Re: [time-nuts] GPS with 10KHz output

[Chris Albertson]

If you ned the 10KHz, Jupiter is one that has been used.  I think a
10KHz GPS will make your GPSDO converge quickly but for long term use
a 1Hz GPS works as well and will be easier t replace years from now.
Also a 1HZ GPS with about equivalent performance is MUCH less
expensive (see ebay 271152854221 which is $15)But 10KHz does allow
a simpler design for the GPSDO that can be done 100% analog

On Wed, Sep 18, 2013 at 7:21 PM, Bill Reed  wrote:
> Hi,
>
> Does anyone know the suitability of this module for GPSDO ?
>
> I am new to the group.
>
> Thanks,
>
> Bill R
>
>
>  
> http://www.ebay.com/itm/Navman-jupiter-T-Tu60-GPS-Kit-1pps-10khz-GPS-Module-/260790984470?pt=US_Ham_Radio_Amplifiers&hash=item3cb85a9f16
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-- 

Chris Albertson
Redondo Beach, California
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Re: [time-nuts] New NTBW50AA

[Charles Steinmetz]

Dave wrote:

You didn't say, but I get the feeling maybe I should be getting 
smaller ppt numbers?  When you say  noisy, is high ppt generally a 
result of excess noise (front end NF)?


Hard to say about the ppt numbers -- my TBolts give somewhat lower 
numbers than you are getting, but they use different OCXOs with 
different phaselocking circuitry, so I can't say what would be 
considered normal for the model you have.  Also, as several have said 
already, the GPSDO is measuring itself with itself (no independent 
reference), so its proclamations need to be taken with more than some 
caution.


Excess noise on the GPS signals (from whatever cause) causes timing 
errors in the GPS, which makes the GPS think the oscillator needs 
correction, which leads to DAC adjustments that aren't 
necessary.  But if you are seeing at least some numbers in the 50 dBc 
and higer range, there is nothing further you can do in this 
regard.  (Well, if the model you have supports it, you can set a 
"signal level" mask that will exclude satellites with signals below a 
dBc threshold of your choice.  As with the elevation mask, if you get 
too aggressive you may force the unit into holdover when there are a 
few OK but not great signals.)


As we all have said repeatedly, you need a good, accurate 
survey.  Also, it is the nature of crystal oscillators that when they 
are disturbed (turned off and back on, frequency adjusted, 
handling/moving, fast temperature changes, etc., etc.) that they take 
time to settle back down -- often months.  Now that you have a 
permanent antenna location, do a precision survey, SAVE IT, then let 
the unit sit undisturbed for several months and see where you are.


You are certainly in the ballpark -- there are clearly no gross problems.

Bob presumably knows more than I do about non-TBolt Trimbles (since I 
know nothing about them).  If he says you can't adjust the TC and 
"gain" I'd be inclined to believe him.  (And if you can't adjust the 
"gain," there is no point in measuring the EFC characteristics of the 
OCXO, except for curiosity.)


The antenna is a Lucent PCTEL "GPS-TMG-HR-26N, High Rejection 26dB 
With Enhanced Narrow Band Filtering", apparently for high RF 
environments, only one I've got or tried


You may have read on another thread about narrow bandpass filters 
tending to have rising group delay at the passband edges.  An antenna 
with "Enhanced Narrow Band Filtering" very likely has more group 
delay error than one with more gentle filtering, so it is possible 
that satellites with high doppler shifts are causing the GPS timing 
solution to shift around more than it would with a different 
antenna.  The one you have is presumably good enough for cell timing, 
since that is what it was designed for.  The question is whether the 
lower group delay of an antenna without "Enhanced Narrow Band 
Filtering" would be enough better that you could tell.  Without 
measuring the filters, we can't really predict what to expect.  You 
might ask the seller if he would exchange your antenna for one that 
doesn't have the extra filtering.  You almost certainly don't need it 
in your rural location, and an antenna without it would at least not 
be any worse, all else equal.


Best regards,

Charles



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[time-nuts] GPS with 10KHz output

[Bill Reed]

Hi,

Does anyone know the suitability of this module for GPSDO ?

I am new to the group.

Thanks,

Bill R


 
http://www.ebay.com/itm/Navman-jupiter-T-Tu60-GPS-Kit-1pps-10khz-GPS-Module-/260790984470?pt=US_Ham_Radio_Amplifiers&hash=item3cb85a9f16
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Re: [time-nuts] GPSDO vs Rb standard

[Bob Camp]

Hi

Some numbers:

Your Rb should hold <10 ppt per month. It's 1 second ADEV should be about 10 
ppt as well. (makes it interesting to measure).

Your Rb should hold  < 1 ppt per degree C on average. It will have a nasty 
glitch (around 1 ppt as it steps over a temperature boundary). Best to keep it 
stable to < 0.5 C.

For long(er) averaging times the Rb should have an ADEV that goes as the square 
root of tau. It'll be 10X better at 100 seconds than at 1 second. It *could* be 
100X better at 10,000 seconds except for that glitch. It's not going to get 
beyond 0.2 ppt ADEV without some major help. 

All that said, with simple temperature stabilization, it should let you check 
out your GPSDO for drift. Within the ADEV imposed limits it'll tell you if 
things are holding together on a day to day / week to week basis.

