Re: [time-nuts] Using GPSDO as a Refrence for Protable Amateur Radio Microwave Operations

[jimlux]

On 12/22/16 5:06 PM, Scott Stobbe wrote:

The other interesting aspect, is that if the transceiver is mobile, even at
a lazy pedestrian walking speed of 1 m/s, the resulting Doppler shift is 3
E-9 deltaF.



I always visualize this as "how many wavelengths per second".. so if 
you're at 10 GHz, 3cm wavelength, 1 m/s is 33 Hz.



to 1 sig fig, 1 m/s = 2 mi/hr

if it's a radar (2 way path) the shift is doubled.

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Re: [time-nuts] Using GPSDO as a Refrence for Protable Amateur Radio Microwave Operations

[Scott Stobbe]

The other interesting aspect, is that if the transceiver is mobile, even at
a lazy pedestrian walking speed of 1 m/s, the resulting Doppler shift is 3
E-9 deltaF.

On Thu, Dec 22, 2016 at 4:36 PM, Bob Camp  wrote:

> Hi
>
> For close in phase noise (< 10 Hz) the 10 MHz still wins over the 100 MHz
> after multiplication.
>
> ADEV of the 10 MHz (with or without frequency scale) will be better on the
> higher Q resonator.
> That will always be the low frequency overtone rather than the VHF crystal.
>
> Indeed, a large blank 5 MHz would beat the 10 MHz. It’s a good bet that if
> a 2.5 MHz cold weld
> SC with a 30 mm blank diameter existed, it would beat either one of them
> (Q would be much higher).
> Given the cost of coming up with that part …. not going to happen.
>
> Bob
>
> > On Dec 22, 2016, at 3:26 PM, Scott Stobbe 
> wrote:
> >
> > Well for the same Q a competing oscillator will still take a 20 dB phase
> > noise increase for every frequency decade you scale up to. If Q*f is
> > approximately constant, you take another 20 dB hit in phase noise from
> > degraded Q, totaling 40 dB/decade. Compared to 20 dB/decade plus the
> noise
> > introduced by the phase detector and loop-filter of the PLL.
> > https://en.wikipedia.org/wiki/Leeson's_equation
> >
> > On Thu, Dec 22, 2016 at 10:53 AM, Attila Kinali 
> wrote:
> >
> >> On Wed, 21 Dec 2016 18:59:20 -0800
> >> Chris Albertson  wrote:
> >>
> >>> Why to people always build 10MHz GPSDOs?   If the use of the GPSDO is
> to
> >>> drive a microwave, why not build a MUCH higher frequency GPSDO.Is
> the
> >>> reason that 10MHz crystals just happen to be very good and there are
> not
> >>> good 100MHz ovenized crystals?  Or for portable use could you not use
> the
> >>> 1PPS signal to discipline a microwave oscillator.
> >>
> >> Short answer:
> >> GPSDOs are mostly about high stability, not about low phase noise.
> >> The 10MHz just happend to be a good compromise on stability, phase noise
> >> and usefulnes.
> >>
> >> Long answer:
> >> A GPSDO has to exhibit good stability up to several 100 s to a few 1000
> s.
> >> This dictates that the OCXO used has to have as high long term stability
> >> as possible. To get there you need an as thick crystal lab as possible.
> >> The lower the frequency and the higher the overtone, the better.
> >> Quartz resonators exhibit a nearly constant Q*f, so in first order
> >> approximation, there is no point in choosing a higher frequency
> >> crystal, as the Q will then decrease and thus increase the phase noise
> >> would have been the same as the increased phase noise of a frequency
> >> multiplier. Of course, frequency multiplication is not exactly perfect
> and
> >> the Q*f is not 100% flat. There is a sweet spot where Q*f is maximal
> >> between
> >> 5MHz and 10MHz. For historical reasons, 10MHz has been deemed the more
> >> useful
> >> value and that's the reason we have a lot of 10MHz OCXO. If you go for
> high
> >> stability oscillators, you will see a lot 5MHz OCXOs being used (for the
> >> increased stability). Of course nobody says that these are the only
> >> frequencies that can be used. For example, for specialized use cases you
> >> will find GPSDOs with "odd" frequencies (like the 30.72MHz/61.44MHz used
> >> for LTE).
> >>
> >> As others have already commented, when using GPSDOs as a frequency
> >> reference
> >> for an GHz link, one would use some high frequency oscillator in the
> lower
> >> 100MHz range (using a BAW quartz) or somewhere between 500MHz and
> 1000MHz
> >> (using an SAW quartz) as a low phase noise reference and upconvert this.
> >> Yes, it is possible to discipline such an oscillator directly using GPS,
> >> but for the sake of stability (see above), design reuse and ease of
> >> building/testing, using an 10MHz input is generally the better solution.
> >> This allows to use any device that can produce an 10MHz signal, like
> >> e.g. an Rb vapor cell standard.
> >>
> >>
> >>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.
> >>
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> and 

[time-nuts] TS2100: Upgrading oscillator?

[Bruce Lane]

Good day,

During recent repair efforts on my Symmetricom TS2100, I noticed the
main PC board has silkscreening, and hole patterns, to cover different
types of crystal oscillator.

Might it be possible to upgrade from the standard unit (a DIP-14 form
factor clock oscillator) to, perhaps, an OCXO?

Anyone have a 2100 they can share pictures of? Or, perhaps, one which
has been upgraded?

Just wondering...

Thanks.

-- 
---
Bruce Lane, ARS KC7GR
http://www.bluefeathertech.com
kyrrin (at) bluefeathertech dot com
"Quando Omni Flunkus Moritati" (Red Green)
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[time-nuts] HP 115CR Clock Powerup / Documentation

[Hugh Blemings]

Hi,

I've been fortunate enough to acquire a HP 115CR Frequency 
Divider/Digital Clock - it's electromechanical and I suspect built in 
the mid/late 60s - just slightly older than your humble correspondent.


