This is not exactly Linux, but more of a hardware related comment.
I wonder if it would help to point the interested to
www.febo.com/layer-one, or sort of it, I am typing by heart. John has put
together a number of advices and experimental/measurement reports that is
really interesting to read, since without layer one support we could not
make our software to communicate via radio.
I picked my Radio Shack handheld scanner and tapped the FM detector
output. Then I calibrated it with my 2 m radio, looking at the scope and
moving it 5 up and down. Then I adjusted my 2 meter radio deviation to 10
KHz pk-pk (limiter setting) and adjusted the mic gain a bit BELOW the
threshold of clipping and the results have been excellent, specially with
some rebel cases of users with soundcard modems that could not copy 1200
baud packet reliably before. Clipping was destroying preemphasis, after
the repair and "readjustment for voice" of the 2m radio. TNC levels are
obviously different to microphone levels.
I hope this works for 9600 too. I have no EASY (at will) access to recent
comms lab instrumentation, and this fills the gap.
After this, I have been playing with a couple of programs dealing with
Carson's Rule, and I believe that 7 KHz pk-pk deviation would be OK for
9K6. I have not done this for 9k6 yet myself, I just have played with a
little math, and comparing it with practical results at 1k2, and they
have been pretty illustrative.
73 de Jose, CO2JA
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Ing. Jose A. Amador Fundora | Tel : (537) 20-7814
Dept. de Telecomunicaciones | E-Mail : [EMAIL PROTECTED]
Facultad de Ing. Electrica |
ISPJAE |
