replace the exact functionality of a processor with 
> something else, but simply in general terms for those cases where a processor 
> is not a practical solution, I would like to be able to use a small CPLD or 
> FPGA to obtain similar equivalent functionality, which is that of a power 
> supply monitor/remote controller.
> 
> I would not consider ladder logic an adequate substitute, at least for the 
> level of complexity that we normally require (I am replacing a ladder logic 
> controller with a processor in another project, so I know in that case the 
> functionality gap). There is a state machine at the core, but a great many 
> peripheral functions.
> 
> I checked the Actel parts suggested earlier, and they look promising.
> 
> Didier
> 
>  Sent from my BlackBerry Wireless thingy while I do 
> other things... 
> 
> -Original Message-
> From: paul swed 
> Date: Fri, 5 Feb 2010 09:14:32 
> To: Discussion of precise time and frequency measurement
> Subject: Re: [time-nuts] Small CPLD/FPGA for microcontroller replacement
> 
> Didier that is indeed a tall order.
> But at least since the system already exists you have the established
> requirements in hand.
> So my question is (And I am uneducated in DO-254) is a state machine okay?
> Because it sounds like thats what you are forced into. If true then its much
> more like the traditional relay logic ladder type of solution. Which has
> been pretty good for the railroads for 100 years.
> Other comment is perhaps this particular thread rapidly goes offline to
> respect others.
> 
> On Fri, Feb 5, 2010 at 9:04 AM, Didier Juges  wrote:
> 
>> It looks like I will have to get educated on CPLD/FPGAs on short notice.
>> 
>> My application at the moment will be the replacement of small
>> microcontrollers for military and commercial aviation projects that do not
>> want/tolerate software/firmware (some customers and government regulations
>> do not consider CPLD/FPGA to be containing software, which to a large
>> extent
>> is a matter of opinion, but this is not a thread I wish to start at this
>> time). The FAA in particular puts a much greater burden on microcontrollers
>> than CPLD/FPGAs when it comes to demonstrating compliance to DO-254 in
>> safety critical applications like battery charging.
>> 
>> The microcontrollers I have been using are typically from 20 to 100 pins
>> (Silabs 8051 family) with a lot of integrated peripherals. I understand I
>> will have to use external peripherals like ADC, DAC, probably clock
>> oscillator and such with a CPLD/FPGA, where these functions are currently
>> integrated in my microcontrollers.
>> 
>> Part of the requirement is that the devices be immune (as much as
>> practical)
>> from SEU malfunction. I was told Atmel (or Actel?) makes flash-based small
>> FPGAs that may fit the bill. Most SRAM devices are deemed to be excessively
>> sensitive to SEU, even though I cannot imagine how a CPLD/FPGA could be
>> made
>> that does not use SRAM at all. Maybe it's a matter of quantity? A few
>> working registers may be an acceptable risk, but the entire device
>> operating
>> from SRAM is not acceptable?
>> 
>> I am looking for any information/recommendation on which families to look
>> into.
>> 
>> Thanks in advance,
>> 
>> Didier KO4BB
>> 
>> -Original Message-
>> From: time-nuts-boun...@febo.com [mailto:time-nuts-boun...@febo.com] On
>> Behalf Of John Miles
>> Sent: Thursday, February 04, 2010 8:43 PM
>> To: Discussion of precise time and frequency measurement
>> Subject: Re: [time-nuts] CPLDs for clock dividers
>> 
>> Yeah, Xilinx 11 is pretty nice.  I'm usually allergic to IDEs, especially
>> theirs, but I've been pretty happy with 11 so far.  I find myself using it
>> instead of my tried-and-true makefile for FPGA work, and that's saying
>> something.
>> 
>> -- john, KE5FX
>> 
>> 
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Re: [time-nuts] ADEV vs MDEV

[Bob Camp]

Hi

At least from what I've seen, the Pendulum's seem to work a bit better than the 
other counters you mention. That may simply be a function of their being 
designed much more recently.  It could also be the issue of comparing beat up 
stuff on the bench to brand new stuff on the bench. The CNT-81 is rated to have 
a much better single shot time resolution than the others. 

Yes I realize that in no way addresses the question you asked.

MDEV and ADEV measure slightly different things. Depending on what you are 
looking for MDEV may give you better insight. 

Bob


On Feb 5, 2010, at 10:59 PM, Pete Rawson wrote:

> Efforts are underway to develop a low cost DMTD apparatus with
> demonstrated stability measurements of 1E-13 in 1s. It seems that
> existing TI counters can reach this goal in 10s. (using MDEV estimate
> or 100+s. using ADEV estimate). The question is; does the MDEV tool
> provide an appropriate measure of stability in this time range, or is
> the ADEV estimate a more correct answer? 
> 
> The TI performance I'm referring to is the 20-25 ps, single shot TI,
> typical for theHP5370A/B, the SR620 or the CNT81/91. I have data
> from my CNT81showing MDEV < 1E-13 in 10s. and I believe the
> other counters behave similarly.
> 
> I would appreciate any comments or observations on this topic.
> My motivation is to discover the simplest scheme for making 
> stability measurements at this performance level; this is NOT
> even close to the state-of-the-art, but can still be useful.
> 
> Pete Rawson
> 
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Re: [time-nuts] ADEV vs MDEV

[Bob Camp]

Hi

The counter is not the big issue in DMTD. We seem  The problems lies elsewhere. 
I think we've gone into that pretty deeply in various recent threads.

As a practical bench instrument, the Pendulums are a very good choice. That's 
independent of anything having to do with DMTD. 

Bob


On Feb 5, 2010, at 11:53 PM, Bruce Griffiths wrote:

> Read the data sheet and the various application notes/white papers on the 
> Pendulum site.
> The intrinsic resolution of the Pendulum counter (50ps) is slightly inferior 
> to that of the SR620 and HP5370A/B.
> What they do is statistically process the results of a series of measurements 
> of the input phase taken at short intervals.
> They actually fit a regression line to the resultant series of phase 
> measurements.
> This process inherently filters out some of the noise of the counter.
> If it were possible to do the same thing using an SR620 or HP5370 the noise 
> in the output resolution would be even lower.
> 
> If one is building a conventional DMTD one doesn't actually need resolution 
> for the timestamping device/counter much better than 10ns or so to achieve a 
> resolution of around 1E-13/Tau with say a 100Hz beat frequency and 10MHz 
> inputs to the mixer/phase detector.
> 
> Bruce
> 
> Bob Camp wrote:
>> Hi
>> 
>> At least from what I've seen, the Pendulum's seem to work a bit better than 
>> the other counters you mention. That may simply be a function of their being 
>> designed much more recently.  It could also be the issue of comparing beat 
>> up stuff on the bench to brand new stuff on the bench. The CNT-81 is rated 
>> to have a much better single shot time resolution than the others.
>> 
>> Yes I realize that in no way addresses the question you asked.
>> 
>> MDEV and ADEV measure slightly different things. Depending on what you are 
>> looking for MDEV may give you better insight.
>> 
>> Bob
>> 
>> 
>> On Feb 5, 2010, at 10:59 PM, Pete Rawson wrote:
>> 
>>   
>>> Efforts are underway to develop a low cost DMTD apparatus with
>>> demonstrated stability measurements of 1E-13 in 1s. It seems that
>>> existing TI counters can reach this goal in 10s. (using MDEV estimate
>>> or 100+s. using ADEV estimate). The question is; does the MDEV tool
>>> provide an appropriate measure of stability in this time range, or is
>>> the ADEV estimate a more correct answer?
>>> 
>>> The TI performance I'm referring to is the 20-25 ps, single shot TI,
>>> typical for theHP5370A/B, the SR620 or the CNT81/91. I have data
>>> from my CNT81showing MDEV<  1E-13 in 10s. and I believe the
>>> other counters behave similarly.
>>> 
>>> I would appreciate any comments or observations on this topic.
>>> My motivation is to discover the simplest scheme for making
>>> stability measurements at this performance level; this is NOT
>>> even close to the state-of-the-art, but can still be useful.
>>> 
>>> Pete Rawson
>>> 
>>> ___
>>> time-nuts mailing list -- time-nuts@febo.com
>>> To unsubscribe, go to 
>>> https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts
>>> and follow the instructions there.
>>> 
>>> 
>> 
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>> 
>>   
> 
> 
> 
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Re: [time-nuts] new Al atomic clock publication

[Bob Camp]

Hi

A mixing scheme 20 years in the making 

Bob


On Feb 6, 2010, at 9:49 AM, Magnus Danielson wrote:

> Chris Caudle wrote:
>> No discussion on the new Al based atomic clock paper from NIST?
>> http://arxiv.org/PS_cache/arxiv/pdf/0911/0911.4527v2.pdf
>> "Here we describe an Al+ ion clock with an inaccuracy of 8.6×10−18."
>> Doesn't get more nutty than that.
> 
> Not matching any of my counters all that well... 1,121 PHz with about 8 mHz 
> of line-width. No wonder they had an elaborate mix-down setup just to compare 
> the clocks.
> 
> Cheers,
> Magnus
> 
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Re: [time-nuts] ADEV vs MDEV

[Bob Camp]

Hi

It's possible / likely to injection lock with the tight loop approach and 
get data that's much better than reality. A lot depends on the specific 
oscillators under test and the buffers (if any) between the oscillators and 
mixer.


If your OCVCXO has a tuning slope of 0.1 ppm / volt then a part in 10^14 is 
going to be at the 100 of nanovolts level. Certainly not impossible, but it 
does present it's own set of issues. Lab gear to do it is available, but not 
all that common. DC offsets and their temperature coefficients along with 
thermocouple effects could make things exciting.


There is no perfect way to do any of this, only a lot of compromises here or 
there. Each approach has stuff you need to watch out for.


Bob

--
From: "WarrenS" 
Sent: Saturday, February 06, 2010 2:19 PM
To: "Discussion of precise time and frequency measurement" 


Subject: Re: [time-nuts] ADEV vs MDEV



Peat said:
I would appreciate any comments or observations on the topic of apparatus 
with demonstrated stability measurements.
My motivation is to discover the SIMPLEST scheme for making stability 
measurements at the 1E-13 in 1s  performance level.



If you accept that the measurement is going to limited by the Reference 
Osc,

for Low COST and SIMPLE, with the ability to measure ADEVs at that level,
Can't beat a simple analog version of  NIST's "Tight Phase-Lock Loop 
Method of measuring Freq stability".

http://tf.nist.gov/phase/Properties/one.htm#oneoneFig 1.7


By replacing the "Voltage to freq converter, Freq counter & Printer with a 
Radio shack type PC data logging DVM,
It can be up and running from scratch in under an Hr, with no high end 
test equipment needed.
If you want performance that exceeds the best of most DMTD at low Tau it 
takes a little more work

and a higher speed oversampling ADC data logger and a good offset voltage.

I must add this is not a popular solution (Or a general Purpose one) but
IF  you know analog and have a GOOD osc with EFC to use for the reference,
as far as I've been able to determine it is the BEST SIMPLE answer that 
allows High performance.
Limited by My HP10811 Ref OSC, I'm getting better than 1e-12 in 0.1 sec 
(at 30 Hz Bandwidth)


Basic modified NIST Block Diag attached:
The NIST paper sums it up quite nicely:
'It is not difficult to achieve a sensitivity of a part in e14 per Hz 
resolution

so one has excellent precision capabilities with this system.'

This does not address your other question of ADEV vs MDEV,
What I've described is just a simple way to get the Low cost, GOOD Raw 
data.

What you then do with that Data is a different subject.

You can run the raw data thru one of the many ADEV programs out there, 
'Plotter' being my choice.



Have fun
ws

*

[time-nuts] ADEV vs MDEV
Pete Rawson peterawson at earthlink.net
Sat Feb 6 03:59:18 UTC 2010

Efforts are underway to develop a low cost DMTD apparatus with
demonstrated stability measurements of 1E-13 in 1s. It seems that
existing TI counters can reach this goal in 10s. (using MDEV estimate
or 100+s. using ADEV estimate). The question is; does the MDEV tool
provide an appropriate measure of stability in this time range, or is
the ADEV estimate a more correct answer?

The TI performance I'm referring to is the 20-25 ps, single shot TI,
typical for theHP5370A/B, the SR620 or the CNT81/91. I have data
from my CNT81showing MDEV < 1E-13 in 10s. and I believe the
other counters behave similarly.

I would appreciate any comments or observations on this topic.
My motivation is to discover the simplest scheme for making
stability measurements at this performance level; this is NOT
even close to the state-of-the-art, but can still be useful.

Pete Rawson







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Re: [time-nuts] ADEV vs MDEV

[Bob Camp]

Hi

Unfortunately, the most common approach is to simply say "it's a wide band 
loop, no need to check it "

Bob


On Feb 6, 2010, at 3:30 PM, Bruce Griffiths wrote:

> To a first approximation injection locking alters the loop parameters so its 
> important to measure the actual PLL characteristics with the loop closed and 
> not just use the PLL parameters inferred from the OCXO EFC transfer function 
> etc.
> 
> The noise of the OCXO used as a VCXO will limit the noise floor.
> An ADEV noise floor of 1E-13 isnt likely when using an HP10811A as the VCXO 
> for example.
> 
> Bruce
> 
> Bob Camp wrote:
>> Hi
>> 
>> It's possible / likely to injection lock with the tight loop approach and 
>> get data that's much better than reality. A lot depends on the specific 
>> oscillators under test and the buffers (if any) between the oscillators and 
>> mixer.
>> 
>> If your OCVCXO has a tuning slope of 0.1 ppm / volt then a part in 10^14 is 
>> going to be at the 100 of nanovolts level. Certainly not impossible, but it 
>> does present it's own set of issues. Lab gear to do it is available, but not 
>> all that common. DC offsets and their temperature coefficients along with 
>> thermocouple effects could make things exciting.
>> 
>> There is no perfect way to do any of this, only a lot of compromises here or 
>> there. Each approach has stuff you need to watch out for.
>> 
>> Bob
>> 
>> --
>> From: "WarrenS" 
>> Sent: Saturday, February 06, 2010 2:19 PM
>> To: "Discussion of precise time and frequency measurement" 
>> 
>> Subject: Re: [time-nuts] ADEV vs MDEV
>> 
>>> 
>>> Peat said:
>>>> I would appreciate any comments or observations on the topic of apparatus 
>>>> with demonstrated stability measurements.
>>>> My motivation is to discover the SIMPLEST scheme for making stability 
>>>> measurements at the 1E-13 in 1s  performance level.
>>> 
>>> 
>>> If you accept that the measurement is going to limited by the Reference Osc,
>>> for Low COST and SIMPLE, with the ability to measure ADEVs at that level,
>>> Can't beat a simple analog version of  NIST's "Tight Phase-Lock Loop Method 
>>> of measuring Freq stability".
>>> http://tf.nist.gov/phase/Properties/one.htm#oneoneFig 1.7
>>> 
>>> 
>>> By replacing the "Voltage to freq converter, Freq counter & Printer with a 
>>> Radio shack type PC data logging DVM,
>>> It can be up and running from scratch in under an Hr, with no high end test 
>>> equipment needed.
>>> If you want performance that exceeds the best of most DMTD at low Tau it 
>>> takes a little more work
>>> and a higher speed oversampling ADC data logger and a good offset voltage.
>>> 
>>> I must add this is not a popular solution (Or a general Purpose one) but
>>> IF  you know analog and have a GOOD osc with EFC to use for the reference,
>>> as far as I've been able to determine it is the BEST SIMPLE answer that 
>>> allows High performance.
>>> Limited by My HP10811 Ref OSC, I'm getting better than 1e-12 in 0.1 sec (at 
>>> 30 Hz Bandwidth)
>>> 
>>> Basic modified NIST Block Diag attached:
>>> The NIST paper sums it up quite nicely:
>>> 'It is not difficult to achieve a sensitivity of a part in e14 per Hz 
>>> resolution
>>> so one has excellent precision capabilities with this system.'
>>> 
>>> This does not address your other question of ADEV vs MDEV,
>>> What I've described is just a simple way to get the Low cost, GOOD Raw data.
>>> What you then do with that Data is a different subject.
>>> 
>>> You can run the raw data thru one of the many ADEV programs out there, 
>>> 'Plotter' being my choice.
>>> 
>>> 
>>> Have fun
>>> ws
>>> 
>>> *
>>> 
>>> [time-nuts] ADEV vs MDEV
>>> Pete Rawson peterawson at earthlink.net
>>> Sat Feb 6 03:59:18 UTC 2010
>>> 
>>> Efforts are underway to develop a low cost DMTD apparatus with
>>> demonstrated stability measurements of 1E-13 in 1s. It seems that
>>> existing TI counters can reach this goal in 10s. (using MDEV estimate
>>> or 100+s. using ADEV estimate). The question is; does the MDEV tool
>>> provide an appropriate measure of stability in this time range, 

Re: [time-nuts] ADEV vs MDEV

[Bob Camp]

Hi

A straight heterodyne system will get you to the floor of most 10811's with a 
very simple (2 stage) limiter. As with the DMTD, the counter requirements 
aren't really all that severe. 

Bob


On Feb 6, 2010, at 4:24 PM, WarrenS wrote:

> 
>> "It's possible / likely for injection lock ... to be a problem ..."
> Something I certainly worried about and tested for.
> What I found (for MY case) is that injection lock is NOT a problem.
> The reason being is that unlike most other ways, where the two OSC have to be 
> completely independent,
> The tight loop approach forces the Two Osc to "Lock with something like 60 + 
> db gain,
> so a little stray -80db injection lock coupling that would very much limit 
> other systems has
> no measurable effect at e-13. Just one of the neat little side effects that 
> make the tight loop approach so simple.
> 
>> "then a part in 10^14 is going to be at the 100 of nanovolts level."
> For that example, just need to put a simple discrete 100 to 1 resistor divider
> in-between the control voltage and the EFC and now you have a nice workable 
> 10uv.
> BUT the bigger point is, probable not needed, cause you are NOT going to do 
> any better than the stability of the OSC with a grounded shorted EFC input.
> 
> as you said and I agree is so true:
>> "There is no perfect way to do any of this, only a lot of compromises ... 
>> you need to watch out for".
> But you did not offer any easier way to do it, which is what the original 
> request was for and my answer addressed.
> This is the cheapest easiest way BY FAR to get high performance, at low tau, 
> ADEV numbers that I've seen.
> 
> ws
> ***
> 
> - Original Message - From: "Bob Camp" 
> To: "Discussion of precise time and frequency measurement" 
> 
> Sent: Saturday, February 06, 2010 12:09 PM
> Subject: Re: [time-nuts] ADEV vs MDEV
> 
> 
>> Hi
>> 
>> It's possible / likely to injection lock with the tight loop approach and 
>> get data that's much better than reality. A lot depends on the specific 
>> oscillators under test and the buffers (if any) between the oscillators and 
>> mixer.
>> 
>> If your OCVCXO has a tuning slope of 0.1 ppm / volt then a part in 10^14 is 
>> going to be at the 100 of nanovolts level. Certainly not impossible, but it 
>> does present it's own set of issues. Lab gear to do it is available, but not 
>> all that common. DC offsets and their temperature coefficients along with 
>> thermocouple effects could make things exciting.
>> 
>> There is no perfect way to do any of this, only a lot of compromises here or 
>> there. Each approach has stuff you need to watch out for.
>> 
>> Bob
>> 
>> --
>> From: "WarrenS" 
>> Sent: Saturday, February 06, 2010 2:19 PM
>> To: "Discussion of precise time and frequency measurement" 
>> 
>> Subject: Re: [time-nuts] ADEV vs MDEV
>> 
>>> 
>>> Peat said:
>>>> I would appreciate any comments or observations on the topic of apparatus 
>>>> with demonstrated stability measurements.
>>>> My motivation is to discover the SIMPLEST scheme for making stability 
>>>> measurements at the 1E-13 in 1s  performance level.
>>> 
>>> 
>>> If you accept that the measurement is going to limited by the Reference Osc,
>>> for Low COST and SIMPLE, with the ability to measure ADEVs at that level,
>>> Can't beat a simple analog version of  NIST's "Tight Phase-Lock Loop Method 
>>> of measuring Freq stability".
>>> http://tf.nist.gov/phase/Properties/one.htm#oneoneFig 1.7
>>> 
>>> 
>>> By replacing the "Voltage to freq converter, Freq counter & Printer with a 
>>> Radio shack type PC data logging DVM,
>>> It can be up and running from scratch in under an Hr, with no high end test 
>>> equipment needed.
>>> If you want performance that exceeds the best of most DMTD at low Tau it 
>>> takes a little more work
>>> and a higher speed oversampling ADC data logger and a good offset voltage.
>>> 
>>> I must add this is not a popular solution (Or a general Purpose one) but
>>> IF  you know analog and have a GOOD osc with EFC to use for the reference,
>>> as far as I've been able to determine it is the BEST SIMPLE answer that 
>>> allows High performance.
>>> Limited by My HP10811 Ref OSC, I'm getting better than 1e-12 in 0.1 sec (at 
>>> 30 H

Re: [time-nuts] ADEV vs MDEV

[Bob Camp]

Hi

With most 10811 range oscillators  the impact of a simple bandpass filter is 
low enough to not be a major issue. That's for normal lab temperatures with the 
circuitry in a conventional die cast  box. No guarantee if you open the window 
and let the fresh air blow in during the run.  

That's true with a heterodyne. I can see no obvious reason it would not be true 
on DMTD.

Bob


On Feb 6, 2010, at 5:12 PM, Bruce Griffiths wrote:

> The only major issue with DMTD systems is that they undersample the phase 
> fluctuations and hence are subject to aliasing effects.
> The low pass filter has to have a bandwidth of the same order as the beat 
> frequency or the beat frequency signal will be significantly attenuated.
> Since the phase is only sampled once per beat frequency period the phase 
> fluctuations are undersampled.
> Various attempts to use both zero crossings have not been successful.
> 
> In principle if one can overcome the increased phase shift tempco associated 
> with a bandpass filter, using a bandpass filter can in principle ensure that 
> the phase fluctuations are oversampled.
> 
> 
> Bruce
> 
> Bob Camp wrote:
>> Hi
>> 
>> A straight heterodyne system will get you to the floor of most 10811's with 
>> a very simple (2 stage) limiter. As with the DMTD, the counter requirements 
>> aren't really all that severe.
>> 
>> Bob
>> 
>> 
>> On Feb 6, 2010, at 4:24 PM, WarrenS wrote:
>> 
>>   
>>> 
>>>> "It's possible / likely for injection lock ... to be a problem ..."
>>>>   
>>> Something I certainly worried about and tested for.
>>> What I found (for MY case) is that injection lock is NOT a problem.
>>> The reason being is that unlike most other ways, where the two OSC have to 
>>> be completely independent,
>>> The tight loop approach forces the Two Osc to "Lock with something like 60 
>>> + db gain,
>>> so a little stray -80db injection lock coupling that would very much limit 
>>> other systems has
>>> no measurable effect at e-13. Just one of the neat little side effects that 
>>> make the tight loop approach so simple.
>>> 
>>> 
>>>> "then a part in 10^14 is going to be at the 100 of nanovolts level."
>>>>   
>>> For that example, just need to put a simple discrete 100 to 1 resistor 
>>> divider
>>> in-between the control voltage and the EFC and now you have a nice workable 
>>> 10uv.
>>> BUT the bigger point is, probable not needed, cause you are NOT going to do 
>>> any better than the stability of the OSC with a grounded shorted EFC input.
>>> 
>>> as you said and I agree is so true:
>>> 
>>>> "There is no perfect way to do any of this, only a lot of compromises ... 
>>>> you need to watch out for".
>>>>   
>>> But you did not offer any easier way to do it, which is what the original 
>>> request was for and my answer addressed.
>>> This is the cheapest easiest way BY FAR to get high performance, at low 
>>> tau, ADEV numbers that I've seen.
>>> 
>>> ws
>>> ***
>>> 
>>> - Original Message - From: "Bob Camp"
>>> To: "Discussion of precise time and frequency 
>>> measurement"
>>> Sent: Saturday, February 06, 2010 12:09 PM
>>> Subject: Re: [time-nuts] ADEV vs MDEV
>>> 
>>> 
>>> 
>>>> Hi
>>>> 
>>>> It's possible / likely to injection lock with the tight loop approach and 
>>>> get data that's much better than reality. A lot depends on the specific 
>>>> oscillators under test and the buffers (if any) between the oscillators 
>>>> and mixer.
>>>> 
>>>> If your OCVCXO has a tuning slope of 0.1 ppm / volt then a part in 10^14 
>>>> is going to be at the 100 of nanovolts level. Certainly not impossible, 
>>>> but it does present it's own set of issues. Lab gear to do it is 
>>>> available, but not all that common. DC offsets and their temperature 
>>>> coefficients along with thermocouple effects could make things exciting.
>>>> 
>>>> There is no perfect way to do any of this, only a lot of compromises here 
>>>> or there. Each approach has stuff you need to watch out for.
>>>> 
>>>> Bob
>>>> 
>>>> --
>>>> From: "

Re: [time-nuts] ADEV vs MDEV

[Bob Camp]

Hi

Here's my heterodyne vs tight loop logic:

1) With a heterodyne at around 8 Hz your isolation amplifiers are not as 
critical. Injection locking is a lot less likely at 8 Hz than dead on 
frequency. 
2) You eliminate the need for any form of phase lock.
3) You do need a mixer and a couple of OP-27/37's. 
4) Resistors, capacitors, power supplies are likely the same between the two.
5) For time tagging you'll need a picket fence source - not much money there. 
You could also decide not to time tag.


So far the Hetrodyne is as cheap as the tight lock. Probably a bit cheaper. 
Most of the parts are the same between the two setups, they simply get wired 
differently. 

The only real question is weather your DVM or my junk counter cost more money. 
My counter can be pretty bad and still not "get in the way".  My old (and long 
gone)  Beckman EPUT meter could probably handle the task. Tough to get data out 
of a vacuum tube counter though. 

Most 10811's are not 1x10^-13 at 1 second. A few might be. The vast majority 
are up around 0.8 to 2x10^-12 at one second. They were only specified to make 
5x10^-12 at one second. Both systems are equally limited by the performance of 
the reference oscillator. 

Bob

 
On Feb 6, 2010, at 5:42 PM, WarrenS wrote:

> Bob
> 
> So, if your point is that there are other ways to do it.  ...We Agree
> (And the reason for the advanced methods is so that the counter resolution is 
> not the limiting factor)
> 
> Or are you saying a Tight Phase-Lock Loop" is not the simplest and cheapest 
> way to get 1e13 resolution at 1  sec?
> That I'd have to see something new to believe it.
> 
> Just so things do not get too far off the original topic, here is a reminder:
>>>>> "I would appreciate any comments or observations on the SIMPLEST scheme 
>>>>> for making stability measurements at 1e-13 in one sec."
> ws Answer)  Try the "Tight Phase-Lock Loop Method"
> 
> May want to compare the blocks and equipment needed for A straight heterodyne 
> system, or a DMTD, compared to the Analog "Tight Phase-Lock Loop" Method,  
> AND then see what added problems there are because of injection locking, Osc 
> coupling, Phase noise, ETC, ETC.
> 
> 
> ws
> 
> ***
> 
> - Original Message - From: "Bob Camp" 
> To: "Discussion of precise time and frequency measurement" 
> 
> Sent: Saturday, February 06, 2010 2:03 PM
> Subject: Re: [time-nuts] ADEV vs MDEV
> 
> 
> Hi
> 
> A straight heterodyne system will get you to the floor of most 10811's with a 
> very simple (2 stage) limiter.
> As with the DMTD, the counter requirements aren't really all that severe.
> 
> Bob
> *
> 
> On Feb 6, 2010, at 4:24 PM, WarrenS wrote:
> 
>> 
>>> "It's possible / likely for injection lock ... to be a problem ..."
>> Something I certainly worried about and tested for.
>> What I found (for MY case) is that injection lock is NOT a problem.
>> The reason being is that unlike most other ways, where the two OSC have to 
>> be completely independent,
>> The tight loop approach forces the Two Osc to "Lock with something like 60 + 
>> db gain,
>> so a little stray -80db injection lock coupling that would very much limit 
>> other systems has
>> no measurable effect at e-13. Just one of the neat little side effects that 
>> make the tight loop approach so simple.
>> 
>>> "then a part in 10^14 is going to be at the 100 of nanovolts level."
>> For that example, just need to put a simple discrete 100 to 1 resistor 
>> divider
>> in-between the control voltage and the EFC and now you have a nice workable 
>> 10uv.
>> BUT the bigger point is, probable not needed, cause you are NOT going to do 
>> any better than the stability of the OSC with a grounded shorted EFC input.
>> 
>> as you said and I agree is so true:
>>> "There is no perfect way to do any of this, only a lot of compromises ... 
>>> you need to watch out for".
>> But you did not offer any easier way to do it, which is what the original 
>> request was for and my answer addressed.
>> This is the cheapest easiest way BY FAR to get high performance, at low tau, 
>> ADEV numbers that I've seen.
>> 
>> ws
>> ***
>> 
>> - Original Message - From: "Bob Camp" 
>> To: "Discussion of precise time and frequency measurement" 
>> 
>> Sent: Saturday, February 06, 2010 12:09 PM
>> Subject: Re: [time-nuts] ADEV vs MDEV
>> 
>> 
>>> Hi
>>> 
>>> It's p

Re: [time-nuts] ADEV vs MDEV

[Bob Camp]

Hi

You probably could put a couple of cheap DAC's on a board with a FPGA and 
reduce the data on the fly. I'd guess that would be be in the same $100 range 
as a half way decent sound card. Clock the DAC's off of a 10 MHz reference and 
eliminate the cal issue.