It's similar though not identical to the 115CR shown here 
http://www.leapsecond.com/hpclocks/


I'd like to fire it up - given it's age my thought was to use a current 
limited 24V bench supply and slowly ramp up the voltage the first time - 
would welcome any thoughts on this.  I gather from the supporting 
documentation for the powersupply it's rated at drawing ~250mA


I've been unable to locate a scan of the owners manual or service manual 
online.  Have looked at time-nuts archives, leapsecond.com and hparchive 
to no avail.  There does appear to be a hardcopy available for purchase 
- happy to fall back to this if necessary, but any pointers welcome.


My goal ultimately is to have it on display running, synchronised to a 
GPS disciplied 10MHz source :)


Any thoughts and feedback welcome - this is my first foray into old 
clocks :)


Kind Regards,
Hugh
VK3YYZ/AD5RV
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Re: [time-nuts] SR620 Failure Code.

[Bob Camp]

Hi

> On Dec 22, 2016, at 5:57 PM, Gary Woods  wrote:
> 
> On Thu, 22 Dec 2016 16:50:17 -0500, you wrote:
> 
>> That's just crazy, but that was the problem. 
> 
> It's documented, so it's not a bug.

… so that would make it a feature, right?

Bob

> 
> 
> -- 
> Gary Woods AKA K2AHC- PGP key on request, or at home.earthlink.net/~garygarlic
> Zone 5/4 in upstate New York, 1420' elevation. NY WO G
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Re: [time-nuts] SR620 Failure Code.

[Gary Woods]

On Thu, 22 Dec 2016 16:50:17 -0500, you wrote:

>That's just crazy, but that was the problem. 

It's documented, so it's not a bug.


-- 
Gary Woods AKA K2AHC- PGP key on request, or at home.earthlink.net/~garygarlic
Zone 5/4 in upstate New York, 1420' elevation. NY WO G
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Re: [time-nuts] Problem with HP 83623A 20 GHz sweep generator stepping up/down 100 Hz when not wanted.

[Bob Camp]

Hi


In a country with 50 Hz power lines, figuring out anything at 50, 100 or 150 Hz
is going to be a bit exciting.

Bob

> On Dec 22, 2016, at 4:04 PM, n2lym  wrote:
> 
> Dave,
> 
> Look at it with a narrow band SA and see if it's modulated by 100Hz.
> 
> 73,
> 
> Mike N2LYM
> 
> 
> 
> 
> On Thu, Dec 22, 2016 at 07:39 AM, Dr. David Kirkby (Kirkby Microwave Ltd) 
> wrote:
> 
>> On 22 December 2016 at 03:17, paul swed
> wrote:
>> 
>>> Dave Congratulations on 10 Ghz SSB.
>>> 
>> 
>> This was not a QSO at all. It was simply a one way transmission from a
>> signal generator at my end to a receiver at his end. No QSO was attempted.
>> 
>> 
>>> Now to your question. I will fully believe you are seeing normal behavior
>>> of the generators. Even if its dithering 100 Hz thats pretty amazing. Sweep
>>> gens simply are not stable enough for narrow work like you are trying.
>>> Now I am sure comments will prove me totally wrong.
>>> 
>> 
>> But I find it a bit odd that HP would have a 1 Hz software option on this
>> instrument, if the instrument jumped up/down 100 Hz.
>> 
>> Now I don't yet have the 1 Hz option programmed in, and it might well
>> change the behavior completely, but I'd still like to find a way, if one
>> exists, of checking this with the equipment I have.
>> 
>> The signal generator is no longer supported, but I could try my luck seeing
>> if there are any known problems with this unit, or firmware upgrades
>> available - currently revision 29, May 1991.
>> 
>> 
>> 
>>> But I don't think so. (Have been on 10G SSB over the years also. Only 60
>>> watts plus. Nothing fancy. ;-)  )
>>> Regards
>>> Paul
>>> WB8TSL
>>> 
>> 
>> 60 W is clearly some setup. I also know a lot of people run portable stuff
>> on 10 GHz, where achieving frequency stability is more of a challenge,
>> although less so with GPS. But this is a laboratory instrument, from a
>> reputable manufacturer. I personally would not expected this behavior. I
>> actually purchased this very cheaply (£650 GBP, which would have been about
>> $900 at the time), but they are not cheap to buy now.
>> 
>> 
>> Dave
>> ___
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>> 
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Re: [time-nuts] Problem with HP 83623A 20 GHz sweep generator stepping up/down 100 Hz when not wanted.

[Bill Byrom]

Read about the synthesizer design of that generator here:

https://ia600407.us.archive.org/10/items/Hewlett-Packard_Journal_Vol._42_No._2_1991-04_Hewlett-Packard/Hewlett-Packard_Journal_Vol._42_No._2_1991-04_Hewlett-Packard.pdf


Dave, looking at the graph you posted it appears to me that the shift is
10 Hz, not 100 Hz. It appears to me that is an audio spectrogram. I have
no idea if the frequency shift is in the generator or receiver.


--

Bill Byrom N5BB







On Thu, Dec 22, 2016, at 10:10 AM, David wrote:

> On Thu, 22 Dec 2016 12:39:27 +, you wrote:

> 

>> But I find it a bit odd that HP would have a 1 Hz software option
>> on this
>> instrument, if the instrument jumped up/down 100 Hz.

>> 

>> Now I don't yet have the 1 Hz option programmed in, and it might well
>> change the behavior completely, but I'd still like to find a
>> way, if one
>> exists, of checking this with the equipment I have.

>> 

>> The signal generator is no longer supported, but I could try my
>> luck seeing
>> if there are any known problems with this unit, or firmware upgrades
>> available - currently revision 29, May 1991.

>> 

>> ...

>> 

>> Dave

> 

> I agree with Bill, maybe something is going on at the other end.

> 

> While I do not expect this sort of thing from HP, could they have

> deliberately designed the sweep generator to include those 100 Hz

> bumps unless the 1 HZ software option was purchased?

> 

> Like Paul, I would not expect the kind of stability you need from a

> sweep generator but that 100 Hz jump is just weird.  It does kind of

> remind me of popcorn noise but without a time scale and a longer

> record, it is difficult to tell.

> _

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> https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts

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Re: [time-nuts] SR620 Failure Code.

[W2GPS]

Thanks to Jarl OZ9MO my SR620 is running fine again. He pointed me to the
manual where I found this.

