Dave wrote:
Eh what??
> Square wave generators/dividers and class D/E amplifiers are fine for
> small antennas and low erp but NOT SUITABLE for larger antennas and high
> power. An abundance of LPF and BP filters might help to clean up the
> signal.
I think you're getting confused with high levels of harmonic output, which
class D amplifiers can suffer from if not properly filtered, and sideband
energy from fast rise and fall times of the transmitted envelope.
LPF will NOT help!
I DID NOT SAY A LPF would cure key clicks. I said a LPF would stop
HARMONICS, especially odd harmonics 3/5 etc. from the type of divider/mosfet
amplifiers used on 136 khz. You need a good multi pole LPF with these type of
amplifiers especially with large antennas.
KEY CLICKS were also mentioned in the message about the G3WSC/P transmitter,
and as you say this is due to fast rise times/timing and requires a different
type of filter/circuit.
I was merely pointing out that besides the key clicks, there was a possibility
of radiating odd harmonics if not properly filtered because of the intensity
of the signal with a large antenna.
If more power is to be used from such an installation, a bad situation will
get worse.
G3KEV
This can happen with any kind of amplifier, I key my class D PA with a
tailored rise and fall, series device.
Oh, and by the way, they were using a linear amplifier!
(It was a little bit clicky though...)
Dave 'YXM.
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