[aprssig] on a multi-TNC digipeater, which callsign should be traced?

[Matti Aarnio]

Aprx's approach is to put transmitter callsign on transmitted message
(in trace mode) and at digipeater loop detection to recognize all
radio interface callsigns, including receivers.

At Aprx every transmitter has to have AX.25 compatible callsigns, while
receivers can have anything that APRS-IS accepts.

One of the design goals was to be able to build multiple parallel receivers
(directional antennas, remote receivers,) feeding to single transmitter.
You can build multi-rx on single channel, or cross-band / multi-channel
to single tx. Aprx itself does not restrict you at all on the way of
combining things.

And it still lets you do single channel rx/tx TNC operation like usual.

73 de Matti, OH2MQK