 

"If the UHF prescaler of channel A is selected when the unit is powered off
and then on again, the unit will display "TEST ERROR 34". This error may be
corrected by deselecting the UHF of channel A. To run this procedure, press
input button of channel "A" until UHF is not highlighted. Then turn the
power off and on again."

 

That's just crazy, but that was the problem. 

 

Rick

W2GPS

 

From: W2GPS [mailto:w2...@cnssys.com] 
Sent: December 22, 2016 11:53 AM
To: 'time-nuts@febo.com' 
Subject: SR620 Failure Code.

 

Time-nuts,

 

My SR620 has started reporting "test error 34" on power-up and will do
nothing after that. Does anyone know what that message means? I have a
reasonable lab and I would try to repair the unit myself but I have no
documentation. Is service documentation available or should I just ship it
back to Stanford Research to get fixed?

 

Rick

W2GPS

 

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Re: [time-nuts] SR620 Failure Code.

[Dave M]

Complete manuals, including service info, are available on the net.  Google 
for

SR620 manual

Dave M



W2GPS wrote:

Time-nuts,



My SR620 has started reporting "test error 34" on power-up and will do
nothing after that. Does anyone know what that message means? I have a
reasonable lab and I would try to repair the unit myself but I have no
documentation. Is service documentation available or should I just
ship it back to Stanford Research to get fixed?



Rick

W2GPS


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Re: [time-nuts] Using GPSDO as a Refrence for Protable Amateur Radio Microwave Operations

[Bob Camp]

Hi

For close in phase noise (< 10 Hz) the 10 MHz still wins over the 100 MHz after 
multiplication.

ADEV of the 10 MHz (with or without frequency scale) will be better on the 
higher Q resonator.
That will always be the low frequency overtone rather than the VHF crystal.

Indeed, a large blank 5 MHz would beat the 10 MHz. It’s a good bet that if a 
2.5 MHz cold weld 
SC with a 30 mm blank diameter existed, it would beat either one of them (Q 
would be much higher).
Given the cost of coming up with that part …. not going to happen. 

Bob

> On Dec 22, 2016, at 3:26 PM, Scott Stobbe  wrote:
> 
> Well for the same Q a competing oscillator will still take a 20 dB phase
> noise increase for every frequency decade you scale up to. If Q*f is
> approximately constant, you take another 20 dB hit in phase noise from
> degraded Q, totaling 40 dB/decade. Compared to 20 dB/decade plus the noise
> introduced by the phase detector and loop-filter of the PLL.
> https://en.wikipedia.org/wiki/Leeson's_equation
> 
> On Thu, Dec 22, 2016 at 10:53 AM, Attila Kinali  wrote:
> 
>> On Wed, 21 Dec 2016 18:59:20 -0800
>> Chris Albertson  wrote:
>> 
>>> Why to people always build 10MHz GPSDOs?   If the use of the GPSDO is to
>>> drive a microwave, why not build a MUCH higher frequency GPSDO.Is the
>>> reason that 10MHz crystals just happen to be very good and there are not
>>> good 100MHz ovenized crystals?  Or for portable use could you not use the
>>> 1PPS signal to discipline a microwave oscillator.
>> 
>> Short answer:
>> GPSDOs are mostly about high stability, not about low phase noise.
>> The 10MHz just happend to be a good compromise on stability, phase noise
>> and usefulnes.
>> 
>> Long answer:
>> A GPSDO has to exhibit good stability up to several 100 s to a few 1000 s.
>> This dictates that the OCXO used has to have as high long term stability
>> as possible. To get there you need an as thick crystal lab as possible.
>> The lower the frequency and the higher the overtone, the better.
>> Quartz resonators exhibit a nearly constant Q*f, so in first order
>> approximation, there is no point in choosing a higher frequency
>> crystal, as the Q will then decrease and thus increase the phase noise
>> would have been the same as the increased phase noise of a frequency
>> multiplier. Of course, frequency multiplication is not exactly perfect and
>> the Q*f is not 100% flat. There is a sweet spot where Q*f is maximal
>> between
>> 5MHz and 10MHz. For historical reasons, 10MHz has been deemed the more
>> useful
>> value and that's the reason we have a lot of 10MHz OCXO. If you go for high
>> stability oscillators, you will see a lot 5MHz OCXOs being used (for the
>> increased stability). Of course nobody says that these are the only
>> frequencies that can be used. For example, for specialized use cases you
>> will find GPSDOs with "odd" frequencies (like the 30.72MHz/61.44MHz used
>> for LTE).
>> 
>> As others have already commented, when using GPSDOs as a frequency
>> reference
>> for an GHz link, one would use some high frequency oscillator in the lower
>> 100MHz range (using a BAW quartz) or somewhere between 500MHz and 1000MHz
>> (using an SAW quartz) as a low phase noise reference and upconvert this.
>> Yes, it is possible to discipline such an oscillator directly using GPS,
>> but for the sake of stability (see above), design reuse and ease of
>> building/testing, using an 10MHz input is generally the better solution.
>> This allows to use any device that can produce an 10MHz signal, like
>> e.g. an Rb vapor cell standard.
>> 
>> 
>>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.
>> 
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Re: [time-nuts] Problem with HP 83623A 20 GHz sweep generator stepping up/down 100 Hz when not wanted.

[n2lym]

Dave,

Look at it with a narrow band SA and see if it's modulated by 100Hz.

73,

Mike N2LYM




On Thu, Dec 22, 2016 at 07:39 AM, Dr. David Kirkby (Kirkby Microwave 
Ltd) wrote:



On 22 December 2016 at 03:17, paul swed

 wrote:



Dave Congratulations on 10 Ghz SSB.



This was not a QSO at all. It was simply a one way transmission from a
signal generator at my end to a receiver at his end. No QSO was 
attempted.



Now to your question. I will fully believe you are seeing normal 
behavior
of the generators. Even if its dithering 100 Hz thats pretty amazing. 
Sweep
gens simply are not stable enough for narrow work like you are 
trying.

Now I am sure comments will prove me totally wrong.



But I find it a bit odd that HP would have a 1 Hz software option on 
this

instrument, if the instrument jumped up/down 100 Hz.

Now I don't yet have the 1 Hz option programmed in, and it might well
change the behavior completely, but I'd still like to find a way, if 
one

exists, of checking this with the equipment I have.

