Re: [time-nuts] True Position GPSDP + Rb X72

[ewkehren via time-nuts]

Starting with a 10 second clean up loop for a FEI 5680/GPSDO to now 600 Seconds 
using Wenzel's j circuit for the Tbolt we have a variety of boards. I am 
presently out of country but when back will gladly attach some board designs, 
material cost is minimal  if there is interest.Bert Kehren


Sent from my Galaxy Tab® A
 Original message From: Hal Murray  
Date: 9/23/17  9:39 PM  (GMT-05:00) To: Discussion of precise time and 
frequency measurement  Cc: hmur...@megapathdsl.net Subject: 
Re: [time-nuts] True Position GPSDP + Rb X72 

kb...@n1k.org said:
> If the main use is feeding test gear (and not direct synthesis) an Rb may do
> pretty well. Most instruments assume a dirty reference signal and clean it
> up internally.  

What's the bandwidth on the typical cleanup PLL?  How well does that match 
the noise from a Rb?


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Re: [time-nuts] True Position GPSDP + Rb X72

[Hal Murray]

kb...@n1k.org said:
> If the main use is feeding test gear (and not direct synthesis) an Rb may do
> pretty well. Most instruments assume a dirty reference signal and clean it
> up internally.  

What's the bandwidth on the typical cleanup PLL?  How well does that match 
the noise from a Rb?


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Re: [time-nuts] True Position GPSDP + Rb X72

[Bob kb8tq]

Hi

If the main use is feeding test gear (and not direct synthesis) an Rb may do 
pretty well. Most
instruments assume a dirty reference signal and clean it up internally. 

1 Hz at 20 GHz is 5x10^-11 most sources you measure up there will not be stable 
to 1Hz 
at a 1 second gate. The Rb will be in this vicinity (frequency wise) second to 
second. Long
term drift will not be an issue with monthly calibration. It should be ok for 
temperature in
a constant environment.

Backing off to 1 Hz at 2 GHz takes you down to 5x10^-10. At that point the Rb 
is “plenty good
enough”. Keep it in a reasonably constant environment, calibrate it once a year 
and you’re fine. 

Bob

> On Sep 22, 2017, at 9:32 PM, Stephan Flor via time-nuts  
> wrote:
> 
> The highest frequency I can generate is 2.5 GHz. My counter can measure 20 
> GHz, to 1 HZ. At the moment I'm have a frequency locking problem with the 
> extension module in my HP 8660C, so I can't even get to 2.5 GHz, only 110 MHz 
> at the moment. I gust got some extender boards, so I hope to have it fixed 
> soon. The X72 gives me a solid 10.00 MHz, I would like to see what I get 
> when I use the Rb as a clock for the signal generator, at 2.5 GHz. I guess I 
> only need to verify the calibration with the GPSDO, when I get it, and get it 
> working. Then I can calibrate everything else.
>  So, to make a long answer short, I don't think I need the level of accuracy 
> that these devices are capable of. I just have a neurotic need to try and 
> make things as exact as I possibly can. Also, this is just a hobby, and 
> learning experience for me, so I can take my time to work things out.Thank 
> you,Steve 
> 
>On Thursday, September 21, 2017 12:09 PM, Chris Caudle 
>  wrote:
> 
> 
> On Wed, September 20, 2017 3:44 pm, Stephan Flo via time-nuts wrote:
>> I just wanted a 10 MHz sync for my test equipment that was calibrated.
>> May be the GPSDO is all I need.
> 
> Even an undisciplined rubidium oscillator is going to be very close to
> nominal 10MHz.  You have never stated your desired precision that I have
> seen. The X72 manual says that the output should be within 1E-9 in under
> 10 minutes, and within 5E-11 after 30 minutes.  Does any of the equipment
> you use have finer precision than that?
> 
> -- 
> Chris Caudle
> 
> 
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