If you are down around 10 Hz or worse yet 1 Hz, the AC coupling of the sound 
card will get in the way, even with a bandpass approach. You really don't know 
what they may have in there at the low end. Build it yourself and that stuff's 
not an issue.

Bob


On Feb 6, 2010, at 6:12 PM, Bruce Griffiths wrote:

> If one has a high end sound card then it could be used to implement the 
> bandpass filter and replace the zero crossing detector.
> It may be necessary to insert a pilot tone to calibrate the sound card 
> sampling clock frequency.
> A noise floor of about 1E-13/Tau should be achievable.
> This simplifies the DMTD system by replacing the zero crossing detector with 
> a low gain linear preamp.
> 
> If one analyses the resultant data off line then one can also try out 
> different techniques such as a Costas receiver rather than a simple bandpass 
> filter plus zero crossing detector.
> However 1000 seconds of data for 2 channels of 24 bit samples at 192KSPS will 
> result in a file with a size of at least 1.15GB.
> 
> Bruce
> 
> 
> Bruce Griffiths wrote:
>> If one were to use a bandpass filter with a Q of 10 to filter the beat 
>> frequency output of the mixer, then if the input frequency is 10MHz and the 
>> filter component tempco is 100ppm/C then the resultant phase shift tempco is 
>> about 16ps/C referred to the mixer input frequency.
>> 
>> This phase shift tempco is certainly low enough not to have significant 
>> impact when measuring the frequency stability of a typical 10811A  if the 
>> temperature fluctuations are kept small enough during the run.
>> 
>> The effect of using a bandpass filter with too narrow a bandwidth is to 
>> artificially reduce ADEV for small Tau, so it may be prudent to use a higher 
>> beat frequency that 1Hz or even 10Hz and not calculate ADEV for Tau less 
>> than say 10(??) times the beat frequency period. A trade off between this 
>> and the effect of aliasing is required.
>> 
>> Bruce
>> 
>> Bob Camp wrote:
>>> Hi
>>> 
>>> With most 10811 range oscillators  the impact of a simple bandpass filter 
>>> is low enough to not be a major issue. That's for normal lab temperatures 
>>> with the circuitry in a conventional die cast  box. No guarantee if you 
>>> open the window and let the fresh air blow in during the run.
>>> 
>>> That's true with a heterodyne. I can see no obvious reason it would not be 
>>> true on DMTD.
>>> 
>>> Bob
>>> 
>>> 
>>> On Feb 6, 2010, at 5:12 PM, Bruce Griffiths wrote:
>>> 
>>>> The only major issue with DMTD systems is that they undersample the phase 
>>>> fluctuations and hence are subject to aliasing effects.
>>>> The low pass filter has to have a bandwidth of the same order as the beat 
>>>> frequency or the beat frequency signal will be significantly attenuated.
>>>> Since the phase is only sampled once per beat frequency period the phase 
>>>> fluctuations are undersampled.
>>>> Various attempts to use both zero crossings have not been successful.
>>>> 
>>>> In principle if one can overcome the increased phase shift tempco 
>>>> associated with a bandpass filter, using a bandpass filter can in 
>>>> principle ensure that the phase fluctuations are oversampled.
>>>> 
>>>> 
>>>> Bruce
>>>> 
>>>> Bob Camp wrote:
>>>>> Hi
>>>>> 
>>>>> A straight heterodyne system will get you to the floor of most 10811's 
>>>>> with a very simple (2 stage) limiter. As with the DMTD, the counter 
>>>>> requirements aren't really all that severe.
>>>>> 
>>>>> Bob
>>>>> 
>>>>> 
>>>>> On Feb 6, 2010, at 4:24 PM, WarrenS wrote:
>>>>> 
>>>>> 
>>>>>> 
>>>>>>> "It's possible / likely for injection lock ... to be a problem ..."
>>>>>>> 
>>>>>> Something I certainly worried about and tested for.
>>>>>> What I found (for MY case) is that injection lock is NOT a problem.
>>>>>> The reason being is that unlike most other ways, where the two OSC have 
>>>>>>

Re: [time-nuts] ADEV vs MDEV

[Bob Camp]

Hi

I believe the statement:

"Both systems are equally limited by the reference oscillator"  

was part of the same paragraph as the comment on 10811 short term stability.

Neither system, no matter how well set up will get below the stability of the 
reference oscillator. 

I have indeed read a lot of threads here. I've also tested a *lot* of 
oscillators. Finding a 10811 that consistently does <=1.0x10-^13 at 1 second is 
*not* an easy task.

Far more to the point - the tight loop requires a voltage controlled reference. 
Weather it's a 10811 or something else, it needs voltage control. The 
heterodyne approach does not. You do  need to get luck with your frequencies if 
the heterodyne reference is not tunable. Something like a 10811 is indeed 
needed in a tight lock system. 

Bob


On Feb 6, 2010, at 6:55 PM, WarrenS wrote:

> 
> 
>> "An ADEV noise floor of 1E-13 isn't likely when using an HP10811A as the 
>> VCXO for example."
> 
> How quickly one forgets and gets lost on these long topics.
>>> "If you accept that the measurement is going to limited by the  Reference 
>>> Osc,
>>> for Low COST and SIMPLE,  Can't beat a simple analog version of  NIST's 
>>> "Tight Phase-Lock Loop" "
> 
> And which method are you saying is NOT limited by the Reference Osc??
> Correct, not going to get to 1e-13 at one sec with a HP10811A,
> nor likely with any other Ref Osc that most Freq nuts have.
> SO Seems like that is GOOD enough noise floor limit to use for a "low cost & 
> simple" configuration.
> 
> BTW
> A well setup "Tight Phase-Lock Loop" method will go below that..
> and a good HP 10811A can go below 1e-12 at 0.1 sec. (at a bandwidth of 30 Hz)
> 
> 
> ws
> 
> ***
> Bruce Griffiths said:
> 
>> The noise of the OCXO used as a VCXO will limit the noise floor.
>> An ADEV noise floor of 1E-13 isnt likely when using an HP10811A as the
>> VCXO for example.
> 
> Bruce
> 
> *  Original Topic *
>>> I would appreciate any comments or observations on this topic.
>>> My motivation is to discover the simplest scheme for making
>>> stability measurements at this performance level; this is NOT
>>> even close to the state-of-the-art, but can still be useful.
>>> 
>>> Pete Rawson
> 
> 
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> 


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Re: [time-nuts] ADEV vs MDEV - using sound card

[Bob Camp]

Hi

My main concern with the low frequency pole in the sound card is the quality of 
the R/C used. You can certainly model what ever you have. If they used an 
aluminum electrolytic for the "C" it may not be the same next time you check it 


On a 10 Hz system, a 1 Hz pole is probably not an issue. It might get in the 
way with a 1 Hz beat note. 

Another thing I have only seen in passing: "Sigma Delta's have poor low 
frequency noise characteristics". I haven't dug into it to see if that's really 
true or not. If you buy your own ADC's, you certainly would not be restricted 
to a Sigma Delta.

Even with a cheap pre-built FPGA board, you could look into higher sample rates 
than a conventional sound card. You would drop back to 16 bits, but it might be 
worth it. 

Bob


On Feb 6, 2010, at 6:46 PM, Bruce Griffiths wrote:

> Even better is to toss out the mixers and sample the RF signals directly.
> However suitable ADCs cost $US100 or more each.
> To which one has to add an FPGA and an interface to a PC with sufficient 
> throughput to handle the down converted I + Q samples.
> 
> Bob Camp wrote:
>> Hi
>> 
>> You probably could put a couple of cheap DAC's
> 
> (ADCs are preferable as it avoids having to implement the conversion logic 
> plus comparator required when using a DAC.)
> 
>> on a board with a FPGA and reduce the data on the fly. I'd guess that would 
>> be be in the same $100 range as a half way decent sound card. Clock the 
>> DAC's off of a 10 MHz reference and eliminate the cal issue.
>> 
>> If you are down around 10 Hz or worse yet 1 Hz, the AC coupling of the sound 
>> card will get in the way, even with a bandpass approach. You really don't 
>> know what they may have in there at the low end. Build it yourself and that 
>> stuff's not an issue.
>> 
>> Bob
>> 
>>   
> My sound card has a 1Hz cutoff  RC high pass input filter plus an internal 
> high pass digital filter.
> Its not too difficult to measure the sound card frequency response using a 
> white noise source for example.
> 
> Bruce
>> On Feb 6, 2010, at 6:12 PM, Bruce Griffiths wrote:
>> 
>>   
>>> If one has a high end sound card then it could be used to implement the 
>>> bandpass filter and replace the zero crossing detector.
>>> It may be necessary to insert a pilot tone to calibrate the sound card 
>>> sampling clock frequency.
>>> A noise floor of about 1E-13/Tau should be achievable.
>>> This simplifies the DMTD system by replacing the zero crossing detector 
>>> with a low gain linear preamp.
>>> 
>>> If one analyses the resultant data off line then one can also try out 
>>> different techniques such as a Costas receiver rather than a simple 
>>> bandpass filter plus zero crossing detector.
>>> However 1000 seconds of data for 2 channels of 24 bit samples at 192KSPS 
>>> will result in a file with a size of at least 1.15GB.
>>> 
>>> Bruce
>>> 
>>> 
>>> Bruce Griffiths wrote:
>>> 
>>>> If one were to use a bandpass filter with a Q of 10 to filter the beat 
>>>> frequency output of the mixer, then if the input frequency is 10MHz and 
>>>> the filter component tempco is 100ppm/C then the resultant phase shift 
>>>> tempco is about 16ps/C referred to the mixer input frequency.
>>>> 
>>>> This phase shift tempco is certainly low enough not to have significant 
>>>> impact when measuring the frequency stability of a typical 10811A  if the 
>>>> temperature fluctuations are kept small enough during the run.
>>>> 
>>>> The effect of using a bandpass filter with too narrow a bandwidth is to 
>>>> artificially reduce ADEV for small Tau, so it may be prudent to use a 
>>>> higher beat frequency that 1Hz or even 10Hz and not calculate ADEV for Tau 
>>>> less than say 10(??) times the beat frequency period. A trade off between 
>>>> this and the effect of aliasing is required.
>>>> 
>>>> Bruce
>>>> 
>>>> Bob Camp wrote:
>>>>   
>>>>> Hi
>>>>> 
>>>>> With most 10811 range oscillators  the impact of a simple bandpass filter 
>>>>> is low enough to not be a major issue. That's for normal lab temperatures 
>>>>> with the circuitry in a conventional die cast  box. No guarantee if you 
>>>>> open the window and let the fresh air blow in during the run.
>>>>> 
>>>>> That's true with a heterodyn

Re: [time-nuts] ADEV vs MDEV - using sound card

[Bob Camp]

Hi

Take the outputs of the ADC's, bandpass filter them, do a straight line fit to 
the 100 or so points nearest each zero crossing. Report the result to the PC 
for each zero crossing. Not much data to the PC. Easy to do it all in a fairly 
small FPGA.

Staying down at low frequencies opens up the range of offset oscillators 
available. The higher you go, the tougher it will be to select a good 
reference. 

Bob


On Feb 6, 2010, at 7:57 PM, Bruce Griffiths wrote:

> Bob Camp wrote:
>> Hi
>> 
>> My main concern with the low frequency pole in the sound card is the quality 
>> of the R/C used. You can certainly model what ever you have. If they used an 
>> aluminum electrolytic for the "C" it may not be the same next time you check 
>> it 
>> 
>>   
> One should at least calibrate the effect before and after each run.
> It would be even better to embed such a calibration within each run.
>> On a 10 Hz system, a 1 Hz pole is probably not an issue. It might get in the 
>> way with a 1 Hz beat note.
>> 
>> Another thing I have only seen in passing: "Sigma Delta's have poor low 
>> frequency noise characteristics". I haven't dug into it to see if that's 
>> really true or not. If you buy your own ADC's, you certainly would not be 
>> restricted to a Sigma Delta.
>> 
>>   
> The input noise spectrum for my sound card does indeed rise significantly at 
> low frequencies.
> A beat note of around 100Hz or 1KHz note would be more suitable than lower 
> frequencies.
> With a Costas receiver the equivalent timing noise isn't strongly dependent 
> on the beat frequency.
>> Even with a cheap pre-built FPGA board, you could look into higher sample 
>> rates than a conventional sound card. You would drop back to 16 bits, but it 
>> might be worth it.
>> 
>> Bob
>> 
>> 
>>   
> 1 bit of a 16 bit accurate ADC corresponds to a timing resolution of around 
> 0.48ps referred to a 10MHz mixer input signal.
> The beat frequency amplitude has to be amplified to just below the ADC full 
> scale input.
> 
> Bruce
>> On Feb 6, 2010, at 6:46 PM, Bruce Griffiths wrote:
>> 
>>   
>>> Even better is to toss out the mixers and sample the RF signals directly.
>>> However suitable ADCs cost $US100 or more each.
>>> To which one has to add an FPGA and an interface to a PC with sufficient 
>>> throughput to handle the down converted I + Q samples.
>>> 
>>> Bob Camp wrote:
>>> 
>>>> Hi
>>>> 
>>>> You probably could put a couple of cheap DAC's
>>>>   
>>> (ADCs are preferable as it avoids having to implement the conversion logic 
>>> plus comparator required when using a DAC.)
>>> 
>>> 
>>>> on a board with a FPGA and reduce the data on the fly. I'd guess that 
>>>> would be be in the same $100 range as a half way decent sound card. Clock 
>>>> the DAC's off of a 10 MHz reference and eliminate the cal issue.
>>>> 
>>>> If you are down around 10 Hz or worse yet 1 Hz, the AC coupling of the 
>>>> sound card will get in the way, even with a bandpass approach. You really 
>>>> don't know what they may have in there at the low end. Build it yourself 
>>>> and that stuff's not an issue.
>>>> 
>>>> Bob
>>>> 
>>>> 
>>>>   
>>> My sound card has a 1Hz cutoff  RC high pass input filter plus an internal 
>>> high pass digital filter.
>>> Its not too difficult to measure the sound card frequency response using a 
>>> white noise source for example.
>>> 
>>> Bruce
>>> 
>>>> On Feb 6, 2010, at 6:12 PM, Bruce Griffiths wrote:
>>>> 
>>>> 
>>>>   
>>>>> If one has a high end sound card then it could be used to implement the 
>>>>> bandpass filter and replace the zero crossing detector.
>>>>> It may be necessary to insert a pilot tone to calibrate the sound card 
>>>>> sampling clock frequency.
>>>>> A noise floor of about 1E-13/Tau should be achievable.
>>>>> This simplifies the DMTD system by replacing the zero crossing detector 
>>>>> with a low gain linear preamp.
>>>>> 
>>>>> If one analyses the resultant data off line then one can also try out 
>>>>> different techniques such as a Costas receiver rather than a simple 
>>>>> bandpass filter plus zero crossing 

Re: [time-nuts] ADEV vs MDEV

[Bob Camp]

Hi

Never ever say never to this group when it's an oscillator with an outlandish 
short term stability ...

