[time-nuts] Lightning 1, tbolt 0.

[Scott Newell]

10 MHz output active, no PPS, no comm with LH.

My tbolt was disconnected from the outdoor GPS antenna today, and so 
I wasn't too concerned when we had a strike in the backyard this 
morning. The PC attached to the serial port and PPS output died, and 
that cable was fairly long, so I guess that's what did it in.


Anyone know off hand what part it uses for the serial driver and the 
PPS output buffer? Or is it likely a total loss?


--
newell N5TNL

___
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.

Re: [time-nuts] Meaning of MTBF (was: Reliability of atomic clocks)

[Dr. David Kirkby (Kirkby Microwave Ltd)]

On 30 Mar 2016 09:00, "Jay Grizzard"  wrote:
>
> > It get's "interesting" when you look at the MTBF times on hard disks.
Some
> > of the figures quoted in hours related to an MTBF of over 100 years.
From
> > what I read before, this was based on you replacing the drive at the
end of
> > its service life (typically 3 years for consumer drives and 5 years for
> > enterprise grade disks).



> > I note Seagate have dropped the use of MTBF:
> >
> > http://knowledge.seagate.com/articles/en_US/FAQ/174791en?language=en_US
>
> The article you link here actually explains what MTBF on drives is
> measuring -- and it has nothing to do with when you replace your drives.

That article does not.  But I have read articles from other manufacturers
where the MTBF was defined in terms of drives being replaced at the end of
their service life. Seagate have obviously dropped the use of the term MTBF
for hard dusks.

Dave.
___
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.

Re: [time-nuts] Oleg' s PN test Re: A new member & PN test set

[Bruce Griffiths]

You've missed the point which is that:
1) With 10MHz input frequencies the sum frequency is actually 20MHz which is 
beyond the first resonance of the inductor used.Something better is required. 
The sum frequency is the largest unwanted component that exits the mixer IF 
port.
2) Oleg is restricted in what he has available, rolling ones own conical 
inductor is an option given the iron powder Piconics claim to use is 
potentially available to him locally.

3) Oleg indicated he'd used the rig to measure PN with 60MHz inputs resulting 
in a 120MHz sum frequency output placing even more severe band reject 
requirements on the filter/diplexer.
4) The specified mixer is usable to 500 MHz with resulting sum frequency of 
1GHz. If someone were tempted to use it at those frequencies as is the results 
would be "interesting" to say the least.
Obviously one could select off the shelf components that are satisfactory over 
a small frequency range or for a particular input frequency of interest.. This 
means the filter components have to be changed whenever the measurement 
frequency is changed too much.

However its probably more useful to use a filter that works well over the 
entire range of frequencies for which the mixer is useful.There are many ways 
to achieve this.

Thanks for the confirmation that home made conical inductors can work well. 
A version that worked from say 1MHz to 1GHz would be very useful.
Another potential problem is injection locking:If the VCXO/OCXO under test has 
inadequate reverse isolation then this can occur leading one to falsely 
conclude the VCO/OCXO under test has far better performance than it actually 
has. In effect the injected signal increases the PLL bandwidth far beyond the 
intended value.
Using high reverse isolation amplifiers on the mixer / phase detector input 
ports is one way of ensuring that injection locking doesn't occur.
Bruce
  From: Gerhard Hoffmann 
 To: time-nuts@febo.com 
 Sent: Thursday, 31 March 2016 12:12 PM
 Subject: Re: [time-nuts] Oleg' s PN test Re: A new member & PN test set
   
Am 30.03.2016 um 21:20 schrieb Bruce Griffiths:
> Conical inductors are available that are effectively resonance free to 40GHz
> but the largest value is around 10uH. In principle one could wind one's own
> conical inductor with a larger value, However an iron powder (carbonyl iron -
> available from Ukraine at least via ebay) and epoxy mixture. A cone angle of
> about 15 degrees appears to be suitable.
>
> Failing that, the classical method is to use a series string of inductors of
> increasing value. Even then the various resonances need to be damped.
> Lossy Ferrites and resistors can be useful, however one has to be careful not
> to increase the noise at frequencies of interest.

It doesn't take conical inductors to separate the baseband from the 
carrier at 10 MHz. The
world existed before Piconics and their conical L patents. Yes, we used 
them in our 10 GB/s
fiber optic transceivers, just to see what eye diagrams we could 
achieve. But at €38 a pop they
never ever made it into production. It was just too easy to replace them 
with somewhat more cent stuff.

A colleague even rolled his own from wire, epoxy glue and ferrite beads 
smashed in a mortar.
That looked, hmm, ugly, but performed excellently. Now, you get them 
from MCL and Coilcraft.