The signal generator is no longer supported, but I could try my luck 
seeing

if there are any known problems with this unit, or firmware upgrades
available - currently revision 29, May 1991.



But I don't think so. (Have been on 10G SSB over the years also. Only 
60

watts plus. Nothing fancy. ;-)  )
Regards
Paul
WB8TSL



60 W is clearly some setup. I also know a lot of people run portable 
stuff

on 10 GHz, where achieving frequency stability is more of a challenge,
although less so with GPS. But this is a laboratory instrument, from a
reputable manufacturer. I personally would not expected this behavior. 
I
actually purchased this very cheaply (£650 GBP, which would have been 
about

$900 at the time), but they are not cheap to buy now.


Dave
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Re: [time-nuts] Problem with HP 83623A 20 GHz sweep generator stepping up/down 100 Hz when not wanted.

[Brooke Clarke]

Hi David:

Some time ago I built an automated mixer test system where I first attempted to use HP 8350B sweep generators as the 
sources for the LO and RF inputs, but this failed to work because at the narrow bandwidth settings on the HP 8566 
spectrum analyzer there was way too much phase noise, so I switched to synthesized sweep generators made by HP and 
Wiltron, but I forget the model numbers.

http://www.prc68.com/I/RASS_PP.html#Spur
http://www.prc68.com/I/Images/RASS/Mixer.jpg

The SA was operated at it's narrowest IF bnadwidth (100 Hz?) and I don't remember seeing any amplitude variations, 
whereas when the 8350 was used the amplitude jumped wildly.


So I expect the problem is in the transverter.

--
Have Fun,

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

 Original Message 

I run a test over the weekend with a fellow radio ham. I transmitted 100 mW
or so at 10368.115 MHz from an HP 83623A 10 MHz to 20 GHz sweep generator

http://www.keysight.com/en/pd-101862%3Aepsg%3Apro-pn-83623A/synthesized-sweeper-10-mhz-to-20-ghz-high-power?cc=GB=eng

into a small horn antenna inside my lab.

He was able to receive me about 7 km away, although the signal was quite
week - it was 20 dB above the noise in a 2.9 Hz bandwidth.

What is odd, is that his transceiver + transverter combination indicates
the signal generator is shifting frequency up/down 100 Hz. This is not slow
drift, but a step change - see waterfall picture, where time is on the
vertical axis, and frequency is on the horizontal. Unfortunately I don't
know what the scale is on the vertical axis - I am trying to find out. The
frequency on the x-axis is not the true frequency, but that shown on an 2 m
amateur transceiver, so the true frequency is more than 10 GHz higher.

The step size on this HP sweeper is 1 kHz, so the 100 Hz up/down shift is
not due to a rotary encoder that might be just on the limit of two
frequencies.  Both the internal oscillator and a GPS locked frequency
standard were used during this test. Going from internal to external
reference caused a 450 Hz step in frequency, but did not change this
up/down 100 Hz behavior. So the problem is certainly not the crystal in a
10 MHz reference oscillator, as two have been tried, one of which was
locked to GPS.

Does anyone have an idea what may cause this behavior?

Does anyone have any ideas on the best way to investigate this, given the
signal is at more than 10 GHz?

What I do *not* have is any other signal generator capable of operation at
10 GHz. The only other sig gen I have is a 30 MHz Stanford Research DS345
function generator.

I don't have a TI counter at the minute, but had an offer of $300 accepted
on eBay for a 5370B a couple of days back, so should have a TI counter
soon. (Yes, I have had an 5370B and SR620 in the past, but for various
reasons no longer have them). The 5370B at $300 was a lot cheaper than an
SR620.

Other equipment I have include

* 22 GHz spectrum analyzer
* 30 MHz signal generator
* 20 GHz VNA

but no other signal generator capable of anywhere near 10 GHz.

I do have a couple of double balanced mixers which have RF and IF inputs
that will take 10 GHz, and an IF output that will go from DC to 4 GHz.
Introducing a REALLY long delay might allow the steps to be seen, as the
frequency at the LO and RF inputs of the mixers will be different. But
that's not really practical, as I'd need an awfully long bit of coax.

The 20 GHz vector network analyzer, which could be pressed into service as
a poor (rich) mans microwave signal source, but I suspect the output of
that is quite dirty, as the output is generated from a step recovery diode.
I have not yet tested it on a spectrum analyzer, but the SA has quite a few
spurious signals, so I'm never exactly confident of the SA. But one thing
to possibly is

* Set sweep generator to 10.368 GHz
* Set sweep generator to 10.378 GHz, so there's a 10 MHz difference.
* Mix the VNA + sweeper down to 10 MHz using a double balanced mixer
* Compare the 10 MHz at the output of a mixer to that of a 10 MHz crystal.
Steps of 100 Hz should then be seen I guess.

Any better suggestions?

Someone had kindly given me a key to change the step size of the signal
generator from 1 kHz to 1 Hz. I've not applied that yet, as it is quite a
complex procedure. But the fact the step size of this is 1 kHz, but it is
shifting up/down 100 Hz, does not make sense. Especially given the unit is
capable of 1 Hz resolution, but HP decided to charge extra for 1 Hz steps.
Luckily this is just a software option.

I did wonder if the signal generator was incapable of output the exact
frequency needed, so it was stepped up/down periodically so it gave the
right number of cycles over a long duration. But again, the fact it can
step 1 Hz with just a software upgrade suggest that's not the case.

The radio ham that noticed this step change in frequency is well used to

Re: [time-nuts] Ublox M8N - have I a XO or TCXO ?

[Mike Millen]

On 22/12/2016 16:04, David wrote:

On Wed, 21 Dec 2016 19:29:00 +, you wrote:


You may be able to identify the initial steady current drawn by the TCXO
heater, then the cycling once it's hit the right temp?

If there's no change at all in average current as it warms then it may
not have a TCXO.

Mike

What heater?  The big advantage of a TCXO (temperature compensated)
over an OCXO (oven controlled) is the lack of a heater allows low
power operation.



My mistake... you're quite right.

Brain-fade, I'm afraid.