If you do, somebody is *bound* to turn up with one. 

Bob


On Feb 6, 2010, at 8:32 PM, WarrenS wrote:

> 
> I've never heard of a 1e-13 at 1sec HP 10811, so it may be MORE than hard to 
> find.
> (again not so hard to fine one at 1e-12 and 0.1 sec)
> Agree, a tight PLL is Not as flexible as a heterodyne or a DMTV, and has 
> other limitations.
> Always those darn tradeoffs when you want simple and low cost.
> 
> One trick I've done using the Tight PLL method,  if the reference does NOT 
> have a EFC or it is already used elsewhere such as a GPSDO.
> That is to put the feedback on the Device under test, assuming it has a 
> unused  EFC input.
> Get same simple block and results, Just need to correct for the Tuning gain 
> of the tested Osc.
> 
> ws
> 
> **
> - Original Message - From: "Bob Camp" 
> To: "Discussion of precise time and frequency measurement" 
> 
> Sent: Saturday, February 06, 2010 4:26 PM
> Subject: Re: [time-nuts] ADEV vs MDEV
> 
> 
> Hi
> 
> I believe the statement:
> 
> "Both systems are equally limited by the reference oscillator"
> 
> was part of the same paragraph as the comment on 10811 short term stability.
> 
> Neither system, no matter how well set up will get below the stability of the 
> reference oscillator.
> 
> I have indeed read a lot of threads here. I've also tested a *lot* of 
> oscillators. Finding a 10811 that consistently does <=1.0x10-^13 at 1 second 
> is *not* an easy task.
> 
> Far more to the point - the tight loop requires a voltage controlled 
> reference. Weather it's a 10811 or something else, it needs voltage control. 
> The heterodyne approach does not. You do  need to get luck with your 
> frequencies if the heterodyne reference is not tunable. Something like a 
> 10811 is indeed needed in a tight lock system.
> 
> Bob
> 
> 
> On Feb 6, 2010, at 6:55 PM, WarrenS wrote:
> 
>> 
>> 
>>> "An ADEV noise floor of 1E-13 isn't likely when using an HP10811A as the 
>>> VCXO for example."
>> 
>> How quickly one forgets and gets lost on these long topics.
>>>> "If you accept that the measurement is going to limited by the Reference 
>>>> Osc,
>>>> for Low COST and SIMPLE,  Can't beat a simple analog version of  NIST's 
>>>> "Tight Phase-Lock Loop" "
>> 
>> And which method are you saying is NOT limited by the Reference Osc??
>> Correct, not going to get to 1e-13 at one sec with a HP10811A,
>> nor likely with any other Ref Osc that most Freq nuts have.
>> SO Seems like that is GOOD enough noise floor limit to use for a "low cost & 
>> simple" configuration.
>> 
>> BTW
>> A well setup "Tight Phase-Lock Loop" method will go below that..
>> and a good HP 10811A can go below 1e-12 at 0.1 sec. (at a bandwidth of 30 Hz)
>> 
>> 
>> ws
>> 
>> ***
>> Bruce Griffiths said:
>> 
>>> The noise of the OCXO used as a VCXO will limit the noise floor.
>>> An ADEV noise floor of 1E-13 isnt likely when using an HP10811A as the
>>> VCXO for example.
>> 
>> Bruce
>> 
>> *  Original Topic *
>>>> I would appreciate any comments or observations on this topic.
>>>> My motivation is to discover the simplest scheme for making
>>>> stability measurements at this performance level; this is NOT
>>>> even close to the state-of-the-art, but can still be useful.
>>>> 
>>>> Pete Rawson
>> 
>> 
>> ___
>> time-nuts mailing list -- time-nuts@febo.com
>> To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts
>> and follow the instructions there.
>> 
> 
> 
> 
> 
> 
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Re: [time-nuts] ADEV vs MDEV - using sound card

[Bob Camp]

Hi

Any approach that includes building a low noise synthesizer is opening up a 
whole new set of issues. I would much prefer to do my building at audio. Audio 
parts are cheap, and performance is usually a lot easier to check than at RF.

Bob


On Feb 6, 2010, at 8:30 PM, Bruce Griffiths wrote:

> Which just leaves the minor problem of the offset oscillator.
> 
> One option is to use a phase truncation spur free output frequency from a DDS.
> If one is using the Costas receiver approach the beat frequency need not be a 
> nice round number like 1.KHz.
> 
> Another method is to use a crystal whose frequency is offset a few kHz from 
> 10MHz.
> 
> Yet another is the classical method of dividing 10MHz by 100 and subtracting 
> (using an LSB mixer) the resultant 100KHz from 10MHz to produce 9.9MHz, then 
> divide the 9.9MHz signal by 100 and add (using a USB mixer) the resultant 
> 99kHz signal to the 9.99Mhz signal to produce a 9.999MHz output.
> 
> Bruce
> 
> John Miles wrote:
>> A sound-card back end has always seemed like a pretty reasonable approach to
>> me, if you're inclined to go the DMTD route.  I wouldn't send a 'baseband'
>> signal to the sound card, though -- I'd upconvert it to a few kHz to get
>> away from the numerous bad things that sound cards do near DC.
>> 
>> -- john, KE5FX
>> 
>> 
>>   
>>> Hi
>>> 
>>> My main concern with the low frequency pole in the sound card is
>>> the quality of the R/C used. You can certainly model what ever
>>> you have. If they used an aluminum electrolytic for the "C" it
>>> may not be the same next time you check it 
>>> 
>>> On a 10 Hz system, a 1 Hz pole is probably not an issue. It might
>>> get in the way with a 1 Hz beat note.
>>> 
>>> Another thing I have only seen in passing: "Sigma Delta's have
>>> poor low frequency noise characteristics". I haven't dug into it
>>> to see if that's really true or not. If you buy your own ADC's,
>>> you certainly would not be restricted to a Sigma Delta.
>>> 
>>> Even with a cheap pre-built FPGA board, you could look into
>>> higher sample rates than a conventional sound card. You would
>>> drop back to 16 bits, but it might be worth it.
>>> 
>>> Bob
>>> 
>>> 
>>> On Feb 6, 2010, at 6:46 PM, Bruce Griffiths wrote:
>>> 
>>> 
>>>> Even better is to toss out the mixers and sample the RF signals
>>>>   
>>> directly.
>>> 
>>>> However suitable ADCs cost $US100 or more each.
>>>> To which one has to add an FPGA and an interface to a PC with
>>>>   
>>> sufficient throughput to handle the down converted I + Q samples.
>>> 
>>>> Bob Camp wrote:
>>>>   
>>>>> Hi
>>>>> 
>>>>> You probably could put a couple of cheap DAC's
>>>>> 
>>>> (ADCs are preferable as it avoids having to implement the
>>>>   
>>> conversion logic plus comparator required when using a DAC.)
>>> 
>>>>   
>>>>> on a board with a FPGA and reduce the data on the fly. I'd
>>>>> 
>>> guess that would be be in the same $100 range as a half way
>>> decent sound card. Clock the DAC's off of a 10 MHz reference and
>>> eliminate the cal issue.
>>> 
>>>>> If you are down around 10 Hz or worse yet 1 Hz, the AC
>>>>> 
>>> coupling of the sound card will get in the way, even with a
>>> bandpass approach. You really don't know what they may have in
>>> there at the low end. Build it yourself and that stuff's not an issue.
>>> 
>>>>> Bob
>>>>> 
>>>>> 
>>>>> 
>>>> My sound card has a 1Hz cutoff  RC high pass input filter plus
>>>>   
>>> an internal high pass digital filter.
>>> 
>>>> Its not too difficult to measure the sound card frequency
>>>>   
>>> response using a white noise source for example.
>>> 
>>>> Bruce
>>>>   
>>>>> On Feb 6, 2010, at 6:12 PM, Bruce Griffiths wrote:
>>>>> 
>>>>> 
>>>>> 
>>>>>> If one has a high end sound card then it could be used to
>>>>>>   
>>> implement the bandpass filter and

Re: [time-nuts] ADEV vs MDEV - using sound card

[Bob Camp]

Hi

Occasionally you also come across 5.55 MHz OCXO's that have 5 MHz crystals 
in them. Then you discover just how much short term stability can degrade when 
they move the crystal 55 Hz. Same vendor crystal, same crystal spec., same 
oscillator circuit, not even close on short term stability

Bob


On Feb 6, 2010, at 9:02 PM, Bruce Griffiths wrote:

> JPL resorted to using  a commercial synthesiser set for an offset of 123Hz 
> (to minimise spurs and other artifacts) in their 100MHz N channel mixer 
> system.
> 
> Occasionally one comes across 5.55MHz OCXOs that use 10.000110MHz 
> crystals internally.
> The resultant 55Hz (with 5MHz source) or 110Hz (with 10MHz source) beat 
> frequencies are lie between the hamonincs of either 50Hz or 60Hz line 
> frequencies.
> 
> Bruce
> 
> Bob Camp wrote:
>> Hi
>> 
>> Any approach that includes building a low noise synthesizer is opening up a 
>> whole new set of issues. I would much prefer to do my building at audio. 
>> Audio parts are cheap, and performance is usually a lot easier to check than 
>> at RF.
>> 
>> Bob
>> 
>> 
>> On Feb 6, 2010, at 8:30 PM, Bruce Griffiths wrote:
>> 
>>   
>>> Which just leaves the minor problem of the offset oscillator.
>>> 
>>> One option is to use a phase truncation spur free output frequency from a 
>>> DDS.
>>> If one is using the Costas receiver approach the beat frequency need not be 
>>> a nice round number like 1.KHz.
>>> 
>>> Another method is to use a crystal whose frequency is offset a few kHz from 
>>> 10MHz.
>>> 
>>> Yet another is the classical method of dividing 10MHz by 100 and 
>>> subtracting (using an LSB mixer) the resultant 100KHz from 10MHz to produce 
>>> 9.9MHz, then divide the 9.9MHz signal by 100 and add (using a USB mixer) 
>>> the resultant 99kHz signal to the 9.99Mhz signal to produce a 9.999MHz 
>>> output.
>>> 
>>> Bruce
>>> 
>>> John Miles wrote:
>>> 
>>>> A sound-card back end has always seemed like a pretty reasonable approach 
>>>> to
>>>> me, if you're inclined to go the DMTD route.  I wouldn't send a 'baseband'
>>>> signal to the sound card, though -- I'd upconvert it to a few kHz to get
>>>> away from the numerous bad things that sound cards do near DC.
>>>> 
>>>> -- john, KE5FX
>>>> 
>>>> 
>>>> 
>>>>   
>>>>> Hi
>>>>> 
>>>>> My main concern with the low frequency pole in the sound card is
>>>>> the quality of the R/C used. You can certainly model what ever
>>>>> you have. If they used an aluminum electrolytic for the "C" it
>>>>> may not be the same next time you check it 
>>>>> 
>>>>> On a 10 Hz system, a 1 Hz pole is probably not an issue. It might
>>>>> get in the way with a 1 Hz beat note.
>>>>> 
>>>>> Another thing I have only seen in passing: "Sigma Delta's have
>>>>> poor low frequency noise characteristics". I haven't dug into it
>>>>> to see if that's really true or not. If you buy your own ADC's,
>>>>> you certainly would not be restricted to a Sigma Delta.
>>>>> 
>>>>> Even with a cheap pre-built FPGA board, you could look into
>>>>> higher sample rates than a conventional sound card. You would
>>>>> drop back to 16 bits, but it might be worth it.
>>>>> 
>>>>> Bob
>>>>> 
> 
> 
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Re: [time-nuts] ADEV vs MDEV - using sound card

[Bob Camp]

Hi

The 5 MHz stuff was down at or below 1.5x10^-12 at one second by our measure. 
Others measured them a bit lower than that. We didn't do 100% testing at 10 
sec, so I don't have a lot of data there. The ones 55 Hz higher often came at 
or above 4x10^-12.

