[time-nuts] Frequency Ensemble

[Bob kb8tq]

Hi

….. and here I was wondering if it had ever gone out :) Glad it made it. 

No, I did not run any single frequency units beside it. It is much better than any similar plot
I’ve done in the past on an L1 only part. 

Indeed, as long as you just look at the first ~ 100 seconds, the “reference standard” is less of an issue. 
A fairly typical OCXO will hang in there at 2 ppt or so out to a couple hundred seconds. 
You can get a very good idea of what’s what simply by going out that far. Indeed you might spend
some “quality time” finding a working example of something like a MT-260. That’s part of the fun ….
Some of the better parts will be 5 MHz units. A HP 5335 can come in handy to turn 5 MHz into
10 MHz ….. there are a lot of ways to get that done. 

Yes LH and a TAPPR TICC would also help in the process …. still need those 25 orders :) 

Bob

> On Mar 18, 2019, at 3:29 PM, Dan Kemppainen <dan at irtelemetrics.com> wrote:
> 
> Bob,
> 
> I recalled the plot you posted a few days ago. Nice plot on the F9P, BTW. Thanks for posting that.
> 
> I don't supposed you happened to be recording a similar plot with a L1 only Ublox part at the same time by chance, did you? I think it would be interesting to compare a 6T or M8 part to the F9P. (I lack a standard good enough to compare them to...)
> 
> Thanks!
> Dan
> 
> 
> 
> 
> On 3/18/2019 1:00 PM, time-nuts-request at lists.febo.com wrote:
>> Message: 2
>> Date: Mon, 18 Mar 2019 12:26:55 -0400
>> From: Bob kb8tq<kb8tq at n1k.org>
>> To: Discussion of precise time and frequency measurement
>> 	<time-nuts at lists.febo.com>
>> Subject: Re: [time-nuts] Frequency Ensemble
>> Message-ID:<88460EA2-6034-48D1-A77A-FED1F824D843 at n1k.org>
>> Content-Type: text/plain;	charset=utf-8
>> Hi
>> There are a variety of GPS devices that put out a PPS. uBlox makes some, there
>> are a number of other companies that do so. The PPS comes out modulo the local
>> timebase. On a precision part, there is a ?sawtooth correction? message that also
>> comes out to further quantify the best guess time of that pulse.
>> Noise wise, even with correction you are lucky to get a one second ADEV in the
>> 1 to 2 ppb range with a typical L1 receiver. With a L1 / L2 device like the F9P,
>> you might do a bit better than that.
>> The ADEV of your other sources at short tau will be much better than the GPS PPS
>> noise. As you average out over long periods, the GPS will win the race.
>> Bob
> 
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