[time-nuts] Fury Realhamradio listing
mfeher at eozinc.com
Mon Aug 20 17:57:47 EDT 2007
I only met him once, but, I thought his name was Dave - Mike
Mike B. Feher, N4FS
89 Arnold Blvd.
Howell, NJ, 07731
From: time-nuts-bounces at febo.com [mailto:time-nuts-bounces at febo.com] On
Behalf Of SAIDJACK at aol.com
Sent: Monday, August 20, 2007 3:30 PM
To: time-nuts at febo.com
Subject: Re: [time-nuts] Fury Realhamradio listing
); SAEximRunCond expanded to false
Errors-To: time-nuts-bounces+mfeher=eozinc.com at febo.com RETRY
In a message dated 8/20/2007 02:26:09 Pacific Daylight Time,
nebula at telus.net writes:
>A side effect of the 5 sample average is the opportunity to reduce the
>effective saw tooth error to 1/5 when the GPS LO is adjusted about 0.4 Hz
>high. This causes the GPS pulse position to advance about 20ns every
>and repeat every 5 seconds creating a more stable average.
thanks for the info. Not sure you can say 5 sample averages result in 1/5
the error. I think you have to use 1/sqrt(5) if it's Gaussian noise. Well, a
hanging bridge is hardly Gaussian, so maybe you are right.
I talked to Paul Allan (Mr. Allan deviation) and Jack Kusters who both
worked on the Z3816A development, and while they don't remember specifics,
did think that the unit has a 1ns TI measurement resolution per second.
It would be interesting to use a highly-stable 1PPS source without sawtooth
(another Z3816A, or a Rubidium source etc) and replace the GPS receiver 1PPS
and see how the algorithms handle this...
The question is: how much short to medium term stability improvement can be
achieved with the best available GPS receivers (say an M12M)? Or does it
matter at all as Tom explains, since the loop averages out any STS errors?
We do see differences in our Fury GPSDO when it is running using an M12+
versus an M12M (all else being the same), the M12M receivers seem to have
significantly less diurnal pertrubations than the M12+ (well, we are talking
<+-10ns over a day anyways for the M12+).
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