date:20160811

Thank Attila.  At this point I'm mostly just collecting ideas.  I hope to put 
something to copper in a month or two.
Bob
 -
AE6RV.com

GFS GPSDO list:
groups.yahoo.com/neo/groups/GFS-GPSDOs/info

  From: Attila Kinali 
 To: Bob Stewart ; Discussion of precise time and frequency 
measurement  
 Sent: Thursday, August 11, 2016 5:12 PM
 Subject: Re: [time-nuts] Low cost SDR suitable for phase noise measurement?

On Thu, 11 Aug 2016 19:29:08 + (UTC)
Bob Stewart  wrote:

> It looks like I've asked a question poorly, yet again.  So, let me try
> again.  I have this idea of combining a DMTD with an SDR.  So, said that
> way, it looks like what I really need is a 2-channel audio SDR.  And having
> said that, maybe what I'm looking for is an external USB sound card.  Those
> I can find.  I can probably even figure out how to convert them to DC and
> supply them with a disciplined oscillator, if needed.

If you are going the soundcard way, i would like to point you at
http://time.kinali.ch/phase_noise_measurement/
You can find there two pdfs how to build a phase noise measurement
system using USB soundcards (kindly translated by Azelio Borani).
Adapting this to a DMTD system using two low frequency inputs
shouldn't be too hard. But please be aware that you should not
go below 100Hz or so, if you want to prevent the ADC DC drift to
confund your measurement. Probably even stay around 1kHz.

            Attila Kinali

-- 
Malek's Law:
        Any simple idea will be worded in the most complicated way.

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Re: [time-nuts] Safely getting the electrical length of a connected, antenna feedline

2016-08-11 Thread Joe Leikhim


"The biggest variable will be the velocity factor."

If you determine the length electrically, you will already have the 
electricallength. If you need the physical length, then multiply electrical 
length times the inverse of the velocity factor.


--
Joe Leikhim


Leikhim and Associates

Communications Consultants

Oviedo, Florida

jleik...@leikhim.com

407-982-0446

WWW.LEIKHIM.COM

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Re: [time-nuts] State of the art of crystal oscillator measurements

> If the oscillator output is thru the resonator, then at large offsets,
> the source impedance is reactive.  It can easily have an effective
> temperature less than room temperature.  If this "source" is then
> used with a low noise temperature preamp, it is entirely possible
> to go beyond these supposed theoretical limits that are based
> on T=300K.

Sure, until you try to measure it with a Zo=50R instrument, or otherwise do 
something that involves putting real power into a load.

-- john, KE5FX
Miles Design LLC


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Re: [time-nuts] Low cost SDR suitable for phase noise measurement?

Hi

In a DMTD (or in the equally useful single mixer setup) the advantage for 
frequency measurement 
comes from the downconversion process. The further you downconvert (10 Hz vs 
100 Hz) the
greater your potential resolution. The design approach is to push the beat note 
as low as you 
can without running into other limits. With conventional setups that is in the 
1 to 10 Hz range. 

If you want to fiddle a bit, there is no particular reason why you must use a 
limiter after the 
mixer. An ADC after the mixer could be used to process the audio and estimate 
it’s frequency. 
The same sort of ADC setup might give you some phase noise data. 

The gotcha with all this is that a single mixer / quadrature approach will give 
you *much* better
phase noise data than a single or dual mixer setup. If phase noise is the 
objective, there is no
reason to run the mixer setup as a DMTD. With a DMTD you digitize the carrier 
(audio beat note)
and then try to dig down 195 db to get to the phase noise. With a quadrature 
approach you null out
the carrier. Then all you have to deal with is the noise. 

Bob


> On Aug 11, 2016, at 5:15 PM, Bob Stewart  wrote:
> 
> Hi Bob,
> If I understand the question correctly, yes.  The DMTDs that I've encountered 
> so far use a zero-crossing detector and a TIC.  I wanted to build sort of a 
> hybrid system that has a DMTD front end and an SDR back end.  It seemed to me 
> that that would be sort of half way between a DMTD and a Timepod.  But 
> whereas the Timepod digitizes 4 RF signals, this would digitize 2 audio 
> signals.  It may be that it suffers all the disadvantages of both and has the 
> advantages of neither, but I thought I'd build it and see where it leads.
> As to the 1 to 10 Hz range, doesn't that depend on the heterodyne frequency 
> you choose?  I mean, you don't have to use a 10 Hz offset, do you?
> 
> Bob
>  -
> AE6RV.com
> 
> GFS GPSDO list:
> groups.yahoo.com/neo/groups/GFS-GPSDOs/info
> 
>  From: Bob Camp 
> To: Discussion of precise time and frequency measurement  
> Sent: Thursday, August 11, 2016 3:13 PM
> Subject: Re: [time-nuts] Low cost SDR suitable for phase noise measurement?
> 
> Hi
> 
> Just to clarify:
> 
> You are looking for a way to digitize the output(s) of the mixer(s) in a 
> DMTD. The 
> “target signal” is in the 1 to 10 Hz range.
> 
> Is that correct or are you looking for something to use instead of a DMTD? 
> 
> Bob
> 
> 
>> On Aug 11, 2016, at 3:29 PM, Bob Stewart  wrote:
>> 
>> Hi Brooke,
>> It looks like I've asked a question poorly, yet again.  So, let me try 
>> again.  I have this idea of combining a DMTD with an SDR.  So, said that 
>> way, it looks like what I really need is a 2-channel audio SDR.  And having 
>> said that, maybe what I'm looking for is an external USB sound card.  Those 
>> I can find.  I can probably even figure out how to convert them to DC and 
>> supply them with a disciplined oscillator, if needed.
>> 
>> Bob
>>   -
>> AE6RV.com
>> 
>> GFS GPSDO list:
>> groups.yahoo.com/neo/groups/GFS-GPSDOs/info
>> 
>>   From: Brooke Clarke 
>> To: Discussion of precise time and frequency measurement 
>>  
>> Sent: Thursday, August 11, 2016 1:36 PM
>> Subject: Re: [time-nuts] Low cost SDR suitable for phase noise measurement?
>> 
>> Hi Bob:
>> 
>> The SDR-IQ has a lower frequency limit of 500 Hz.
>> http://www.prc68.com/I/Bats.shtml#SDRIQ
>> 
>> There is a mod that replaces the on board 66 MHz oscillator with one locked 
>> to 10 MHz.
>> 
>> -- 
>> Have Fun,
>> 
>> Brooke Clarke, N6GCE
>> http://www.PRC68.com
>> http://www.end2partygovernment.com/2012Issues.html
>> The lesser of evils is still evil.
>> 
>>  Original Message 
>>> A number of posts have appeared about Zynq SDRs on the "Shera revisited" 
>>> thread.  So, I'd like to ask the more general question: Are there any low 
>>> cost SDRs that are suitable for measuring phase noise when coupled with a 
>>> DMTD?  I believe what I'm looking for is something with enough bits to work 
>>> in the audio range down to DC.  Yes, I could use a modified sound card, but 
>>> I'm really looking for something not sound card related.  My thought was to 
>>> use a DMTD with a heterodyne frequency of maybe 5KHz.
>>> 
>>> Bob -
>>> AE6RV.com
>>> 
>>> GFS GPSDO list:
>>> groups.yahoo.com/neo/groups/GFS-GPSDOs/info
>>> ___
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>>> and follow the instructions there.
>>> 
>> 
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Re: [time-nuts] Low cost SDR suitable for phase noise measurement?

Hi Bob,
If I understand the question correctly, yes.  The DMTDs that I've encountered 
so far use a zero-crossing detector and a TIC.  I wanted to build sort of a 
hybrid system that has a DMTD front end and an SDR back end.  It seemed to me 
that that would be sort of half way between a DMTD and a Timepod.  But whereas 
the Timepod digitizes 4 RF signals, this would digitize 2 audio signals.  It 
may be that it suffers all the disadvantages of both and has the advantages of 
neither, but I thought I'd build it and see where it leads.
As to the 1 to 10 Hz range, doesn't that depend on the heterodyne frequency you 
choose?  I mean, you don't have to use a 10 Hz offset, do you?

Bob
 -
AE6RV.com

GFS GPSDO list:
groups.yahoo.com/neo/groups/GFS-GPSDOs/info

  From: Bob Camp 
 To: Discussion of precise time and frequency measurement  
 Sent: Thursday, August 11, 2016 3:13 PM
 Subject: Re: [time-nuts] Low cost SDR suitable for phase noise measurement?

Hi

Just to clarify:

You are looking for a way to digitize the output(s) of the mixer(s) in a DMTD. 
The 
“target signal” is in the 1 to 10 Hz range.

Is that correct or are you looking for something to use instead of a DMTD? 

Bob

> On Aug 11, 2016, at 3:29 PM, Bob Stewart  wrote:
> 
> Hi Brooke,
> It looks like I've asked a question poorly, yet again.  So, let me try again. 
>  I have this idea of combining a DMTD with an SDR.  So, said that way, it 
> looks like what I really need is a 2-channel audio SDR.  And having said 
> that, maybe what I'm looking for is an external USB sound card.  Those I can 
> find.  I can probably even figure out how to convert them to DC and supply 
> them with a disciplined oscillator, if needed.
> 
> Bob
>  -
> AE6RV.com
> 
> GFS GPSDO list:
> groups.yahoo.com/neo/groups/GFS-GPSDOs/info
> 
>      From: Brooke Clarke 
> To: Discussion of precise time and frequency measurement  
> Sent: Thursday, August 11, 2016 1:36 PM
> Subject: Re: [time-nuts] Low cost SDR suitable for phase noise measurement?
> 
> Hi Bob:
> 
> The SDR-IQ has a lower frequency limit of 500 Hz.
> http://www.prc68.com/I/Bats.shtml#SDRIQ
> 
> There is a mod that replaces the on board 66 MHz oscillator with one locked 
> to 10 MHz.
> 
> -- 
> Have Fun,
> 
> Brooke Clarke, N6GCE
> http://www.PRC68.com
> http://www.end2partygovernment.com/2012Issues.html
> The lesser of evils is still evil.
> 
>  Original Message 
>> A number of posts have appeared about Zynq SDRs on the "Shera revisited" 
>> thread.  So, I'd like to ask the more general question: Are there any low 
>> cost SDRs that are suitable for measuring phase noise when coupled with a 
>> DMTD?  I believe what I'm looking for is something with enough bits to work 
>> in the audio range down to DC.  Yes, I could use a modified sound card, but 
>> I'm really looking for something not sound card related.  My thought was to 
>> use a DMTD with a heterodyne frequency of maybe 5KHz.
>> 
>> Bob -
>> AE6RV.com
>> 
>> GFS GPSDO list:
>> groups.yahoo.com/neo/groups/GFS-GPSDOs/info
>> ___
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Re: [time-nuts] State of the art of crystal oscillator measurements

2016-08-11 Thread Richard (Rick) Karlquist




On 8/11/2016 3:47 PM, John Miles wrote:

Right, I'm speaking specifically of L(f).  The device being driven by the 
oscillator doesn't care about the NF of the driver stage, only what a PN 
analyzer would measure at the output jack.