Bob


On Sep 18, 2013, at 8:32 PM, Bob Stewart  wrote:

> Bob, I've been mulling over the question of a case, and I was thinking of 
> getting a 2M brick amp and putting it inside, bolted upside down to the heat 
> sink.  Good idea?  Anybody got a busted one?
> 
> Bob
> 
> 
> 
> 
> 
>> 
>> From: Bob Camp 
>> To: Discussion of precise time and frequency measurement 
>>  
>> Sent: Wednesday, September 18, 2013 7:22 PM
>> Subject: Re: [time-nuts] GPSDO vs Rb standard
>> 
>> 
>> Hi
>> 
>> The Rb's have a couple of issues:
>> 
>> 1) Its been years since they were set on frequency and they do have a yearly 
>> drift rate
>> 2) They have a temperature coefficient of drift that may be fairly large 
>> (0.1 ppb over -30 to +70)
>> 3) They self heat quite a bit, so they do move temperature / need a heatsink
>> 
>> The solution to the temperature issue is a servo controlled fan. The 
>> solution to the first drift / accuracy issue is to calibrate them against 
>> something else.
>> 
>> Bob
>> 
>> 
>> On Sep 18, 2013, at 7:13 PM, "John C. Westmoreland, P.E." 
>>  wrote:
>> 
>>> Azelio and Fellow Time Nuts,
>>> 
>>> Isn't the GPS 1PPS signal supposed to be 'precise' to within what error?  I
>>> imagine this is in the specs of the specific receiver -
>>> but I was wondering if some of you have actually measured what that is -
>>> and could report the numbers that you have found.
>>> 
>>> Thanks!
>>> John Westmoreland
>>> 
>>> 
>>> 
>>> On Wed, Sep 18, 2013 at 3:07 PM, Azelio Boriani 
>>> wrote:
>>> 
 Instead of using the Rb's PPS, use the GPS receiver's PPS. Maybe you
 will find out that the Rb is slow... you can also check the Rb's PPS
 against the GPS's PPS.
 
 On Wed, Sep 18, 2013 at 11:47 PM, Bob Stewart  wrote:
> I hooked the Rb's 1PPS to the trigger input on my old Tek 455, 10MHz
> GPSDO to Channel A, .05us trace, and turned the lights out so I could
> see it.  The 10MHz is marching right to left about 1 cycle every 20
> seconds.  So, can I say that the Rb considers my GPSDO to be too fast by
 about 5ppb?
> 
> 
> Bob
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[time-nuts] HP 5350A Frequency Counter EPROMs

[Bert, VE2ZAZ]

HI,

Sorry to come in with a Out-of-Topic question, but I am stuck. I am trying to 
bring an HP 5350A frequency counter back to life. I am looking for the two 
EPROM loads. If you can help, please contact me direct.

Thanks,

Bert, VE2ZAZ
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Re: [time-nuts] GPSDO vs Rb standard

[Bob Camp]

Hi

There are lots of case solutions. A busted piece of HP gear is a nice way to 
come up with a case. Heatsink material is available from several web sites cut 
to order quite cheap. A simple computer fan is way more air than you will ever 
need. The obvious missing link is the controller. I'd run something up with a 
micro talking to a 4 wire fan header. That way you have tach feedback on the 
fan and all the PWM stuff is driven on the fan end. More or less a weekend 
project on a piece of pert board. Maybe a bit more than that if you do a pc 
board. 

(yes I realize this heading horribly close to talking about building things …. 
alarm bells are ringing somewhere…..)

Bob

On Sep 18, 2013, at 8:32 PM, Bob Stewart  wrote:

> Bob, I've been mulling over the question of a case, and I was thinking of 
> getting a 2M brick amp and putting it inside, bolted upside down to the heat 
> sink.  Good idea?  Anybody got a busted one?
> 
> Bob
> 
> 
> 
> 
> 
>> 
>> From: Bob Camp 
>> To: Discussion of precise time and frequency measurement 
>>  
>> Sent: Wednesday, September 18, 2013 7:22 PM
>> Subject: Re: [time-nuts] GPSDO vs Rb standard
>> 
>> 
>> Hi
>> 
>> The Rb's have a couple of issues:
>> 
>> 1) Its been years since they were set on frequency and they do have a yearly 
>> drift rate
>> 2) They have a temperature coefficient of drift that may be fairly large 
>> (0.1 ppb over -30 to +70)
>> 3) They self heat quite a bit, so they do move temperature / need a heatsink
>> 
>> The solution to the temperature issue is a servo controlled fan. The 
>> solution to the first drift / accuracy issue is to calibrate them against 
>> something else.
>> 
>> Bob
>> 
>> 
>> On Sep 18, 2013, at 7:13 PM, "John C. Westmoreland, P.E." 
>>  wrote:
>> 
>>> Azelio and Fellow Time Nuts,
>>> 
>>> Isn't the GPS 1PPS signal supposed to be 'precise' to within what error?  I
>>> imagine this is in the specs of the specific receiver -
>>> but I was wondering if some of you have actually measured what that is -
>>> and could report the numbers that you have found.
>>> 
>>> Thanks!
>>> John Westmoreland
>>> 
>>> 
>>> 
>>> On Wed, Sep 18, 2013 at 3:07 PM, Azelio Boriani 
>>> wrote:
>>> 
 Instead of using the Rb's PPS, use the GPS receiver's PPS. Maybe you
 will find out that the Rb is slow... you can also check the Rb's PPS
 against the GPS's PPS.
 
 On Wed, Sep 18, 2013 at 11:47 PM, Bob Stewart  wrote:
> I hooked the Rb's 1PPS to the trigger input on my old Tek 455, 10MHz
> GPSDO to Channel A, .05us trace, and turned the lights out so I could
> see it.  The 10MHz is marching right to left about 1 cycle every 20
> seconds.  So, can I say that the Rb considers my GPSDO to be too fast by
 about 5ppb?
> 
> 
> Bob
> ___
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>> 
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Re: [time-nuts] GPSDO vs Rb standard

[Bob Stewart]

Bob, I've been mulling over the question of a case, and I was thinking of 
getting a 2M brick amp and putting it inside, bolted upside down to the heat 
sink.  Good idea?  Anybody got a busted one?

