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VE2HAR > MT63 07.03.05 09:30l 111 Lines 4883 Bytes #-7503 (0) @ WW
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Subj: [MT63] 20m Olivia experiment results
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Sent: 050307/0659z @:VE2HAR.#MTL.QC.CAN.NOAM Laval #:39989 $:16413sentto
Hi All. The following is a description of Olivia tests Steve, WM5Z, and I (Dave, K7CCC)
conducted March 6 on 14.107 MHz, between 2100 and 2200 UTC. The results are
subjective and non-technical, but we think you'll find some interesting tidbits about
this new mode.
Our path was 1,064 miles, from Las Cruces, NM to Enterprise, OR. I used a sloping
180' end-fed longwire for an antenna, oriented N-S and the end 40' up in a tree,
while Steve has a fan dipole for 160-20m up 32'. No towers, no directivity, no
nuthin'. Gary, WA6DTX, monitored our tests from Southern California with an off-
center-fed dipole 35' up, and reported that he copied almost everything
Steve's radio is a Yaesu Mk V Field, while I have an IC-706 Mk II for digital work. Of
course, no amplifiers were harmed in the making of these tests!
Steve's computer, a 2.4 P4 GHz, was running gMFSK on the Fedora 3 Linux platform,
while I used the Cygwin/Windows executables written by Pawel, SP9VRC, in two DOS
windows under Win98 on a cast-off P-II 200 MHz machine.
Steve and I started by establishing communications in Olivia's default mode of 32
tones within 1,000 Hz bandwidth. We both experienced 100 percent print at both 50
W and 5 W, notably after we moved up 500Hz to avoid a packet station.
Settings of 16 tones and 500 Hz produced the same results at both power settings,
just with slightly slower print. At 50 W, Steve reported that I was S7 on his meter,
while I sent him an S6. The noise level at my QTH was sitting right around S3, and
when we went QRP, Steve's signals hovered between S3 and S4, but I never lost a
character.
Then we went to a setting of 32 tones in 250 Hz of bandwidth. What a change! The
text, while running between 75 to 100 percent copy, slowed to a crawl at 7.81 baud
and 0.6 characters per second. The spacing of the tones was quite narrow.
Next we went to 8/250 and the print was much better, near perfect at both at 50 and
5 W. As a tuning aid, I was sampling the audio out of the back of the 706 and feeding
that to a old laptop running DigiPan, so I could use the panoramic display. The
difference between 32 tones and 8 tones in the same bandwidth was visually
appreciable. Much wider tones made for a more robust contact. While a tad slower
throughput than with the default 32/1000 (2.4 cps at 32/1000 vs. 1.5 cps at 8/250),
we were having a solid QSO and taking up one-quarter of the bandwidth, which all
digital operators can appreciate.
Then Steve suggested we go for broke and set up at 4 tones and 125 Hz bandwidth.
Surprisingly, this set-up was as good or better than 8/250. The baud rate was the
same (31.25), although we lost one-third of the character rate, dropping to 1.0 cps.
We decided to go to low power again, and at the end of Steve's transmission, he
revealed he'd been at 200 mW, as low as the Mk V Field would go. Whoa! At times his
signal faded out altogether, but on the receiving end, I only lost one character. The
software was actually copying below the noise! I cranked down the 706 to its limit, 1
W, and we carried on from there, with flawless print on Steve's side and I only lost
one more character in two more transmissions.
Clearly, Olivia is a very solid digital mode. Steve's observation that it would be very
good for emergency communications is well-taken. A robust mode, able to be so
effective with low power and wire antennas, is valuable, indeed, especially with the
approach of the solar cycle minimum. The next thing to do is try some of this on 80
meters, and, as Gary suggests, try low symbol set-ups like 4/500 4/1000 8/500 and
8/1000. Lower symbol rate in a wider bandwidth should result in an even more
robust mode, Gary notes. It looks like 4/2000 would exceed the HF 300 baud limit,
though.
Thanks for reading; comments are "looked forward to". 73, Dave - K7CCC
Following is a table showing the five set-ups we tried, with some speed/throughput
data:
Set-up CPS WPM* Baud
32/1000 2.4 24 31.25
32/250 0.6 6 7.81
16/500 2.0 20 31.25
8/250 1.5 15 31.25
4/125 1.0 10 31.25
*'Word' defined as 5 letters and a space
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