Ron D'Eau Claire wrote:
An interesting idea for noise blanking, Geoff: turning the L.O. on and off.
But keying an oscillator like that always produces sidebands around the
oscillator frequency. That has its own issues when that oscillator is used
as an L.O.
Geoff is talking about keying a flip-flop which is between the LO and
the mixer. It can be used to gate the LO signal (as well as to convert
the mixer signal to the 50% duty cycle square wave required for the type
of mixer that he recommends). He's not recommending keying the LO itself.
I wasn't aware of any dynamic range issues when using a noise blanker. The
big issue I've noticed is the appearance of the inevitable mixing products.
They are not normally a bother, but I have noticed an odd signal from time
to time when using the noise blanker and, sure enough, it disappeared when I
turned the blanker off.
Well, these mixing products are exactly what is meant by a 'dynamic
range issue'. Loud signals outside of the passband cause undesired
responses, which make it hard to hear weak signals. I know that the K2
noise blanker and the one in my TS850 cannot be used in a contest
situation because the profusion of loud signals generates a tremendous
amount of junk.
--
73,
Vic, K2VCO
Fresno CA
http://www.qsl.net/k2vco
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