Bob





>
> From: Bob Camp 
>To: Discussion of precise time and frequency measurement  
>Sent: Wednesday, September 18, 2013 7:22 PM
>Subject: Re: [time-nuts] GPSDO vs Rb standard
> 
>
>Hi
>
>The Rb's have a couple of issues:
>
>1) Its been years since they were set on frequency and they do have a yearly 
>drift rate
>2) They have a temperature coefficient of drift that may be fairly large (0.1 
>ppb over -30 to +70)
>3) They self heat quite a bit, so they do move temperature / need a heatsink
>
>The solution to the temperature issue is a servo controlled fan. The solution 
>to the first drift / accuracy issue is to calibrate them against something 
>else.
>
>Bob
>
>
>On Sep 18, 2013, at 7:13 PM, "John C. Westmoreland, P.E." 
> wrote:
>
>> Azelio and Fellow Time Nuts,
>> 
>> Isn't the GPS 1PPS signal supposed to be 'precise' to within what error?  I
>> imagine this is in the specs of the specific receiver -
>> but I was wondering if some of you have actually measured what that is -
>> and could report the numbers that you have found.
>> 
>> Thanks!
>> John Westmoreland
>> 
>> 
>> 
>> On Wed, Sep 18, 2013 at 3:07 PM, Azelio Boriani 
>> wrote:
>> 
>>> Instead of using the Rb's PPS, use the GPS receiver's PPS. Maybe you
>>> will find out that the Rb is slow... you can also check the Rb's PPS
>>> against the GPS's PPS.
>>> 
>>> On Wed, Sep 18, 2013 at 11:47 PM, Bob Stewart  wrote:
 I hooked the Rb's 1PPS to the trigger input on my old Tek 455, 10MHz
 GPSDO to Channel A, .05us trace, and turned the lights out so I could
 see it.  The 10MHz is marching right to left about 1 cycle every 20
 seconds.  So, can I say that the Rb considers my GPSDO to be too fast by
>>> about 5ppb?
 
 
 Bob
 ___
 time-nuts mailing list -- time-nuts@febo.com
 To unsubscribe, go to
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 and follow the instructions there.
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Re: [time-nuts] GPSDO vs Rb standard

[Bob Camp]

Hi

When I want to tune an Rb, I just hook up to it with a terminal program and 
hack away at it. There's not a lot to the protocol.

Bob


On Sep 18, 2013, at 6:49 PM, Bob Stewart  wrote:

> Hi Bob,
> 
> As always, thanks for your informed help.  I had been reaching the same 
> conclusion, but needed unbiased confirmation.  I think the RUBY4 software 
> does what I want?  I'll look into it.
> 
> Bob
> 
> 
> 
> 
> 
>> 
>> From: Bob Camp 
>> To: Discussion of precise time and frequency measurement 
>>  
>> Sent: Wednesday, September 18, 2013 5:01 PM
>> Subject: Re: [time-nuts] GPSDO vs Rb standard
>> 
>> 
>> Hi
>> 
>> One cycle of 10 MHz would be 100 ns. 100 ns per second would be 100 ppb. 
>> 100ns per 20 seconds would indeed be 5 ppb.
>> 
>> Since the Rb is *stable* but not *accurate*, the real question is - how much 
>> does the 5 ppb change by? The Rb can't tell you if the GPSDO is correct. The 
>> best it can do is tell you if it changed. If you can demonstrate that the 
>> GPSDO is locked up, and that it's stable for many days, you can reasonably 
>> conclude that the GPSDO is accurate. 
>> 
>> I'd say the first step is to get the Rb tuned closer to the GPSDO. You 
>> should be looking for < 0.01 ppb changes. That's going to be tough with a 5 
>> ppb offset. 
>> 
>> Bob
>> 
>> On Sep 18, 2013, at 5:47 PM, Bob Stewart  wrote:
>> 
>>> I hooked the Rb's 1PPS to the trigger input on my old Tek 455, 10MHz 
>>> GPSDO to Channel A, .05us trace, and turned the lights out so I could 
>>> see it.  The 10MHz is marching right to left about 1 cycle every 20 
>>> seconds.  So, can I say that the Rb considers my GPSDO to be too fast by 
>>> about 5ppb?
>>> 
>>> 
>>> Bob
>>> ___
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>>> and follow the instructions there.
>> 
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>> 
>> 
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Re: [time-nuts] GPSDO vs Rb standard

[Bob Camp]

Hi

The purpose here is to estimate the stability of a GPSDO. For that, you don't 
need "perfect". You simply need to get the Rb close enough that it's error is 
manageable.

Bob

On Sep 18, 2013, at 8:18 PM, Azelio Boriani  wrote:

> The GPS's PPS wanders but it can be used to have an idea whether your
> Rb is fast or slow. How much the wander will be, depends on the type
> of GPS receiver, the antenna position and the survey, the GPS clock
> granularity (the sawtooth). Given a suitable amount of time (5
> minutes, for example) you can see if the Rb PPS is fast or slow. I
> have measured up to 200nS of PPS peak-to-peak wander using a Z3815A as
> a reference.
> 
> On Thu, Sep 19, 2013 at 1:37 AM, Bob Stewart  wrote:
>> Hi John and Azelio,
>> 
>> The problem with the GPS 1PPS is the +/- 52ns sawtooth.  Without some magic 
>> hardware, you're left with using a stable 1PPS and then calibrating that to 
>> the correct frequency.  If my software does what my math says it does, then 
>> my OCXO is very close to correct.  Testing is time consuming to say the 
>> least.
>> 
>> Bob
>> 
>> 
>> 
>> 
>> 
>>> 
>>> From: "John C. Westmoreland, P.E." 
>>> To: Discussion of precise time and frequency measurement 
>>> 
>>> Sent: Wednesday, September 18, 2013 6:13 PM
>>> Subject: Re: [time-nuts] GPSDO vs Rb standard
>>> 
>>> 
>>> Azelio and Fellow Time Nuts,
>>> 
>>> Isn't the GPS 1PPS signal supposed to be 'precise' to within what error?  I
>>> imagine this is in the specs of the specific receiver -
>>> but I was wondering if some of you have actually measured what that is -
>>> and could report the numbers that you have found.
>>> 
>>> Thanks!
>>> John Westmoreland
>>> 
>>> 
>>> 
>>> On Wed, Sep 18, 2013 at 3:07 PM, Azelio Boriani 
>>> wrote:
>>> 
 Instead of using the Rb's PPS, use the GPS receiver's PPS. Maybe you
 will find out that the Rb is slow... you can also check the Rb's PPS
 against the GPS's PPS.
 
 On Wed, Sep 18, 2013 at 11:47 PM, Bob Stewart  wrote:
> I hooked the Rb's 1PPS to the trigger input on my old Tek 455, 10MHz
> GPSDO to Channel A, .05us trace, and turned the lights out so I could
> see it.  The 10MHz is marching right to left about 1 cycle every 20
> seconds.  So, can I say that the Rb considers my GPSDO to be too fast by
 about 5ppb?
> 
> 
> Bob
> ___
> time-nuts mailing list -- time-nuts@febo.com
> To unsubscribe, go to
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 To unsubscribe, go to
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 and follow the instructions there.
 
