Posted by
Karl Larsen on
Sep 01, 2006; 1:23pm
URL: http://elecraft.85.s1.nabble.com/KX1-improvements-tp393532p393541.html
As you study the act of mixing, you discover it is non-linear.
Somewhere there needs to be a non-linear device with current flowing
through it usually caused by the LO power injected into it. That is why
the LO needs to be a large signal.
The bad part of a mixer is it mixes with EVERYTHING! So we put band
pass filters in front of the mixer trying to keep unwanted signals out.
This is not very effective.
A double balanced mixer is just one that keeps the LO signal out of
the mixer output, a good idea. But it doesn't effect other inputs except
to the extent it tends to attenuate even products.
After you go down this path you discover a mixer is a nasty thing.
It is sure nice when you find a cheap chip that has everything you want
in a mixer. If your designing a receiver you use it.
73 Karl K5DI
Ron D'Eau Claire wrote:
> Thanks for the feedback, Geoff!
>
> I can see, intuitively, an advantage of doing the switching in the more
> predictable environment of the L.O. chain instead of the signal path with
> who-knows-what coming along the bandpass and feeding relatively high-gain
> amplifiers after it! Especially when you're already providing a switching
> square wave as the L.O. signal itself.
>
> It reinforces my long-standing belief that mixers produce bizarre
> environments, electrically, not much unlike what Alice found down the rabbit
> hole!
>
> Ron AC7AC
>
>
> _______________________________________________
> Elecraft mailing list
> Post to:
[hidden email]
> You must be a subscriber to post to the list.
> Subscriber Info (Addr. Change, sub, unsub etc.):
>
http://mailman.qth.net/mailman/listinfo/elecraft
>
> Help:
http://mailman.qth.net/subscribers.htm> Elecraft web page:
http://www.elecraft.com>
>
>
_______________________________________________
Elecraft mailing list
Post to:
[hidden email]
You must be a subscriber to post to the list.
Subscriber Info (Addr. Change, sub, unsub etc.):
http://mailman.qth.net/mailman/listinfo/elecraft
Help:
http://mailman.qth.net/subscribers.htmElecraft web page:
http://www.elecraft.com