[Elecraft] Re: KX1 mixer discussion

[Vic K2VCO]

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