>>> ___
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>>> 
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>>> 
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Re: [time-nuts] GPSDO vs Rb standard

[Bob Camp]

Hi

The Rb's have a couple of issues:

1) Its been years since they were set on frequency and they do have a yearly 
drift rate
2) They have a temperature coefficient of drift that may be fairly large (0.1 
ppb over -30 to +70)
3) They self heat quite a bit, so they do move temperature / need a heatsink

The solution to the temperature issue is a servo controlled fan. The solution 
to the first drift / accuracy issue is to calibrate them against something else.

Bob


On Sep 18, 2013, at 7:13 PM, "John C. Westmoreland, P.E." 
 wrote:

> Azelio and Fellow Time Nuts,
> 
> Isn't the GPS 1PPS signal supposed to be 'precise' to within what error?  I
> imagine this is in the specs of the specific receiver -
> but I was wondering if some of you have actually measured what that is -
> and could report the numbers that you have found.
> 
> Thanks!
> John Westmoreland
> 
> 
> 
> On Wed, Sep 18, 2013 at 3:07 PM, Azelio Boriani 
> wrote:
> 
>> Instead of using the Rb's PPS, use the GPS receiver's PPS. Maybe you
>> will find out that the Rb is slow... you can also check the Rb's PPS
>> against the GPS's PPS.
>> 
>> On Wed, Sep 18, 2013 at 11:47 PM, Bob Stewart  wrote:
>>> I hooked the Rb's 1PPS to the trigger input on my old Tek 455, 10MHz
>>> GPSDO to Channel A, .05us trace, and turned the lights out so I could
>>> see it.  The 10MHz is marching right to left about 1 cycle every 20
>>> seconds.  So, can I say that the Rb considers my GPSDO to be too fast by
>> about 5ppb?
>>> 
>>> 
>>> Bob
>>> ___
>>> 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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>> To unsubscribe, go to
>> https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts
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>> 
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Re: [time-nuts] GPSDO vs Rb standard

[Azelio Boriani]

The GPS's PPS wanders but it can be used to have an idea whether your
Rb is fast or slow. How much the wander will be, depends on the type
of GPS receiver, the antenna position and the survey, the GPS clock
granularity (the sawtooth). Given a suitable amount of time (5
minutes, for example) you can see if the Rb PPS is fast or slow. I
have measured up to 200nS of PPS peak-to-peak wander using a Z3815A as
a reference.

On Thu, Sep 19, 2013 at 1:37 AM, Bob Stewart  wrote:
> Hi John and Azelio,
>
> The problem with the GPS 1PPS is the +/- 52ns sawtooth.  Without some magic 
> hardware, you're left with using a stable 1PPS and then calibrating that to 
> the correct frequency.  If my software does what my math says it does, then 
> my OCXO is very close to correct.  Testing is time consuming to say the least.
>
> Bob
>
>
>
>
>
>>
>> From: "John C. Westmoreland, P.E." 
>>To: Discussion of precise time and frequency measurement 
>>Sent: Wednesday, September 18, 2013 6:13 PM
>>Subject: Re: [time-nuts] GPSDO vs Rb standard
>>
>>
>>Azelio and Fellow Time Nuts,
>>
>>Isn't the GPS 1PPS signal supposed to be 'precise' to within what error?  I
>>imagine this is in the specs of the specific receiver -
>>but I was wondering if some of you have actually measured what that is -
>>and could report the numbers that you have found.
>>
>>Thanks!
>>John Westmoreland
>>
>>
>>
>>On Wed, Sep 18, 2013 at 3:07 PM, Azelio Boriani 
>>wrote:
>>
>>> Instead of using the Rb's PPS, use the GPS receiver's PPS. Maybe you
>>> will find out that the Rb is slow... you can also check the Rb's PPS
>>> against the GPS's PPS.
>>>
>>> On Wed, Sep 18, 2013 at 11:47 PM, Bob Stewart  wrote:
>>> > I hooked the Rb's 1PPS to the trigger input on my old Tek 455, 10MHz
>>> > GPSDO to Channel A, .05us trace, and turned the lights out so I could
>>> > see it.  The 10MHz is marching right to left about 1 cycle every 20
>>> > seconds.  So, can I say that the Rb considers my GPSDO to be too fast by
>>> about 5ppb?
>>> >
>>> >
>>> > Bob
>>> > ___
>>> > time-nuts mailing list -- time-nuts@febo.com
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>>> https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts
>>> > and follow the instructions there.
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>>>
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>>
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Re: [time-nuts] GPSDO vs Rb standard

[Bob Stewart]

Hi John and Azelio,

The problem with the GPS 1PPS is the +/- 52ns sawtooth.  Without some magic 
hardware, you're left with using a stable 1PPS and then calibrating that to the 
correct frequency.  If my software does what my math says it does, then my OCXO 
is very close to correct.  Testing is time consuming to say the least.

Bob





>
> From: "John C. Westmoreland, P.E." 
>To: Discussion of precise time and frequency measurement  
>Sent: Wednesday, September 18, 2013 6:13 PM
>Subject: Re: [time-nuts] GPSDO vs Rb standard
> 
>
>Azelio and Fellow Time Nuts,
>
>Isn't the GPS 1PPS signal supposed to be 'precise' to within what error?  I
>imagine this is in the specs of the specific receiver -
>but I was wondering if some of you have actually measured what that is -
>and could report the numbers that you have found.
>
>Thanks!
>John Westmoreland
>
>
>
>On Wed, Sep 18, 2013 at 3:07 PM, Azelio Boriani 
>wrote:
>
>> Instead of using the Rb's PPS, use the GPS receiver's PPS. Maybe you
>> will find out that the Rb is slow... you can also check the Rb's PPS
>> against the GPS's PPS.
>>
>> On Wed, Sep 18, 2013 at 11:47 PM, Bob Stewart  wrote:
>> > I hooked the Rb's 1PPS to the trigger input on my old Tek 455, 10MHz
>> > GPSDO to Channel A, .05us trace, and turned the lights out so I could
>> > see it.  The 10MHz is marching right to left about 1 cycle every 20
>> > seconds.  So, can I say that the Rb considers my GPSDO to be too fast by
>> about 5ppb?
>> >
>> >
>> > Bob
>> > ___
>> > time-nuts mailing list -- time-nuts@febo.com
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>> https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts
>> > and follow the instructions there.
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Re: [time-nuts] GPSDO vs Rb standard

[John C. Westmoreland, P.E.]

