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
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) aol.com
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
11 Copies of UIview in Action on One Computer!
Live Off-The-Air APRS Activity Maps
Nice! I wonder if it will work for me since I only do SWL with my RSPdx.
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