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Subject:	Re: [geda-user] [OT] Wireless communication 101
From:	"Bob Paddock (graceindustries AT gmail DOT com) [via geda-user AT delorie DOT com]" <geda-user AT delorie DOT com>
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> As I said, I can't influence the RF part, only the ones and zeros that are encoded onto the carrier. I also can't change at this stage the simplex operation.

As in always TX -> RX or just one direction between the two at a time
(half duplex)?

> Thanks for the OT prompt. I've amended the subject line and will let the thread die out -- I wasn't looking for lengthy discourse anyway, just a few pointers. I will look at the ARRL handbook.

While also at ARRL book store look at the Packet related items and at
the TAPR web site.  Maybe you want to be in Chicago on Oct 9th for the
2015 digital conference?  https://www.tapr.org/  TAPR has lots of
Interesting Stuff.

Also download and play with FLDigi http://www.w1hkj.com/download.html
Look through the modes such as PSK31 and BPSK63 et.al. on low
bandwidth (and slow) signals.  There are bout 40 different
modulations, encoding etc.
Source code is available.

AX.25 is the standard used for Amateur Packet Radio.


I've had good results adapting the sliding-window protocol from Hydra
for my com applications over the years.  It is based on the older
ZMODEM sliding window stuff.
Search for 'hydra' here ; http://archives.thebbs.org/ra90c.htm

Also look up 'Error Correcting Codes' and CRCs (prepare for eye glaze
over if try to figure out the math of CRC Galois Fields of limited
Syndrome Length... Most people just copy the code found on Internet,
some of which is popular and mathematically wrong).

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