Azelio and Fellow Time Nuts,

Isn't the GPS 1PPS signal supposed to be 'precise' to within what error?  I
imagine this is in the specs of the specific receiver -
but I was wondering if some of you have actually measured what that is -
and could report the numbers that you have found.

Thanks!
John Westmoreland



On Wed, Sep 18, 2013 at 3:07 PM, Azelio Boriani wrote:

> Instead of using the Rb's PPS, use the GPS receiver's PPS. Maybe you
> will find out that the Rb is slow... you can also check the Rb's PPS
> against the GPS's PPS.
>
> On Wed, Sep 18, 2013 at 11:47 PM, Bob Stewart  wrote:
> > I hooked the Rb's 1PPS to the trigger input on my old Tek 455, 10MHz
> > GPSDO to Channel A, .05us trace, and turned the lights out so I could
> > see it.  The 10MHz is marching right to left about 1 cycle every 20
> > seconds.  So, can I say that the Rb considers my GPSDO to be too fast by
> about 5ppb?
> >
> >
> > Bob
> > ___
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Re: [time-nuts] GPSDO vs Rb standard

[Azelio Boriani]

Instead of using the Rb's PPS, use the GPS receiver's PPS. Maybe you
will find out that the Rb is slow... you can also check the Rb's PPS
against the GPS's PPS.

On Wed, Sep 18, 2013 at 11:47 PM, Bob Stewart  wrote:
> I hooked the Rb's 1PPS to the trigger input on my old Tek 455, 10MHz
> GPSDO to Channel A, .05us trace, and turned the lights out so I could
> see it.  The 10MHz is marching right to left about 1 cycle every 20
> seconds.  So, can I say that the Rb considers my GPSDO to be too fast by 
> about 5ppb?
>
>
> Bob
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Re: [time-nuts] GPSDO vs Rb standard

[Bob Stewart]

Hi Bob,

As always, thanks for your informed help.  I had been reaching the same 
conclusion, but needed unbiased confirmation.  I think the RUBY4 software does 
what I want?  I'll look into it.

Bob





>
> From: Bob Camp 
>To: Discussion of precise time and frequency measurement  
>Sent: Wednesday, September 18, 2013 5:01 PM
>Subject: Re: [time-nuts] GPSDO vs Rb standard
> 
>
>Hi
>
>One cycle of 10 MHz would be 100 ns. 100 ns per second would be 100 ppb. 100ns 
>per 20 seconds would indeed be 5 ppb.
>
>Since the Rb is *stable* but not *accurate*, the real question is - how much 
>does the 5 ppb change by? The Rb can't tell you if the GPSDO is correct. The 
>best it can do is tell you if it changed. If you can demonstrate that the 
>GPSDO is locked up, and that it's stable for many days, you can reasonably 
>conclude that the GPSDO is accurate. 
>
>I'd say the first step is to get the Rb tuned closer to the GPSDO. You should 
>be looking for < 0.01 ppb changes. That's going to be tough with a 5 ppb 
>offset. 
>
>Bob
>
>On Sep 18, 2013, at 5:47 PM, Bob Stewart  wrote:
>
>> I hooked the Rb's 1PPS to the trigger input on my old Tek 455, 10MHz 
>> GPSDO to Channel A, .05us trace, and turned the lights out so I could 
>> see it.  The 10MHz is marching right to left about 1 cycle every 20 
>> seconds.  So, can I say that the Rb considers my GPSDO to be too fast by 
>> about 5ppb?
>> 
>> 
>> Bob
>> ___
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Re: [time-nuts] Decent GPS Antenna Active/PassiveRecommendation

[Gerald Chafee]

Oh - sorry - did not mean it that way.

I wants to let you know you can talk to them and they will work with you
(and sometimes get a better deal if you write a check and can wait ).

Glad to see what you have done - I am just starting back in the precise
time work, but I used to work in USAF with precise time with Loran C. Guess
that is gone (for now :) ).

Jerry


On Wed, Sep 18, 2013 at 5:24 PM, quartz55  wrote:

> Gerald,
> I wasn't trying to make any derogatory remarks about RGR.  I did email him
> about the Nortel unit I got and he responded quickly with an appropriate
> answer, so my dealings with them have been fine.  I actually bought some
> other stuff from him after the GPS unit. I'm happy with what I've gotten
> from them.
>
> Dave
> ___
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Re: [time-nuts] GPSDO vs Rb standard

[Bob Camp]

Hi

One cycle of 10 MHz would be 100 ns. 100 ns per second would be 100 ppb. 100ns 
per 20 seconds would indeed be 5 ppb.

Since the Rb is *stable* but not *accurate*, the real question is - how much 
does the 5 ppb change by? The Rb can't tell you if the GPSDO is correct. The 
best it can do is tell you if it changed. If you can demonstrate that the GPSDO 
is locked up, and that it's stable for many days, you can reasonably conclude 
that the GPSDO is accurate. 

I'd say the first step is to get the Rb tuned closer to the GPSDO. You should 
be looking for < 0.01 ppb changes. That's going to be tough with a 5 ppb 
offset. 

