On Fri, 2011-12-30 at 09:59 -0600, donroden@hiwaay.net wrote:
> I disagree.
>
> If the RF chain is clean, audio chain distortion will only be heard as
> audio distorton on the main channel.
If and only if, the bandwidth of the baseband signal fed to the
modulator is band limited to the width of the main channel (Unless there
is a RF BPF further up the chain limiting the transmitted bandwith,
often one of the RX filters is used in the transmit IF path).
It is possible to provide all the bandwidth control at baseband, but you
have to be very careful about broadband noise, and any non linearity in
the RF chain can undo a lot of hard work with regard to envelope rise
times in SSB and data modes.
ALC is insidious in this respect as the control is usually applied after
the channel bandwidth filters, and so the resulting mixing products are
not well controlled, particularly as the loop dynamics are not well
defined in general.
IME serious CW splatter is usually squarely down to the exciter keying
envelope or hot switching the PA, unless you get really silly with drive
levels the amplifier nonlinearities have only a modest effect.
73 2E0CHE, Dan.
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