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[aprssig] 10m & 1000 Hz shift

Robert Bruninga bruninga at usna.edu
Sun Nov 27 22:17:37 UTC 2005


>>> jimlux at earthlink.net 11/27/05 4:32 PM >>>
>Updated design goals for a 10m APRS tracker:
> >
> > 1) Xtal controlled 25W tracker on 28.187 MHz
> > 2) Operates straight FSK at 1200 baud 1000 Hz shift

>Differential propagation will likely cause numerous problems 
>with 1000 Hz  shift on any sort of skywave 10m path...
>Don't try to use a modulation designed for wireline comms 
>and its peculiarities on a skywave path.

I think you maybe missed the beginning of this thread.
That is that this is for LOCAL direct use, not for skywave.
In fact, Skywave would make a mess out of everything.
The only reason for going to 10m was because of the
simplicity of a kit, easy use of CB antennas, lack of 
criticality, etc.   But actually, since skywave would
really mess it up big time, maybe we should consider
going back to 6m which is where the thread really 
began.   But then there are less economies of scale,
since I dont think the Europeans have that band.  So
it would be a USA centric solution.  But it doesnt matter,
it is for LOCAL use, and no one can drive across the 
Atlantic anyway...

>Trying to shoehorn it into some other format because 
>you happen to have  legacy modems is probably 
>a bad plan.

Agree completely if the goal was skywave.  But
it wasnt.  The goal was a cheap kit  transceiver
on another band for LOCAL tracking to allow for
uninterrupted other use of 2m from the same
mobile without intereference.  It only makes sense
to use the same TNC/modem we already use.

de WB4APR, Bob







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