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Dear Jim, LF group,
The average LF aerial together with losses of the
tuner coil and ground loss poses a Q of about 100. It means, that after putting
RF on the aerial the RF amplitude will rise to 90 percent of its end-value after
about 1.6 msec. Also by switching -off RF power 10 percent remains after 1.6
msec.
This gives a ==natural==albeit insufficient
limitation of the radiated bandwidth.
By using an active opamp lowpass clickfilter
designed for optimally flat phase response with a -3dB cut-off freq. of 25 Hz
rise and fall times of about 30msec are obtained. This is pretty well for 15wpm
CW speed. With a much smaller bandwidth the signal sounds ==woolly== and is
difficult to copy.
The radiated RF bandwidth is then about 160
Hz for keyng components stronger than -40 dB below fundamental.
I think it is good enough for practical
use.
73's de Harry,
PA0LQ.
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