Roger Halstead wrote:

On Fri, 07 Nov 2003 12:39:37 -0800, Jim Weir wrote:

Back in the old days we did it by trial and error and glommed onto what worked
best. When the digital computer came along, we got a full blown printout of the
inter/cross/spuri mod products across a frequency band and picked a
frequency(ies) for the IF that produced minimum spurious products.

Note the word MINIMUM. There has never been a receiver produced by the
superheterodyne process that is totally free of spurious, including the
magnificent Collins S-line or 51J series of receivers.

And they were tube type equipment which I think did far better at
rejecting intermod than transistors. OTOH todays FETs are pretty good.

Of course a miser is a mixer is a mixer ... which was designed to mix
the signals. It takes sojme careful design to prevent unwanted signals
from getting into (and out of) the mixer.

As you say, none of them are perfect.

Roger Halstead (K8RI EN73 & ARRL Life Member)
www.rogerhalstead.com
N833R World's oldest Debonair? (S# CD-2)



I am sorry that I missed the beginning of the thread.

The King KX170 series is an excellent, if old, radio; and should be able to
regect the FM and VHF-TV band signals from as near as a couple of miles.

Nonetheless, your problem sounds like "front end overload" which is made
worse if the receiver has become slightly detuned over time. Therefore,
even though I usually assert that at least 80% of radio problems are really
antennas and other airframe wiring, I really thing that you will end up
sending the KX170 to the shop in order to solve this problem.

Peter