G'day Stewart,
Once again congratulations on the success of WOLF !!! You have done a good
job in bringing another step forward in the game. I have been looking with
interest at your web site and found it very interesting. There is just
one thing I don't understand on the site:-
start quote :-
"Multitone FSK, etc.
I believe that sending multiple tones at once is not suitable for
weak-signal LF work. Virtually all PA's in use are limited by PEP (rather
than thermally). Therefore, sending two tones requires that each be 6 dB
below the level permitted for a single tone, to avoid clipping the envelope.
Compared with sending the tones sequentially, there is a still a 3 dB loss,
even after allowing for the longer durations. "
end quote :-
The thing I don't understand is how did you manage to create a BPSK signal
(which I understand WOLF is) without creating two symmetrical sidebands ???
I thought if you generated a BPSK signal at some rate it would create at
least one pair of sidebands (two tones). All my simulations do this.
How did you manage to eliminate the two tones ?
The second thing I don't understand is that you say there is a 6dB penalty.
This is true for linear systems. However, one of the recommended methods
for WOLF (apparently widely used} is to use a XOR gate phase switcher.
Using this scheme the penalty is 3.92dB, not 6dB. Taking into account the
longer durations (which you correctly identify gives 3dB gain) the penalty
is only 0.92dB compared to a single tone.
73s Steve Olney (VK2ZTO/AXSO - QF56IK : Lat -33 34 07, Long +150 44 40)
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ULF, ELF, VLF & LF Experimentation
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