>
> and eliminating the broadband noise that synthesized
> radios
> transmit both below and above the band they are
> transmitting
> on.
I went through this here getting ready to duplex on 160.
In nearly all radios I've looked at the noise doesn't come
from the synthesizers. It comes from the early IF stages in
the transmitter just after the narrow filter if the radio
transmits through one.
This is important to know because reducing the transmitter
power setting often increases transmitter composite noise if
it comes from or before the ALC gain limiting device.
I've had radios with exceptionally clean synthesizers that
had terrible broadband noise. In the FT1000 series most of
the noise comes from the area around the dual gate FET used
for ALC control. Fortunately the PA filters knock the
already low noise down to insignificant levels on the
harmonic bands. Unfortunately it is largely a difficult to
fix in-band problem.
It's especially important to not have any corona or arcing
in anything from the PA stage right through to the antenna
and everything around the antenna. A good reason to make
solid connections and bond things.
73 Tom
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