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RE: [Discuss-gnuradio] APCO 25

From: Ettus, Matt
Subject: RE: [Discuss-gnuradio] APCO 25
Date: Fri, 17 Jan 2003 15:06:44 -0800

> You have the source code to the IMBE vocoder? Or enough 
> specification to
> write one?

There is enough spec to write one, I believe, but that isn't necessary.
There are a bunch of free vocoders which could be easily substituted.  It
won't work for ham to fire department comms, but ham to ham would be fine.

> Once you've got that part, the rest is (relatively) easy. 
> Unfortunately, the 
> last time I poked at this problem, IMBE was patented by DVSI, 
> and unavailable
> (code OR specs needed to write your own) for this sort of application.

Very true

> As far as monitoring APCO25, once an agency goes digital, 
> there's no real
> performance penalty to go encrypted. For ham use, that's not 
> a problem.

Not sure what your point is here, but the specs are there for the
encryption, but you don't have to use them.

By the way, while encrypted communications is illegal on ham bands,
cryptographically signing transmissions is not, nor are cryptographically
secure passwords and logins.  So you can't keep other people from listening
to you, you can keep them from pretending to be you.  I'm not sure if this
is possible in APCO25, but it would be interesting.


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