Bob


On Feb 6, 2010, at 9:40 PM, Bruce Griffiths wrote:

> As a matter of interest just how bad were those OCXOs?
> 
> e.g. what was the ballpark ADEV for 1s, 10s etc.?
> 
> Bruce
> 
> Bob Camp wrote:
>> Hi
>> 
>> Occasionally you also come across 5.55 MHz OCXO's that have 5 MHz 
>> crystals in them. Then you discover just how much short term stability can 
>> degrade when they move the crystal 55 Hz. Same vendor crystal, same crystal 
>> spec., same oscillator circuit, not even close on short term stability
>> 
>> Bob
>> 
>> 
>> On Feb 6, 2010, at 9:02 PM, Bruce Griffiths wrote:
>> 
>>   
>>> JPL resorted to using  a commercial synthesiser set for an offset of 123Hz 
>>> (to minimise spurs and other artifacts) in their 100MHz N channel mixer 
>>> system.
>>> 
>>> Occasionally one comes across 5.55MHz OCXOs that use 10.000110MHz 
>>> crystals internally.
>>> The resultant 55Hz (with 5MHz source) or 110Hz (with 10MHz source) beat 
>>> frequencies are lie between the hamonincs of either 50Hz or 60Hz line 
>>> frequencies.
>>> 
>>> Bruce
>>> 
>>> Bob Camp wrote:
>>> 
>>>> Hi
>>>> 
>>>> Any approach that includes building a low noise synthesizer is opening up 
>>>> a whole new set of issues. I would much prefer to do my building at audio. 
>>>> Audio parts are cheap, and performance is usually a lot easier to check 
>>>> than at RF.
>>>> 
>>>> Bob
>>>> 
>>>> 
>>>> On Feb 6, 2010, at 8:30 PM, Bruce Griffiths wrote:
>>>> 
>>>> 
>>>>   
>>>>> Which just leaves the minor problem of the offset oscillator.
>>>>> 
>>>>> One option is to use a phase truncation spur free output frequency from a 
>>>>> DDS.
>>>>> If one is using the Costas receiver approach the beat frequency need not 
>>>>> be a nice round number like 1.KHz.
>>>>> 
>>>>> Another method is to use a crystal whose frequency is offset a few kHz 
>>>>> from 10MHz.
>>>>> 
>>>>> Yet another is the classical method of dividing 10MHz by 100 and 
>>>>> subtracting (using an LSB mixer) the resultant 100KHz from 10MHz to 
>>>>> produce 9.9MHz, then divide the 9.9MHz signal by 100 and add (using a USB 
>>>>> mixer) the resultant 99kHz signal to the 9.99Mhz signal to produce a 
>>>>> 9.999MHz output.
>>>>> 
>>>>> Bruce
>>>>> 
>>>>> John Miles wrote:
>>>>> 
>>>>> 
>>>>>> A sound-card back end has always seemed like a pretty reasonable 
>>>>>> approach to
>>>>>> me, if you're inclined to go the DMTD route.  I wouldn't send a 
>>>>>> 'baseband'
>>>>>> signal to the sound card, though -- I'd upconvert it to a few kHz to get
>>>>>> away from the numerous bad things that sound cards do near DC.
>>>>>> 
>>>>>> -- john, KE5FX
>>>>>> 
>>>>>> 
>>>>>> 
>>>>>> 
>>>>>>   
>>>>>>> Hi
>>>>>>> 
>>>>>>> My main concern with the low frequency pole in the sound card is
>>>>>>> the quality of the R/C used. You can certainly model what ever
>>>>>>> you have. If they used an aluminum electrolytic for the "C" it
>>>>>>> may not be the same next time you check it 
>>>>>>> 
>>>>>>> On a 10 Hz system, a 1 Hz pole is probably not an issue. It might
>>>>>>> get in the way with a 1 Hz beat note.
>>>>>>> 
>>>>>>> Another thing I have only seen in passing: "Sigma Delta's have
>>>>>>> poor low frequency noise characteristics". I haven't dug into it
>>>>>>> to see if that's really true or not. If you buy your own ADC's,
>>>>>>> you certainly would not be restricted to a Sigma Delta.
>>>>>>> 
>>>>>>> Even with a cheap pre-built FPGA board, you could look into
>>>>>>> higher sample rates than a conventional sound card. You would
>>>>>>> drop back to 16 bits, but it might be worth it.
>>>>>>> 
>>>>>>> Bob
>>>>>>> 
>>>>>>> 
>>> 
>>> 
> 
> 
> 
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Re: [time-nuts] ADEV vs MDEV - using sound card

[Bob Camp]

Hi

If it's a DMTD the offset oscillator is less of an issue than either of the 
oscillators being tested.

If it's a heterodyne beat note system, then there are only two oscillators. 
They both contribute equally.

A DMTD with the reference synthesized off of one of the "DUT" inputs looks a 
lot like a heterodyne if you do everything right. 

The constraints on the LO used to drive the sound card or counter are somewhat 
relaxed since they are on the other side of the down conversion. That's true 
weather you are talking about the heterodyne or DMTD.

Bob


On Feb 6, 2010, at 10:28 PM, John Miles wrote:

> Any noise or drift in the "2nd LO", so to speak, would be common-mode
> between the two channels.  It shouldn't be all that critical.
> 
> -- john, KE5FX
> 
>> -Original Message-
>> From: time-nuts-boun...@febo.com [mailto:time-nuts-boun...@febo.com]on
>> Behalf Of Bob Camp
>> Sent: Saturday, February 06, 2010 5:52 PM
>> To: Discussion of precise time and frequency measurement
>> Subject: Re: [time-nuts] ADEV vs MDEV - using sound card
>> 
>> 
>> Hi
>> 
>> Any approach that includes building a low noise synthesizer is
>> opening up a whole new set of issues. I would much prefer to do
>> my building at audio. Audio parts are cheap, and performance is
>> usually a lot easier to check than at RF.
>> 
>> Bob
>> 
>> 
>> On Feb 6, 2010, at 8:30 PM, Bruce Griffiths wrote:
>> 
>>> Which just leaves the minor problem of the offset oscillator.
>>> 
>>> One option is to use a phase truncation spur free output
>> frequency from a DDS.
>>> If one is using the Costas receiver approach the beat frequency
>> need not be a nice round number like 1.KHz.
>>> 
>>> Another method is to use a crystal whose frequency is offset a
>> few kHz from 10MHz.
>>> 
>>> Yet another is the classical method of dividing 10MHz by 100
>> and subtracting (using an LSB mixer) the resultant 100KHz from
>> 10MHz to produce 9.9MHz, then divide the 9.9MHz signal by 100 and
>> add (using a USB mixer) the resultant 99kHz signal to the 9.99Mhz
>> signal to produce a 9.999MHz output.
>>> 
>>> Bruce
>>> 
>>> John Miles wrote:
>>>> A sound-card back end has always seemed like a pretty
>> reasonable approach to
>>>> me, if you're inclined to go the DMTD route.  I wouldn't send
>> a 'baseband'
>>>> signal to the sound card, though -- I'd upconvert it to a few
>> kHz to get
>>>> away from the numerous bad things that sound cards do near DC.
>>>> 
>>>> -- john, KE5FX
>>>> 
>>>> 
>>>> 
>>>>> Hi
>>>>> 
>>>>> My main concern with the low frequency pole in the sound card is
>>>>> the quality of the R/C used. You can certainly model what ever
>>>>> you have. If they used an aluminum electrolytic for the "C" it
>>>>> may not be the same next time you check it 
>>>>> 
>>>>> On a 10 Hz system, a 1 Hz pole is probably not an issue. It might
>>>>> get in the way with a 1 Hz beat note.
>>>>> 
>>>>> Another thing I have only seen in passing: "Sigma Delta's have
>>>>> poor low frequency noise characteristics". I haven't dug into it
>>>>> to see if that's really true or not. If you buy your own ADC's,
>>>>> you certainly would not be restricted to a Sigma Delta.
>>>>> 
>>>>> Even with a cheap pre-built FPGA board, you could look into
>>>>> higher sample rates than a conventional sound card. You would
>>>>> drop back to 16 bits, but it might be worth it.
>>>>> 
>>>>> Bob
>>>>> 
>>>>> 
>>>>> On Feb 6, 2010, at 6:46 PM, Bruce Griffiths wrote:
>>>>> 
>>>>> 
>>>>>> Even better is to toss out the mixers and sample the RF signals
>>>>>> 
>>>>> directly.
>>>>> 
>>>>>> However suitable ADCs cost $US100 or more each.
>>>>>> To which one has to add an FPGA and an interface to a PC with
>>>>>> 
>>>>> sufficient throughput to handle the down converted I + Q samples.
>>>>> 
>>>>>> Bob Camp wrote:
>>>>>> 
>>>>>>> Hi
>>>>>>> 
>>>>>>

Re: [time-nuts] ADEV vs MDEV - DMTD sound card

[Bob Camp]

Hi

That was actually talking about a heterodyne system.

Indeed a good digitizer could be used with a DMTD. One thing I have not looked 
into is the DC accuracy required if you go that way. Some of these approaches 
have odd little gotcha's. By analogy with a heterodyne setup it might not. 
That's not always the best way to analyze things 

Bob

On Feb 7, 2010, at 3:50 AM, Magnus Danielson wrote:

> Bob Camp wrote:
>> Hi
>> I believe the statement:
>> "Both systems are equally limited by the reference oscillator"  was part of 
>> the same paragraph as the comment on 10811 short term stability.
>> Neither system, no matter how well set up will get below the stability of 
>> the reference oscillator.
> 
> For DMTD systems the transfer oscillator noise can be partially cancelled. 
> You do have two inputs, but you then play three-cornered hat tricks. However, 
> for a DMTD system to be able to cancel noise, good time-correlation between 
> channels is needed to make the noise-integration time-periods of both 
> channels to match up. The more they are apart, the bigger difference in noise 
> it is between the channels and thus it will fail to cancel. Thus, 
> phase-alignment prior to ZCDs could be a treatment. Using the audio channel 
> approach avoids the issue as the full-wave signal is being used and time 
> correlation between samples is high, an approach not available when DMTD was 
> developed.
> 
> Cheers,
> Magnus - while visiting fellow time-nut
> 
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Re: [time-nuts] Frequency comparison

[Bob Camp]

Hi

Which HP counter(s) do you have?

The method you are using now with a scope can give you good accuracy if your 
clocks are close to each other and you watch things for a long enough time.

Bob


On Feb 7, 2010, at 10:04 AM, Raj wrote:

> Hi! all Time-Nuts,
> 
>For a newbie like myself at GPSDO & Rb oscillators etc. what method of 
> frequency comparison would you gurus recommend ? Any articles on this subject 
> ? 
> 
>Available test instruments are: Scopes digital & Analog, counters with 
> 0.01 Hz display at 10 Mhz (HP & Racall-Dana).
> 
>Currently I am comparing the phase between two 10 Mhz and adjusting 
> for the lowest drift visually on the scope and phase drift on the Racall-Dana 
> 1992.
> 
>Your suggestions I would like to use for calibrating the Rb oscillator 
> with a GPSDO.
> 
> Regards
> 
> -- 
> Raj, VU2ZAP
> Bangalore, India. 
> 
> 
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Re: [time-nuts] Frequency comparison

[Bob Camp]

Hi

The rubidium *should* be good at the 1x10^-11 level. The GPSDO can be better 
than that. The issue is that neither one is very good in the short term. 
Measurement periods of hours are not unusual to get things right. If GPS 
with your antenna location is good at the 10 ns level, that's 1x10^-8 per 
second. 10,000 seconds will get you to 1x10^-12. That's good enough to 
calibrate the rubidium. The calibration standard should always be much 
better than the thing you are calibrating.


No matter what you do, it's a "watching grass grow" sort of thing. Some sort 
of automation is a good idea.


One approach (of *many*):

Your GPSDO probably has a 1 pps coming out of it.
Your Racal can measure time between two 1 pps pulses (if I remember that 
model correctly)

Divide the rubidium down to 1 pps and look at it relative to the Racal.
Log data out of the Racal so you can go back and see what's happened.

That's not going to work very well if the Racal does not have some kind of 
serial or GPIB output.


There are a lot of other approaches.  Cost can become a factor.  For some 
the budget for this sort of thing is quite large. For others low cost / 
build it yourself is what makes sense. Are you looking at setting up a lab, 
or just want to get the Rubidium on frequency?


Bob


--
From: "Raj" 
Sent: Sunday, February 07, 2010 10:25 AM
To: "Discussion of precise time and frequency measurement" 


Subject: Re: [time-nuts] Frequency comparison


Hi Bob,

   I have a HP5350B with the oven (probably standard) continuously 
powered. The Racall-Dana is with a OCXO that I have added. The Racall has 
a phase comparison between A-B inputs.


   I am just comparing 10 MHz frequencies. I see one cycle drift in 
greater than 100 seconds to 10 minutes, painful to watch and adjust!


Raj

At 07-02-10, you wrote:

Hi

Which HP counter(s) do you have?

The method you are using now with a scope can give you good accuracy if 
your clocks are close to each other and you watch things for a long enough 
time.


Bob


On Feb 7, 2010, at 10:04 AM, Raj wrote:


Hi! all Time-Nuts,

   For a newbie like myself at GPSDO & Rb oscillators etc. what 
method of frequency comparison would you gurus recommend ? Any articles 
on this subject ?


   Available test instruments are: Scopes digital & Analog, counters 
with 0.01 Hz display at 10 Mhz (HP & Racall-Dana).


   Currently I am comparing the phase between two 10 Mhz and 
adjusting for the lowest drift visually on the scope and phase drift on 
the Racall-Dana 1992.


   Your suggestions I would like to use for calibrating the Rb 
oscillator with a GPSDO.


Regards

--
Raj, VU2ZAP
Bangalore, India.


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--
Raj, VU2ZAP
Bangalore, India.


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Re: [time-nuts] No 1 PPS output on a Tbolt

[Bob Camp]

Hi

The 5345 should see it if it's set to 50 ohm termination and DC coupling. A 
sweep of the trigger from about 1.5 to 3.5 volts should show it there over 
most of the sweep.


Bob

--
From: "SAL CORNACCHIA" 
Sent: Sunday, February 07, 2010 11:06 AM
To: "Discussion of precise time and frequency measurement" 


Subject: Re: [time-nuts] No 1 PPS output on a Tbolt


Oscilloscope and 5345A Counter, the Tbolt software shows all green.
 Best regards,
Sal C. Cornacchia
Electronic RF Microwave Engineer (Ret.)








From: "Stan, W1LE" 
To: Discussion of precise time and frequency measurement 


Sent: Sun, February 7, 2010 10:47:42 AM
Subject: Re: [time-nuts] No 1 PPS output on a Tbolt

Hello Sal,

What are you monitoring the PPS output with ??

It is a short duration pulse.

What does the TboltMON software (available at the trimble website) show ?

What does Lady Heather indicate ?
(She is just waiting to massage your numbers.)

Stan, W1LE




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Re: [time-nuts] No 1 PPS output on a Tbolt

[Bob Camp]

HI

A lot depends on just how tired the tube in your scope is. Some of these scopes 
have spent a lot of hours turned on and wearing out the filament 

The easy thing to do is to vary the trigger point and watch the "trigger" 
light. It should tell you if the pulse is there or not. If it's not, then 
either it's turned off or there's something keeping the electrons from getting 
to you (like a blown chip). 

Bob


On Feb 7, 2010, at 8:56 PM, Bruce Griffiths wrote:

> John Ackermann N8UR wrote:
>> Sal, what sweep time are you using on the scope?  I believe the TBolt PPS is 
>> only microseconds wide, so you may need to speed up the sweep time to around 
>> 100us/div or faster to see it accurately.  And you may need to mess with 
>> delaying the sweep to get the pulse on the screen.
>> 
>> John
>> 
>> 
> You would need to delay the sweep by 0.99s to get the leading edge on 
> screen if the internal scope vertical delay line is insufficient.
> 
> With a sweep speed of 2us/div the entire pulse is clearly visible (even 
> without a viewing hood and light from a window (overcast sky) falling 
> directly on the screen) without any delayed sweep.
> NB trigger on the leading edge which has a positive slope.
> 
> Bruce
> 
> 
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Re: [time-nuts] Frequency comparison

[Bob Camp]

Hi

If you mix the RB and GPS down with a mixer you eventually will run into a
problem. 

As you set them both very close to frequency, the output is a noisy DC
signal rather than a sine wave. Since each source can drift either up or
down for a short period of time, it can be hard to tell what's going on with
a zero crossing detector. It is much better to capture the output voltage
with a strip chart or the digital equivalent. 

