[time-nuts] Comparing the frequency of two gpsdo's.
EWKehren at aol.com
EWKehren at aol.com
Sat Nov 13 21:42:45 UTC 2010
Thank you Will remember it. Thought I had stayed within the guidelines.
Bert
In a message dated 11/13/2010 3:45:21 P.M. Eastern Standard Time,
jra at febo.com writes:
Bert, I just approved your message, so it should show up soon. The reason
for the size increase is that the internet email format is 7-bit ASCII, so
a binary file has to be encoded down from 8 bits and grows as a result.
John
On Nov 13, 2010, at 3:32 PM, EWKehren at aol.com wrote:
> 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
>>
>>
>>
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