[aprssig] APRS on all Radios!!!!

Stephen H. Smith wa8lmf2 at aol.com
Sun Aug 17 15:55:52 EDT 2008

Wes Johnston, AI4PX wrote:
> Since many repeaters use PL tones, I can see how a low tone might get 
> in the way of any given PL tone.... 67hz is the lowest PL tone, so 
> this "data" could be sent at <67hz.  Since we have two power standards 
> on 50 and 60hz, best to avoid those frequencies too.  maybe split the 
> difference at 55hz?  or somewhere between 60 and 67 hz?  62.5 might be 
> a nice frequency.  Of course we have to select a frequency that has no 
> harmonic on any standard PL tone frequency.
> I have yet to understand how the average "joe ham" will inject low 
> frequency audio?  Perhaps using the 9k6 pin on the mini-din?

The 9K6 pin on the mini-din is one of two RECEIVE outputs.  There is 
only one TX (audio input) pin on the DIN.   It's usage/coupling is 
switched (on some radios) by menu options for 1200/9600 baud packet.   

If present, this option changes the single input from A/C coupled 
bandwidth-limited (usually through the same pre-emphasized audio channel 
used for voice) for 1200 baud,  to DC-coupled wide-bandwidth 
no-pre-emphasis directly to the modulator for 9600 operation.     Older 
pre-processor-and-menu "dumb" radios were hard-wired to one or the other. 


Stephen H. Smith    wa8lmf (at) aol.com
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