For any 50-ohm source, the practical L(f) floor is -177 dBm/Hz - the carrier 
power in dBm.  No oscillator with an output of 0 dBm can be quieter than -177 
dBc/Hz at any offset, but an oscillator that puts out +20 dBm could approach 
-197 dBc/Hz.

Given a proverbial black box containing a +17 dBm oscillator that measures -195 dBc/Hz at 
100 kHz, the interesting question is, "What's in the box?"  There could be a 
passive resonator that's shaving off the broadband noise after the last active stage 
without contributing additive noise of its own.  Another possibility might be 
cross-spectral collapse due to correlated thermal noise from the splitter.

-- john, KE5FX
Miles Design LLC



If the oscillator output is thru the resonator, then at large offsets,
the source impedance is reactive.  It can easily have an effective
temperature less than room temperature.  If this "source" is then
used with a low noise temperature preamp, it is entirely possible
to go beyond these supposed theoretical limits that are based
on T=300K.

Rick
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Re: [time-nuts] State of the art of crystal oscillator measurements

-177dBm /Hz at 300 deg  SSB phase noise is correct, not because AM/  FM but 
Single Sideband Energy .
In my last QEX paper I showed the measured AM and FM levels and how to  
calculate them.

73 de Ulrich 

xx

In a message dated 8/11/2016 9:00:11 P.M. Eastern Daylight Time,  
mfe...@eozinc.com writes:

That is  interesting. We always used -174 and not -177 as it was concluded 
that at  those low levels AM and PM noise are not discernible, so, the total 
noise  density per Hz was -174. This must be relatively new since I worked 
in  industry. We had a bunch of PhDs from Lincoln helping as well and they 
always  used -174. This sounds like one of those instrument manufacturers 
gimmick to  make the numbers look better :). 

Your last statement is why I started  to question the claims initially. - 
Mike 

Mike B. Feher, EOZ Inc.
89  Arnold Blvd.
Howell, NJ, 07731
732-886-5960 office
908-902-3831  cell

-Original Message-
From: time-nuts  [mailto:time-nuts-boun...@febo.com] On Behalf Of John Miles
Sent: Thursday,  August 11, 2016 7:57 PM
To: 'Discussion of precise time and frequency  measurement'
Subject: Re: [time-nuts] State of the art of crystal  oscillator 
measurements

-177 = the -174 dBm/Hz SSB thermal noise floor  at 25C, less 3 dB to 
account for the usual assumption that half of it is AM,  half PM.   

dBm/Hz is obviously equivalent to dBc/Hz for a 0  dBm carrier.  

Anyone who claims to measure noise in a 1 Hz  bandwidth below -177 dBm/Hz 
at room temperature is either doing something  wrong somewhere, or doing 
something amazing somewhere.

-- john,  KE5FX
Miles Design LLC

> -Original Message-
> From:  time-nuts [mailto:time-nuts-boun...@febo.com] On Behalf Of Mike 
>  Feher
> Sent: Thursday, August 11, 2016 4:15 PM
> To: 'Discussion  of precise time and frequency measurement'
> Subject: Re: [time-nuts]  State of the art of crystal oscillator 
> measurements
> 
>  That is why I asked what the Po was. Where did the 177 come from? L(f)  
> is single sided. This is not my first "rodeo" in these matters. 73 -  
> Mike
> 
> Mike B. Feher, EOZ Inc.
> 89 Arnold  Blvd.
> Howell, NJ, 07731
> 732-886-5960 office
>  908-902-3831 cell
>  

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Re: [time-nuts] State of the art of crystal oscillator measurements

That is interesting. We always used -174 and not -177 as it was concluded that 
at those low levels AM and PM noise are not discernible, so, the total noise 
density per Hz was -174. This must be relatively new since I worked in 
industry. We had a bunch of PhDs from Lincoln helping as well and they always 
used -174. This sounds like one of those instrument manufacturers gimmick to 
make the numbers look better :). 

Your last statement is why I started to question the claims initially. - Mike 

Mike B. Feher, EOZ Inc.
89 Arnold Blvd.
Howell, NJ, 07731
732-886-5960 office
908-902-3831 cell


-Original Message-
From: time-nuts [mailto:time-nuts-boun...@febo.com] On Behalf Of John Miles
Sent: Thursday, August 11, 2016 7:57 PM
To: 'Discussion of precise time and frequency measurement'
Subject: Re: [time-nuts] State of the art of crystal oscillator measurements

-177 = the -174 dBm/Hz SSB thermal noise floor at 25C, less 3 dB to account for 
the usual assumption that half of it is AM, half PM.   

dBm/Hz is obviously equivalent to dBc/Hz for a 0 dBm carrier.  

Anyone who claims to measure noise in a 1 Hz bandwidth below -177 dBm/Hz at 
room temperature is either doing something wrong somewhere, or doing something 
amazing somewhere.

-- john, KE5FX
Miles Design LLC

> -Original Message-
> From: time-nuts [mailto:time-nuts-boun...@febo.com] On Behalf Of Mike 
> Feher
> Sent: Thursday, August 11, 2016 4:15 PM
> To: 'Discussion of precise time and frequency measurement'
> Subject: Re: [time-nuts] State of the art of crystal oscillator 
> measurements
> 
> That is why I asked what the Po was. Where did the 177 come from? L(f) 
> is single sided. This is not my first "rodeo" in these matters. 73 - 
> Mike
> 
> Mike B. Feher, EOZ Inc.
> 89 Arnold Blvd.
> Howell, NJ, 07731
> 732-886-5960 office
> 908-902-3831 cell
> 

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Re: [time-nuts] State of the art of crystal oscillator measurements

-177 = the -174 dBm/Hz SSB thermal noise floor at 25C, less 3 dB to account for 
the usual assumption that half of it is AM, half PM.   

dBm/Hz is obviously equivalent to dBc/Hz for a 0 dBm carrier.  

Anyone who claims to measure noise in a 1 Hz bandwidth below -177 dBm/Hz at 
room temperature is either doing something wrong somewhere, or doing something 
amazing somewhere.

-- john, KE5FX
Miles Design LLC

> -Original Message-
> From: time-nuts [mailto:time-nuts-boun...@febo.com] On Behalf Of Mike
> Feher
> Sent: Thursday, August 11, 2016 4:15 PM
> To: 'Discussion of precise time and frequency measurement'
> Subject: Re: [time-nuts] State of the art of crystal oscillator measurements
> 
> That is why I asked what the Po was. Where did the 177 come from? L(f) is
> single sided. This is not my first "rodeo" in these matters. 73 - Mike
> 
> Mike B. Feher, EOZ Inc.
> 89 Arnold Blvd.
> Howell, NJ, 07731
> 732-886-5960 office
> 908-902-3831 cell
> 

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Re: [time-nuts] State of the art of crystal oscillator measurements

Good point, the 'milliwatt' part of 'dBm' takes the E^2/R part out of the math. 
 If we were speaking of dBv/Hz, the system Zo would need to be considered to 
determine the power.  

-- john, KE5FX
Miles Design LLC

> -Original Message-
> From: time-nuts [mailto:time-nuts-boun...@febo.com] On Behalf Of Richard
> (Rick) Karlquist
> Sent: Thursday, August 11, 2016 3:01 PM
> To: Discussion of precise time and frequency measurement
> Subject: Re: [time-nuts] State of the art of crystal oscillator measurements
> 
> Zo doesn't matter for these purposes.
> dBm works just as well for 75 ohm systems.
> 

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Re: [time-nuts] State of the art of crystal oscillator measurements

That is why I asked what the Po was. Where did the 177 come from? L(f) is 
single sided. This is not my first "rodeo" in these matters. 73 - Mike 

Mike B. Feher, EOZ Inc.
89 Arnold Blvd.
Howell, NJ, 07731
732-886-5960 office
908-902-3831 cell


-Original Message-
From: time-nuts [mailto:time-nuts-boun...@febo.com] On Behalf Of John Miles
Sent: Thursday, August 11, 2016 4:22 PM
To: 'Discussion of precise time and frequency measurement'
Subject: Re: [time-nuts] State of the art of crystal oscillator measurements

Remember that L(f) is expressed in dBc/Hz, not dBm/Hz.  If it were dBm/Hz, then 
kT would be the limit.  But in dBc/Hz terms, the limit is 177 + the DUT's 
output power in dBm.  

Assuming a 50 ohm system, of course.

