Jim,
And for the ultimate in TA DX, consider my little "TAG" Lowfer setup on
185.800 kHz in Maine. The 1-watt Class D PA is fed with a keyed 24V
power supply with a sine-shaped rise/fall time of about 5ms. This
greatly reduced clicks around the QTH. The mice that hang around the
exciter box with the nice proportional oven haven't offered any
preference. But in the winter, they seem to appreciate WOLF, which is
strange from a predatory point of view.
JA
Leaving out the envelope shaping results in "key clicks" when the phase
transitions occur, and a wider bandwidth. One can ask the question "does
this matter?" Probably yes it does if you are running 1kW on 136k. But
there are plenty of clicks on VLF already, so I doubt anyone would
notice at 9kHz ;-) Certainly, the US "Lowfer" LF stations with their 1W
TXs used Wolf successfully with class D or E amplifiers and no envelope
shaping.
You could use a linear PA to generate the envelope-shaped signal. In the
2001 tests I used the Decca class D PA with the DC supplied via a high
level series modulator, in conjunction with a phase modulated carrier,
to generate the amplitude-modulated BPSK. The transmitter used dedicated
waveform-generating hardware, with the binary message code burned onto
an EPROM. With WOLF GUI, at least changing the transmitted message
should be quicker...
Cheers, Jim Moritz
73 de M0BMU
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