But for a 10 or 100 MHz lowpass, that's way over the top. Not even if 
you are nuts.

regards, Gerhard


___
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.


  
___
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.

Re: [time-nuts] high rev isolation amps

[Charles Steinmetz]

Rick wrote:

If only this were true.  Authors at NIST have consistently told me 
that the conditions of working for the government preclude them from 
mentioning the names of vendors.  Thus you get generic JEDEC 
transistor numbers.  Along with the fact that JEDEC numbers are 
useless concerning unspecified parameters, it tends to make NIST 
designs non-reproducible.


It's often much worse than that.  NBS/NIST tends to require new 
designs to be compatible with existing equipment crates and frames, 
so designs are routinely compromised by legacy form factors, 
technologies, power supply availabilities, and other considerations 
that preclude building the best widget they know how to 
design.  (There are some other contributing factors, as well.)  You 
might think NIST wouldn't settle for anything less than the best they 
can do, but in fact "good enough" often rules the day.


can you please let the group in on the actual vendors and part 
numbers of the new era transistors accidentally having low flicker noise?


Zetex (Diodes, Inc) pioneered this new technology.  There was some 
discussion on the list last summer (see, for example, 
). 
There are also some discussions in the volt-nuts list archives.


I (and others) discovered these parts back in the '90s and have been 
using them "off label" for ultra-low voltage noise designs for 20-odd 
years.  Then, the 3rd Edition of Horowitz and Hill's "The Art of 
Electronics" made it public knowledge.  (Speaking of which, Chapter 8 
is absolutely essential reading for anyone who even pretends to be 
designing low noise circuits.)


Best regards,

Charles


___
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.

Re: [time-nuts] Oleg' s PN test Re: A new member & PN test set

[Gerhard Hoffmann]

Am 30.03.2016 um 21:20 schrieb Bruce Griffiths:

Conical inductors are available that are effectively resonance free to 40GHz
but the largest value is around 10uH. In principle one could wind one's own
conical inductor with a larger value, However an iron powder (carbonyl iron -
available from Ukraine at least via ebay) and epoxy mixture. A cone angle of
about 15 degrees appears to be suitable.

Failing that, the classical method is to use a series string of inductors of
increasing value. Even then the various resonances need to be damped.
Lossy Ferrites and resistors can be useful, however one has to be careful not
to increase the noise at frequencies of interest.


It doesn't take conical inductors to separate the baseband from the 
carrier at 10 MHz. The
world existed before Piconics and their conical L patents. Yes, we used 
them in our 10 GB/s
fiber optic transceivers, just to see what eye diagrams we could 
achieve. But at €38 a pop they
never ever made it into production. It was just too easy to replace them 
with somewhat more cent stuff.


A colleague even rolled his own from wire, epoxy glue and ferrite beads 
smashed in a mortar.
That looked, hmm, ugly, but performed excellently. Now, you get them 
from MCL and Coilcraft.


But for a 10 or 100 MHz lowpass, that's way over the top. Not even if 
you are nuts.


regards, Gerhard


___
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.

Re: [time-nuts] Oleg' s PN test Re: A new member & PN test set

[Bruce Griffiths]

On Thursday, March 31, 2016 08:20:19 AM Bruce Griffiths wrote:
> The first inductor self resonance is much lower than it need be. EPCOS have
> a range of inductors which have a much higher first self resonance
> frequency.
> 
> The other problem is that inductors have several resonances alternating
> between parallel and series resonance. In short, your inductor model is
> inadequate and gives false predictions. You actually need to measure the
> filter response.
> 
> Conical inductors are available that are effectively resonance free to 40GHz
> but the largest value is around 10uH. In principle one could wind one's own
> conical inductor with a larger value, However an iron powder (carbonyl iron
> - available from Ukraine at least via ebay) and epoxy mixture

 filling/core is required. 

>  A cone angle of about 15 degrees appears to be suitable.
> 
> Failing that, the classical method is to use a series string of inductors of
> increasing value. Even then the various resonances need to be damped. Lossy
> Ferrites and resistors can be useful, however one has to be careful not to
> increase the noise at frequencies of interest.
> 
> Bruce
> 
Note correction above.

Bruce


___
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.

Re: [time-nuts] Segal law: freq difference for GPSDO

[Bob Camp]

Hi

To contribute to the survey process, you need at least 4 satellites in the 
“locked on” state. More is better and 
4 may or may not get you into survey. If you are struggling to get enough 
stateless, it’s usually an antenna issue.