-- john, KE5FX
Miles Design LLC


> -Original Message-
> From: time-nuts [mailto:time-nuts-boun...@febo.com] On Behalf Of Mike 
> Feher
> Sent: Thursday, August 11, 2016 12:51 PM
> To: 'Discussion of precise time and frequency measurement'; 
> ka2...@aol.com; t...@leapsecond.com
> Cc: enrico.rubi...@gmail.com
> Subject: Re: [time-nuts] State of the art of crystal oscillator 
> measurements
> 
> kT is indeed relevant for a physical implementation. - Mike
> 
> Mike B. Feher, EOZ Inc.
> 89 Arnold Blvd.
> Howell, NJ, 07731
> 732-886-5960 office
> 908-902-3831 cell

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Re: [time-nuts] State of the art of crystal oscillator measurements

Values  of kT at 25°C (298 K) Units  kT = 4.11×10−21 _J_ 
(https://en.wikipedia.org/wiki/Joule)   kT = 4.114 pN⋅nm  kT = 9.83×10−22 _cal_ 
(https://en.wikipedia.org/wiki/Calorie)   kT = 25.7 _meV_ 
(https://en.wikipedia.org/wiki/Electron-volt)Related quantities  kT/hc = 
200 cm-1  kT/e = 25.7 _mV_ 
(https://en.wikipedia.org/wiki/Volt)   RT = kT ⋅ _NA_ 
(https://en.wikipedia.org/wiki/Avogadro's_number)  = 2.479 _kJ⋅mol-1_ 
(https://en.wikipedia.org/wiki/Joule_per_mole)   u = 0.593 _kcal⋅mol−1_ 
(https://en.wikipedia.org/wiki/Kilocalorie_per_mole)   _h_ 
(https://en.wikipedia.org/wiki/Planck_constant) 
/kT = 0.16 _ps_ (https://en.wikipedia.org/wiki/Picosecond) 
 
 
In a message dated 8/11/2016 7:02:13 P.M. Eastern Daylight Time,  
j...@miles.io writes:

Right,  I'm speaking specifically of L(f).  The device being driven by the  
oscillator doesn't care about the NF of the driver stage, only what a PN  
analyzer would measure at the output jack.

For any 50-ohm source, the  practical L(f) floor is -177 dBm/Hz - the 
carrier power in dBm.  No  oscillator with an output of 0 dBm can be quieter 
than 
-177 dBc/Hz at any  offset, but an oscillator that puts out +20 dBm could 
approach -197  dBc/Hz.

Given a proverbial black box containing a +17 dBm oscillator  that measures 
-195 dBc/Hz at 100 kHz, the interesting question is, "What's in  the box?"  
There could be a passive resonator that's shaving off the  broadband noise 
after the last active stage without contributing additive  noise of its own. 
 Another possibility might be cross-spectral collapse  due to correlated 
thermal noise from the splitter.   

--  john, KE5FX
Miles Design LLC


> -Original  Message-
> From: time-nuts [mailto:time-nuts-boun...@febo.com] On  Behalf Of KA2WEU--
> - via time-nuts
> Sent: Thursday, August 11,  2016 2:37 PM
> To: time-nuts@febo.com
> Subject: Re: [time-nuts]  State of the art of crystal oscillator 
measurements
> 
> NO, the  maximum  possible noise dynamic range is ( 177 +  Pout)   [dBm]  
-
> Transistor large signal NF ( dB),
>  the  signal to noise ration is dimensionless 
>  

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Re: [time-nuts] State of the art of crystal oscillator measurements

Right, I'm speaking specifically of L(f).  The device being driven by the 
oscillator doesn't care about the NF of the driver stage, only what a PN 
analyzer would measure at the output jack.

For any 50-ohm source, the practical L(f) floor is -177 dBm/Hz - the carrier 
power in dBm.  No oscillator with an output of 0 dBm can be quieter than -177 
dBc/Hz at any offset, but an oscillator that puts out +20 dBm could approach 
-197 dBc/Hz.

Given a proverbial black box containing a +17 dBm oscillator that measures -195 
dBc/Hz at 100 kHz, the interesting question is, "What's in the box?"  There 
could be a passive resonator that's shaving off the broadband noise after the 
last active stage without contributing additive noise of its own.  Another 
possibility might be cross-spectral collapse due to correlated thermal noise 
from the splitter.   

-- john, KE5FX
Miles Design LLC


> -Original Message-
> From: time-nuts [mailto:time-nuts-boun...@febo.com] On Behalf Of KA2WEU--
> - via time-nuts
> Sent: Thursday, August 11, 2016 2:37 PM
> To: time-nuts@febo.com
> Subject: Re: [time-nuts] State of the art of crystal oscillator measurements
> 
> NO, the maximum  possible noise dynamic range is ( 177 +  Pout)  [dBm]  -
> Transistor large signal NF ( dB),
>  the signal to noise ration is dimensionless 
> 

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Re: [time-nuts] Working with SMT parts.

2016-08-11 Thread Graham / KE9H

The best type of stereo microscope to use for SMT assembly is referred to
as an "Inspection Microscope."
Magnification greater than 10 is not needed or desirable for normal
assembly.
Something in the range of 5 to 10 works well.
A wide field of view and a good light source are desirable.

Just as Brooke says, my "zoom" always stays on the lowest setting. (Same as
his, 0.7 times 10x = 7)

--- Graham

==

On Thu, Aug 11, 2016 at 1:57 PM, Brooke Clarke  wrote:

> Hi Bob:
>
> I don't think it's so much the stereo microscope as the related
> equipment.  I have a Bausch & Lomb StereoZoom 4  and the dial is always at
> the lowest setting (0.7dial * 10X objective = 7 power).
> For another reason I got a Nikon SMZ-U microscope and discovered that it's
> so tall that it can not be used for SMT work.
> http://www.prc68.com/I/NikonSMZ-U.html
> So an important parameter is is length from the eyepiece to the
> objective.  If that get to be long then you can not easily use it.
>
> Using an arm type support is very desirable.  These have a heavy metal
> base with an horizontal arm.  You can swing the arm over whatever you're
> working one and easily move the scope up or down as needed.
> This all done while in a standard chair on a work bench/table.
>
> Although an old fashioned illuminator will work, see top photo:
> http://www.prc68.com/I/SMT.shtml#Mag
> A ring light is much more convenient (scroll down a little).
>
> Also the soldering iron tip to grip distance should be as short as you can
> get.  (1.5" = burned fingers, 0.5" should be better)
>
> --
> Have Fun,
>
> Brooke Clarke
> http://www.PRC68.com
> http://www.end2partygovernment.com/2012Issues.html
> The lesser of evils is still evil.
>
>  Original Message 
>
>> What are the important parameters regarding purchase of a stereo
>> microscope?  I see some on ebay for around $50; are those good?
>> Bob
>>
>>  On Thursday, August 11, 2016 10:00 AM, Didier Juges <
>> shali...@gmail.com> wrote:
>>
>>   I concur. I have been using ExpressPCB extensively over the last 2 years
>> with great satisfaction now that it is possible to get Gerber files from
>> them.
>> I typically use the mini board pro service (3 bare boards, 2 sided with
>> solder mask and silk screen) for prototypes and then buy the Gerbers to
>> have production quantities done overseas.
>> The boards are of high quality and the service is very fast at a very
>> reasonable price.
>> The only gotcha with regard to Gerber files is that you can only buy
>> Gerbers for boards that you have actually bought from them, so the process
>> is to buy the prototypes, then if you are happy with those, buy the
>> Gerbers
>> for that design.
>>
>> Didier KO4BB
>>
>> On Tue, Aug 9, 2016 at 3:06 PM, Brooke Clarke  wrote:
>>
>> Hi:
>>>
>>> I've had good luck using any of the the ExpressPCB services that include
>>> solder mask with surface mount parts where the pitch is 0.05" (half
>>> normal
>>> DIP) and hand soldering (requires stereo microscope).
>>> http://www.prc68.com/I/BTSG.shtml (battery top signal generator)
>>> http://www.prc68.com/I/Images/ICS525v1o.jpg
>>>
>>> http://www.prc68.com/I/SMT.shtml 
>>>
>>> --
>>> Have Fun,
>>>
>>> Brooke Clarke
>>> http://www.PRC68.com
>>> http://www.end2partygovernment.com/2012Issues.html
>>> The lesser of evils is still evil.
>>>
>>>
>>> ___
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Re: [time-nuts] Working with SMT parts.

2016-08-11 Thread Chuck Harris

Lots of good suggestions have already been made, but for
me, a boom style stereo microscope, with a distance between
the objective, and the focal point of at least 3 inches works
fairly well...

One other thing that may force your decision, if you are
older, your eyes will likely have lots of "floaters", which
are debris that floats around in your eyeballs.  This debris
floats in and out of the center of your field of view, and
looks like a bunch of translucent worms, or shadows.

Your brain, the magnificent organ that it is, tries to compensate
for your eye's degradation, and as long as your eyes can move
about in your field of view, it effectively removes the floaters
from the scenes you are viewing.

However, if you use a stereo microscope, your eye position
is fixed by the very limited amounts of off axis motion
that will allow a through optical channel.  This lack of off
axis motion will emphasize your floaters in a great way, and you
will see *every* *single* *one*, clearly, as if it were something
you really wanted to view.  Some times, the floaters will cover
the exact thing you need to see clearly, and you will have to
move it off axis by moving it on the microscope stage.

The only answer to this problem, is to either have perfect eyes,
or to use a microscope where you are looking at a screen, rather
than through a pair of oculars.  This way, your eyes can dart
around, and inspect what they need to see clearly, and the
floaters will be ignored by your brain.

As far as I know, there is only one optical microscope built this
way, and it is the very expensive Mantis.

Because of the great expense of flat screen optical microscopes,
most modern SMD viewing equipment is going to the trivially cheap
method of using a CCD/CMOS color video camera and an LCD screen.

You can do a lot with a cheap USB camera mounted to a boom, a fiber
optic light source, or a ring light, and a laptop computer to
display the image.

-Chuck Harris

Bob Albert via time-nuts wrote:
> What are the important parameters regarding purchase of a stereo microscope?  
> I
> see some on ebay for around $50; are those good? Bob
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Re: [time-nuts] Low cost SDR suitable for phase noise measurement?

2016-08-11 Thread Attila Kinali

On Thu, 11 Aug 2016 19:29:08 + (UTC)
Bob Stewart  wrote:

> It looks like I've asked a question poorly, yet again.  So, let me try
> again.  I have this idea of combining a DMTD with an SDR.  So, said that
> way, it looks like what I really need is a 2-channel audio SDR.  And having
> said that, maybe what I'm looking for is an external USB sound card.  Those
> I can find.  I can probably even figure out how to convert them to DC and
> supply them with a disciplined oscillator, if needed.

