Posted by
Vic K2VCO on
Aug 31, 2006; 6:42pm
URL: http://elecraft.85.s1.nabble.com/KX1-improvements-tp393532p393542.html
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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