APRS Messenger is a free Windows program that ties everything on the receive end together.

It interfaces with the computers sound card to decode and display the digital audio "packets" heard by a HF radio.

Because the method of propagation is SSB HF and we use the Internet to collect reports, the number of receive stations necessary to provide adequate coverage is small in comparison to VHF.

Freetrak was designed from the ground up to work with APRS Messenger.

It will decode with most multimode digital programs, but only APRS Messenger has CRC16 checksum validation of the data.

The screen capture below is what APRS Messenger shows when the PSK63 version Freetrak transmits. Both conventional and compressed outputs are displayed here along with what the signal looks like on the waterfall display.