Mike

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Re: [time-nuts] Using GPSDO as a Refrence for Protable Amateur Radio Microwave Operations

[Scott Stobbe]

Well for the same Q a competing oscillator will still take a 20 dB phase
noise increase for every frequency decade you scale up to. If Q*f is
approximately constant, you take another 20 dB hit in phase noise from
degraded Q, totaling 40 dB/decade. Compared to 20 dB/decade plus the noise
introduced by the phase detector and loop-filter of the PLL.
https://en.wikipedia.org/wiki/Leeson's_equation

On Thu, Dec 22, 2016 at 10:53 AM, Attila Kinali  wrote:

> On Wed, 21 Dec 2016 18:59:20 -0800
> Chris Albertson  wrote:
>
> > Why to people always build 10MHz GPSDOs?   If the use of the GPSDO is to
> > drive a microwave, why not build a MUCH higher frequency GPSDO.Is the
> > reason that 10MHz crystals just happen to be very good and there are not
> > good 100MHz ovenized crystals?  Or for portable use could you not use the
> > 1PPS signal to discipline a microwave oscillator.
>
> Short answer:
> GPSDOs are mostly about high stability, not about low phase noise.
> The 10MHz just happend to be a good compromise on stability, phase noise
> and usefulnes.
>
> Long answer:
> A GPSDO has to exhibit good stability up to several 100 s to a few 1000 s.
> This dictates that the OCXO used has to have as high long term stability
> as possible. To get there you need an as thick crystal lab as possible.
> The lower the frequency and the higher the overtone, the better.
> Quartz resonators exhibit a nearly constant Q*f, so in first order
> approximation, there is no point in choosing a higher frequency
> crystal, as the Q will then decrease and thus increase the phase noise
> would have been the same as the increased phase noise of a frequency
> multiplier. Of course, frequency multiplication is not exactly perfect and
> the Q*f is not 100% flat. There is a sweet spot where Q*f is maximal
> between
> 5MHz and 10MHz. For historical reasons, 10MHz has been deemed the more
> useful
> value and that's the reason we have a lot of 10MHz OCXO. If you go for high
> stability oscillators, you will see a lot 5MHz OCXOs being used (for the
> increased stability). Of course nobody says that these are the only
> frequencies that can be used. For example, for specialized use cases you
> will find GPSDOs with "odd" frequencies (like the 30.72MHz/61.44MHz used
> for LTE).
>
> As others have already commented, when using GPSDOs as a frequency
> reference
> for an GHz link, one would use some high frequency oscillator in the lower
> 100MHz range (using a BAW quartz) or somewhere between 500MHz and 1000MHz
> (using an SAW quartz) as a low phase noise reference and upconvert this.
> Yes, it is possible to discipline such an oscillator directly using GPS,
> but for the sake of stability (see above), design reuse and ease of
> building/testing, using an 10MHz input is generally the better solution.
> This allows to use any device that can produce an 10MHz signal, like
> e.g. an Rb vapor cell standard.
>
>
> 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
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Re: [time-nuts] SR620 Failure Code.

[Bob Camp]

Hi

There are a number of SRS 620’s with big block letter warning sheets taped to 
the top
of them about error 34. It is a *very* common thing to run into and (obviously) 
something
the guys in the repair shop get tired of really fast.

Bob

> On Dec 22, 2016, at 1:27 PM, Magnus Danielson  
> wrote:
> 
> Rick,
> 
> On 12/22/2016 05:53 PM, W2GPS wrote:
>> Time-nuts,
>> 
>> My SR620 has started reporting "test error 34" on power-up and will do
>> nothing after that. Does anyone know what that message means? I have a
>> reasonable lab and I would try to repair the unit myself but I have no
>> documentation. Is service documentation available or should I just ship it
>> back to Stanford Research to get fixed?
> 
> The manual, which you can download for free from SRS, says (page 57):
> 
> "If the UHF prescaler of channel A is selected when
> the unit is powered off and then on again, the unit
> will display “TEST ERROR 34”. This error may be
> corrected by deselecting the UHF of channel A. To
> run this procedure, press input button of channel
> “A” until UHF is not highlighted. Then turn the
> power off and on again."
> 
> So RTFM and execute accordingly might be all that you need to do.
> 
> Best Regards,
> Magnus
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Re: [time-nuts] u-blox LEAH M8F

[Bob Camp]

Hi

There are a couple of issues in multi GNSS timing. One is the basic time offset 
between systems (maybe a few ns, maybe a lot more). The next is the accuracy
of the estimate of that offset (again maybe a few ns, maybe …). After that you 
get into things like survey accuracy. Position hold is a single fixed location 
that
gets applied to all systems. If the “right”survey is here for this system and 
there
for that system, there will be an error one way or the other. Do they agree to 
CM or M
or 10’s of M? Some places they agree very well. Other places not so much ….

Lots of messy details.

Bob


> On Dec 22, 2016, at 12:23 PM, Scott Stobbe  wrote:
> 
> There was an interesting comment in the Lea-m8f datasheet,
> "In strong signal clear-sky applications the best time pulse consistency
> between neighbouring receivers is
> achieved when using a single GNSS because of the small time offsets between
> different GNSS systems. "
> 
> 
> On Thu, Dec 22, 2016 at 8:01 AM John Haine 
> wrote:
> 
>> I was slightly imprecise in my previous posting about ubx timing modules
>> 
>> and a few people have raised queries in the list or by email.
>> 
>> 
>> 
>> What I should have said is that this module is designed as a precise
>> 
>> low-noise /frequency /reference so it directly generates the 30.72 MHz
>> 
>> needed in LTE infrastructure from a GPS disciplined VCTCXO.  As I
>> 
>> understand it, the usual 10 MHz output is digitally generated and
>> 
>> jitters, so can't be used as a reference in high performance radio
>> 
>> systems.  One could use a phase-locked synth to multiply up from the 1
>> 
>> PPS signal but given the large ratio needed this is prone to generating
>> 
>> its own noise.  The M8F does it all internally and is therefore
>> 
>> preferred if what you want is a low noise frequency reference, though
>> 
>> its frequency may not be ideal if for example you wanted 10 MHz - you
>> 
>> could get 10.24 MHz by dividing by 3 but 10 MHz is trickier.
>> 
>> 
>> 
>> --
>> 
>> John Haine
>> 
>> 9 Parkway
>> 
>> Shudy Camps
>> 
>> Cambridge
>> 
>> CB21 4RQ
>> 
>> 
>> 
>> 01799 584773 (T)
>> 
>> 07841 322831 (M)
>> 
>> 
>> 
>> ___
>> 
>> time-nuts mailing list -- time-nuts@febo.com
>> 
>> To unsubscribe, go to
>> https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts
>> 
>> and follow the instructions there.
>> 
>> 
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Re: [time-nuts] SR620 Failure Code.

