[Lowfer] Testing Modes

[John Andrews]

I did some brief tests this morning to compare various modes that have been
used by Lowfers in recent years. The work was done on 185.800, using my 10
mW exciter fed through attenuators into a small loop. My receiver and rx
loop were set up as normal, and were picking up the usual mid-day noise. I
used QRSS3 as the reference point. I selected a signal level that could be
confidently read without a knowledge of the text. Here are the results:

PSK31        +11 dB
PSKAM10    +4 dB
QRSS3        0 dB
Jason            -11dB
QRSS30        -11 dB
WOLF        -15 dB (6 minutes for clear copy)

I could not control the outside noise level during the tests, so that plus
my errors might make a couple of dB difference in either direction. I did
not do QRSS60 or slower, but it should be on a par with WOLF based on tests
with LEK and BRO some time ago.

Comments:
1. PSK31 and PSKAM10 have much greater throughput than the other modes. Even
with errors, you might pick up enough useful text at lower signal levels.
2. PSKAM10 needs to sync onto the signal. After that, it may hold through a
signal drop. But it wouldn't re-sync at that lower level.
3. I am surprised by the Jason results, and want to pursue that. I wouldn't
have expected it to be on a par with QRSS30. I suspect that in a real-world
situation, missed characters and re-syncs would be more common than in this
simple test.
4. I would like to do MS100 BPSK comparisons, but have never been able to
run Africam with either computer in the shack, despite much advice from Bill
DeCarle.

John Andrews