Couple of months ago I’ve been looking for open source software that a radio amateur could use. I came across app_rpt that is an application for Asterisk with many many interesting features. What is Asterisk then? Asterisk is an open source telephony software that knows many telecom protocols, SIP, MEGACO, IAX (Asterisk own VoIP protocol) just to name a few.
In Asterisk one can distinguish applications and channels although from programmer point of view there is no difference, both being shared libraries.
Channels are the ones used to get or to send calls to/from Asterisk although Asterisk does not distinguish between FXO (Foreign eXchange office) and FXS (Foreign eXchange Station). Applications could do whatever they want with data gotten from the channels it connected to.
Looking at the features Asterisk provides one could imagine at least couple of use cases for Asterisk and its usage in ham radio. Basically the Asterisk could be seen as a PBX able to communicate with other exchanges via various physical links and protocols while locally it can be connected to a radio station.
Now speaking about app_rpt application, it is initiated by Jim Dixon WB6NIL and its intention is to supply a full software repeater package with all modern repeater and remote base functionality included. It’s home with full details and options is here:
How app_rpt works: the communication with radio station is through a channel driver that uses specific hardware:
– Quad PCI adapter
– CM108 chip USB soundcard with some GPIO pins for signalling like PTT, COR, CTCSS decoding.
App_rpt does not provide only standalone repeater controller functionality but also is able to be integrated into networks like Echolink and IRLP through corresponding channel drivers (chan_echolink.so and chan_irlp.so)
My situation is that I do not own any of the hardware that app_rpt is able to work with nor able to buy them easily. Therefore I decided to implement a simpler interface for my radio station based on ALSA and use serial port for signalling.