[Azelio Boriani]

Here you can find all about the SR620:

search for SR620.

On Thu, Dec 22, 2016 at 5:53 PM, W2GPS  wrote:
> Time-nuts,
>
>
>
> My SR620 has started reporting "test error 34" on power-up and will do
> nothing after that. Does anyone know what that message means? I have a
> reasonable lab and I would try to repair the unit myself but I have no
> documentation. Is service documentation available or should I just ship it
> back to Stanford Research to get fixed?
>
>
>
> Rick
>
> W2GPS
>
>
>
> ___
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Re: [time-nuts] SR620 Failure Code.

[Magnus Danielson]

Rick,

On 12/22/2016 05:53 PM, W2GPS wrote:

Time-nuts,

My SR620 has started reporting "test error 34" on power-up and will do
nothing after that. Does anyone know what that message means? I have a
reasonable lab and I would try to repair the unit myself but I have no
documentation. Is service documentation available or should I just ship it
back to Stanford Research to get fixed?


The manual, which you can download for free from SRS, says (page 57):

"If the UHF prescaler of channel A is selected when
the unit is powered off and then on again, the unit
will display “TEST ERROR 34”. This error may be
corrected by deselecting the UHF of channel A. To
run this procedure, press input button of channel
“A” until UHF is not highlighted. Then turn the
power off and on again."

So RTFM and execute accordingly might be all that you need to do.

Best Regards,
Magnus
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[time-nuts] SR620 Failure Code.

[W2GPS]

Time-nuts,

 

My SR620 has started reporting "test error 34" on power-up and will do
nothing after that. Does anyone know what that message means? I have a
reasonable lab and I would try to repair the unit myself but I have no
documentation. Is service documentation available or should I just ship it
back to Stanford Research to get fixed?

 

Rick

W2GPS

 

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Re: [time-nuts] u-blox LEAH M8F

[Scott Stobbe]

There was an interesting comment in the Lea-m8f datasheet,
"In strong signal clear-sky applications the best time pulse consistency
between neighbouring receivers is
achieved when using a single GNSS because of the small time offsets between
different GNSS systems. "


On Thu, Dec 22, 2016 at 8:01 AM John Haine 
wrote:

> I was slightly imprecise in my previous posting about ubx timing modules
>
> and a few people have raised queries in the list or by email.
>
>
>
> What I should have said is that this module is designed as a precise
>
> low-noise /frequency /reference so it directly generates the 30.72 MHz
>
> needed in LTE infrastructure from a GPS disciplined VCTCXO.  As I
>
> understand it, the usual 10 MHz output is digitally generated and
>
> jitters, so can't be used as a reference in high performance radio
>
> systems.  One could use a phase-locked synth to multiply up from the 1
>
> PPS signal but given the large ratio needed this is prone to generating
>
> its own noise.  The M8F does it all internally and is therefore
>
> preferred if what you want is a low noise frequency reference, though
>
> its frequency may not be ideal if for example you wanted 10 MHz - you
>
> could get 10.24 MHz by dividing by 3 but 10 MHz is trickier.
>
>
>
> --
>
> John Haine
>
> 9 Parkway
>
> Shudy Camps
>
> Cambridge
>
> CB21 4RQ
>
>
>
> 01799 584773 (T)
>
> 07841 322831 (M)
>
>
>
> ___
>
> time-nuts mailing list -- time-nuts@febo.com
>
> To unsubscribe, go to
> https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts
>
> and follow the instructions there.
>
>
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Re: [time-nuts] Problem with HP 83623A 20 GHz sweep generator stepping up/down 100 Hz when not wanted.

[David]

On Thu, 22 Dec 2016 12:39:27 +, you wrote:

>But I find it a bit odd that HP would have a 1 Hz software option on this
>instrument, if the instrument jumped up/down 100 Hz.
>
>Now I don't yet have the 1 Hz option programmed in, and it might well
>change the behavior completely, but I'd still like to find a way, if one
>exists, of checking this with the equipment I have.
>
>The signal generator is no longer supported, but I could try my luck seeing
>if there are any known problems with this unit, or firmware upgrades
>available - currently revision 29, May 1991.
>
>...
>
>Dave

I agree with Bill, maybe something is going on at the other end.

While I do not expect this sort of thing from HP, could they have
deliberately designed the sweep generator to include those 100 Hz
bumps unless the 1 HZ software option was purchased?

Like Paul, I would not expect the kind of stability you need from a
sweep generator but that 100 Hz jump is just weird.  It does kind of
remind me of popcorn noise but without a time scale and a longer
record, it is difficult to tell.
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Re: [time-nuts] Ublox M8N - have I a XO or TCXO ?

[David]

On Wed, 21 Dec 2016 19:29:00 +, you wrote:

> Can anyone comment on the following data, and whether they think the
> oscillator in "my" M8N is a XO or a TCXO ?
>
>Can you monitor the current draw from cold (ambient)?
>
>You may be able to identify the initial steady current drawn by the TCXO
>heater, then the cycling once it's hit the right temp?
>
>If there's no change at all in average current as it warms then it may
>not have a TCXO.
>
>Mike

What heater?  The big advantage of a TCXO (temperature compensated)
over an OCXO (oven controlled) is the lack of a heater allows low
power operation.
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Re: [time-nuts] Using GPSDO as a Refrence for Protable Amateur Radio Microwave Operations

[Attila Kinali]

On Wed, 21 Dec 2016 18:59:20 -0800
Chris Albertson  wrote:

> Why to people always build 10MHz GPSDOs?   If the use of the GPSDO is to
> drive a microwave, why not build a MUCH higher frequency GPSDO.Is the
> reason that 10MHz crystals just happen to be very good and there are not
> good 100MHz ovenized crystals?  Or for portable use could you not use the
> 1PPS signal to discipline a microwave oscillator.