Bob
 
On Sep 18, 2013, at 5:47 PM, Bob Stewart  wrote:

> I hooked the Rb's 1PPS to the trigger input on my old Tek 455, 10MHz 
> GPSDO to Channel A, .05us trace, and turned the lights out so I could 
> see it.  The 10MHz is marching right to left about 1 cycle every 20 
> seconds.  So, can I say that the Rb considers my GPSDO to be too fast by 
> about 5ppb?
> 
> 
> Bob
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Re: [time-nuts] New NTBW50AA

[Bob Camp]

Hi

1) Have you done a 3 day long survey at any of the locations? You need to do 
that to get the errors down. 
2) Fiddling with the gain and filter settings on a NTBW50 isn't useful. The 
unit does *not* work the same way as a TBolt. Just leave them alone.
3) Because of the way the uint works there is *no* way to translate the LH 
display to frequency stability. 
4) The OCXO in that unit is at least as good as a typical MV89. Since you have 
no way to "tune" the unit, replacing the OCXO is not a good idea. Also you may 
have to buy (and run long term ADEV tests on) a dozen MV89's before you get a 
"good" one. 

If you want to check the *stability* of the GSPDO, get a cheap Rb. That's the 
*only* way to know what's going on. There is no display / measurement / 
technique that will answer the question looking at the GPSDO alone. 

Bob

On Sep 18, 2013, at 10:11 AM, quartz55  wrote:

> Moved antenna to fence line on a 10' emt.  Nothing much seems to change no 
> matter what I do, so I guess this is what I'm locked into unless I start 
> getting carried away.  I still get generally about a 400 ppt swing with the 
> OSC, about 20 ns swing with the PPS and the other things are just what they 
> are. Different filters and surveys don't seem to change anything that I've 
> seen.  I like the antenna better at the fence. but I had to add another 30' 
> of RG-6.  I have about 100' of FSJ4-50B that I have no use for right now, but 
> I doubt that will do anything for me.  
> http://i251.photobucket.com/albums/gg287/DogTi/time/20139-181346_zps31fb89be.jpg
> 
> Is this acceptable?  From what I deduce, I can expect to get accuracy of 
> +-0.2 Hz at 1GHz?  I was hoping for another decimal.  This should be plenty 
> good to get mHz accuracy at 100 MHz if I can even measure that using SpecLab. 
>  Seems to me Arthur was getting much smaller swings on his ppt with his older 
> Nortel.
> 
> I did figure out the temp thing and found a link where it's explained, but I 
> have a new chip coming and expect to change it, but I doubt if anything will 
> change except the reported temp will most likely track to less than 1° C 
> unlike it's doing now.
> 
> Would it be worth looking into the MV89A OCXO as a replacement to get better 
> ppt?  I haven't done any looking into my OCXO yet to see what it's spec sheet 
> may be.
> 
> Still waiting on a chip inductor that I messed up in the TS-2000 so I can get 
> the XRef working.
> 
> Dave
> N3DT
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[time-nuts] GPSDO vs Rb standard

[Bob Stewart]

I hooked the Rb's 1PPS to the trigger input on my old Tek 455, 10MHz 
GPSDO to Channel A, .05us trace, and turned the lights out so I could 
see it.  The 10MHz is marching right to left about 1 cycle every 20 
seconds.  So, can I say that the Rb considers my GPSDO to be too fast by about 
5ppb?


Bob
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Re: [time-nuts] Decent GPS Antenna Active/PassiveRecommendation

[quartz55]

Gerald,
I wasn't trying to make any derogatory remarks about RGR.  I did email him 
about the Nortel unit I got and he responded quickly with an appropriate 
answer, so my dealings with them have been fine.  I actually bought some other 
stuff from him after the GPS unit. I'm happy with what I've gotten from them.

Dave
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Re: [time-nuts] Decent GPS Antenna Active/PassiveRecommendation

[Gerald Chafee]

Hi Dave,

Hopefully not too far off topic, just wanted to chime in here.

I have known the people at RDR Electronics (I live in NY and am not
affiliated with them) for over 15 years. I used to live in the Denver area
and got to know the original owners. They used to buy industrial aerospace
surplus cheap and turn it around quick.

They are like us in that they like to tinker around with equipment (many
times much more expensive than most of us could afford). They have respect
for us time nuts ;).

I have never known them to not stand by something they sold.

They do sell direct outside of auctions - just look them up online in the
Denver area. They are easy to talk to and nice people. If you are wondering
how many items they may have, ask them. They are not trying to hide
anything. They do need to turn a profit like any company.

I am ready to spend $1000 + on an item soon and I would not flinch at
giving it to them.

They do answer their emails and will listen to you if you are looking for a
special setup for a good price. They occasionally come across a one of a
kind oddball item and would sell direct rather than post on an auction.

My only concern I have ever heard was from outside the U.S.  They have
to turn stuff around fast and can't take on the risk of issues with
international shipments from what I have heard.

Sorry for what sounds like a commercial. I really have no current
connection, but wanted to let you know what you could expect.


On Sun, Sep 15, 2013 at 10:34 PM, quartz55  wrote:

> I got the Lucent 26dB antenna with my Nortel and it seems fine, although I
> have nothing to compare it to.  It seems like a fine commercial unit and
> comes with the protector mount.  I don't know what RDR bids are running up
> to, but at $30 plus $11 shipping, you might as well buy the whole Nortel
>  GPSTM and the antenna for $150 delivered.  He doesn't let on how many of
> either he has.
>
> Dave
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Re: [time-nuts] New NTBW50AA

[quartz55]

Thanks Charles,

I have tried the &a command and that is where LH put the numbers, TC from 100 
to 500, Damp from 1.2 (that's how it came) to 1.0, and it changed the gain from 
1.2 to 1.403.  I could certainly try playing with the DAC voltage. I haven't 
written anything to the prom yet, I think, when I turn the unit off and back on 
it seems to revert to where it was when I got it, but that's only been a few 
times and for a few minutes, it's been on nearly since I got the antenna 
installed on Sep 9, or 9 days.  I haven't done a precision survey at this 
location either, but it didn't seem to make any difference at the other 
locations.

As far as dBc, I've seen numbers in the 50's at this location and I don't think 
I've seen that before, but nothing scientific about any of the locations or 
numbers.  This location sees to the east and west probably better than the 
others, south should be about the same.  Actually right now I'm seeing 2 in the 
60's and one at 71.5.

I wasn't going to change the OCXO willy-nilly, I'll have to explore this one 
first.  I'll see if I can find any info on this OCXO.

