New VARA-HF Softmodem A Spectacular Improvement For HF APRS


[this project was inspired by the continuing search for a successor to CCW's "APRS Messenger" HF APRS-over-PSK63 program.]

After spending nearly the entire New Year's 3-day weekend twiddling TCP/IP settijngs, serial port emulators, sound card drivers, etc,   I now have the VARA high-performance HF soft-modem working with the UIview and PinPoint APRS programs to transmit far more robust HF APRS than classic AX.25 packet. 

I am using a stack of components from "VSPE" (Virtual Serial Ports Emulator) to create a serial-to-TCPIP bridge to connect the serial-only KISS output of UIview to the network (TCP/IP) KISS connection provided in the VARA soft-modem. 

For nearly 40 years, HF APRS has used classic 300-baud 200-Hz-shift HF packet (mostly on 30 meters) as it's transport layer. However, packet is a horrible mode on HF with poor immunity to noise and HF selective fading.  I've been using the "UZ7HO Soundmodem" soundcard "soft TNC" (arguably the best HF packet TNC - hardware or software) for this purpose. However, it still falls far short of modes like MFSK16 or PSK63 for  weak-signal-plagued-with-multipath  data operation. 

For about two years, I have been experimenting with using FLdigi as a KISS modem for HF APRS on both 30 and 60 meters.  60 meters tends to be a noisy band, putting a premium on data modes that can perform error-free at low signal-to-noise ratios.  My web site about this is here:


Over the weekend of the 6th and 7th of January , I conducted a road test comparing the performance of APRS over traditional HF 300-baud AX.25 packet  vs  APRS using the VARA modem on 60 meters.  This was a 500-mile / 800 Km round-trip from central Michigan (East Lansing area) to west suburban Chicago and back.  VARA was overwhelmingly superior - by least an order of magnitude!

The full details, including a brief background on VARA,  are on a new page on my web site at:


Stephen H. Smith    wa8lmf (at)
Skype:        WA8LMF
EchoLink:  Node #  14400  [Think bottom of the 2-meter band]
Home Page:

-- APRS over FLdigi Modes  --

60-Meter APRS!   HF NVIS APRS Igate Now Operating

Flying Digipeater!

11 Copies of UIview in Action on One Computer!  
Live Off-The-Air APRS Activity Maps

Rob Q

Nice! I wonder if it will work for me since I only do SWL with my RSPdx.