Short answer:
GPSDOs are mostly about high stability, not about low phase noise.
The 10MHz just happend to be a good compromise on stability, phase noise
and usefulnes.

Long answer:
A GPSDO has to exhibit good stability up to several 100 s to a few 1000 s.
This dictates that the OCXO used has to have as high long term stability
as possible. To get there you need an as thick crystal lab as possible.
The lower the frequency and the higher the overtone, the better.
Quartz resonators exhibit a nearly constant Q*f, so in first order
approximation, there is no point in choosing a higher frequency
crystal, as the Q will then decrease and thus increase the phase noise
would have been the same as the increased phase noise of a frequency
multiplier. Of course, frequency multiplication is not exactly perfect and
the Q*f is not 100% flat. There is a sweet spot where Q*f is maximal between
5MHz and 10MHz. For historical reasons, 10MHz has been deemed the more useful
value and that's the reason we have a lot of 10MHz OCXO. If you go for high
stability oscillators, you will see a lot 5MHz OCXOs being used (for the
increased stability). Of course nobody says that these are the only
frequencies that can be used. For example, for specialized use cases you
will find GPSDOs with "odd" frequencies (like the 30.72MHz/61.44MHz used
for LTE). 

As others have already commented, when using GPSDOs as a frequency reference
for an GHz link, one would use some high frequency oscillator in the lower
100MHz range (using a BAW quartz) or somewhere between 500MHz and 1000MHz
(using an SAW quartz) as a low phase noise reference and upconvert this.
Yes, it is possible to discipline such an oscillator directly using GPS,
but for the sake of stability (see above), design reuse and ease of
building/testing, using an 10MHz input is generally the better solution.
This allows to use any device that can produce an 10MHz signal, like
e.g. an Rb vapor cell standard.


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
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Re: [time-nuts] Using GPSDO as a Refrence for Protable Amateur Radio Microwave Operations

[jimlux]

On 12/21/16 9:08 PM, John Hawkinson wrote:

Chris Albertson  (and Bob Camp ):

Why to people always build 10MHz GPSDOs?


Because "a lot" (...) of amateur radio microwave equipment is designed
off the shelf to accept an external 10 MHz input. [And other kinds of
equipment, too.] If you're not designing from the ground-up, then it makes
a lot of sense.

-


In most cases, folks want good close in phase noise - 5 and 10 MHz are 
in the sweet spot of having good close in phase noise even after the 
20log(N) bump from multiplying it up.  A 100 MHz oscillator takes less 
multiplication, but because the crystal is physically smaller, it 
probably doesn't have phase noise that is lower than a 10 MHz multiplied up.


if you're multiplying up to 8 or 10 or 32 GHz, whether you start at 10 
or 100, it's still a lot of multiplying.  If you're using a PLL, the 
frequency gets divided down into the phase/frequency comparator, and 
dividing down from 10 is no different than dividing down from 100.
If you're doing chains of multipliers up, then starting a 10 gives you a 
bit more flexibility to design the multiplier chain in terms of where 
the various frequencies wind up, so as to avoid "inband" spurs later on.


Most ham radio designs tend to be mixes and matches of previous widgets. 
The whole transverter model, starting with 10 meters or 2 meters, and 
then mixing, converting, multiplying, etc. is great if you're trying to 
re-use stuff you already have, gradually adding bands, or trying to use 
30-40 year old surplus microwave gear.  It's not necessarily a good 
approach if you were starting from scratch and using modern components.



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Re: [time-nuts] u-blox LEAH M8F

[David J Taylor]

I was slightly imprecise in my previous posting about ubx timing modules 
and a few people have raised queries in the list or by email.


What I should have said is that this module is designed as a precise 
low-noise /frequency /reference so it directly generates the 30.72 MHz 
needed in LTE infrastructure from a GPS disciplined VCTCXO.  As I 
understand it, the usual 10 MHz output is digitally generated and 
jitters, so can't be used as a reference in high performance radio 
systems.  One could use a phase-locked synth to multiply up from the 1 
PPS signal but given the large ratio needed this is prone to generating 
its own noise.  The M8F does it all internally and is therefore 
preferred if what you want is a low noise frequency reference, though 
its frequency may not be ideal if for example you wanted 10 MHz - you 
could get 10.24 MHz by dividing by 3 but 10 MHz is trickier.


John Haine
==

I discovered an interesting comparison with the Jackson LTE-Lite here:

 http://www.jackson-labs.com/assets/uploads/main/Comparative_analysis.pdf

Cheers,
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] Ublox M8N - have I a XO or TCXO ?

[Didier Juges]

TCXO usually refers to Temperature Compensated Crystal Oscillator (no heater), 
as opposed to Oven Controlled Crystal Oscillator (OCXO) which has an oven.
I would not expect a TCXO to become warm or draw more current at power up. An 
OCXO would.

Didier KO4BB

On December 21, 2016 1:29:00 PM CST, Mike Millen  
wrote:
>
> Can anyone comment on the following data, and whether they think
>the
>
> oscillator in "my" M8N is a XO or a TCXO ?
>
>
>Can you monitor the current draw from cold (ambient)?
>
>You may be able to identify the initial steady current drawn by the
>TCXO
>heater, then the cycling once it's hit the right temp?
>
>If there's no change at all in average current as it warms then it may
>not have a TCXO.
>
>Mike
>
>
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-- 
Sent from my Moto-X wireless tracker while I do other things.
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Re: [time-nuts] Ublox M8N - have I a XO or TCXO ?

[EB4APL]

TCXO is not an OCXO, they don't have an oven. They compensate the 
temperature induced drift using a temperature sensor, a microcontroller  
and a table or parameter set for adjusting the output frequency. BTW, 
for some applications they are unsuitable as they adjust the frequency 
in steps.



Regards,

Ignacio EB4APL

El 21/12/2016 a las 20:29, Mike Millen escribió:


 Can anyone comment on the following data, and whether they think the


oscillator in "my" M8N is a XO or a TCXO ?



Can you monitor the current draw from cold (ambient)?

