[GPS_Standard] PIC Software

[Andreas Stefan]

Hello Bert,
thank you for the quick answer. I understand, my idea was not really good, hi.
All the best, 73
Andreas
-----Ursprüngliche Nachricht-----
Von: "Bert, VE2ZAZ" <ve2zaz at sympatico.ca>
Gesendet: 16.04.07 14:33:11
An:  <gps_standard at mailman.qth.net>
Betreff: Re: [GPS_Standard] PIC Software


Hello Andreas,


The way the firmware is built relies on 1-second (actually, 16-second)
windows to compute the frequency offset. This provides the ability to use
8-bit and 16-bit registers to count for almost everything, which is easily
manageable with an 8-bit PIC. Using a 10KHz as the window gate would force
the firmware to count much larger numbers. It would require a complete
re-design of the front end firmware and would not really decrease the
initial acquisition time, and would offer no improvement on accuracy.

A 100us (1/10KHz) sampling window for a 10MHz signal would give a resolution
of one Hz in 1000 10MHz cycles. This resolution would provide the ability to
detect only 10KHz off frequency on the 10MHz signal. Your oscillator
normally has a 1Hz end-to-end tuning range! So we would have to take orders
of magniture more of these samples to get a decent resolution....which
brings us back to the current 16-second window! It provides a one Hz in
160,000,000 cycles resolution, or 1/16 of Hz of the 10MHz... Unfortunately,
we are dealing with high accuracy here! No way out... And besides, the vast
majority of GPS receivers on the market provide only a 1 PPS output.

I hope that I have answered your question. If not, let me know.

Regards,

Bert, VE2ZAZ

----- Original Message -----
From: "Andreas Stefan" <andreas.stefan at web.de>
To: <gps_standard at mailman.qth.net>
Sent: Monday, April 16, 2007 5:42 AM
Subject: [GPS_Standard] PIC Software


Hello List, hello Bert,
my name is Andreas, DL5MGD.
First let me say thanks for a very fine piece of hard- and software dear
Bertrand.
I have one question. My gps receiver delivers not only the 1pps sig, but
also a 10kHz sig which is locked to the 1pps sig. Is it possible to convert
the software for the pic so that the user can decide if he wants to use the
1pps or the 10kHz sig as reference for the fll? So the locking time can be
increased (i think, hi)
73
Andreas, DL5MGD
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