If you are going the soundcard way, i would like to point you at
http://time.kinali.ch/phase_noise_measurement/
You can find there two pdfs how to build a phase noise measurement
system using USB soundcards (kindly translated by Azelio Borani).
Adapting this to a DMTD system using two low frequency inputs
shouldn't be too hard. But please be aware that you should not
go below 100Hz or so, if you want to prevent the ADC DC drift to
confund your measurement. Probably even stay around 1kHz.

Attila Kinali

-- 
Malek's Law:
Any simple idea will be worded in the most complicated way.
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Re: [time-nuts] State of the art of crystal oscillator measurements

2016-08-11 Thread Richard (Rick) Karlquist


Zo doesn't matter for these purposes.
dBm works just as well for 75 ohm systems.

On 8/11/2016 1:22 PM, John Miles wrote:

Remember that L(f) is expressed in dBc/Hz, not dBm/Hz.  If it were dBm/Hz, then 
kT would be the limit.  But in dBc/Hz terms, the limit is 177 + the DUT's 
output power in dBm.

Assuming a 50 ohm system, of course.

-- john, KE5FX
Miles Design LLC



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Re: [time-nuts] State of the art of crystal oscillator measurements

Hi

The gotcha is that you don’t *have* to have a 50 ohm system. An output stage 
with
a narrow band tuned tank is one example of a very “not 50 ohms” system. 

There is also a whole debate around the “is 50 ohm source into 50 ohm load 
really 25 ohms”. 
That will give you a 3 db delta to bet beers about. The 3 db split of thermal 
noise between AM
noise and PM noise is fairly well accepted, but it still can be challenged. 

So is the floor -174 - 3 = -177 or is it something else …. 

If we have a -195.4 dbc/ Hz oscillator that puts out < 18 dbm in a 50 ohm 
system it’s not -177 or
it’s not a 50 ohm system. 

Bob

> On Aug 11, 2016, at 4:47 PM, John Miles  wrote:
> 
> Or rather -(177+DUT output power in dBm).  The minus sign makes the 
> difference between the thermal floor and a nuclear war!
> 
> -- john, KE5FX
> Miles Design LLC
> 
>> Remember that L(f) is expressed in dBc/Hz, not dBm/Hz.  If it were dBm/Hz,
>> then kT would be the limit.  But in dBc/Hz terms, the limit is 177 + the 
>> DUT's
>> output power in dBm.
> 
> 
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Re: [time-nuts] State of the art of crystal oscillator measurements

2016-08-11 Thread Tom Holmes

I am quite intrigued by two things here:
1. What improvements were made to the instruments, and 

2. What were the instrument settings and test setups?

Thanks.

Tom Holmes, N8ZM

-Original Message-
From: time-nuts [mailto:time-nuts-boun...@febo.com] On Behalf Of KA2WEU--- via 
time-nuts
Sent: Thursday, August 11, 2016 4:34 PM
To: time-nuts@febo.com
Subject: Re: [time-nuts] State of the art of crystal oscillator measurements

See below 

In a message dated 8/11/2016 4:30:47 P.M. Eastern Daylight Time,  
j...@miles.io writes:

Remember  that L(f) is expressed in dBc/Hz, not dBm/Hz.  If it were dBm/Hz, 
then kT  would be the limit.  But in dBc/Hz terms, the limit  is 177 + the 
DUT's output power in dBm - transistor large signal NF in dB  .  

Assuming a 50 ohm system, of course.

-- john,  KE5FX
Miles Design LLC

> -Original Message-
>  From: time-nuts [mailto:time-nuts-boun...@febo.com] On Behalf Of Mike
>  Feher
> Sent: Thursday, August 11, 2016 12:51 PM
> To: 'Discussion  of precise time and frequency measurement';
> ka2...@aol.com;  t...@leapsecond.com
> Cc: enrico.rubi...@gmail.com
> Subject: Re:  [time-nuts] State of the art of crystal oscillator 
measurements
>  
> kT is indeed relevant for a physical implementation. - Mike
>  
> Mike B. Feher, EOZ Inc.
> 89 Arnold Blvd.
> Howell, NJ,  07731
> 732-886-5960 office
> 908-902-3831  cell

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Re: [time-nuts] State of the art of crystal oscillator measurements

NO, the maximum  possible noise dynamic range is ( 177 +  Pout)  [dBm]  - 
Transistor large signal NF ( dB),
 the signal to noise ration is dimensionless 

In a message dated 8/11/2016 5:00:43 P.M. Eastern Daylight Time,  
j...@miles.io writes:

Or  rather -(177+DUT output power in dBm).  The minus sign makes the  
difference between the thermal floor and a nuclear war!

-- john,  KE5FX
Miles Design LLC

> Remember that L(f) is expressed in  dBc/Hz, not dBm/Hz.  If it were 
dBm/Hz,
> then kT would be the  limit.  But in dBc/Hz terms, the limit is 177 + the 
DUT's
> output  power in  dBm.

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Re: [time-nuts] State of the art of crystal oscillator measurements

Or rather -(177+DUT output power in dBm).  The minus sign makes the difference 
between the thermal floor and a nuclear war!

-- john, KE5FX
Miles Design LLC

> Remember that L(f) is expressed in dBc/Hz, not dBm/Hz.  If it were dBm/Hz,
> then kT would be the limit.  But in dBc/Hz terms, the limit is 177 + the DUT's
> output power in dBm.


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Re: [time-nuts] State of the art of crystal oscillator measurements

See below 

In a message dated 8/11/2016 4:30:47 P.M. Eastern Daylight Time,  
j...@miles.io writes:

Remember  that L(f) is expressed in dBc/Hz, not dBm/Hz.  If it were dBm/Hz, 
then kT  would be the limit.  But in dBc/Hz terms, the limit  is 177 + the 
DUT's output power in dBm - transistor large signal NF in dB  .  

Assuming a 50 ohm system, of course.

-- john,  KE5FX
Miles Design LLC

> -Original Message-
>  From: time-nuts [mailto:time-nuts-boun...@febo.com] On Behalf Of Mike
>  Feher
> Sent: Thursday, August 11, 2016 12:51 PM
> To: 'Discussion  of precise time and frequency measurement';
> ka2...@aol.com;  t...@leapsecond.com
> Cc: enrico.rubi...@gmail.com
> Subject: Re:  [time-nuts] State of the art of crystal oscillator 
measurements
>  
> kT is indeed relevant for a physical implementation. - Mike
>  
> Mike B. Feher, EOZ Inc.
> 89 Arnold Blvd.
> Howell, NJ,  07731
> 732-886-5960 office
> 908-902-3831  cell

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Re: [time-nuts] Safely getting the electrical length of a connectedantenna feedline

2016-08-11 Thread Tom Van Baak

FYI: In Didier's post below, the correct URL is:

http://www.ko4bb.com/getsimple/index.php?id=coax-cable-impedance-matching

I'm guessing a mobile spell checker changed his " id= " to " I'd= " (even 
though it was part of a URL).

/tvb

- Original Message - 
From: "Didier Juges" 
To: "Bob Albert" ; "Discussion of precise time and 
frequency measurement" 
Sent: Thursday, August 11, 2016 11:20 AM
Subject: Re: [time-nuts] Safely getting the electrical length of a 
connectedantenna feedline


I used the PPS from a Thunderbolt (fast rise lime, low rep frequency, was 
handy) and a digital storage scope and a couple of resistors to make a 
reflectometer based on this experiment:

www.ko4bb.com/getsimple/index.php?I'd=coax-cable-impedance-matching

You can very clearly see a 50 ohm/75 ohm mismatch.

The biggest variable will be the velocity factor.

Didier KO4BB


On August 8, 2016 2:18:02 PM CDT, Bob Albert via time-nuts  
wrote:
>I host a group called something like HF Antennas. There I posted a
>link to an article on how to measure coaxial cable. The easiest way is
>with a spectrum analyzer and a tracking generator.
>You connect the generator to the analyzer through a Tee that goes to
>the unknown coax. You will see a group of peaks and nulls over the
>spectrum. The spacing is a half wave of the cable. The match needs to
>not be good to see the nulls best, and you will need to know the
>propagation constant of the cable. Chances are, the match won't be
>good over the entire range so you are okay with that. Propagation
>constant of most coaxial cable runs around 66%.
>You can also use a TDR setup but you'll have to make one, with a pulser
>and a 'scope. I downloaded a circuit for a pulser that uses one IC. I
>have the parts but haven't built it yet, as I am stalled by the problem
>of connecting to a 14 pin SMD part. The IC uses one part as an
>oscillator and the other 5 in parallel to drive 50 Ohms. Again, you
>use a Tee and measure the time for a reflection, bearing in mind that
>the trip is two ways over the same cable and the time shown will be
>double the time for the calculation.
>Bob
> 
>
>On Monday, August 8, 2016 12:00 PM, Bob Stewart  wrote:
> 
>
>Earlier this year, with some help, I pulled the dish off of an old
>DishTV antenna on the roof and put a 5V bullet antenna on the mast. I
>also pulled a new cable through by attaching it to the old one. The
>problem is that I was not able to measure the new cable. So, the
>question is, without going back on the roof in this heat, how can I
>measure the electrical length of the line I pulled? 
>
>I was thinking of using my 8640B signal generator and sending some RF
>back up the line to get a quarter wavelength at the null. But that
>assumes a lot, including that the other end is open at 3MHz, or
>whatever the frequency works out to be, as well as that the high
>voltage on the antenna end won't be high enough to blow the LNA.
>
>So, how much RF I can safely send up the line? I've got an 8558B
>spectrum analyzer, but it's not on the bench, and it would be easier to
>use my scope, which sadly is a 70s vintage Tek 455. Do I put this all
>together with a lead from the generator to a tee at the measuring
>device and tune for a null? My experience at getting precise
>measurements on anything longer than a few inches is effectively none,
>but I'd guess that I want less than 0.5V at the LNA during this test. 
>Oh, and I do have an 8444A tracking generator that can output -10 dbm
>as well as a 10 db attenuator within easy access. That could get a
>quick spot on the null point.
>
>Most importantly, of course is the question of whether this will even
>work. 
>
>Bob -
>AE6RV -
>AE6RV.com
>
>GFS GPSDO list:
>groups.yahoo.com/neo/groups/GFS-GPSDOs/info
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-- 
Sent from my Moto-X wireless tracker while I do other things.
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Re: [time-nuts] State of the art of crystal oscillator measurements

Remember that L(f) is expressed in dBc/Hz, not dBm/Hz.  If it were dBm/Hz, then 
kT would be the limit.  But in dBc/Hz terms, the limit is 177 + the DUT's 
output power in dBm.  