Bob

> On Mar 30, 2016, at 1:38 PM, Vlad  wrote:
> 
> 
> 
> TB has three satellites in "green" state. I'll have a look to the issue 
> closely. Looks like "StarLoc II" little "deaf" in compare with TB.
> If its not locked - it could explain why OCXO is out of its 10Mhz. Its just 
> not disciplined.
> 
> 
> 
> On 2016-03-30 10:48, Chris Caudle wrote:
>> On Wed, March 30, 2016 12:04 am, Vlad wrote:
>>> https://www.patoka.ca/OCXO/TBvsSL/StarLocIImonitor.png
>> That unit is in holdover, it will not produce an accurate 10MHz output.
>> Only one satellite is in view, so either it does not have a good
>> connection to an antenna, or the receiver is broken.
>> How many usable satellites does the Thunderbolt show?
> 
> -- 
> WBW,
> 
> V.P.
> ___
> 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.

___
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.

[time-nuts] HP 5335A Manual FS

[Perry Sandeen via time-nuts]

List,
I have a HP 5335A counter factory manual VGC.
$20 PLUS postage from 92220.
Please reply off list if interested.
Regards,
Perrier
___
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.

Re: [time-nuts] Oleg' s PN test Re: A new member & PN test set

[Bruce Griffiths]

The first inductor self resonance is much lower than it need be. EPCOS have a 
range of inductors which have a much higher first self resonance frequency.

The other problem is that inductors have several resonances alternating 
between parallel and series resonance. In short, your inductor model is 
inadequate and gives false predictions. You actually need to measure the filter 
response.

Conical inductors are available that are effectively resonance free to 40GHz 
but the largest value is around 10uH. In principle one could wind one's own 
conical inductor with a larger value, However an iron powder (carbonyl iron - 
available from Ukraine at least via ebay) and epoxy mixture. A cone angle of 
about 15 degrees appears to be suitable.

Failing that, the classical method is to use a series string of inductors of 
increasing value. Even then the various resonances need to be damped.
Lossy Ferrites and resistors can be useful, however one has to be careful not 
to increase the noise at frequencies of interest.

Bruce

On Wednesday, March 30, 2016 06:11:51 PM Oleg Skydan wrote:
> --
> From: "Bruce Griffiths" 
> Sent: Wednesday, March 30, 2016 7:29 AM
> To: "Discussion of precise time and frequency measurement"
> 
> Subject: Re: [time-nuts] Oleg' s PN test Re:  A new member & PN test set
> 
> > One hidden issue you don't address is that operation of the 40uH inductor
> > at
> > frequencies above its parallel resonance may allow substantial RF at the
> > sum
> > of the LO and RF frequencies to appear at the opamp input.
> > 120MHz at the 797 input will likely lead to RF rectification effects in
> > the
> > opamp input stage. The resultant offset will create a number of issues
> > including operation away from the quadrature point.
> > Unless you use something like a series string of inductors and/or a
> > conical
> > inductor the first parallel resonance of the 40uH inductor is likely to be
> > somewhat below 120MHz.
> 
> Ohhh... I do not like words like "substantial", "much more" and etc. I like
> numbers and tests. ;)
> 
> So I looked at the Murrata inductors datasheets, and it appeared 40uH
> inductor will have SRF in 10MHz region. But it does not mean that pi-LPF
> will not work at the higher frequencies. Actually it mean that our LPF will
> have response similar to the elliptic filters.
> 
> So let's draw the model with the inductor with self resonance at 10MHz and
> well at 120MHz and 1MHz to see how bad the response is:
> 1MHz: http://skydan.in.ua/PNTestSet/1MSRF.png
> 10MHz: http://skydan.in.ua/PNTestSet/10MSRF.png
> 120MHz: http://skydan.in.ua/PNTestSet/120MSRF.png
> 
> As we can see the RF+LO product will be attenuated more than 60dB in all
> cases. So, your comments? Would you like me to measure the RF voltage at the
> AD797 input in the real "test set"?
> 
> > However 50 ohms to ground at the LC filter output shouldn't be necessary.
> > A somewhat larger value should suffice.
> 
> I made some experiments trying to find the optimal value of the resistor at
> the LC filter output. The phase detector gain grew along with the resistor
> value, but so did the harmonics level. So I needed to apply more attenuation
> to the input signal to stay in the linear region. The resulting "test set"
> noise floor was almost identical for 50..300Ohm values (300Ohm was a bit
> better at offsets grater then 2kHz and a bit worse closer). Large values
> noticeably degraded the performance.
> 
> I suppose the noise floor can be lowered only if better LNA will be used
> (currently the LNA noise dominates the PD noise), or if the levels on the
> mixer will be increased (this will require higher level mixer and/or new
> calibration routine if the mixer will not be in a linear region).
> 
> All the best!
> Oleg
> 
> 
> ___
> 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.

