When I look at the data that the VP is sending to the Z3801A, all I see
are the Ba, Bb, and Bn commands. I don't know if any of those have
enough low level information to play with.
But if this is a firmware issue, shouldn't there be lots of Z3801As with
this problem? I suspect that there's a fault with my unit, but I can't
imagine what. I've got good signal levels. The SYST:STAT command shows
levels of > 200 on a 1-255 scale for some satellites.
Ed
On 11/6/2012 12:41 PM, Bob Camp wrote:
Hi
At least some of the Motorola receivers passed across per satellite timing
information. That would allow you to play with what you used or didn't use
in the firmware.
Bob
-----Original Message-----
From: time-nuts-boun...@febo.com [mailto:time-nuts-boun...@febo.com] On
Behalf Of Hal Murray
Sent: Tuesday, November 06, 2012 1:15 PM
To: Discussion of precise time and frequency measurement
Subject: Re: [time-nuts] Z3801A Problem
li...@rtty.us said:
If the firmware is fine tuning something, (like s/n or elevation) that
would
explain the first issue. If it's something like s/n where they may be
averaging values, then a single bad packet *could* mess up their averaging
and "turn it all off".
What can the firmware do if it decides that it doesn't like a satellite?
The
GPS receiver does the math and sends over the PPS. How would the firmware
adjust that calculation to not use a particular satellite?
You can set the elevation mask angle. I don't see a way to set a S/N
filter.
(I assume the mask angle gets passed to the GPS receiver.)
You can tell it to ignore specific satellites. I assume that list gets
passed to the receiver. The firmware might be able to use that mechanism
for
S/N filtering, but the timing seems wrong. If the S/N for a sat is too low,
the firmware would have to ignore the data for that second, tell the
receiver
to ignore that sat, and hope the data for the next second is good.
It might work if S/N only changes slowly, but I don't think that's the case
for things like multipath.
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