[aprssig] APRS on all Radios!!!!

Bob Bruninga bruninga at usna.edu
Sun Aug 17 15:28:34 EDT 2008

> Wouldn't the 120-Hz subcarrier still be 
> problematic for phase modulated rigs?

I didnt think so, since here are guaranteed transistions evry bit independent of the data.

> Why not simply use something like MIC-E?
>[and] something like a 4-kHz [PSK31] subcarrier...
> transmitter for the downlink? 
> build and market a kit for the end user 
> MIC-E/PSK-31 gadget?)  What could be 

I was going to endorse this as another good approach except for one thing.  The Mic-E to be done right has to be installed so that it is inseries with the existing Mic-PTT.  If this is not done, all the advantages of PTT-tail operation are lost as a much much longer TXD and lockup are reuired even if the PTT is dropped evern for milliseconds.  It is this cutting of the mic-cord that is one of the issues that has prevented Mic_E from really taking off.

A sub-audible dongle plugged into the radio's DIN connector runs completely independently of normal operation, so that is why I thought it was a more practical approach...

But the idea of "super-audible" solves the problem of the combination of PL and this APRS DPL on the same channel.


----- Original Message ----- 
From: "Bob Bruninga " <bruninga at usna.edu>
To: "'TAPR APRS Mailing List'" <aprssig at lists.tapr.org>
Sent: Sunday, August 17, 2008 9:28 AM
Subject: Re: [aprssig] APRS on all Radios!!!!


>> Needs careful thought/design.
>> This is a problem for Phase modulated rigs
>> because of ... low freq components...
> Could it simply be PSK-31 encoded? What is the lowest carrier tone that 
> can carrry PSK-31? Some APRS dongles already are starting to decode 
> PSK-31.  And with say a 120 Hz carrier, it would seem that it would remain 
> sub-audible?  We would of course add CRC checks to make each info packet 
> complete.


> Bob, WB4APR

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