You may be able to identify the initial steady current drawn by the TCXO
heater, then the cycling once it's hit the right temp?

If there's no change at all in average current as it warms then it may
not have a TCXO.

Mike


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Re: [time-nuts] Problem with HP 83623A 20 GHz sweep generator stepping up/down 100 Hz when not wanted.

[Dr. David Kirkby (Kirkby Microwave Ltd)]

On 22 December 2016 at 01:35, Brooke Clarke  wrote:

> Hi David:
>
> Do you have a comb generator?
>

No.

Dave
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Re: [time-nuts] Problem with HP 83623A 20 GHz sweep generator stepping up/down 100 Hz when not wanted.

[Dr. David Kirkby (Kirkby Microwave Ltd)]

On 22 December 2016 at 03:51, Tom Knox  wrote:

> If it is any help, the 836XXA/B series are all capable of 1Hz resolution
> but are locked at 1KHz unless you enter the license key for option 008. So
> it could be software/firmware related.
>
> Happy Merry;
>
> Thomas Knox
>

I have the license key - not exactly via an official means I might add. I
would not be surprised if that changed the behavior in some way, but I'd
like to resolve this problem, if one exists, before the upgrade.

Dave
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Re: [time-nuts] Problem with HP 83623A 20 GHz sweep generator stepping up/down 100 Hz when not wanted.

[Dr. David Kirkby (Kirkby Microwave Ltd)]

On 22 December 2016 at 03:17, paul swed  wrote:

> Dave Congratulations on 10 Ghz SSB.
>

This was not a QSO at all. It was simply a one way transmission from a
signal generator at my end to a receiver at his end. No QSO was attempted.


> Now to your question. I will fully believe you are seeing normal behavior
> of the generators. Even if its dithering 100 Hz thats pretty amazing. Sweep
> gens simply are not stable enough for narrow work like you are trying.
> Now I am sure comments will prove me totally wrong.
>

But I find it a bit odd that HP would have a 1 Hz software option on this
instrument, if the instrument jumped up/down 100 Hz.

Now I don't yet have the 1 Hz option programmed in, and it might well
change the behavior completely, but I'd still like to find a way, if one
exists, of checking this with the equipment I have.

The signal generator is no longer supported, but I could try my luck seeing
if there are any known problems with this unit, or firmware upgrades
available - currently revision 29, May 1991.



> But I don't think so. (Have been on 10G SSB over the years also. Only 60
> watts plus. Nothing fancy. ;-)  )
> Regards
> Paul
> WB8TSL
>

60 W is clearly some setup. I also know a lot of people run portable stuff
on 10 GHz, where achieving frequency stability is more of a challenge,
although less so with GPS. But this is a laboratory instrument, from a
reputable manufacturer. I personally would not expected this behavior. I
actually purchased this very cheaply (£650 GBP, which would have been about
$900 at the time), but they are not cheap to buy now.


Dave
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Re: [time-nuts] Ublox M8N - have I a XO or TCXO ?

[Mike Millen]

 Can anyone comment on the following data, and whether they think the


oscillator in "my" M8N is a XO or a TCXO ?



Can you monitor the current draw from cold (ambient)?

You may be able to identify the initial steady current drawn by the TCXO
heater, then the cycling once it's hit the right temp?

If there's no change at all in average current as it warms then it may
not have a TCXO.

Mike


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Re: [time-nuts] Using GPSDO as a Refrence for Protable Amateur Radio Microwave Operations

[Mike Seguin]

On 12/21/2016 2:06 PM, Eric Haskell wrote:

I am microwave amateur radio operator. A friend was discussing using an

eBay purchased Trimble 57963-D for providing a 10 MHz reference.

As you stated, the time needed for position hold is significant. For my 
microwave gear that needs 10 MHz in the field, I use a Jackson Labs 
LTE-Lite.


http://www.jackson-labs.com/index.php/products/lte_lite

It can be run in "mobile" mode. I have used it to discipline gear I run 
up to 241 GHz. Most of the disciplined LO's are Axtal in the 100 MHz 
range. It also supports 'position/hold' mode for use in a fixed position 
such as at home in my shop.


There was a group buy a while back.

Frankly, absolute frequency accuracy is a bit less of an issue than it 
used to be because so many of us now use SDR's for panadapters on 
receive. We can "see" 48/96/192 kHz of bandwidth at once so if a signal 
is off a few kHz and moves a bit, no big deal.


If you are trying to do weak signal digital modes, that's another story.

Mike

--

73,
Mike, N1JEZ
"A closed mouth gathers no feet"
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[time-nuts] u-blox LEAH M8F

[John Haine]

I was slightly imprecise in my previous posting about ubx timing modules 
and a few people have raised queries in the list or by email.


What I should have said is that this module is designed as a precise 
low-noise /frequency /reference so it directly generates the 30.72 MHz 
needed in LTE infrastructure from a GPS disciplined VCTCXO.  As I 
understand it, the usual 10 MHz output is digitally generated and 
jitters, so can't be used as a reference in high performance radio 
systems.  One could use a phase-locked synth to multiply up from the 1 
PPS signal but given the large ratio needed this is prone to generating 
its own noise.  The M8F does it all internally and is therefore 
preferred if what you want is a low noise frequency reference, though 
its frequency may not be ideal if for example you wanted 10 MHz - you 
could get 10.24 MHz by dividing by 3 but 10 MHz is trickier.


--
John Haine
9 Parkway
Shudy Camps
Cambridge
CB21 4RQ

01799 584773 (T)
07841 322831 (M)

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Re: [time-nuts] Problem with HP 83623A 20 GHz sweep generator stepping up/down 100 Hz when not wanted.

[wb6bnq]

Dr. David Kirkby (Kirkby Microwave Ltd) wrote:


snip ..

The radio ham that noticed this step change in frequency is well used to
listening on 10 GHz, and hearing beacons. So I think its reasonable to
assume that the problem is not his end, but my end.

Any thoughts, which do NOT include purchasing a second expensive 20 GHz
signal generator. They are around $10,000 each, so a bit out of my price
range.

Dave
 


Dave,

I would not automatically assume that the problem is at your end of 
things.  It could well be something has gone wrong at the other end.


BillWB6BNQ

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