Bob 

-Original Message-
From: time-nuts-boun...@febo.com [mailto:time-nuts-boun...@febo.com] On
Behalf Of Raj
Sent: Monday, February 08, 2010 10:34 AM
To: dan...@verizon.net; Discussion of precise time and frequency measurement
Subject: Re: [time-nuts] Frequency comparison

Hi Dan,

Low tech. Yes! IMHO I think its easier for my mind to track an
analog indication of Delta-V. I am more analog oriented.. my son OTOH may be
able to read a last digit flickering digital display better than me!.

I am other wise thinking of a DIY gizmo: 

Mix two signals in an SBL1 or Eq. 
Take the phase/DC IF difference out
Make a zero crossing detector or similar
Timimg the event. Wait for the event in other words!
Twiddle the preset again and see what happens.

The human mind does a lot more processing than the above with an
analog display..

Cheers
Raj, vu2zap

>Raj wrote:
>>
>>I was thinking of feeding two 10 Mhz signals to two ports of a SBL-1 or
similar and taking the DC
>>output at the IF port into an opamp or analog meter. This was visually
easier to adjust the drift between two frequencies by just watching the
needle move. A stationary needle over a couple of hours would be the best!
>>
>>  
>Raj, I did exactly this but with an old chart recorder attached to the
mixer IF port.  This allows one to leave the room and not have to watch for
hours or days.   I was able to adjust my -hp- rubidium unit this way against
gps to better than one cycle per day.
>
>Low tech but effective.
>
>Dan
>
>
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-- 
Raj, VU2ZAP
Bangalore, India. 


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Re: [time-nuts] No 1 PPS output on a Tbolt

[Bob Camp]

Hi

I keep an old fashion "logic probe" lying around for this sort of thing. If
the light flashes, I have a signal. Much easier than a scope.

Bob

-Original Message-
From: time-nuts-boun...@febo.com [mailto:time-nuts-boun...@febo.com] On
Behalf Of Joseph M Gwinn
Sent: Monday, February 08, 2010 12:21 PM
To: Discussion of precise time and frequency measurement
Subject: Re: [time-nuts] No 1 PPS output on a Tbolt

The 1PPS signal is actually quite strong.  I would hook a telephone 
receiver or perhaps a little speaker to the 1PPS output and listen.  The 
signal should make an audible click once per second.

Joe Gwinn


time-nuts-boun...@febo.com wrote on 02/08/2010 12:01:46 PM:

> From:
> 
> Mark Sims 
> 
> To:
> 
> 
> 
> Date:
> 
> 02/08/2010 12:11 PM
> 
> Subject:
> 
> [time-nuts] No 1 PPS output on a Tbolt
> 
> Sent by:
> 
> time-nuts-boun...@febo.com
> 
> 
> Make sure that the 1 PPS  output is enabled...  It can be 
> turned off by software and that mode can be set in EEPROM.
> 
> Also,  many scopes have great difficulty showing a 10 uS pulse 
> at a 1 PPS rep rate.  Digital scopes might not sample it in 
> normal display modes (envelope or glitch capture mode can 
> help).  It can easily get lost on an analog display... 
> _
> Your E-mail and More On-the-Go. Get Windows Live Hotmail Free.
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Re: [time-nuts] True to there word.

[Bob Camp]

Hi

WWVB is pretty safe. When they do a cost/benefit thing on these services,
they take a look at how many taxpayers are using the service as intended.
The "mission" of WWWVB is to put out time signals. There are a *lot* of
taxpayers with WWVB "atomic clocks" on their walls. 

Bob

-Original Message-
From: time-nuts-boun...@febo.com [mailto:time-nuts-boun...@febo.com] On
Behalf Of Don Henderickx
Sent: Monday, February 08, 2010 4:07 PM
To: Discussion of precise time and frequency measurement
Subject: [time-nuts] True to there word.

The lights went out (actually red) on my Austron 2100 r this morning. 
(whats  next WWVB ?)
Don H

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Re: [time-nuts] Frequency comparison

[Bob Camp]

Hi

With the 1 pps approach, you can spot jumps or shifts of >1,000,000 cycles
worth of 10MHz without major trouble. With a mixer approach spotting a slip
of jump of one cycle can be difficult. 

The difference sounds pretty minor. If you are looking for odd things
happening over a period of many days, it's pretty significant. 

At 1x10^-11 frequency offset:

The mixer goes through one cycle of 10 MHz in ~ 3 hours. 
The counters go through one cycle of 1 pps in ~ 3,000 years. 

If the Rb is at 1x10^-9 the numbers are 100X quicker. 

Since the GPSDO takes > 1 1/2 hours to give an adequately accurate reading
to calibrate 1x10^-11, there's no rushing the process. That's not warm up
time, or lock time on the GPSDO. It's the time you need to watch if for in
order to know it's output frequency to a sufficient level of precision. 

Bob



-Original Message-
From: time-nuts-boun...@febo.com [mailto:time-nuts-boun...@febo.com] On
Behalf Of Joop
Sent: Monday, February 08, 2010 4:27 PM
To: Joop
Cc: time-nuts@febo.com
Subject: [time-nuts] Frequency comparison

At 07-02-10, John Ackermann wrote:
>Hi Raj --
>
>You've already gotten some good answers.  If all you want to do is 
>measure the frequency offset rather than characterize the stability, a 
>simple approach is to first get as close as you can by adjust for 
>minimum march of the 10 MHz signals across the oscilloscope, then use 
>either the Racal counter or the digital o'scope to measure the delay 
>between the two signals and how it changes over time, preferably 
>measuring at 1 PPS rather than 10 MHz.
>
>In other words, measure the time difference between the leading edge of 
>the PPS signals, averaging for a while (depending on how close the two 
>already are) to improve resolution and reduce the noise.  Write down the 
>delay figure, note the wall clock time, wait a while, then come back and 
>measure the delay again.  The change in delay over the elapsed time will 
>tell you the frequency offset, e.g., if you see 1 microsecond per day, 
>that's 1.16x10e-11.
>
>Adjust and repeat.  As others have mentioned, being a time-nut requires 
>patience. :-)
>
>It's best to do this at a lower frequency than 10 MHz, and ideally at 1 
>PPS, as there's only 100 nanoseconds between cycle slips at 10 MHz, and 
>that limits how long you'll be able to measure before you've drifted a 
>complete cycle.
>
>73,
>John
>
Ok, the past few days I have been working on exactly the same thing. That
is, adjust an LPRO to my homemade GPSDO.
Good to know I followed a proven procedure. Initially I wanted to build
two PPSDIV/TADD circuits but did not have the right PICs. Instead I used
two PIC12F devices and put them on the same veroboard. The software for
only a single 1Hz output was not too complex.

There was also a Racal 1992 I could use to measure and log the phase
shift. If that would not have been the case I probably would have tried a
XOR port to both (synched) outputs and use an R + C to measure the DC
voltage. That would make a nice little gadget for people not having a
high-res counter. Also the TADD 74AC04 drivers would not be needed this
way.

Anyway, I finally dared to adjust the LPRO.
Can somebody tell if the following seems normal?
* The LPRO measured 1.77 E-10 high (before any adjustment)
* Lamp voltage is about 5.7V
* The GPSDO 1Hz pulse seems to move (noise like) + or - 15ns around its
linear regression line
* The LPRO takes more than 8 hours (perhaps even 24) to reach the 1E-11
level?
The last point is guessing since my GPS signal is super stable. I thought
I managed to adjust it to that level after the LPRO had been powered on for
more than 24 hours. But powering it on two days later shows a higher drift
after 5 hours than where left before.

Also I would like to know if I have to repeat this procedure once it is
built into its final enclosure. Right now it is open on the bench and
clamped to a heatsink. Temperature might be different inside a box.

Cheers,
Joop



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Re: [time-nuts] True to there word. - Fancy WWVB

[Bob Camp]

Hi

People rarely want to use WWVB mobile. The location of the transmitter and 
receiver can be looked up on a map. The time of sunrise at both locations 
should be something that could be calculated. 

Assuming you are willing to put up with all of that, you should be able to do a 
first order correction on the shifts. The question obviously is - just how good 
would the net result be? Is it a 5:1 sort of thing or do you get a couple of 
orders of magnitude?

Bob

On Feb 8, 2010, at 6:40 PM, J. Forster wrote:

> Yes, but WWVB is a PITA to use (because of the diurnal shifts) compared to
> LORAN.
> 
> -John
> 
> ===
> 
> 
>> Hi
>> 
>> WWVB is pretty safe. When they do a cost/benefit thing on these services,
>> they take a look at how many taxpayers are using the service as intended.
>> The "mission" of WWWVB is to put out time signals. There are a *lot* of
>> taxpayers with WWVB "atomic clocks" on their walls.
>> 
>> Bob
>> 
>> -Original Message-
>> From: time-nuts-boun...@febo.com [mailto:time-nuts-boun...@febo.com] On
>> Behalf Of Don Henderickx
>> Sent: Monday, February 08, 2010 4:07 PM
>> To: Discussion of precise time and frequency measurement
>> Subject: [time-nuts] True to there word.
>> 
>> The lights went out (actually red) on my Austron 2100 r this morning.
>> (whats  next WWVB ?)
>> Don H
>> 
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>> 
>> 
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> 
> 
> 
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Re: [time-nuts] Frequency comparison - LPRO

[Bob Camp]

Hi

There's a multi turn pot and reference built into the LPRO. It's already 
driving the C field tuning. I assume you are leaving it in there. You should be 
able to get the unit to  less than 5x10^-11 without a lot of crazy effort. 

With any luck, the LPRO TC plus a few months drift should be sub 1x10^-10. Net, 
you need 2x10^-10 or so of tuning range with a ~ monthly touch up. 

The normal tuning sensitivity is obviously much to large (10X) for this. The 
answer is actually fairly simple. Just put a nice big resistor in series with 
the electronic tune pin. No extra pots, references or other sources of added 
error. Just make sure the resistor has fairly good TC and you should be ok. 

Bob


On Feb 8, 2010, at 6:29 PM, Neville Michie wrote:

> 
> Hi,
> I am setting up an LPRO in a steel box (for a little additional magnetic 
> shielding).
> The power supply is a linear in a separate box (separate the magnetic fields).
> In the LPRO box is a 5V voltage reference (2 x LT1009) which is used across a
> pair of trim pots (coarse and fine) with two front panel jacks for a high 
> impedance
> DVM to set the frequency trim voltage f the LPRO.
> The LPRO is insulated with more than an inch of foam plastic and a small fan
> (on the outside of the box) is used to control the 1/2 inch aluminium plate 
> that the
> LPRO is bolted to to about 38*C. The temperature control is much better than 
> 1/10 degree.
> Inside the box is a decimal divider with outputs down to 1Hz, and a phase 
> detector
> composed of 2 D latches (CMOS) the output of which is filtered and fed to a 
> strip
> chart recorder or data logger.
> I have a TBOLT connected to a decimal divider, so I can compare the phase 
> with the LPRO.
> At  10kHz I get 1microsecond per month resolution ~ 2x10^12. As errors show up
> the trim voltage can be adjusted with the DVM by an amount that is easy  to 
> calculate.
> So with a bit of time and without much in the way of high precision timing 
> gear I hope
> to be able to get the LPRO adjusted to the limits of its precision, and I 
> avoid the short term
> fluctuations in the TBOLT output.
> After a year or so I will be able to tell you how well it works.
> 
> cheers, Neville Michie
> 
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Re: [time-nuts] True to there word. - Fancy WWVB

[Bob Camp]

Hi

Yes indeed, you need to be sure you don't get a cycle slip. That's not trivial 
when the signal goes to zero while moving phase. 

There I think you need to depend on something like a reasonable OCXO and a long 
time constant loop. That brings in other problems. I assume that you are going 
to have to train your loop to "expect" the ID shifts and time markers. Again, 
they are predictable. It's just software 

More or less:

Take all of the things you can compute about the signal and feed them in. Lock 
the "computed" signal against the received signal. Way less complex than what 
they do with GPS. Since it's all *very* slow, a beater PC can easily keep up 
with all the adjustment math. 

Bob


On Feb 8, 2010, at 8:28 PM, J. Forster wrote:

> If you track for a day, and draw a straight line throught the diurnal
> shift, you can easily see a frequency drift of 45 degrees. That's 1/8
> cycle of 60 KHz or about 2 uS. So 2x 10 E-6 out of 10 E5, so you can see 2
> x 10 E-11 in a day.
> 
> ASSUMING the lock does not break.
> 
> -John
> 
> ===
> 
> 
> 
>> Hi
>> 
>> People rarely want to use WWVB mobile. The location of the transmitter and
>> receiver can be looked up on a map. The time of sunrise at both locations
>> should be something that could be calculated.
>> 
>> Assuming you are willing to put up with all of that, you should be able to
>> do a first order correction on the shifts. The question obviously is -
>> just how good would the net result be? Is it a 5:1 sort of thing or do you
>> get a couple of orders of magnitude?
>> 
>> Bob
>> 
>> On Feb 8, 2010, at 6:40 PM, J. Forster wrote:
>> 
>>> Yes, but WWVB is a PITA to use (because of the diurnal shifts) compared
>>> to
>>> LORAN.
>>> 
>>> -John
>>> 
>>> ===
>>> 
>>> 
 Hi
 
 WWVB is pretty safe. When they do a cost/benefit thing on these
 services,
 they take a look at how many taxpayers are using the service as
 intended.
 The "mission" of WWWVB is to put out time signals. There are a *lot* of
 taxpayers with WWVB "atomic clocks" on their walls.
 
 Bob
 
 -Original Message-
 From: time-nuts-boun...@febo.com [mailto:time-nuts-boun...@febo.com] On
 Behalf Of Don Henderickx
 Sent: Monday, February 08, 2010 4:07 PM
 To: Discussion of precise time and frequency measurement
 Subject: [time-nuts] True to there word.
 
 The lights went out (actually red) on my Austron 2100 r this morning.
 (whats  next WWVB ?)
 Don H
 
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>>> 
>>> 
>>> 
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Re: [time-nuts] True to there word. - Fancy WWVB

[Bob Camp]

Hi

I suspect there is more to the compensation process than just time of day. At 
some point it would get a bit crazy to collect all the data. It would be 
interesting to look into though. 

I'm by no means suggesting that WWVB would replace Loran. My *guess* is that it 
would be competitive with skywave Loran-C.  I've locked an Austron 2100 to the 
European chains. It can indeed be done. The only real issue is how good the 
result is (or isn't).

