[App_rpt-users] App_rpt with USB sound interfaces, other questions

John Goerzen jgoerzen at complete.org
Thu Mar 29 14:49:21 EDT 2012

Hi folks,

I've been a Linux person for many years, and also an Asterisk user for 
many years, and the prospect of integrating these two with my amateur 
radio hobby has me excited.  I have been studying sample config files 
and source code, but am nevertheless a bit confused.

I have a RigExpert TI-5 interface, which could be thought of as a more 
featureful version of a SignaLink USB.  I'll give more details on my 
setup below, but basically what I have is:

    * A full-duplex ALSA device, in which the receive frequency is
      mapped to the right channel, and the transmit frequency to the
      left.  (Though I think I can make it such that a program that
      opens the device in mono mode will get the right thing.)
    * The serial interface to the rig is at /dev/ttyUSB0
    * Control is at /dev/ttyUSB1.  In specific, DTR must always be off,
      and RTS must be raised to key PTT.

Other audio interfaces to this system, whether on Linux or Windows, 
operate quite nicely with this setup.  svxlink is another Linux-based 
repeater project that runs well.  Echolink runs fine under VirtualBox, etc.

Getting the audio into Asterisk shouldn't be a big deal.  After all, 
chan_alsa ought to be able to do that right off.  So now I'm on to the 
app_rpt configuration.  I think I can figure most of it out, but the bit 
I haven't been able to figure out yet is PTT keying.  I can't seem to 
figure out how it indicates PTT in what seems to be the something of a 
default config, nor how I might get it to raise RTS for me.

My particular setup -

You might think of it logically as two transceivers connected to two 
SignaLink USB devices.  In reality, it's just a Kenwood TS-2000 
connected to a RigExpert TI-5.

One feature of this radio is that it has two fully-independent 
transceivers, and is capable of full-duplex operation so long as each 
transceiver is tuned to a different band.  So, for instance, I can have 
an input frequency on the 2m band, an output frequency on the 70cm band, 
and I have an instant repeater... just with a 300MHz offset ;-)   In 
fact, the radio has a built-in repeater feature, although it is 
extremely limited in features.

Furthermore, the TS-2000 has separate audio outputs for both 
transceivers, and it can keep one of them open even while it's 
transmitting on the other transceiver.

The RigExpert USB interface takes these separate audio outputs from the 
TS-2000 and maps one to the left audio channel and the other to the 
right audio channel as it feeds them to the PC.  The RigExpert is also 
capable of full-duplex operation.  So I tell something like svxlink that 
my transmitter is on the left channel, the receiver is on the right 
channel, and there we have it: instant homebrew repeater, completely 
full-duplex, like a regular repeater in every way except the unusually 
large offset. I'd like to be able to do the same with Asterisk.

Thanks for any ideas,

-- John

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