Assuming a 50 ohm system, of course.

-- john, KE5FX
Miles Design LLC


> -Original Message-
> From: time-nuts [mailto:time-nuts-boun...@febo.com] On Behalf Of Mike
> Feher
> Sent: Thursday, August 11, 2016 12:51 PM
> To: 'Discussion of precise time and frequency measurement';
> ka2...@aol.com; t...@leapsecond.com
> Cc: enrico.rubi...@gmail.com
> Subject: Re: [time-nuts] State of the art of crystal oscillator measurements
> 
> kT is indeed relevant for a physical implementation. - Mike
> 
> Mike B. Feher, EOZ Inc.
> 89 Arnold Blvd.
> Howell, NJ, 07731
> 732-886-5960 office
> 908-902-3831 cell

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Re: [time-nuts] Low cost SDR suitable for phase noise measurement?

Hi

Just to clarify:

You are looking for a way to digitize the output(s) of the mixer(s) in a DMTD. 
The 
“target signal” is in the 1 to 10 Hz range.

Is that correct or are you looking for something to use instead of a DMTD? 

Bob


> On Aug 11, 2016, at 3:29 PM, Bob Stewart  wrote:
> 
> Hi Brooke,
> It looks like I've asked a question poorly, yet again.  So, let me try again. 
>  I have this idea of combining a DMTD with an SDR.  So, said that way, it 
> looks like what I really need is a 2-channel audio SDR.  And having said 
> that, maybe what I'm looking for is an external USB sound card.  Those I can 
> find.  I can probably even figure out how to convert them to DC and supply 
> them with a disciplined oscillator, if needed.
> 
> Bob
>  -
> AE6RV.com
> 
> GFS GPSDO list:
> groups.yahoo.com/neo/groups/GFS-GPSDOs/info
> 
>  From: Brooke Clarke 
> To: Discussion of precise time and frequency measurement  
> Sent: Thursday, August 11, 2016 1:36 PM
> Subject: Re: [time-nuts] Low cost SDR suitable for phase noise measurement?
> 
> Hi Bob:
> 
> The SDR-IQ has a lower frequency limit of 500 Hz.
> http://www.prc68.com/I/Bats.shtml#SDRIQ
> 
> There is a mod that replaces the on board 66 MHz oscillator with one locked 
> to 10 MHz.
> 
> -- 
> Have Fun,
> 
> Brooke Clarke, N6GCE
> http://www.PRC68.com
> http://www.end2partygovernment.com/2012Issues.html
> The lesser of evils is still evil.
> 
>  Original Message 
>> A number of posts have appeared about Zynq SDRs on the "Shera revisited" 
>> thread.  So, I'd like to ask the more general question: Are there any low 
>> cost SDRs that are suitable for measuring phase noise when coupled with a 
>> DMTD?  I believe what I'm looking for is something with enough bits to work 
>> in the audio range down to DC.  Yes, I could use a modified sound card, but 
>> I'm really looking for something not sound card related.  My thought was to 
>> use a DMTD with a heterodyne frequency of maybe 5KHz.
>> 
>> Bob -
>> AE6RV.com
>> 
>> GFS GPSDO list:
>> groups.yahoo.com/neo/groups/GFS-GPSDOs/info
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Re: [time-nuts] State of the art of crystal oscillator measurements

kT is indeed relevant for a physical implementation. - Mike 

Mike B. Feher, EOZ Inc.
89 Arnold Blvd.
Howell, NJ, 07731
732-886-5960 office
908-902-3831 cell

-Original Message-
From: time-nuts [mailto:time-nuts-boun...@febo.com] On Behalf Of Richard (Rick) 
Karlquist
Sent: Thursday, August 11, 2016 1:40 PM
To: Discussion of precise time and frequency measurement; ka2...@aol.com; 
t...@leapsecond.com
Cc: enrico.rubi...@gmail.com
Subject: Re: [time-nuts] State of the art of crystal oscillator measurements

On 8/11/2016 5:01 AM, Mike Feher wrote:

> This may be a naive question, but, how can you achieve results that 
> are so close to, and sometimes at further out are below kT? Thanks & 
> 73 - Mike

> Mike B. Feher, EOZ Inc.
>

kT per see is not the relevant parameter.  It is the ratio between kT and 
signal level that determines the limit on phase noise.  Also, when you extract 
an oscillator signal through the resonator, then at offsets from the carrier, 
the resonator filters out noise and the output noise can be way below kT.  
Ulrich first published on this in 1977.  Earliest reference I know of.
I actually remember reading it in 1977.

The old HP608 signal generator routinely produced far out phase noise floor 
well below kT.  AFAIK, for this particular spec, it better than any other 
signal generator ever built.  What's the secret?  It has a tracking 
POST-selector filter that follows the oscillator when you turn the mechanical 
tuning knob.  There is a little tracking adjustment knob to peak it.  Not 
really magic.

Rick
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Re: [time-nuts] Low cost SDR suitable for phase noise measurement?

Hi Brooke,
It looks like I've asked a question poorly, yet again.  So, let me try again.  
I have this idea of combining a DMTD with an SDR.  So, said that way, it looks 
like what I really need is a 2-channel audio SDR.  And having said that, maybe 
what I'm looking for is an external USB sound card.  Those I can find.  I can 
probably even figure out how to convert them to DC and supply them with a 
disciplined oscillator, if needed.

Bob
 -
AE6RV.com

GFS GPSDO list:
groups.yahoo.com/neo/groups/GFS-GPSDOs/info

  From: Brooke Clarke 
 To: Discussion of precise time and frequency measurement  
 Sent: Thursday, August 11, 2016 1:36 PM
 Subject: Re: [time-nuts] Low cost SDR suitable for phase noise measurement?
   
Hi Bob:

The SDR-IQ has a lower frequency limit of 500 Hz.
http://www.prc68.com/I/Bats.shtml#SDRIQ

There is a mod that replaces the on board 66 MHz oscillator with one locked to 
10 MHz.

-- 
Have Fun,

Brooke Clarke, N6GCE
http://www.PRC68.com
http://www.end2partygovernment.com/2012Issues.html
The lesser of evils is still evil.

 Original Message 
> A number of posts have appeared about Zynq SDRs on the "Shera revisited" 
> thread.  So, I'd like to ask the more general question: Are there any low 
> cost SDRs that are suitable for measuring phase noise when coupled with a 
> DMTD?  I believe what I'm looking for is something with enough bits to work 
> in the audio range down to DC.  Yes, I could use a modified sound card, but 
> I'm really looking for something not sound card related.  My thought was to 
> use a DMTD with a heterodyne frequency of maybe 5KHz.
>
> Bob -
> AE6RV.com
>
> GFS GPSDO list:
> groups.yahoo.com/neo/groups/GFS-GPSDOs/info
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Re: [time-nuts] Shera revisted

2016-08-11 Thread Attila Kinali

Hoi Bert,

On Wed, 10 Aug 2016 09:33:30 -0400
Bert Kehren via time-nuts  wrote:

> I get repeated requests for info on Shera mainly for Rb applications. Shera 
>  has a successful history controlling Rb's.  Two things are a problem. The  
> AD 1861 is not only unavailable but also never intended for precise DAC  
> applications. The LTC 1655 makes a perfect replacement ,16 bits is more than  
> enough and covers range and resolution. What is needed is someone proficient 
>  with PIC assembly programming. We have the recommended changes.
> Second logic IC's are also outdated and hard to get. The solution is simple 
>  an Altera 32 cell 10 nsec. gate array, readily still available for less 
> than $  2, we have done a design and will gladly share once the PIC has been 
> modified  and tetsted.

What is your goal here? Simply a rebuild of the Shera controller
using current components?

I'm asking, because if you go the way of using a CPLD anyways, you could
throw in another $2 for an opamp to build a time-to-amplitude converter
(à la PICTIC II) and boost the resolutiong from 40ns to <100ps.
As you would be measuring the PPS relative to the local clock, you
would need only one "leg" of the PICTIC II (ie just one TAC plus a single ADC).

I guess you were refering to the 5M40Z from Altera, which can be had
for $1 at mouser. If you go slightly up in price to $1.5, you can get
an ICE40LP384 from Lattice with 384 LUTs, wastly enhancing your capabilities.

Yes, that would require a bit more than just changing a couple of
asm instructions, but would be worthwhile nontheless.
Especially if you are going to extend the system with pressure and
temperature compenstation anyways.

And I am with Chris on the topic of rewriting it in C, even if it's more
effort. Depending on what you actually do, part of the code can be
reused from open source projects out there, thus minimizing the actual work.

Attila Kinali

PS: If you are doing the CPLD/FPGA coding in VHDL and need help, let me know.

-- 
Malek's Law:
Any simple idea will be worded in the most complicated way.
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Re: [time-nuts] Safely getting the electrical length of a connected antenna feedline

Why is velocity factor an issue?  Aren't we only interested in the electrical 
time from one end of the coax to the other?
Bob
 -
AE6RV.com

GFS GPSDO list:
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  From: Didier Juges 
 To: Bob Albert ; Discussion of precise time and frequency 
measurement  
 Sent: Thursday, August 11, 2016 1:20 PM
 Subject: Re: [time-nuts] Safely getting the electrical length of a connected 
antenna feedline
   
I used the PPS from a Thunderbolt (fast rise lime, low rep frequency, was 
handy) and a digital storage scope and a couple of resistors to make a 
reflectometer based on this experiment:

www.ko4bb.com/getsimple/index.php?I'd=coax-cable-impedance-matching

You can very clearly see a 50 ohm/75 ohm mismatch.