The antenna is a Lucent PCTEL "GPS-TMG-HR-26N, High Rejection 26dB With 
Enhanced Narrow Band Filtering", apparently for high RF environments, only one 
I've got or tried, it came with the Nortel from RDR.  About 130' of RG-6 and 
with the 26dB gain and a 4 dB noise figure, it's probably swamping any loss in 
the cable or NF of the RX.

You didn't say, but I get the feeling maybe I should be getting smaller ppt 
numbers?  When you say  noisy, is high ppt generally a result of excess noise 
(front end NF)?

When I get a chance I'll play with the DAC voltage.

Dave
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Re: [time-nuts] New NTBW50AA

[Charles Steinmetz]

I still get generally about a 400 ppt swing with 
the OSC, about 20 ns swing with the PPS and the 
other things are just what they are. Different 
filters and surveys don't seem to change anything that I've seen.

 *   *   *
Is this acceptable?


You seem to have a reasonably decent view of the 
sky, judging by the numbers of satellites you are 
able to track, but the signal quality is lower 
than I expect (note: my only Trimble GPSDO 
experience is with TBolts).  I'd expect the 
signal reports to be mostly from 40 dBc upwards, 
while yours run from low 30s to barely 40 (IIRC, 
this hasn't changed materially as you've moved 
the antenna multiple times).  Your results look 
consistent with those signal readings.  I don't 
recall -- have you tried a different 
antenna?  It's also possible that the front end 
in that particular GPS is noisier than the TBolts I'm familiar with.


Also, I see that the oscillator loop gain is set 
for 1.4 Hz/v.  I have no idea what is normal for 
the OCXOs used in that unit.  Have you verified 
this yourself?  (Turn disciplining off, then 
manually run the DAC voltage up and down while 
watching the frequency on a counter.)  Lowering 
the GPSDO loop gain may improve matters.  Or 
not.  (IIRC, this may mean setting "gain" to a 
higher number -- the "gain" does not SET the loop 
gain at that value, it tells the digital loop 
"expect the oscillator to have this EFC characteristic.")


I did figure out the temp thing and found a link 
where it's explained, but I have a new chip 
coming and expect to change it, but I doubt if 
anything will change except the reported temp 
will most likely track to less than 1° C unlike it's doing now.


That would be my expectation, too.

Would it be worth looking into the MV89A OCXO as 
a replacement to get better ppt?  I haven't done 
any looking into my OCXO yet to see what it's spec sheet may be.


That depends on whether or not the remaining 
errors you are seeing are attributable to the 
oscillator.  The remaining errors can be classed 
broadly as (i) noisy/wandering OCXO, and (ii) 
adjustments to the DAC that the GPS thinks it 
should make.  In your case, they look more like 
class (ii) than class (i) to me.  Before you 
switch out the OXCO, let the crystal that is in 
the unit now settle down for a few months of 
uninterrupted running.  The class (i) errors 
should go down by themselves.  If the errors you 
see do not go down, it is more evidence that your 
limitation is noise in the GPS, not the OCXO.


Best regards,

Charles



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Re: [time-nuts] New NTBW50AA

[quartz55]

Moved antenna to fence line on a 10' emt.  Nothing much seems to change no 
matter what I do, so I guess this is what I'm locked into unless I start 
getting carried away.  I still get generally about a 400 ppt swing with the 
OSC, about 20 ns swing with the PPS and the other things are just what they 
are. Different filters and surveys don't seem to change anything that I've 
seen.  I like the antenna better at the fence. but I had to add another 30' of 
RG-6.  I have about 100' of FSJ4-50B that I have no use for right now, but I 
doubt that will do anything for me.  
http://i251.photobucket.com/albums/gg287/DogTi/time/20139-181346_zps31fb89be.jpg

Is this acceptable?  From what I deduce, I can expect to get accuracy of +-0.2 
Hz at 1GHz?  I was hoping for another decimal.  This should be plenty good to 
get mHz accuracy at 100 MHz if I can even measure that using SpecLab.  Seems to 
me Arthur was getting much smaller swings on his ppt with his older Nortel.

I did figure out the temp thing and found a link where it's explained, but I 
have a new chip coming and expect to change it, but I doubt if anything will 
change except the reported temp will most likely track to less than 1° C unlike 
it's doing now.

Would it be worth looking into the MV89A OCXO as a replacement to get better 
ppt?  I haven't done any looking into my OCXO yet to see what it's spec sheet 
may be.

Still waiting on a chip inductor that I messed up in the TS-2000 so I can get 
the XRef working.

Dave
N3DT
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Re: [time-nuts] My FE-5680A Came In Today

[Bob Camp]

Hi

If you re-tune the Rb, the already divided down output on the pps will be at a 
really odd rate. You can use it, but unwrapping the phase is going to be 
"interesting" (= it will wrap a lot).

There are other ways to do things. One is to synthesize a highly accurate 100Hz 
off of the Rb output. That's going to require some dividers. You also get into 
the multiple phase wrap issue quicker than with a pps.  

Bob




On Sep 17, 2013, at 9:07 PM, Bob Stewart  wrote:

> D'oh!  But is there a way I can run for let's say 200 pulses on the B channel 
> and see the count on the A channel?
> 
> 
> 
> 
> 
>> 
>> From: Bob Camp 
>> To: Discussion of precise time and frequency measurement 
>>  
>> Sent: Tuesday, September 17, 2013 7:54 PM
>> Subject: Re: [time-nuts] My FE-5680A Came In Today
>> 
>> 
>> Hi
>> 
>> For checking things like GPSDO's the pps is actually much more useful than 
>> the 10 MHz. Just do the count one to the other trick and you have a very 
>> good way to test what's going on. In it's normal configuration it should 
>> tune to within about 1 ppt of the proper frequency. That would be 10,000,000 
>> Hz / 1,000,000,000,000  or 1 ns every thousand seconds on the pps. 
>> 
>> Bob
>> 
>> On Sep 17, 2013, at 8:37 PM, Bob Stewart  wrote:
>> 
>>> Hi,
>>> 
>>> I'm just looking for an accurate standard for my GSPDO PLL coding.  As it 
>>> is, I've been depending on others who have these to tell me the code works. 
>>>  I understand that when these are retuned to 10MHz, they're .005Hz off due 
>>> to the DDS.  I'm good with that.  =)
>>> 
>>> Bob
>>> 
>>> 
>>> 
>>> 
>>> 
 
 From: Bob Camp 
 To: Discussion of precise time and frequency measurement 
  
 Sent: Tuesday, September 17, 2013 7:30 PM
 Subject: Re: [time-nuts] My FE-5680A Came In Today
 
 
 Hi
 
 Keep in mind that these things make a pretty awful 10 MHz standard. They 
 are spur monsters in a big way. They won't drive your counter nuts, but 
 for anything that wants signal purity - watch out.
 