___
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.

Re: [time-nuts] high rev isolation amps

[Richard (Rick) Karlquist]

On 3/30/2016 8:18 AM, Tim Shoppa wrote:



There's a real beauty to many of the NIST designs - using topology and
jellybean parts to achieve the performance, rather than selected devices.

Tim N3QE




If only this were true.  Authors at NIST have consistently told me
that the conditions of working for the government preclude them from
mentioning the names of vendors.  Thus you get generic JEDEC transistor
numbers.  Along with the fact that JEDEC numbers are useless concerning
unspecified parameters, it tends to make NIST designs non-reproducible.
Not arguing that they didn't really get whatever results they present.

My understanding is that "CATV" transistors are all derived originally
from the 2N3866, FWIW.

Special request to Charles Steinmetz:  can you please let the group in
on the actual vendors and part numbers of the new era transistors 
accidentally having low flicker noise?  Many thanks!


Rick N6RK
___
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.

Re: [time-nuts] Segal law: freq difference for GPSDO

[Vlad]

TB has three satellites in "green" state. I'll have a look to the issue 
closely. Looks like "StarLoc II" little "deaf" in compare with TB.
If its not locked - it could explain why OCXO is out of its 10Mhz. Its 
just not disciplined.




On 2016-03-30 10:48, Chris Caudle wrote:

On Wed, March 30, 2016 12:04 am, Vlad wrote:

https://www.patoka.ca/OCXO/TBvsSL/StarLocIImonitor.png


That unit is in holdover, it will not produce an accurate 10MHz output.
Only one satellite is in view, so either it does not have a good
connection to an antenna, or the receiver is broken.
How many usable satellites does the Thunderbolt show?


--
WBW,

V.P.
___
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.

Re: [time-nuts] high rev isolation amps

[Charles Steinmetz]

Poul-Henning  wrote:

I would have expected them to use capacitance optimized transistors, 
also known as UHF transistors ?   Something like BFQ19 maybe ?


One of the main problems in isolation (and distribution) amplifiers 
is excessive additive (historically called "residual") phase noise 
due to AM to PM conversion in the amplifier.  The worst AM noise 
turns out to be flicker noise (1/f noise) in the transistors at 
baseband frequencies.  RF transistors typically have much higher 
flicker noise (by orders of magnitude), including 1/f corner 
frequencies that are decades higher, than general-purpose 
transistors.  The fact that most of the converted PM noise is at 1/f 
frequencies is doubly insidious, because it is close in to the 
carrier (and, therefore, essentially impossible to remove by filtering).


So, the best transistors for low phase noise design (of both 
amplifiers and oscillators) are transistors that have low flicker 
noise and low 1/f corners -- consistent, of course, with having 
sufficient gain at the RF frequencies of interest.  These days, there 
is a whole new class of BJTs that were designed for high current 
density and very low saturation voltage, some of which have 
astonishingly low flicker noise and also good gain-bandwidth products 
(f-sub-Ts).  Today's low phase noise designs often take advantage of 
these "accidental" characteristics of the new transistors.


Best regards,

Charles


___
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.

Re: [time-nuts] Segal law: freq difference for GPSDO

[Chris Caudle]

On Wed, March 30, 2016 12:04 am, Vlad wrote:
> https://www.patoka.ca/OCXO/TBvsSL/StarLocIImonitor.png

That unit is in holdover, it will not produce an accurate 10MHz output.
Only one satellite is in view, so either it does not have a good
connection to an antenna, or the receiver is broken.
How many usable satellites does the Thunderbolt show?

-- 
Chris Caudle


___
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.

Re: [time-nuts] high rev isolation amps

[Tim Shoppa]

I usually call those "CATV transistors" :-). 2N5109 etc. They also have
very reasonable power dissipations and despite being "UHF transistors" they
are most commonly used today in low-frequency work where high IP3 is
crucial.

That said, it is possible that going to multiple consecutive common-base
stages with jellybean transistors, is good enough, that layout and
packaging become more important than using specialized transistors.

There's a real beauty to many of the NIST designs - using topology and
jellybean parts to achieve the performance, rather than selected devices.

Tim N3QE

On Wed, Mar 30, 2016 at 2:28 AM, Poul-Henning Kamp 
wrote:

> 
> In message , Bob Camp
> writes:
>
> >There were (and maybe still are) SOT-89 versions of the 2N3804 and
> >3906. They will handle more power than most of the other versions.
> >That gives you better Vce on the string. They also have less
>
> Stupid question:  I would have expected them to use capacitance
> optimized transistors, also known as UHF transistors ?
>
> Something like BFQ19 maybe ?
>
> --
> 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.
> ___
> 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.
>
___
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.

