On UHF, comparisons between Olivia 8-250 and Olivia 16-500 have shown
that Olivia 16-500 survives the Doppler effects better than the more
narrow Olivia 8-250 (lower error rate), so we now use Contestia 16-500
on UHF all the time, since it is twice as fast as Olivia 16-500, has a
lower error rate than Olivia 8-250, and bandwidth is not at a premium on
UHF. This also is after daily tests over more than a month, under all
sorts of adverse conditions.
On our VHF FM simplex ragchew net, we use DominoEx 8 for our
twice-weekly net as it reaches more weak stations than even MT63-1000
can, and handles multipath very well. DominoEx 8 works well for stations
over a 35 mile radius where many signals are far under limiting, and is
reasonably fast. Because we are ragchewing, and not passing traffic, the
speed of MT63-2000 is not needed, but the better weak signal performance
of DominoEx is very badly needed.
For weak signal FM dxing, DominoEX 4 on FM works as well as SSB phone.
If you can copy a station on SSB phone, you can switch to FM with the
same antenna and power, and the error rate will be approximately the
same. This means that operators that only have an FM transceiver can
also work the same distances as SSB phone stations, if they can find
another station using FM.
We have tried every available mode, over and over, and find that
Contestia on UHF and DominoEx on VHF FM simplex work the best for us for
casual operating.
73 - Skip KH6TY
David Kleber wrote:
Our group has settled on the specific modes we use through trial and
error under the exact conditions and bands we would find ourselves
using in an emergency. By running 3 nets a week for well over a year
now, we've found that on 80m and 10m, Olivia 8/500 is the best
compromise for speed, accuracy, tuning forgiveness and bandwidth for
shorter messages and keyboard chat. On occasion we have to switch to
the much slower 16/500 olivia, but that's rare.
For larger messages and spreadsheets on 80m and 10m we use MT63 1k
long. We do a broadcast transmission with a WRAP file and then go
around the table with amazingly good results with all but the stations
reporting the weakest rx signals.
On FM we use MT63 2k long. Again, it seems to be the best compromise
for speed, accuracy and tuning forgiveness.
Interestingly enough, there are a ton of new digital sound card emcomm
and traffic nets popping up on 80m, many of which tried MFSK16, Domino
and others, but they all seem to land on 8/500 olivia just like we
did. And I've heard nothing but good things from those using MT63 2k
long on FM. We have tried the PSK modes (including R) as well as the
very wide/fast MFSK and Olivia modes on FM, but nothing seems to out
perform MT63 2k long.
Anyway, my point is that on paper and s/n ratio tests, many modes come
out as looking better than Olivia and MT63, but there's no substitute
for running MANY nets with more than one other station under varying
conditions.
We're always willing to try new modes, but we always wind up with
Olivia and MT63 being the best overall fit for our needs here in WPA.
-Dave, KB3FXI
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