 Bob
 
 On Sep 17, 2013, at 8:14 PM, Bob Stewart  wrote:
 
> Hi Bob,
> 
> Yeah, I figured that retuning it would lose the 1PPS.  No biggie.  There 
> are a number of those little connectors in this device, and the two that 
> have cables connected use a flat 90 degree connector with a coax that's a 
> bit smaller than RG-174.  I just want to snap a pigtail on it and lead it 
> out through a notch in the cover where the DB-9 connector is.  There are 
> several examples on the web where people solder wires to the connector 
> and to the RS-232 header.  I'd just as soon avoid soldering wires if I 
> can.
> 
> Bob
> 
> 
> 
> 
> 
>> 
>> From: Bob Camp 
>> To: Discussion of precise time and frequency measurement 
>>  
>> Sent: Tuesday, September 17, 2013 7:06 PM
>> Subject: Re: [time-nuts] My FE-5680A Came In Today
>> 
>> 
>> Hi
>> 
>> If you retune it, you probably will throw off the pps. The pps drive 
>> strength is a bit weak, so you need to be careful looking for it. On 
>> some units there is a software command to enable / disable it (as in pps 
>> only when warmed up and locked - like a gps). The can / cover on the 
>> unit is mu metal (Rb's are mag sensitive). If you drill a hole in it, 
>> you are likely to impact it's mag shielding properties. 
>> 
>> Bob
>> 
>> 
>> On Sep 17, 2013, at 6:21 PM, Bob Stewart  wrote:
>> 
>>> My FE-5680A Rb standard came in today.  After the usual inspections 
>>> etc, I fired it up and I have the purple haze.  The native output is 
>>> 8.38860798/9 (last digit jitter) as read on my 5335A using my GPSDO as 
>>> an external standard.  I've got a ways to go before it's all setup, but 
>>> this is looking good.  Does it warmup and change frequency at all, or 
>>> can I retune it to 10MHz and use it as a reference without any further 
>>> ado?
>>> 
>>> Can someone tell me what type of socket that is where you tap off the 
>>> RF?  It looks sort of like a uFL connector, but a bit bigger.  I'd 
>>> rather avoid hacking and soldering on this if I can.  
>>> 
>>> Bob - AE6RV
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>> 
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> time-nuts maili

Re: [time-nuts] FCC politics vs their engineers...

[Rob Kimberley]

I remember a story told to me many years ago, about a discussion between an
American Astronaut and a Russian Cosmonaut. 

It goes along something like this...

Astronaut to Cosmonaut:  " I wouldn't be happy sitting on the top of that
low technology rocket"

Cosmonaut to Astronaut: "I would rather that than sit at the top of a pile
of low bids"

Rob K



-Original Message-
From: time-nuts-boun...@febo.com [mailto:time-nuts-boun...@febo.com] On
Behalf Of J. Forster
Sent: 17 September 2013 19:19
To: Discussion of precise time and frequency measurement
Subject: Re: [time-nuts] FCC politics vs their engineers...

"It is hard to imagine a more stupid or more dangerous way of making
decisions than by putting those decisions in the hands of people who pay no
price for being wrong." - Thomas Sowell

YMMV,

-John

===



> Was it not always so?? Remember the politicians pay the bills not the 
> engineers!
> Alan
> G3NYK
>
> - Original Message -
> From: "Eric Williams" 
> To: "Discussion of precise time and frequency measurement"
> 
> Sent: Tuesday, September 17, 2013 7:04 PM
> Subject: Re: [time-nuts] FCC politics vs their engineers...
>
>
>> "He tells me with some bitterness that politics triumphed over all of 
>> the objections of the engineering staff to LS and that this is not 
>> the first time that this has happened."
>>
>> That's how we ended up with Challenger and Columbia.
>>
>>
>> On Tue, Sep 17, 2013 at 6:46 AM, Michael Baker 
>> wrote:
>>
>>> Time-Nutters--
>>>
>>> Jim wrote:
>>> snip
>>> > That's why the FCC granted a "conditional" waiver of the rules.  
>>> > It was politically expedient, and I would imagine that the 
>>> > engineers at the FCC thought "there's no way they'll be able to 
>>> > demonstrate no interference"
>>>
>>> Charles wrote:
>>> snip
>>> > The Commission not only thought LS would demonstrate 
>>> > non-interference, it put its thumb on the scale until the public 
>>> > outcry became too loud to ignore (the GPS interests took forever 
>>> > to wake up -- that didn't happen until all of the comment periods 
>>> > were long closed).  It just didn't matter what the staff engineers 
>>> > thought -- which is business  as usual at the FCC.
>>> --**--
>>>
>>> A friend of mine was one of the FCC lead supervisory engineers that 
>>> was involved in the LS fiasco.  He tells me that there were 
>>> technical reports, evaluation summaries and strong opinions offered 
>>> by the engineering staff that provided a number of reasons why the 
>>> LS project should be denied.  He tells me that most of these 
>>> engineering studies got buried and ignored.
>>> He tells me with some bitterness that politics triumphed over all of 
>>> the objections of the engineering staff to LS and that this is not 
>>> the first time that this has happened.
>>>
>>> Mike Baker
>>> Gainesville, FL  USA
>>>
>>> __**_
>>> time-nuts mailing list -- time-nuts@febo.com To unsubscribe, go to 
>>> https://www.febo.com/cgi-bin/** 
>>> mailman/listinfo/time-nuts>> info/time-nuts>
>>> and follow the instructions there.
>>>
>> ___
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>
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> and follow the instructions there.
>
>


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