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Subject: Re: [geda-user] [OT] Wireless communication 101
From: "Chris Smith (space DOT dandy AT icloud DOT com) [via geda-user AT delorie DOT com]" <geda-user AT delorie DOT com>
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Date: Wed, 23 Sep 2015 15:55:00 +0100
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> On 23 Sep 2015, at 13:06, Bob Paddock (graceindustries AT gmail DOT com) [via geda-user AT delorie DOT com] <geda-user AT delorie DOT com> wrote:
> 
>> 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)?

Strictly simplex, not 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).


Sadly I’m on the wrong side of the pond for TAPR, but thanks for all the links.  Lots of reading ahead. :)

Chris
—
Chris Smith <space DOT dandy AT icloud DOT com>