Bob


On Feb 8, 2010, at 8:49 PM, J. Forster wrote:

> I was using a HP 105B and 117A before the Austron 2100F and still have
> them. From what I remember, the diurnal shift was not repeatable.
> 
> By looking at an output from the 117A and syncing the 'scope to the 105B,
> I could assess the quality of the signal pretty well. Sometimes it was
> stable, sometimes it was jittering all over the place by a cycle or more.
> 
> Bottom line is, IMO, WWVB is no substitute for LORAN.
> 
> I'm still hoping that the european chains will be usable.
> 
> YMMV,
> 
> -John
> 
> 
> 
> 
>> Hi
>> 
>> Yes indeed, you need to be sure you don't get a cycle slip. That's not
>> trivial when the signal goes to zero while moving phase.
>> 
>> There I think you need to depend on something like a reasonable OCXO and a
>> long time constant loop. That brings in other problems. I assume that you
>> are going to have to train your loop to "expect" the ID shifts and time
>> markers. Again, they are predictable. It's just software 
>> 
>> More or less:
>> 
>> Take all of the things you can compute about the signal and feed them in.
>> Lock the "computed" signal against the received signal. Way less complex
>> than what they do with GPS. Since it's all *very* slow, a beater PC can
>> easily keep up with all the adjustment math.
>> 
>> Bob
>> 
>> 
>> On Feb 8, 2010, at 8:28 PM, J. Forster wrote:
>> 
>>> If you track for a day, and draw a straight line throught the diurnal
>>> shift, you can easily see a frequency drift of 45 degrees. That's 1/8
>>> cycle of 60 KHz or about 2 uS. So 2x 10 E-6 out of 10 E5, so you can see
>>> 2
>>> x 10 E-11 in a day.
>>> 
>>> ASSUMING the lock does not break.
>>> 
>>> -John
>>> 
>>> ===
>>> 
>>> 
>>> 
 Hi
 
 People rarely want to use WWVB mobile. The location of the transmitter
 and
 receiver can be looked up on a map. The time of sunrise at both
 locations
 should be something that could be calculated.
 
 Assuming you are willing to put up with all of that, you should be able
 to
 do a first order correction on the shifts. The question obviously is -
 just how good would the net result be? Is it a 5:1 sort of thing or do
 you
 get a couple of orders of magnitude?
 
 Bob
 
 On Feb 8, 2010, at 6:40 PM, J. Forster wrote:
 
> Yes, but WWVB is a PITA to use (because of the diurnal shifts)
> compared
> to
> LORAN.
> 
> -John
> 
> ===
> 
> 
>> Hi
>> 
>> WWVB is pretty safe. When they do a cost/benefit thing on these
>> services,
>> they take a look at how many taxpayers are using the service as
>> intended.
>> The "mission" of WWWVB is to put out time signals. There are a *lot*
>> of
>> taxpayers with WWVB "atomic clocks" on their walls.
>> 
>> Bob
>> 
>> -Original Message-
>> From: time-nuts-boun...@febo.com [mailto:time-nuts-boun...@febo.com]
>> On
>> Behalf Of Don Henderickx
>> Sent: Monday, February 08, 2010 4:07 PM
>> To: Discussion of precise time and frequency measurement
>> Subject: [time-nuts] True to there word.
>> 
>> The lights went out (actually red) on my Austron 2100 r this morning.
>> (whats  next WWVB ?)
>> Don H
>> 
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>> 
>> 
>> 
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> 
> 
> 
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>>> 
>>> 
>>> 
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Re: [time-nuts] True to there word. - Fancy WWVB

[Bob Camp]

Hi

My assumption is that that the same propagation effects that move the phase 
also delay the arrival of the modulation. The ID on WWVB is a 45 degree (?) 
carrier phase shift. At the very least, I think you would need to let the loop 
know about that.

I do hardware one week and software the next. Right now I'm writing a bunch of 
Perl 

Bob


On Feb 8, 2010, at 8:51 PM, Bob Paddock wrote:

> On Mon, Feb 8, 2010 at 8:40 PM, Bob Camp  wrote:
> 
>> I assume that you are going to have to train your loop to "expect" the ID 
>> shifts and time
>> markers. Again, they are predictable.
> 
> Would it not be easier to use the WWVB Zero-Crossings to sync something?
> Then the power shifts should not mater.
> 
>> It's just software 
> 
> You must be a hardware person... :-)
> 
> 
> 
> -- 
> http://www.wearablesmartsensors.com/
> http://www.softwaresafety.net/
> http://www.designer-iii.com/
> http://www.unusualresearch.com/
> 
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Re: [time-nuts] True to there word.

[Bob Camp]

Hi

I suppose you could pull down weather data off of the internet. It might be 
easier than it sounds. My guess is that it's actually more difficult than it 
sounds

Bob


On Feb 8, 2010, at 10:44 PM, WarrenS wrote:

> 
> Concerning WWVB from someone that used it way back to check my reference for 
> a few years before I had GPS.
> 
> Short conclusion, with what I was doing and the equipment I had (a WWVB 
> receiver Tracor 599),
> Its Ok to about 1 part in 1e9  for most of the day and with luck and care on 
> a good day, to a few parts in e10.
> 
> It was pretty useless at night, hard to keep track of what cycle it was on, 
> too much jumping around and time shift drift.
> It was completely useless at the diurnal shift, It went to zero for a few 
> minutes,
> lost sync and then came back with a new random sync on the 60 KHz phase and 
> the 100KHz reference Freq.
> During the winter season it made a better weather station than a Freq 
> standard,
> with the day time fluxuations being more a function of the weather between 
> Calif and Colorado than of my Osc.
> It was OK in the summer, but I could still use it to predict bad weather 
> in-between me and the transmitter.
> 
> Don't think you would NEVER ever want to lock on to it for a WWVB-DO, It is 
> just used to watch for phase drift during the lucky part of the day.
> 
> Oh, I don't miss them good ol days.
> 
> ws
> 
> **
>> Hi
> 
>> My assumption is that that the same propagation effects that move the phase 
>> also delay the arrival of the modulation. The ID on WWVB is a 45 degree (?) 
>> >carrier phase shift. At the very least, I think you would need to let the 
>> loop know about that.
> 
>> I do hardware one week and software the next. Right now I'm writing a bunch 
>> of Perl 
> 
>> Bob
> 
> *
> On Feb 8, 2010, at 8:51 PM, Bob Paddock wrote:
> 
>> On Mon, Feb 8, 2010 at 8:40 PM, Bob Camp  wrote:
>> 
>>> I assume that you are going to have to train your loop to "expect" the ID 
>>> shifts and time
>>> markers. Again, they are predictable.
>> 
>> Would it not be easier to use the WWVB Zero-Crossings to sync something?
>> Then the power shifts should not mater.
>> 
>>> It's just software 
>> 
>> You must be a hardware person... :-)
>> 
> 
> 
> 
>> Yes, but WWVB is a PITA to use (because of the diurnal shifts) compared to
>> LORAN.
>> 
>> -John
>> 
>> ===
>> 
>>> Hi
>>> 
>>> WWVB is pretty safe. When they do a cost/benefit thing on these services,
>>> they take a look at how many taxpayers are using the service as intended.
>>> The "mission" of WWWVB is to put out time signals. There are a *lot* of
>>> taxpayers with WWVB "atomic clocks" on their walls.
>>> 
>>> Bob
>>> 
>>> -Original Message-
>>> Subject: [time-nuts] True to there word.
>>> 
>>> The lights went out (actually red) on my Austron 2100 r this morning.
>>> (whats  next WWVB ?)
>>> Don H
> 
> 
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Re: [time-nuts] Frequency comparison

[Bob Camp]

Hi

Efratom became part of Datum a while ago. They changed the marking on the 
LPRO's after the ownership change.

Same product, just a new name on the door.

Bob


On Feb 9, 2010, at 7:28 AM, Joop wrote:

>> It is best to leave your stable quartz and Rubidium oscillators 
>> running continuously, preferably on a UPS in case of power failure, 
>> for best results.
>> 
>> Best regards,
>> 
>> Charles
>> 
> 
> I can understand. But I will not need that high accuracy very often. 
> So I just wanted to examine what can be expected after power-on. Just
> saving a bit of environment where possible.
> 
>> From a Datum LPRO specifications document I read:
> 
> Warm-up: (at -20°C) (at 25°C)
> Time to Lock: < 8.7 min < 5.4 min
> Time to <1E-9: <10.2 min <7.3 min
> Time to <4E-10: <12.7 min <10.6 min
> 
> Frequency Retrace: <±2.5E-11
> (after 24 hrs power on @ 25°C & up to 48 hrs power off)
> 
> I guess my readings are all within the above specs. The retrace value is
> probably the limiting factor. 2.5E-11 translates in my setup to 90ns/hour.
> Which looks being reached already in about 2 hours after power-on. So if
> the Efratom is essentially the same as the Datum, then all looks fine.
> 
> Joop
> 
> 
> 
> 
> 
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Re: [time-nuts] TBolt self survey

[Bob Camp]

Hi

GPS altitude is a bit different than map altitude. There is a recent thread
if you want all the details of why. Once you do the self survey, just accept
what ever it comes up with for altitude. If it's off by 100 meters, just
accept it and move on.

Bob

-Original Message-
From: time-nuts-boun...@febo.com [mailto:time-nuts-boun...@febo.com] On
Behalf Of Raj
Sent: Tuesday, February 09, 2010 11:01 AM
To: Discussion of precise time and frequency measurement
Subject: Re: [time-nuts] TBolt self survey

Thanks Stan,

Will do in first thing in the morning.

At 09-02-10, you wrote:
>Hello Raj,
>
>that location is probably where the coordinates were last saved. or there
abouts
>Or those are the default factory settings from memory,
>and new coordinates were never saved.
>
>redo the survey and save the results.
>
>using T'boltMON V2.60 on a PC:
>
>go to menu "set up",  then "self survey",   click on the "save position
flag"
>then "set survey",
>then "save segment",
>then "close"
>
>redo the survey and afterwards verify the local coordinates were saved.
>
>Lady Heather (software) can also be utilzed for these functions.
>
>Any problems, please advise.
>
>Stan, W1LE
>
>
>
>Raj wrote:
>>Can someone point me to info that would clarify why my Tbolt's
self survey puts my house (AFAIK ~920M ASL, 13N 77.35E) in the Pacific
ocean, south of Vancouver and west of Seattle and about 10 meters under
water. I am doing something wrong for sure!
>>
>>My sons iPhone gives me right co-ordinates but it's way off the
altitude.
>>
>>Regards
>>
>>  
>
>
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-- 
Raj, VU2ZAP
Bangalore, India. 


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Re: [time-nuts] HP K04 59991A Frequency multiplier comparator

[Bob Camp]

Hi

Was that an actual product or is it a one off?

We had similar stuff at Motorola when I started out. They were old even
then. The HP box seems to be one step past where the evolution of the
Motorola boxes died out. 

Bob

-Original Message-
From: time-nuts-boun...@febo.com [mailto:time-nuts-boun...@febo.com] On
Behalf Of Corby Dawson
Sent: Tuesday, February 09, 2010 1:44 PM
To: time-nuts@febo.com
Subject: [time-nuts] HP K04 59991A Frequency multiplier comparator

Hi,

I just listed a HP K04 59991A frequency multiplier comparator on ebay
320486215475

Details in the listing but any questions welcome.

Corby Dawson

Small Business Tools
Compete with the big boys.  Click here to find products to benefit your
business.
http://thirdpartyoffers.juno.com/TGL2141/c?cp=449dCqJRjJmqGt1gNkEtsgAAJ1ABLZ
FyqoH-WnHH1GJ345whAAYAAADNAAARMQA=
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Re: [time-nuts] Low phase noise VCO

[Bob Camp]

Hi

At 64 MHz you can go with a 3rd overtone crystal. If your temperature range is 
modest, you can pull it further than you would ever need to. 

You should be able to get good enough phase noise on the VCXO that you can use 
a pretty narrow loop. That's good news, it lets you use an IC phase detector 
and normal dividers. 

Bob


On Feb 9, 2010, at 6:41 PM, Nick Foster wrote:

> 
> Gentlemen,
> 
> Not being an oscillator guru, I thought I'd ask here. I'm building up a 
> fixed-frequency 64MHz PLL oscillator which uses a 10MHz reference. The 
> reference is a homebrew HP 10544A-based GPSDO which seems to work OK. I've 
> built a phase comparator based on a CoolRunner-II CPLD which implements a 
> flip-flop phase-frequency comparator just like the CMOS 4046. Seems to work 
> great, although I haven't put it to the test yet with respect to phase noise. 
> So all I need now is the VCO.
> 
> Right now, all I need is 64MHz to clock a software-defined radio, so I was 
> thinking about using a VCXO. I see lots of solutions using LC oscillators, 
> but very few using crystals because overtone crystals can't be pulled very 
> far at all. So my question is, what type of oscillator would you recommend 
> for this project, an overtone crystal oscillator like a Butler, or an LC 
> oscillator? Is there a particular oscillator topology you favor, or (better 
> yet) a schematic of one you like?
> 
> Thanks,
> Nick
> 
> _
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Re: [time-nuts] Low phase noise VCO

[Bob Camp]

Hi

Would 65 MHz work as well as 64? It certainly would be easier to come up with.

Bob


On Feb 9, 2010, at 6:41 PM, Nick Foster wrote:

> 
> Gentlemen,
> 
> Not being an oscillator guru, I thought I'd ask here. I'm building up a 
> fixed-frequency 64MHz PLL oscillator which uses a 10MHz reference. The 
> reference is a homebrew HP 10544A-based GPSDO which seems to work OK. I've 
> built a phase comparator based on a CoolRunner-II CPLD which implements a 
> flip-flop phase-frequency comparator just like the CMOS 4046. Seems to work 
> great, although I haven't put it to the test yet with respect to phase noise. 
> So all I need now is the VCO.
> 
> Right now, all I need is 64MHz to clock a software-defined radio, so I was 
> thinking about using a VCXO. I see lots of solutions using LC oscillators, 
> but very few using crystals because overtone crystals can't be pulled very 
> far at all. So my question is, what type of oscillator would you recommend 
> for this project, an overtone crystal oscillator like a Butler, or an LC 
> oscillator? Is there a particular oscillator topology you favor, or (better 
> yet) a schematic of one you like?
> 
> Thanks,
> Nick
> 
> _
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Re: [time-nuts] Low phase noise VCO

[Bob Camp]

Hi

With most SDR's a spur on the clock creates a spur in the radio. No matter how 
you do your multiply, you will wind up with some sub-harmonics running around. 
Much better / easier / quicker to start at 64 or 65 MHz.