The biggest variable will be the velocity factor.

Didier KO4BB

  
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Re: [time-nuts] Working with SMT parts.

2016-08-11 Thread Bob Darlington

I use a Nikon and a Meiji that I picked up surplus on the cheap.

Lighting matters.  Fostec ring illuminators are okay, but I prefer
something with gooseneck arms so I actually do have shadows.  Light from a
particular angle can help rather than nice uniform illumination.

#1 recommendation I have for a stereo microscope for soldering use is get
one that can take a filter disc.  In the very least put some saran wrap
around the bottom.  Condensing flux vapors make a mess of the optics over
the years.

#2 is recognizing you don't need all that much magnification to do the
work.  50x is a lot of magnification.  Way more than you need for 0402
parts.

I've also found that brains are a pretty amazing PID controller.  10x
magnification seems to result in 1/10th the hand shake.

-Bob


On Thu, Aug 11, 2016 at 11:24 AM, Bob Albert via time-nuts <
time-nuts@febo.com> wrote:

> What are the important parameters regarding purchase of a stereo
> microscope?  I see some on ebay for around $50; are those good?
> Bob
>
>
> On Thursday, August 11, 2016 10:00 AM, Didier Juges <
> shali...@gmail.com> wrote:
>
>
>  I concur. I have been using ExpressPCB extensively over the last 2 years
> with great satisfaction now that it is possible to get Gerber files from
> them.
> I typically use the mini board pro service (3 bare boards, 2 sided with
> solder mask and silk screen) for prototypes and then buy the Gerbers to
> have production quantities done overseas.
> The boards are of high quality and the service is very fast at a very
> reasonable price.
> The only gotcha with regard to Gerber files is that you can only buy
> Gerbers for boards that you have actually bought from them, so the process
> is to buy the prototypes, then if you are happy with those, buy the Gerbers
> for that design.
>
> Didier KO4BB
>
> On Tue, Aug 9, 2016 at 3:06 PM, Brooke Clarke  wrote:
>
> > Hi:
> >
> > I've had good luck using any of the the ExpressPCB services that include
> > solder mask with surface mount parts where the pitch is 0.05" (half
> normal
> > DIP) and hand soldering (requires stereo microscope).
> > http://www.prc68.com/I/BTSG.shtml (battery top signal generator)
> > http://www.prc68.com/I/Images/ICS525v1o.jpg
> >
> > http://www.prc68.com/I/SMT.shtml 
> >
> > --
> > Have Fun,
> >
> > Brooke Clarke
> > http://www.PRC68.com
> > http://www.end2partygovernment.com/2012Issues.html
> > The lesser of evils is still evil.
> >
> >
> > ___
> > time-nuts mailing list -- time-nuts@febo.com
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> > ailman/listinfo/time-nuts
> > and follow the instructions there.
> >
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Re: [time-nuts] Working with SMT parts.

2016-08-11 Thread Brooke Clarke

Hi Bob:

I don't think it's so much the stereo microscope as the related equipment. I have a Bausch & Lomb StereoZoom 4 and the
dial is always at the lowest setting (0.7dial * 10X objective = 7 power).

For another reason I got a Nikon SMZ-U microscope and discovered that it's so
tall that it can not be used for SMT work.
http://www.prc68.com/I/NikonSMZ-U.html
So an important parameter is is length from the eyepiece to the objective. If that get to be long then you can not
easily use it.

Using an arm type support is very desirable. These have a heavy metal base with an horizontal arm. You can swing the
arm over whatever you're working one and easily move the scope up or down as needed.

This all done while in a standard chair on a work bench/table.

Although an old fashioned illuminator will work, see top photo:
http://www.prc68.com/I/SMT.shtml#Mag
A ring light is much more convenient (scroll down a little).

Also the soldering iron tip to grip distance should be as short as you can get. (1.5" = burned fingers, 0.5" should be
better)

--
Have Fun,

Brooke Clarke
http://www.PRC68.com
http://www.end2partygovernment.com/2012Issues.html
The lesser of evils is still evil.

Original Message

What are the important parameters regarding purchase of a stereo microscope? I
see some on ebay for around $50; are those good?
Bob

On Thursday, August 11, 2016 10:00 AM, Didier Juges
wrote:

I concur. I have been using ExpressPCB extensively over the last 2 years
with great satisfaction now that it is possible to get Gerber files from
them.
I typically use the mini board pro service (3 bare boards, 2 sided with
solder mask and silk screen) for prototypes and then buy the Gerbers to
have production quantities done overseas.
The boards are of high quality and the service is very fast at a very
reasonable price.
The only gotcha with regard to Gerber files is that you can only buy
Gerbers for boards that you have actually bought from them, so the process
is to buy the prototypes, then if you are happy with those, buy the Gerbers
for that design.

Didier KO4BB

On Tue, Aug 9, 2016 at 3:06 PM, Brooke Clarke wrote:

Hi:

I've had good luck using any of the the ExpressPCB services that include
solder mask with surface mount parts where the pitch is 0.05" (half normal
DIP) and hand soldering (requires stereo microscope).
http://www.prc68.com/I/BTSG.shtml (battery top signal generator)
http://www.prc68.com/I/Images/ICS525v1o.jpg

http://www.prc68.com/I/SMT.shtml

--
Have Fun,

Brooke Clarke
http://www.PRC68.com
http://www.end2partygovernment.com/2012Issues.html
The lesser of evils is still evil.

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Re: [time-nuts] Working with SMT parts.

2016-08-11 Thread Brooke Clarke

Hi Didier:

Another option is to send the free ExpressPCB files to FAR Circuits for production. This can be very cost effective if
you only need a simple circuit. Vias not supported.

www.farcircuits.net/EXPRESS%20PCB%20DOC.doc

--
Have Fun,

Brooke Clarke
http://www.PRC68.com
http://www.end2partygovernment.com/2012Issues.html
The lesser of evils is still evil.

Original Message

Didier KO4BB

On Tue, Aug 9, 2016 at 3:06 PM, Brooke Clarke wrote:

Hi:

http://www.prc68.com/I/SMT.shtml

--
Have Fun,

Brooke Clarke
http://www.PRC68.com
http://www.end2partygovernment.com/2012Issues.html
The lesser of evils is still evil.

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Re: [time-nuts] Working with SMT parts.

Hi Bob,
You want to get something along the lines of ebay item 272331719376 or 
262202931320.  The boom is pretty important, otherwise how do you get your 
boards under the microscope if they're not very small?  Some time ago, I got a 
Bausch & Lomb Stereo 3 with 10X oculars and a 0.5 barlow.  The zoom scale on 
the scope reads 0.7 to 3.  This, combined with the 10X oculars gives it a zoom 
range of 7X to 30X.  This is a bit strong for doing PCB work, so the 0.5 barlow 
cuts that in half to 3.5X to 15X which is just about right.  I leave the boom 
at the right height to do soldering on the bench, but don't have the lateral 
thumbscrew on the boom tightened, so I can move the scope left and right or out 
of the way.  I wouldn't pay extra for a fancy light system like you'll see on 
many auctions.  Instead, I bought an LED light ring to go around the barlow 
lens on the bottom.  It has a brightness control, so it works out well.

As far as the board suppliers, I tried ExpressPCB at first, but they're pretty 
expensive, and you're stuck with their board size.  So, I switched to 
OshPark.com.  They don't supply proprietary board design software, which is 
fine, because there is a free version of Eagle, or you can use Kicad like I do. 
 (Kicad can output Gerber files.)  I believe that both Mouser and DigiKey have 
free board design software, as well.  But, the risk with those is that they 
either go away or become pay systems.
Bob - AE6RV
 -
AE6RV.com

GFS GPSDO list:
groups.yahoo.com/neo/groups/GFS-GPSDOs/info

  From: Bob Albert via time-nuts 
 To: Discussion of precise time and frequency measurement  
 Sent: Thursday, August 11, 2016 12:24 PM
 Subject: Re: [time-nuts] Working with SMT parts.
   
What are the important parameters regarding purchase of a stereo microscope?  I 
see some on ebay for around $50; are those good?
Bob
 

  
  
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Re: [time-nuts] Low cost SDR suitable for phase noise measurement?

2016-08-11 Thread Brooke Clarke


Hi Bob:

The SDR-IQ has a lower frequency limit of 500 Hz.
http://www.prc68.com/I/Bats.shtml#SDRIQ

There is a mod that replaces the on board 66 MHz oscillator with one locked to 
10 MHz.

--
Have Fun,

Brooke Clarke, N6GCE
http://www.PRC68.com
http://www.end2partygovernment.com/2012Issues.html
The lesser of evils is still evil.

 Original Message 

A number of posts have appeared about Zynq SDRs on the "Shera revisited" 
thread.  So, I'd like to ask the more general question: Are there any low cost SDRs that 
are suitable for measuring phase noise when coupled with a DMTD?  I believe what I'm 
looking for is something with enough bits to work in the audio range down to DC.  Yes, I 
could use a modified sound card, but I'm really looking for something not sound card 
related.  My thought was to use a DMTD with a heterodyne frequency of maybe 5KHz.

Bob -
AE6RV.com

GFS GPSDO list:
groups.yahoo.com/neo/groups/GFS-GPSDOs/info
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Re: [time-nuts] Safely getting the electrical length of a connected antenna feedline

2016-08-11 Thread Didier Juges

I used the PPS from a Thunderbolt (fast rise lime, low rep frequency, was 
handy) and a digital storage scope and a couple of resistors to make a 
reflectometer based on this experiment:

www.ko4bb.com/getsimple/index.php?I'd=coax-cable-impedance-matching

You can very clearly see a 50 ohm/75 ohm mismatch.

The biggest variable will be the velocity factor.