Re: [time-nuts] Oleg' s PN test Re: A new member & PN test set

[Oleg Skydan]

--
From: "Bruce Griffiths" 
Sent: Wednesday, March 30, 2016 7:29 AM
To: "Discussion of precise time and frequency measurement" 


Subject: Re: [time-nuts] Oleg' s PN test Re:  A new member & PN test set

One hidden issue you don't address is that operation of the 40uH inductor 
at
frequencies above its parallel resonance may allow substantial RF at the 
sum

of the LO and RF frequencies to appear at the opamp input.
120MHz at the 797 input will likely lead to RF rectification effects in 
the

opamp input stage. The resultant offset will create a number of issues
including operation away from the quadrature point.
Unless you use something like a series string of inductors and/or a 
conical

inductor the first parallel resonance of the 40uH inductor is likely to be
somewhat below 120MHz.


Ohhh... I do not like words like "substantial", "much more" and etc. I like 
numbers and tests. ;)


So I looked at the Murrata inductors datasheets, and it appeared 40uH 
inductor will have SRF in 10MHz region. But it does not mean that pi-LPF 
will not work at the higher frequencies. Actually it mean that our LPF will 
have response similar to the elliptic filters.


So let's draw the model with the inductor with self resonance at 10MHz and 
well at 120MHz and 1MHz to see how bad the response is:

1MHz: http://skydan.in.ua/PNTestSet/1MSRF.png
10MHz: http://skydan.in.ua/PNTestSet/10MSRF.png
120MHz: http://skydan.in.ua/PNTestSet/120MSRF.png

As we can see the RF+LO product will be attenuated more than 60dB in all 
cases. So, your comments? Would you like me to measure the RF voltage at the 
AD797 input in the real "test set"?



However 50 ohms to ground at the LC filter output shouldn't be necessary.
A somewhat larger value should suffice.


I made some experiments trying to find the optimal value of the resistor at 
the LC filter output. The phase detector gain grew along with the resistor 
value, but so did the harmonics level. So I needed to apply more attenuation 
to the input signal to stay in the linear region. The resulting "test set" 
noise floor was almost identical for 50..300Ohm values (300Ohm was a bit 
better at offsets grater then 2kHz and a bit worse closer). Large values 
noticeably degraded the performance.


I suppose the noise floor can be lowered only if better LNA will be used 
(currently the LNA noise dominates the PD noise), or if the levels on the 
mixer will be increased (this will require higher level mixer and/or new 
calibration routine if the mixer will not be in a linear region).


All the best!
Oleg


___
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.

Re: [time-nuts] Phase noise test set reference articles

[Attila Kinali]

On Tue, 29 Mar 2016 10:53:17 -0400
Charles Steinmetz  wrote:

> Since there seems to be some interest in DIY phase noise test sets, I 
> put together the following list of references relevant to such a 
> project, with some comments.  I have a ZIP file of these items (about 
> 35MB), but so far have been unsuccessful in uploading it to Didier's 
> site.  If anyone has suggestions for hosting it, please let me know 
> *offlist*.


It has been uploaded to Didier's site. But as sorting it in will
take some time, i mirrored it at:

http://time.kinali.ch/Phase_noise_measurement_references.zip

Attila Kinali
-- 
It is upon moral qualities that a society is ultimately founded. All 
the prosperity and technological sophistication in the world is of no 
use without that foundation.
 -- Miss Matheson, The Diamond Age, Neil Stephenson
___
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.

[time-nuts] Mike Monet, please contact me

[Stéphane Rey]

Sorry for flooding the list but can't find a working email to contact 
you Mike.


Thanks and cheers
Stephane
___
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.

Re: [time-nuts] high rev isolation amps

[Poul-Henning Kamp]

In message , Bob Camp writes:

>There were (and maybe still are) SOT-89 versions of the 2N3804 and
>3906. They will handle more power than most of the other versions.
>That gives you better Vce on the string. They also have less

Stupid question:  I would have expected them to use capacitance
optimized transistors, also known as UHF transistors ?

Something like BFQ19 maybe ?

-- 
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.
___
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.

Re: [time-nuts] high rev isolation amps

[Charles Steinmetz]

Bob wrote:

There were (and maybe still are) SOT-89 versions of the 2N3804 and 
3906. They will handle more power than most of the other versions. 
That gives you better Vce on the string.


Bruce wrote:


The PZT3904 and PZT3906 are still available.


With most of these old circuits reducing the LF noise contribution 
to the emitter/collector current by the biasing circuit by utilising 
lower noise power supplies and/or using improved biasing methods can 
improve the clse in PN significantly.


