[time-nuts] Z3801A Problem

[Bob Camp]

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-bounces at febo.com [mailto:time-nuts-bounces at 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


lists at 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.



-- 
These are my opinions.  I hate spam.




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