Work done by Chris G4HYG suggested that narrowband PSK63 modulation would work better for HF-APRS than the 300-baud FSK more commonly used, so he developed his APRS Messenger program to include this facility.
This program runs on a Windows PC and uses the sound-card and the COM port to interface to the transceiver in the usual way.
We started testing on a frequency of 10.1497 MHz, at the top of the 30m band. This was relatively quiet, apart from when the band is blotted out by interference from the sky-wave RADAR system on Cyprus!
The program was released worldwide in late February 2010, and is now being widely used on 30m across Europe and in the USA.
We're also planning to do some tests on 2m, to see how the direct working range can be extended by using PSK63 in place of the existing 1200 baud AFSK on an FM carrier.
And the latest enhancement to the APRS Messenger program has provided a TCP/IP port from which it can send data to the Radio Mobile program, and so display the locations of received APRS stations on a map.