The lower transistors on the totem pole operate in current mode and 
typically have only 3-5v from C to E, so their dissipation is very 
low even if the standing current is high.  I used TO-92 and SOT-23 
transistors there.  The top transistor, which must develop the output 
voltage, dissipates more than a TO-92 or SOT-23 should be asked to 
handle, even with a good heatsink, so I typically used TO-5 (TO-39) 
or SOT-89 transistors (with heatsinks) there.


It is definitely true that the published NIST designs did not 
minimize circuit noise.  I used *much* larger base bypass capacitors, 
and improved capacitance multipliers.  I also used separate 
capacitance multipliers for the base divider string and the collector 
supply.  I played with ultra-low-noise DC regulators on each base and 
for the collector supply, which gave modest improvements in both 
noise and distortion -- but the added complexity was not justified by 
the gains, IMO.  I did find that doing without the interstage 
resistors (from the collector of one transistor to the emitter of the 
next higher transistor) reduced both noise (modestly) and distortion 
(slightly).  In the very rare cases when a circuit oscillated (I 
experimented with *many* combinations of transistors), I used ferrite 
beads in place of the resistors or on one or more of the base 
leads.  Choosing transistors with very low base spreading resistance 
was another key to lowering noise.


Best regards,

Charles


___
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.

Re: [time-nuts] high rev isolation amps

[Bruce Griffiths]

Using a higher dissipation transistor package for the output stage is also the 
strategy adopted in some commercial versions of these amplifiers. 
Note that the amplifier with the 4:1 (turns ratio) output transformer and 300 
ohm resistor in series with the primary of the input transformer is intended to 
have its input connected in parallel with 5 others to form a 6 output 
distribution amplifier.
If it is redesigned for a 50 ohm input with a 2: (turns ratio) output 
transformer the PN floor is reduced significantly.
The biggest drawback for some applications is the 24-28V power supply.A 12V or 
lower voltage supply would be nice.This can only be achieved (without unduly 
raising the amplifier PN floor) by something like a folded cascade of NPN + PNP 
+ NPN CB stages or by transformer coupling between stages. Using a CB input 
stage has the advantage that the input signal voltage swing doesn't reduce the 
available collector voltage swing as much as in a CE stage. 

Bruce
 

  From: Charles Steinmetz 
 To: Discussion of precise time and frequency measurement  
 Sent: Wednesday, 30 March 2016 5:51 PM
 Subject: Re: [time-nuts] high rev isolation amps
   
Bob wrote:

>There were (and maybe still are) SOT-89 versions of the 2N3804 and 
>3906. They will handle more power than most of the other versions. 
>That gives you better Vce on the string.

Bruce wrote:

>The PZT3904 and PZT3906 are still available.

>With most of these old circuits reducing the LF noise contribution 
>to the emitter/collector current by the biasing circuit by utilising 
>lower noise power supplies and/or using improved biasing methods can 
>improve the clse in PN significantly.

The lower transistors on the totem pole operate in current mode and 
typically have only 3-5v from C to E, so their dissipation is very 
low even if the standing current is high.  I used TO-92 and SOT-23 
transistors there.  The top transistor, which must develop the output 
voltage, dissipates more than a TO-92 or SOT-23 should be asked to 
handle, even with a good heatsink, so I typically used TO-5 (TO-39) 
or SOT-89 transistors (with heatsinks) there.

It is definitely true that the published NIST designs did not 
minimize circuit noise.  I used *much* larger base bypass capacitors, 
and improved capacitance multipliers.  I also used separate 
capacitance multipliers for the base divider string and the collector 
supply.  I played with ultra-low-noise DC regulators on each base and 
for the collector supply, which gave modest improvements in both 
noise and distortion -- but the added complexity was not justified by 
the gains, IMO.  I did find that doing without the interstage 
resistors (from the collector of one transistor to the emitter of the 
next higher transistor) reduced both noise (modestly) and distortion 
(slightly).  In the very rare cases when a circuit oscillated (I 
experimented with *many* combinations of transistors), I used ferrite 
beads in place of the resistors or on one or more of the base 
leads.  Choosing transistors with very low base spreading resistance 
was another key to lowering noise.

