[aprssig] New VARA-HF Softmodem A Spectacular Improvement For HF APRS

Stephen H Smith WA8LMF2 at aol.com
Mon Jan 9 00:18:42 EST 2023

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 APRSpoint APRS 

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 transmission method. 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 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 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) aol.com
Skype:        WA8LMF
EchoLink:  Node #  14400  [Think bottom of the 2-meter band]
Home Page: http://wa8lmf.net

-- 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

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