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[aprssig] PIC processor for APRS info for D-STAR mobiles?

Stephen H. Smith wa8lmf2 at aol.com
Sun Jul 6 05:27:55 UTC 2008


Wes Johnston, AI4PX wrote:
> Yes, I got a partial answer.  So does the low speed GMSK data transit 
> a voice grade repeater?  I know that afsk 1200baud packet will.  Will 
> the 4800baud digital voice signal do the same?
>  

I doubt it.    GMSK is not FSKed audio tones applied to an audio input 
of an FM transmittter.   It is essentially direct FSK of the carrier in 
a manner somewhat like 9600 baud packet.     Just as with 9600 baud 
"classic packet" you would have to have a direct (probably DC-coupled) 
connection between the receiver discriminator and TX modulator.     
Normally it would be repeated in a manner more like a digipeater only 
full duplex.  I.e. modem attached to RX discriminator to extract 
baseband serial data stream, then serial data into a second modem 
modulating the TX on another frequency simultaneously.    (This allows 
the data to be regenerated and retimed before retransmission.)




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