Didier KO4BB


On August 8, 2016 2:18:02 PM CDT, Bob Albert via time-nuts  
wrote:
>I host a group called something like HF Antennas.  There I posted a
>link to an article on how to measure coaxial cable.  The easiest way is
>with a spectrum analyzer and a tracking generator.
>You connect the generator to the analyzer through a Tee that goes to
>the unknown coax.  You will see a group of peaks and nulls over the
>spectrum.  The spacing is a half wave of the cable.  The match needs to
>not be good to see the nulls best, and you will need to know the
>propagation constant of the cable.  Chances are, the match won't be
>good over the entire range so you are okay with that.  Propagation
>constant of most coaxial cable runs around 66%.
>You can also use a TDR setup but you'll have to make one, with a pulser
>and a 'scope.  I downloaded a circuit for a pulser that uses one IC.  I
>have the parts but haven't built it yet, as I am stalled by the problem
>of connecting to a 14 pin SMD part.  The IC uses one part as an
>oscillator and the other 5 in parallel to drive 50 Ohms.  Again, you
>use a Tee and measure the time for a reflection, bearing in mind that
>the trip is two ways over the same cable and the time shown will be
>double the time for the calculation.
>Bob
> 
>
>On Monday, August 8, 2016 12:00 PM, Bob Stewart  wrote:
> 
>
>Earlier this year, with some help, I pulled the dish off of an old
>DishTV antenna on the roof and put a 5V bullet antenna on the mast.  I
>also pulled a new cable through by attaching it to the old one.  The
>problem is that I was not able to measure the new cable.  So, the
>question is, without going back on the roof in this heat, how can I
>measure the electrical length of the line I pulled?  
>
>I was thinking of using my 8640B signal generator and sending some RF
>back up the line to get a quarter wavelength at the null.  But that
>assumes a lot, including that the other end is open at 3MHz, or
>whatever the frequency works out to be, as well as that the high
>voltage on the antenna end won't be high enough to blow the LNA.
>
>So, how much RF I can safely send up the line?  I've got an 8558B
>spectrum analyzer, but it's not on the bench, and it would be easier to
>use my scope, which sadly is a 70s vintage Tek 455.  Do I put this all
>together with a lead from the generator to a tee at the measuring
>device and tune for a null?  My experience at getting precise
>measurements on anything longer than a few inches is effectively none,
>but I'd guess that I want less than 0.5V at the LNA during this test. 
>Oh, and I do have an 8444A tracking generator that can output -10 dbm
>as well as a 10 db attenuator within easy access.  That could get a
>quick spot on the null point.
>
>Most importantly, of course is the question of whether this will even
>work.  
>
>Bob -
>AE6RV -
>AE6RV.com
>
>GFS GPSDO list:
>groups.yahoo.com/neo/groups/GFS-GPSDOs/info
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>  
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Re: [time-nuts] Working with SMT parts.

2016-08-11 Thread Bob Albert via time-nuts

What are the important parameters regarding purchase of a stereo microscope?  I 
see some on ebay for around $50; are those good?
Bob

On Thursday, August 11, 2016 10:00 AM, Didier Juges  
wrote:

 I concur. I have been using ExpressPCB extensively over the last 2 years
with great satisfaction now that it is possible to get Gerber files from
them.
I typically use the mini board pro service (3 bare boards, 2 sided with
solder mask and silk screen) for prototypes and then buy the Gerbers to
have production quantities done overseas.
The boards are of high quality and the service is very fast at a very
reasonable price.
The only gotcha with regard to Gerber files is that you can only buy
Gerbers for boards that you have actually bought from them, so the process
is to buy the prototypes, then if you are happy with those, buy the Gerbers
for that design.

Didier KO4BB

On Tue, Aug 9, 2016 at 3:06 PM, Brooke Clarke  wrote:

> Hi:
>
> I've had good luck using any of the the ExpressPCB services that include
> solder mask with surface mount parts where the pitch is 0.05" (half normal
> DIP) and hand soldering (requires stereo microscope).
> http://www.prc68.com/I/BTSG.shtml (battery top signal generator)
> http://www.prc68.com/I/Images/ICS525v1o.jpg
>
> http://www.prc68.com/I/SMT.shtml 
>
> --
> Have Fun,
>
> Brooke Clarke
> http://www.PRC68.com
> http://www.end2partygovernment.com/2012Issues.html
> The lesser of evils is still evil.
>
>
> ___
> time-nuts mailing list -- time-nuts@febo.com
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> ailman/listinfo/time-nuts
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>
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[time-nuts] Low cost SDR suitable for phase noise measurement?

A number of posts have appeared about Zynq SDRs on the "Shera revisited" 
thread.  So, I'd like to ask the more general question: Are there any low cost 
SDRs that are suitable for measuring phase noise when coupled with a DMTD?  I 
believe what I'm looking for is something with enough bits to work in the audio 
range down to DC.  Yes, I could use a modified sound card, but I'm really 
looking for something not sound card related.  My thought was to use a DMTD 
with a heterodyne frequency of maybe 5KHz.

Bob -
AE6RV.com

GFS GPSDO list:
groups.yahoo.com/neo/groups/GFS-GPSDOs/info
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Re: [time-nuts] State of the art of crystal oscillator measurements

2016-08-11 Thread Richard (Rick) Karlquist




On 8/11/2016 5:01 AM, Mike Feher wrote:


This may be a naive question, but, how can you achieve results that are so
close to, and sometimes at further out are below kT? Thanks & 73 - Mike



Mike B. Feher, EOZ Inc.



kT per see is not the relevant parameter.  It is the
ratio between kT and signal level that determines the
limit on phase noise.  Also, when you extract an
oscillator signal through the resonator, then at offsets
from the carrier, the resonator filters out noise and
the output noise can be way below kT.  Ulrich first
published on this in 1977.  Earliest reference I know of.
I actually remember reading it in 1977.

The old HP608 signal generator routinely produced far
out phase noise floor well below kT.  AFAIK, for this
particular spec, it better than any other signal generator
ever built.  What's the secret?  It has a tracking
POST-selector filter that follows the oscillator when
you turn the mechanical tuning knob.  There is a little
tracking adjustment knob to peak it.  Not really magic.

Rick
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Re: [time-nuts] Working with SMT parts.

2016-08-11 Thread Didier Juges

I concur. I have been using ExpressPCB extensively over the last 2 years
with great satisfaction now that it is possible to get Gerber files from
them.
I typically use the mini board pro service (3 bare boards, 2 sided with
solder mask and silk screen) for prototypes and then buy the Gerbers to
have production quantities done overseas.
The boards are of high quality and the service is very fast at a very
reasonable price.
The only gotcha with regard to Gerber files is that you can only buy
Gerbers for boards that you have actually bought from them, so the process
is to buy the prototypes, then if you are happy with those, buy the Gerbers
for that design.

Didier KO4BB

On Tue, Aug 9, 2016 at 3:06 PM, Brooke Clarke  wrote:

> Hi:
>
> I've had good luck using any of the the ExpressPCB services that include
> solder mask with surface mount parts where the pitch is 0.05" (half normal
> DIP) and hand soldering (requires stereo microscope).
> http://www.prc68.com/I/BTSG.shtml (battery top signal generator)
> http://www.prc68.com/I/Images/ICS525v1o.jpg
>
> http://www.prc68.com/I/SMT.shtml 
>
> --
> Have Fun,
>
> Brooke Clarke
> http://www.PRC68.com
> http://www.end2partygovernment.com/2012Issues.html
> The lesser of evils is still evil.
>
>
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Re: [time-nuts] PRS10

2016-08-11 Thread Mike Cook


> Le 11 août 2016 à 12:15, Martyn Smith  a écrit :
> 
> Hello,
> 
> I have a strange fault on a PRS10.  Wondered if anyone had seen it.
> 
> I am running a PRS10 and at the same time monitoring its FC (the frequency 
> control value) and Status byte data values.
> 
> So normally, the Status shows are all zeros, except 2nd from last is a 1, 
> showing the unit is not receiving any 1 pps signals.
> 
> What happens is the FC value suddenly jumps from its current setting (-150 
> for example) to zero, for no apparent reason.  

if -150 is really what you saw, then it is out of bounds as the two values 
returned by fc? are both +ve.
if they go to zero, check the eeprom values
fc!?
58,5485,1534,1434  for example
If they are reasonable then possible the eeprom is not being read correctly 
after reset. 

> 
> Then a short while later, the Rubidium's status bytles go crazy, mostly to FF.

This indicates a microprocessor reset .  After a power cycle you can see:
st? 
255,255,255,243,162,255  ie most  FF
when you read again you get the current values
st?
0,0,0,0,130,0 for example
then if you reset the microprocessor
RS 1
PRS_10
st?
255,255,255,243,162,255  back to the initial state 
st?
0,0,0,0,130,0

So it looks like you are getting resets. Possibly from brown outs. Maybe a low 
power condition at reset prevents eprom data being read correctly.

Are the affected RBs on the same power supplies? 


> 
> Then the rubidium goes back to the previous correct state (all zeros) but the 
> FC value is now zero.
> 
> If you do connect a 1 pps, you get the same fault.
> 
> The confusing thing is I've suddenly seen this on 3 or 4 different 
> rubidium's.  Some brand new, some five years old. 
> 
> Obviously suspect the power supply, but it doesn't seem to be that.
> 
> Best Regards
> 
> Martyn 
> 
> 
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"The power of accurate observation is commonly called cynicism by those who 
have not got it. »
George Bernard Shaw

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[time-nuts] Looking to find an antenna for a TrueTime XL-DC

2016-08-11 Thread Gregory Beat

Here is the Manual for the True Time XL-DC (circa 1997-1999)
http://glacier.lbl.gov/gtp/DOM/Support/xl-dc-manual.pdf

gb

Sent from iPad Air
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Re: [time-nuts] Shera revisted

2016-08-11 Thread bownes


There are also some nice cypresses semiconductor parts that are similar and 
have a really nice dev environment. 
Basically a core surrounded by programmable logic. Code in C ore close to it. 



