[time-nuts] Comparing the frequency of two gpsdo's.

EWKehren at aol.com EWKehren at aol.com
Sat Nov 13 20:32:22 UTC 2010


Hi
I give up a 113.3 K picture attachment no text turns into 157 K. I tried.  
It is particular frustrating when seeing how much bandwidth is wasted with  
garbage that has nothing to do with time and frequency.
Bert Kehren
 
 
In a message dated 11/13/2010 2:14:04 P.M. Eastern Standard Time,  
lists at rtty.us writes:

Hi

Ok, so right now you are looking at about 10 degrees out  of 360 where one 
cycle is 100 ns. More or less you are in the 3 ns range.  

Some cheap stuff that will do better:

HP 5334
HP 5335
HP  5345
HP 5370
HP 5371

All are in the "sub $300" range on the  normal sites. Some are sub $100. 
All are available with GPIB for  logging.

For a bit more money

HP 53131
SR 620

You may  find one for sub $1000. Often you see them listed for nutty 
prices. I  certainly would not pay anywhere near $1,000 for either one. 

The one  I'd go for is the 5334. It's smaller than the rest. They likely 
are the  cheapest of the group. The ones I have *seem* to be more reliable 
than some of  the rest of the stuff listed. 

All of them can run in any one of three  modes:

1) PPS to PPS timing
2) PPS to 10 MHz edge timing
3) 10  MHz to 10 MHz timing

Number 2 on the list seems to have the fewest  issues. 

A completely different approach:

Pump both signals into  a phase detector (RPD-1 or X-OR or what ever) and 
use a DVM to log the  voltage. You can get some super  overkill DVM's for 
less than you can get  any of the counters. They will easily get you into the 
sub ns range on  resolution. Weather the setup will be accurate at this or 
that  level is  in the "that depends" category.

Bob


On Nov 13, 2010, at  11:18 AM, Mark Spencer wrote:

> Hello:
> 
> I'm looking  for some advice about ways I can compare the frequency of 
two gpsdo's.   To date I have been using an oscilloscope that supports phase 
measurements to  measure the small (typically 10 degreees or so at 10 mhz) 
change in phase  between the two signals over a period of a few hours and then 
calculating the  frequency change.
> 
> I realize this is sub optimal but I wanted  to use the gear on hand.   
Recently the phase measurement fuction of  my scope has stopped working.  
> 
> As the useage I have  ever found for the phase measurement function in my 
scope was comparing the  frequencies between gpsdo's I'm thinking it might 
be better to invest in some  other equipment rather then getting the scope 
fixed.
> 
> Any  thoughts as to what could be obtained used for less than 1K that 
would be  suited for this type of measurement ?
> 
> Regards
>  
> Mark S
> 
> 
> 
>  _______________________________________________
> time-nuts mailing list  -- time-nuts at febo.com
> To unsubscribe, go to  
https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts
> and follow the  instructions  there.


_______________________________________________
time-nuts  mailing list -- time-nuts at febo.com
To unsubscribe, go to  
https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts
and follow the  instructions there.



More information about the time-nuts mailing list