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

Bob Camp lists at rtty.us
Sat Nov 13 19:12:29 UTC 2010


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.




More information about the time-nuts mailing list