Bob


On Feb 9, 2010, at 8:32 PM, Bruce Griffiths wrote:

> Thats not very useful when you want the 4th harmonic as its amplitude is zero 
> fro a 25% duty cycle.
> Using a duty cycle of 1/8, 3/8 or 5/8 will maximise the amplitude of the 4th 
> harmonic.
> 
> see:
> http://www.wenzel.com/pdffiles1/pdfs/choose.pdf
> 
> Bruce
> 
> Max Robinson wrote:
>> If you start with a square wave odd order is all you can get but if you 
>> start with a pulse with a 25% duty cycle you can get even order.  It's best 
>> to optimize the pulse width for the harmonic you want.
>> 
>> Regards.
>> 
>> Max.  K 4 O D S.
>> 
>> Email: m...@maxsmusicplace.com
>> 
>> Transistor site http://www.funwithtransistors.net
>> Vacuum tube site: http://www.funwithtubes.net
>> Music site: http://www.maxsmusicplace.com
>> 
>> To subscribe to the fun with transistors group send an email to.
>> funwithtransistors-subscr...@yahoogroups.com
>> 
>> To subscribe to the fun with tubes group send an email to,
>> funwithtubes-subscr...@yahoogroups.com
>> 
>> - Original Message - From: "Nick Foster" 
>> To: 
>> Sent: Tuesday, February 09, 2010 6:35 PM
>> Subject: Re: [time-nuts] Low phase noise VCO
>> 
>> 
>>> 
 From: b...@iaxs.net
 To: time-nuts@febo.com
 Date: Tue, 9 Feb 2010 18:24:39 -0600
 Subject: Re: [time-nuts] Low phase noise VCO
 
 Which leads me to ask a novice question:
 
 Why not pull a 16 MHz crystal and multiply to 64 MHz?
 
 If you count down from 64 to 10 MHz, isn't the multiplication inside the
 PLL?
 
 Perhaps the noise is multiplied by 4, but would it work for the intended
 purpose?
 
 Bill Hawkins
>>> 
>>> Can you do x4 multipliers? I thought odd-order harmonics were usually used 
>>> for multipliers. I'd be happy to be wrong!
>>> 
>>> Nick
>>> 
> 
> 
> 
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Re: [time-nuts] Low phase noise VCO

[Bob Camp]

Hi

A good 64 MHz VCXO should have *better* phase noise at 100 Hz than the 
multiplied 10 MHz out of a GPSDO. Even if you don't hit "state of the art" at 
100 Hz, it will be better past a few hundred Hz. 

A narrow loop is just fine. 

If the bandwidth gets to wide, you have to start worrying about the noise floor 
of the dividers and the phase detectors. With a narrow loop, a $1 or $2 all in 
one PLL / divider chip will do just fine. If you try to lock up something 
that's got -160 dbc/hz on a 10 MHz reference, that's not going to be the case.

If you are building a VCXO from scratch, build more than one. Set up a simple 
quadrature / mixer / sound card phase noise tester. If you already have a good 
sound card, the rest of it is a sub $100 investment. Then you will know what 
you have.

Bob 


On Feb 10, 2010, at 12:36 AM, Nick Foster wrote:

> 
> You're right, it's for a USRP. I just got annoyed with the constant frequency 
> offset, so I'm rolling my own. Turns out there isn't much available for good 
> off-the-shelf 64MHz VCXOs. The USRP2 has built-in support for 10MHz sync, but 
> not having one, I'm left to what I do have. Can't injection lock the 
> oscillator on board, as it's a self-contained square-wave clock. So it looks 
> like I'm going to try my hand at a Butler VCXO.
> 
> That said, I know that for PLLs, the maximum control loop bandwidth you can 
> use is limited by the pullability of your oscillator: if you use a VCXO with 
> very low Kv, you might end up with a maximum useful loop bandwidth of 10Hz. 
> No sense in using a 10544A to tune that! The phase noise performance would be 
> pretty awful, since you can't tightly lock the reference oscillator to it. So 
> does it make more sense to use a high-Q LC oscillator instead, with a much 
> higher Kv? I'd be able to phase-lock it much more tightly to the reference 
> oscillator. Plus, a 64MHz LC oscillator is pretty easy to build.
> 
> 
> --n
> 
>> Date: Tue, 9 Feb 2010 21:50:57 -0700
>> From: d...@montana.com
>> To: time-nuts@febo.com
>> Subject: Re: [time-nuts] Low phase noise VCO
>> 
>> Hi Bob and all:
>> This is interesting, because I suspect this frequency source is for an
>> Ettus Research USRP. A little further downtimeline I will be faced with
>> this problem as well. The SDR is designed already and requires a 64 MHz
>> clock, especially as this clock is used for the microwave transmit and
>> receive front ends. I had planned a synthesizer filtered...
>> The oscillator that is in the USRP that I have is good only to about 1
>> part in 10^8 or so for accuracy, better in stability. maybe the existing
>> osc. can be injection locked, or temp controlled in place.
>> Don
>> 
>> Bob Camp
>>> Hi
>>> 
>>> With most SDR's a spur on the clock creates a spur in the radio. No matter
>>> how you do your multiply, you will wind up with some sub-harmonics running
>>> around. Much better / easier / quicker to start at 64 or 65 MHz.
>>> 
>>> Bob
>>> 
>>> 
>>> On Feb 9, 2010, at 8:32 PM, Bruce Griffiths wrote:
>>> 
>>>> Thats not very useful when you want the 4th harmonic as its amplitude is
>>>> zero fro a 25% duty cycle.
>>>> Using a duty cycle of 1/8, 3/8 or 5/8 will maximise the amplitude of the
>>>> 4th harmonic.
>>>> 
>>>> see:
>>>> http://www.wenzel.com/pdffiles1/pdfs/choose.pdf
>>>> 
>>>> Bruce
>>>> 
>>>> Max Robinson wrote:
>>>>> If you start with a square wave odd order is all you can get but if you
>>>>> start with a pulse with a 25% duty cycle you can get even order.  It's
>>>>> best to optimize the pulse width for the harmonic you want.
>>>>> 
>>>>> Regards.
>>>>> 
>>>>> Max.  K 4 O D S.
>>>>> 
>>>>> Email: m...@maxsmusicplace.com
>>>>> 
>>>>> Transistor site http://www.funwithtransistors.net
>>>>> Vacuum tube site: http://www.funwithtubes.net
>>>>> Music site: http://www.maxsmusicplace.com
>>>>> 
>>>>> To subscribe to the fun with transistors group send an email to.
>>>>> funwithtransistors-subscr...@yahoogroups.com
>>>>> 
>>>>> To subscribe to the fun with tubes group send an email to,
>>>>> funwithtubes-subscr...@yahoogroups.com
>>>>> 
>>>>> - Original Message - From: "Nick Foster"
>>>>> 
>>>&g

Re: [time-nuts] injection locking

[Bob Camp]

Hi

That's the problem. 

There's no debate that you can injection lock oscillators. The problem is that 
the analytic side of designing an injection lock system  is a bit lacking. 

With a PLL there's an over abundance of information on how to do the design, 
how to analyze it, and how to test it. You can optimize loop bandwidth, phase 
margin, noise performance, and component selection. A paper design pretty is 
going to be a pretty good start on a working circuit.  There are an over 
abundance of free tools to do a design with. 

Again, the point is not weather one works and the other does not. They both 
work. There's just a *whole* lot more stuff out there on PLL's.

PLL chips are dirt cheap ($1 ~ $2 for most). Even a PIC to set them up is sub 
$1. They do have limits and you need to understand those limits. If you can get 
the job done with one, it's a simple way to go. 

Bob


On Feb 10, 2010, at 7:50 AM, Joop wrote:

>> You can even build an injection locked divide by 5 stage.
>> Choosing the right oscillator topology and injection method allows high 
>> level injection to be used with an LC oscillator.
>> 
>> Bruce
>> 
> 
> Are there references to some practical circuits? That would be great.
> 
> A google search on "injection locking" and "synchronous oscillator"
> results in a lot of conceptual descriptions but nothing that one can build,
> try out and study. Maybe some of the scientific articles or books contain
> circuits, but I am not a IEEE member.
> 
> Cheers,
> Joop
> 
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Re: [time-nuts] Low phase noise VCO

[Bob Camp]

Hi

In general the synthesized parts are not real low noise.  You can do better 
with $5 worth of parts and some tinkering time.


Bob

--
From: "Nick Foster" 
Sent: Wednesday, February 10, 2010 4:08 PM
To: 
Subject: Re: [time-nuts] Low phase noise VCO



That's a great suggestion, Ulrich. Thanks. It took all of five minutes to 
implement in VHDL, and looks great.


I also found Fox's "Xpresso" line of miniature synthesized VCXOs, and the 
numbers look pretty compelling. CMOS output, too. And, the best part, 
they're available off-the-shelf. Does anyone have experience with these in 
low-noise applications? They're ludicrously expensive (Digikey lists them 
for $47/ea in short qty), but if I can get some samples from Fox, it'll 
save me a lot of grief.


I'll let you all know how it works out, and Don, if I get samples and they 
work OK I'll mail you some.


Nick


From: df...@ulrich-bangert.de
To: time-nuts@febo.com
Date: Wed, 10 Feb 2010 09:02:30 +0100
Subject: Re: [time-nuts] Low phase noise VCO

Nick,

altough you have been asking for advice for the VCO I would like to draw
your attention on how you can improve your phase detector. Edge-triggered
phase detectors are not bad, the even can work as frequency detectors if 
you
are far from lock and help you to gain lock where a XOR would not. 
However,

once you are CLOSE to a phase lock, a simple XOR makes the better phase
detector with less phase noise. There is a VERY easy circuit that 
marriages
the best of both worlds. Google for the AD9901 frequence/phase detector 
and
mimic their schematic of the first page into your CPLD. Have done this 
with
different CPLDS from XILINX and ALTERA and has always worked very well 
for

me in terms of frequency locking range and low phase noise.

Best regards
Ulrich Bangert

> -Ursprungliche Nachricht-
> Von: time-nuts-boun...@febo.com
> [mailto:time-nuts-boun...@febo.com] Im Auftrag von Nick Foster
> Gesendet: Mittwoch, 10. Februar 2010 00:41
> An: time-nuts@febo.com
> Betreff: [time-nuts] Low phase noise VCO
>
>
>
> Gentlemen,
>
> Not being an oscillator guru, I thought I'd ask here. I'm
> building up a fixed-frequency 64MHz PLL oscillator which uses
> a 10MHz reference. The reference is a homebrew HP
> 10544A-based GPSDO which seems to work OK. I've built a phase
> comparator based on a CoolRunner-II CPLD which implements a
> flip-flop phase-frequency comparator just like the CMOS 4046.
> Seems to work great, although I haven't put it to the test
> yet with respect to phase noise. So all I need now is the VCO.
>
> Right now, all I need is 64MHz to clock a software-defined
> radio, so I was thinking about using a VCXO. I see lots of
> solutions using LC oscillators, but very few using crystals
> because overtone crystals can't be pulled very far at all. So
> my question is, what type of oscillator would you recommend
> for this project, an overtone crystal oscillator like a
> Butler, or an LC oscillator? Is there a particular oscillator
> topology you favor, or (better yet) a schematic of one you like?
>
> Thanks,
> Nick
>
> _
> Hotmail: Powerful Free email with security by Microsoft.
> http://clk.atdmt.com/GBL/go/201469230/direct/01/
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> time-nuts mailing list -- time-nuts@febo.com
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Re: [time-nuts] Advice on 10 MHz isolation/distribution amplifier

[Bob Camp]

Hi

How quiet does in need to be (phase noise)?

How clean does it need to be (harmonics)?

How much isolation / how much gain do you need?

How well do the outputs need to be matched / do you need a broad band match?

Does the issue with transformers also extend to other inductors?

Is cost / military components / small size / radiation tolerance an issue?

The answer to your question could be any of several bipolar transistor 
circuits, op amps, right up to "can't be done" based on some of the answers.


Bob

--
From: "life speed" 
Sent: Wednesday, February 10, 2010 8:27 PM
To: 
Subject: [time-nuts] Advice on 10 MHz isolation/distribution amplifier


Hello everyone,

I am new to this list, happened across it while searching on distribution 
amplifiers.


I need to design a 10 MHz isolation/distribution amplifier with two 
outputs for a high-vibration wide temperature range environment.  I was 
considering using a design based on the NIST article 'A new 5 and 10 MHz 
distribution amp', most likely the third incarnation, as I cannot tolerate 
modulation of the signal via the transformer.


I have looked at the work by Gerhard Hoffman, which is impressive. 
However, the transformer remains.  I should mention I am also limited to 
15V power supply, and need to output into 50 ohms at 10 dBm.  Ideally DC 
current will be minimized, preferably 20 - 30 mA per channel.  I can 
generate a negative power supply if necessary, but would prefer not to.


If anybody can offer tips so I don't undertake to reinvent the wheel, it 
would be appreciated.


Thanks in advance,
 - Lifespeed




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Re: [time-nuts] Advice on 10 MHz isolation/distribution amplifier

[Bob Camp]

Hi

Is your OCXO vibration isolated?

If not and it's got "typical" g sensitivity, your phase noise in an aircraft 
may be much worse than the static numbers.


If you are sending the signal a distance to your systems, a balanced feed 
may be the only way you will deliver a clean signal at the far end.


Bob

--
From: "life speed" 
Sent: Wednesday, February 10, 2010 10:03 PM
To: 
Subject: Re: [time-nuts] Advice on 10 MHz isolation/distribution amplifier


Avoiding transformers and inductors will make it virtually impossible to
achieve very low phase noise as the dc gain from say the base of any
transistor in the chain to the output will degrade the flicker phase
noise. Using transformers or using an inductor to shunt any collector
resistors reduces the flicker phase modulation to low levels.

JPL in the past has built capacitively coupled complementary symmetry
isolation amplifiers that avoid transformers but suffer from dc loop
gains of around 3 or so.

Using complementary symmetry can be a good way of keeping the dc current
down.

How much reverse isolation do you need?
How low does the phase noise floor need to be?
What about flicker phase noise, how low does that need to be?

Bruce

Right, what do I really need? I only have a really good 10 MHz OCXO 
crystal oscillator to distribute, so about -120 dBc at 10 Hz, -140 dBc/Hz 
at 100 Hz, - 150 dBc/Hz at 1KHz, and -155 dBc/Hz noise floor.  No maser or 
cesium clock, living in the world of practical realities here.  Of course 
I would like to be 3 - 6 dB better than the OCXO numbers.


Reverse isolation is my primary interest in the distribution amplifier 
approach, although the OCXO is good enough that a sloppy approach could 
contaminate the phase noise also.  I would like to accomplish at least 100 
dB reverse isolation at frequencies below 20 MHz, but more is better in 
this case.  The 10 MHz is running all over a noisy aircraft, to 
potentially noisy receivers.


In reading up on the subject, I have come to understand that DC gain is 
the bane of close-in phase noise.  Given that flicker noise is such a 
headache for we frequency synthesizer designers, I guess this should come 
as no surprise.


Clay (AKA Lifespeed)




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