From: Bob Camp
Hi
Once the sat's all arrive at the antenna, a fixed delay (in general) does
not impact things a lot. The gotcha with the filter is that it's delay is
unequal across the GPS band. Doppler puts the sat's all over the place. That
gives some more delay than others. Having unequal delay on sats is indeed an
issue. As the filter changes delay with temperature things will move a bit
more. Since it's a "frequency high on approach / low on departure" sort of
thing it will average out on each pass. The main impact would be an increase
in wander.
Bob
====================================
Bob,
I am thinking about exact time measurement - getting your PPS edge exactly
on the nanosecond. People can add in the length of the cable as an offset,
so they must also need to enter any delay through any filters, mustn't they?
Agreed that for position alone it doesn't matter as much. It's the
antenna's approximate position which will be measured.
Your points about dispersion in the filter, and temperature coefficient of
delay are good ones.
Cheers,
David
--
SatSignal Software - Quality software written to your requirements
Web: http://www.satsignal.eu
Email: david-tay...@blueyonder.co.uk
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