Best regards,

Charles


___
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.


  
___
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.

Re: [time-nuts] Meaning of MTBF (was: Reliability of atomic clocks)

[Jay Grizzard]

> It get's "interesting" when you look at the MTBF times on hard disks. Some
> of the figures quoted in hours related to an MTBF of over 100 years. From
> what I read before, this was based on you replacing the drive at the end of
> its service life (typically 3 years for consumer drives and 5 years for
> enterprise grade disks). So no individual drive was ever expected to last
> 100 years, but if you kept replacing the drives ever 3~5 years, the average
> time of an unexpected failure would be 100 years. I guess its a bit like a
> car - the engine might run for 250,000 miles, but if you never change the
> oil or the camshaft belt, it is not going to last.
> 
> I note Seagate have dropped the use of MTBF:
> 
> http://knowledge.seagate.com/articles/en_US/FAQ/174791en?language=en_US

The article you link here actually explains what MTBF on drives is
measuring -- and it has nothing to do with when you replace your drives.

MTBF is basically expressed as "1 failure per N power-on hours". So if
you have a MTBF of 100,000 hours and you have 100 drives running
continuously, you will (on average) have one failure every ~42 days (1000
hours). If you have 100,000 drives, you'll have (on average) one failure
every hour. MTBF does not address the expected life of any specific
drive in any way.

(It also does not address the bathtub curve that drive failures tend
to follow -- there's a high 'infant mortality' rate for new drives, 
then a number of years of service with a low failure rate, followed by an
increase in failure rate after some number of years.)

FWIW, there have been a few interesting things published on drive failure
rates. One of the most interesting is a study[1] Google published in 2007,
which drew some rather unexpected conclusions (e.g. drive temperature is
not associated with failure rate, except at the higher ends of the
temperature range). Backblaze (a cloud backup provider) also publishes
regular reports on drive reliability[2], and have been for a few years now.

-j

1. 
http://static.googleusercontent.com/media/research.google.com/en//archive/disk_failures.pdf

2. https://www.backblaze.com/blog/hard-drive-reliability-q4-2015/
___
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.

Re: [time-nuts] Segal law: freq difference for GPSDO

[Henry Hallam]

On Tue, Mar 29, 2016 at 5:48 PM, Vlad  wrote:
>
> I tried to see the 1PPS on my oscilloscope. Here is the series of
> screenshots from that experiment:
>
> https://www.patoka.ca/OCXO/TBvsSL/

>From those scope shots it looks like one or both of the GPSDOs does
not have any kind of lock to GPS time.  The PPS leading edges from the
two receivers should be aligned to within a few tens to hundreds of
nanoseconds, but yours are hundreds of milliseconds apart.

The screenshot you have at
https://www.patoka.ca/OCXO/TBvsSL/StarLocIImonitor.png shows a
receiver only tracking one satellite, which is not sufficient.  Maybe
the antenna signal connection to that unit is poor or maybe it's
defective. The filename says StarLoc but the window title says
Thunderbolt, which is it?

Good luck,
Henry
___
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.

Re: [time-nuts] Oleg' s PN test Re: A new member & PN test set

[Bruce Griffiths]

One hidden issue you don't address is that operation of the 40uH inductor at 
frequencies above its parallel resonance may allow substantial RF at the sum 
of the LO and RF frequencies to appear at the opamp input.
120MHz at the 797 input will likely lead to RF rectification effects in the 
opamp input stage. The resultant offset will create a number of issues 
including operation away from the quadrature point.
Unless you use something like a series string of inductors and/or a conical 
inductor the first parallel resonance of the 40uH inductor is likely to be 
somewhat below 120MHz.