> On Aug 11, 2016, at 07:06, Bob Camp  wrote:
> 
> Hi
> 
> To your earlier point, there are a number of fairly low cost boards with 
> Zynq’s on them. 
> They aren’t into the $5 range, but they are not that much more than one of 
> the Beagle 
> boards. 
> 
> Bob
> 
> 
>> On Aug 10, 2016, at 11:18 PM, Chris Albertson  
>> wrote:
>> 
>> Thanks for pointing out the Zynq.  Wow you get a dual core ARM and an
>> FPGA all in one package.   It seems overkill for a GPSDO but not the
>> type you are making as you can transferring the time out of the GPSDO
>> using PTP.
>> 
>> The Zyng looks to the the perfect platform for low-cost SDR.
>> 
>> On Wed, Aug 10, 2016 at 2:30 PM, Joakim Langlet
>>  wrote:
>>> Dear time-nuts,
>>> 
>>> My name is Joakim Langlet (SM0OET) and I just recently joined this list. As
>>> Brooks Shera was mentioned, I remembered that I was referenced in the
>>> footnotes of the original article in the QST - July 1998. It feels almost
>>> historical now. Brooks bought a few OCXOs from me.
>>> 
>>> I am currently working on a GPS stabilized OCXO.
>>> It is based on a Xilinx Zynq FPGA as the processor and counter arrangement.
>>> The hardware is starting to take shape. The control voltage of a 20 MHz OCXO
>>> is set by a DAC coupling from which I hope to set the voltage in very small
>>> steps.
>>> The OCXO has a CMOS level output which is converted to LVDS and is wired to
>>> the FPGA board. The Xilinx Zynq take a minimum frequency of 19 MHz as input
>>> to the PLL of the clock tile. My intention is to scale up the clock to some
>>> where a bit over 200 MHz to be fed to the counters.The 1 PPS from the GPS
>>> receiver is also fed into the FPGA to gate the counters.
>>> 
>>> The reason for my choice of processor is that I want to run Linux on it in
>>> order benefit from the large software base. Time distribution using PTPv2
>>> and a nice web-application to visualize and control what is going on inside
>>> is part of the intended concept.
>>> 
>>> I still have a long way to the finish line but I will try to present some
>>> results as I proceed.
>>> 
>>> I am following what is written on this list with great interest. It feels
>>> good to know that I am not the only nut 
>>> 
>>> BR/
>>> Joakim
>>> ___
>>> 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.
>> 
>> 
>> 
>> -- 
>> 
>> Chris Albertson
>> Redondo Beach, California
>> ___
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> 
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[time-nuts] KO4BB Manuals

2016-08-11 Thread Didier Juges

Thank you to those who let me know of an issue with my Manuals site last
week and this week.

It turns out that the primary issue was not lack of disk space (even though
that was going to be an issue very soon, so that has been fixed
preemptively) but an issue with the download app.

In the process of fixing this (which is now complete), I noticed that about
3.7 millions pdf documents have been downloaded from my site through the
manuals download app since October 2014. That's about 168,000/month average.

The time-nuts group as a whole has been supplying a significant portion of
the visitors overall but by far the biggest downloader has been the Chinese
site Baidu. It seems like they have downloaded the 26,000 files I have
several times over... Still a very small fraction of the total, which
includes visitors from over 200 countries.

Thank you all for your participation and support!

Didier KO4BB

www.ko4bb.com
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Re: [time-nuts] State of the art of crystal oscillator measurements

2016-08-11 Thread David J Taylor


Ulrich -

This may be a naive question, but, how can you achieve results that are so
close to, and sometimes at further out are below kT? Thanks & 73 - Mike 


Mike B. Feher, EOZ Inc.
===

.. by reducing T?

David
--
SatSignal Software - Quality software written to your requirements
Web: http://www.satsignal.eu
Email: david-tay...@blueyonder.co.uk
Twitter: @gm8arv
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Re: [time-nuts] Heathkit clock available

2016-08-11 Thread jimlux


On 8/10/16 8:03 PM, Chris Albertson wrote:


But for sure a GPS module, a handful of buttons, 7 7-seg LEDs (I’d display a 10 
Hz digit), a little phototransistor dimming circuit and an ATMega… $99 retail? 
Certainly doable.


Almost everyone one Earth already owns a GPS sync'd alarm clock.  My
iPhone does all I need, pretty decent sync to UTC, big numbers I can
read without glasses and it makes noise when I need to get up.  The
iPhone sells for way over $100.   But any cheap $99 android tablet can
function as a digital clock.   All You need is a stand.   These phones
has pretty much obsoleted alarm clocks, cameras, Dedicated GPS
receivers for car navigation, and 100 other things


Except where you're in an environment that cannot tolerate devices with 
radios or portable data storage; both of which a mobile phone provides. 
That's where a conventional clock (alarm or otherwise) or timekeeper is 
needed.


One can argue, of course, that one does not need "time-nuts" level alarm 
clock accuracy in such an environment, and if you did:
a) you would go through the hoops to bring a GPS receiver and associated 
computing devices/electronics in
b) you'd probably just buy an off the shelf box - you'd have the budget 
AND the hoops would be easier to jump than with something homegrown.



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Re: [time-nuts] Shera revisted

2016-08-11 Thread jimlux


On 8/10/16 8:18 PM, Chris Albertson wrote:

Thanks for pointing out the Zynq.  Wow you get a dual core ARM and an
FPGA all in one package.   It seems overkill for a GPSDO but not the
type you are making as you can transferring the time out of the GPSDO
using PTP.

The Zyng looks to the the perfect platform for low-cost SDR.


There are SDRs based on the Zynq.


http://zedboard.org/product/zynq-sdr-ii-eval
http://www.mathworks.com/hardware-support/zynq-sdr.html
http://gnuradio.org/redmine/projects/gnuradio/wiki/Embedded

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Re: [time-nuts] Shera revisted

Hi

To your earlier point, there are a number of fairly low cost boards with Zynq’s 
on them. 
They aren’t into the $5 range, but they are not that much more than one of the 
Beagle 
boards. 

Bob


> On Aug 10, 2016, at 11:18 PM, Chris Albertson  
> wrote:
> 
> Thanks for pointing out the Zynq.  Wow you get a dual core ARM and an
> FPGA all in one package.   It seems overkill for a GPSDO but not the
> type you are making as you can transferring the time out of the GPSDO
> using PTP.
> 
> The Zyng looks to the the perfect platform for low-cost SDR.
> 
> On Wed, Aug 10, 2016 at 2:30 PM, Joakim Langlet
>  wrote:
>> Dear time-nuts,
>> 
>> My name is Joakim Langlet (SM0OET) and I just recently joined this list. As
>> Brooks Shera was mentioned, I remembered that I was referenced in the
>> footnotes of the original article in the QST - July 1998. It feels almost
>> historical now. Brooks bought a few OCXOs from me.
>> 
>> I am currently working on a GPS stabilized OCXO.
>> It is based on a Xilinx Zynq FPGA as the processor and counter arrangement.
>> The hardware is starting to take shape. The control voltage of a 20 MHz OCXO
>> is set by a DAC coupling from which I hope to set the voltage in very small
>> steps.
>> The OCXO has a CMOS level output which is converted to LVDS and is wired to
>> the FPGA board. The Xilinx Zynq take a minimum frequency of 19 MHz as input
>> to the PLL of the clock tile. My intention is to scale up the clock to some
>> where a bit over 200 MHz to be fed to the counters.The 1 PPS from the GPS
>> receiver is also fed into the FPGA to gate the counters.
>> 
>> The reason for my choice of processor is that I want to run Linux on it in
>> order benefit from the large software base. Time distribution using PTPv2
>> and a nice web-application to visualize and control what is going on inside
>> is part of the intended concept.
>> 
>> I still have a long way to the finish line but I will try to present some
>> results as I proceed.
>> 
>> I am following what is written on this list with great interest. It feels
>> good to know that I am not the only nut 
>> 
>> BR/
>> Joakim
>> ___
>> 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.
> 
> 
> 
> -- 
> 
> Chris Albertson
> Redondo Beach, California
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Re: [time-nuts] State of the art of crystal oscillator measurements

Ulrich -

 

This may be a naive question, but, how can you achieve results that are so
close to, and sometimes at further out are below kT? Thanks & 73 - Mike 

 

Mike B. Feher, EOZ Inc.

89 Arnold Blvd.

Howell, NJ, 07731

732-886-5960 office

908-902-3831 cell

 

From: ka2...@aol.com [mailto:ka2...@aol.com] 
Sent: Thursday, August 11, 2016 7:03 AM
To: time-nuts@febo.com; t...@leapsecond.com
Cc: enrico.rubi...@gmail.com; mfe...@eozinc.com
Subject: Re: [time-nuts] State of the art of crystal oscillator measurements

 

Good morning,

 

the difference between the two phase noise FWSP systems is the lower noise
internal 10 MHz reference crystal  oscillator (optimized )  as well as also
some of the internal FSWP circuits custom  optimized . The output power was
17 dBm, but we also have build one oscillator with  12 dBm output power and
noise  similar values.

 

This is part of a PhD project which I supervise .   For values so close to
the carrier you need a very low noise power supply and a well shielded
Faraday cage . The measurement with ca 100  correlation took about 2 hours.
Also the heating circuit needs to be low noise and well decoupled .

 

The 100 Hz value of the better analyzer seems suspicious , It needs to be
further  investigated.

 

All very exciting and time consuming .

 

Ulrich 

 

 

 

 

 

In a message dated 8/10/2016 11:02:25 P.M. Eastern Daylight Time,
mfe...@eozinc.com writes:

These seem extremely fantastic results for a 100 MHz oscillator. I am
curious what the Po of the oscillators are Regards - Mike 

Mike B. Feher, EOZ Inc.
89 Arnold Blvd.
Howell, NJ, 07731
732-886-5960 office
908-902-3831 cell


-Original Message-
From: time-nuts [mailto:time-nuts-boun...@febo.com] On Behalf Of Tom Van
Baak
Sent: Wednesday, August 10, 2016 9:19 PM
To: Discussion of precise time and frequency measurement
Cc: enrico.rubi...@gmail.com
Subject: Re: [time-nuts] State of the art of crystal oscillator measurements

Attached is a GIF of the table Ulrich wants to share.

Note time-nuts is a plain text mailing list so any rtf or html formatting is
discarded.
On the bright side, PDF or data or image attachments are allowed with no
problem.

/tvb

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Re: [time-nuts] State of the art of crystal oscillator measurements