Aprs-soundmodem

This page describes the modifications and setup required to get a linux box (a Raspberry Pi) working as an aprs iGate.

sound levels

Alsa is used for the sound system. To check the proper input levels use the command:

arecord -Dhw:0 -c2 -d 0 -fdat /dev/null -vvv

This will show a rolling output of the recorded sound levels. More alsa options: alsa

Alsamixer and aumix can both set the sound levels and the following settings are near optimal for me:

Alsamixer:

PCM Capture: Line

Line capture input level: 70

Everything else in alsamixer can be set to mute

Btw, if F4 doesn't toggle the recording view, try the TAB key

Aumix:

Recording device: Line

Pcm level: 100%

All other levels (including line, as it's line-out) can be set to zero

a program called netcat (or ncat) can be used to send single character to the soundmodem ip address (if using MKISS).

syntax:

netcat -u 44.10.10.1 5000

when issuing the above command user input is expected. Simply type a letter, followed by <ENTER> and the soundmodem should start making AX.25 noises.