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Re: Subject: [Discuss-gnuradio] APCO 25

From: Dave Emery
Subject: Re: Subject: [Discuss-gnuradio] APCO 25
Date: Sat, 18 Jan 2003 22:21:39 -0500
User-agent: Mutt/1.4i

On Sat, Jan 18, 2003 at 06:34:54PM +0530, Arif wrote:
> <matt>
> We have all the specs for APCO25.  Is there anyone interested in trying this
> with GNURadio?  It would be a nice way to get introduced to programming with
> it,
> and shouldn't be that hard.
> Matt
> </matt>
> Hi Matt,
> Could you point me to the specs, I'll give it a shot.
> thanks

        As has already been mentioned, there is a patent problem with
IMBE.   There have already been several private efforts to implement
APCO-25 decoders (no encoders I know of) that remained unreleased to
the hobbyist/public safety scanning or ham/rf hacker open source worlds
because of the patent issue.   The first of these was probably finished
around 4-5 years ago...

        Of course if someone could only persuade DVSI and MIT to
allow release of open source IMBE for ham and private non commercial
experimentation everything would be hunky dory.   Perhaps Gnu-radio,
which originated with work done at MIT by the son of a distinquished
MIT professor might provide the incentive to get them to allow
a license for strictly non-commercial ham and rf hacking use.

        Unfortunately APCO-25 with some other vocoder will not
interoperate with existing radios - and for both scanning and ham
use the ability to communicate with real APCO-25 radios is pretty
much key to utility of the result.   Nice as general purpose
gnu-radio implementations might be, even a laptop with Cardbus
SDR radio cards (which certainly don't exist yet for gnu-radio)
is nowhere near as practical, rugged or portable as a real Motorola
or EF Johnson or other APCO-25 handheld.   And this is likely to
remain true until a whole SDR ht usable on hame bands comes into

        Thus gnu-radio might be very nice for a base type installation
but not for mobile or handheld use where existing surplus radios
are likely to be best for some time.

        Dave Emery N1PRE,  address@hidden  DIE Consulting, Weston, Mass. 
PGP fingerprint = 2047/4D7B08D1 DE 6E E1 CC 1F 1D 96 E2  5D 27 BD B0 24 88 C3 18

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