Hello Jim & LF group,
That is indeed another way to have a look at it. But I would't try to make
a perfect envelloped BPSK signal (that would take a filter with a Q of many
1000) but a signal that has a bandwidth that is approximately the same as
that of a normal CW signal.
The same way as the key clicks are surpressed by soft keying (avoiding
steep slopes) I would try to avoid the 'steep' phase jumps and spread the
180 degrees phase change over a few milliseconds.
73, Rik ON7YD
At 18:05 26/03/01 +0000, you wrote:
Dear Rik, LF Group,
Another way of looking at this modulation method is that the high Q
tuned circuit acts as a narrow filter which removes the unwanted
sidebands of your "rude" BPSK - the signal will certainly be
amplitude modulated at the output of the tuned circuit; in fact it will
look very similar to the "ideal" envelope-modulated BPSK signal.
This is effectively another way of generating the BPSK signal,
analagous to generating SSB by the filter method. But
unfortunately, any clipping or AGC will distort the amplitude
envelope, which in turn will re-introduce unwanted sidebands.
Of course, if the filter was placed at the transmitter output, this
criticism would not apply. But although it is probably possible,
producing an antenna tuning network with a loaded Q of 700 would
be quite difficult.
Cheers, Jim Moritz
73 de M0BMU
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