Bruce

On Monday, March 28, 2016 11:04:45 PM Oleg Skydan wrote:
> Hi, everybody!
> 
> OK. Let's start. Here is the schematics of the "test set"
> http://skydan.in.ua/PNTestSet/PN%20Test%20set.pdf . It consists of three
> small
> boards:
> 1. Mixer board - a simple mixer (500MHz ADE-1+) with 200kHz pi-LPF at the
> mixer output.
> 2. LNA board - a non-inverting low noise AF amplifier based on AD797 with
> switchable 20/40dB gain.
> 3. PLL board - contains two TL071 OP amps. One is inverting amplifier, the
> other is PLL integrator. The R4,R8,R2,R7,C8 sets the PLL parameters - gain,
> passband and damping factor. Loop parameters are also dependent of signal
> levels and VCO tuning sensitivity. So you may need to correct them if your
> setup differs from mine - VCXO's I use have tuning sensitivity approx
> 100Hz/V and I set RF level at mixer near 0dBm with LO level near +7dBm. If
> you want to build universal test set you will need to use some switchs to
> allow setting different loop parameters (I just use my soldering iron and
> change parts if needed :) ).
> 
> The power supply is a simple design based on 7812/7912 regulators.
> 
> I use the E-MU 0202 USB external sound card and laptop PC as the AF spectrum
> analyzer.
> 
> You will also need some cables. Different fixed attenuators or switchable
> one will be also helpful.
> 
> I also have several homemade low noise VCXOs for some frequencies (7MHz,
> 10MHz, 14.318MHz, 60MHz) which I use as the reference signal sources to make
> measurements at these frequencies.
> 
> Another option is to test two identical oscillators (or other signal
> sources). Assuming that both signals will have identical phase noise
> characteristics we can correct the results by 3dB (or just add 3dB
> correction during calibration).
> 
> The calibration and use is simple.
> 1. Set LNA gain to 20dB.
> 2. Set the FFT parameters - flattop window, small (2048..4096) points number
> and short averaging in SA software.
> 3. Connect reference signal to LO mixer port and signal you are going to
> test to RF mixer port through the attenuator. Do not close the PLL yet.
> 4. Set the beat level a bit less then the sound card full scale using the
> attenuator. Check the beat harmonics levels - they should be at least 30dB
> lower then the beat level (add more attenuation if harmonics are higher).
> 5. Now set the spectrum analyzer calibration so that beat level is at -27dB
> if you measure against low noise reference VXCO, or -30dB if you use two
> identical oscillators.
> 6. Switch the LNA to 40dB gain.
> 7. Set SA software to Blackman window, 131072points/96kHz SR/necessary
> averaging, close PLL, wait for the lock, measure the phase noise.
> 
> Why I am calibrating to -27/-30dB:
> 20dB because the LNA gain is 20dB less during the calibration (compared to
> measurement time)
> 1dB because of FFT parameters 96k/131072 = 0.73Hz * 1.73 (Blackman window) =
> 1.267Hz, 10 log10(1.267) = 1.03dB
> 6dB is the correction inherent to used calibration method
> additional 3dB needed in case of testing identical oscillators.
> 
> Now some words about results. The noise floor of this test set depends of
> the signals levels, and with the optimal levels it is in -160..-170dBc/Hz
> range (depending of the offset from the carrier). It completely satisfies my
> needs, better results can be achieved with the higher level mixer and/or
> better LNA. I just used parts that I had :).
> 
> Here http://skydan.in.ua/PNTestSet/Screen%20(420)-e.png is an example of the
> phase noise measurements results of my homemade low noise 60MHz VCXO (two
> identical units were measured). The results at the offsets greater then
> 1kHz should be corrected cause the oscillators noise is too close to test
> set noise (the real oscillator noise is a bit lower then the displayed
> one). The test set noise floor and calibration spectrum is also there.
> 
> The boards also have other use.
> 
> For example I was able to measure my home made 60MHz VCXO harmonic content
> http://skydan.in.ua/PNTestSet/Screen%20(414)-e.png using the mixer, LNA
> boards and signal generator. I have no spectrum analyzer so it is a big help
> to me :).
> 
> Power supply noise can be investigated with the LNA board and sound card.
> Look at this screen http://skydan.in.ua/PNTestSet/Screen%20(431)-e.png to
> see how bad the LDO regulator noise can be and a great difference in noise
> 

Re: [time-nuts] Segal law: freq difference for GPSDO

[Vlad]

May be somebody could recognize, what 10.014 Mhz could be used for 
?


It sort of looks more like an unlocked OCXO than a magic frequency.
Measure phase instead of frequency; see how the phase drifts over time.
Also check if the magic frequency varies or drifts over time.
See if the offset is constant in spite of a one hour power cycle of
either GPSDO.



To feed my curiosity, I disassembled Starloc II to have a look what is 
inside. There is Motorola GPS module and DATUM OCXO.
I measured 5V ref (stamped on PCB). Its looks good. The OCXO has 12V on 
its VSS pin. No visible damage there.
I put it back. I think its possible to replace DATUM OCXO by Morion. The 
pinout and voltage is the same. Moruib is slightly bigger in size, but 
should feet the case with minor modifications. However I postpone this 
exercise for now.


I don't have "native" software to manage StarLoc. But since its TSIP and 
I was using TB Monitor to see some information.


Here is how its looks like:

https://www.patoka.ca/OCXO/TBvsSL/StarLocIImonitor.png


Also there is series of screenshot from my Oscilloscope where I tried to 
compare 1PPS outputs



https://www.patoka.ca/OCXO/TBvsSL/



The TBolt/LH screen seems ok. Send some RS232 commands to the StarLoc.
Verify they are both receiving a good number of SV, and maybe even a
lot of the same set of SVN.


I am not sure if StarLoc is responsive for any commands. I need to dig 
it little more.



You can also remove the antenna on one or both units. See if the
unusual frequency offset and the ADEV curve looks the same with or
without antenna.


Thanks for the advise !


--
WBW,

V.P.
___
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.