msg ) writes:
Michael A. Terrell wrote:

I only have one portable receiver, the RS DX-375, which is kept in
my hurricane emergency kit. It was bought on price, alone...

I had one and was quite disappointed by its image response (even in
the absence of strong signal IMD, overloading, etc.). For example,
WWV on 10 Mhz was equally strong on 9545 kHz. I never saw the
schematic so I know nothing about its front end and evidently
it is single conversion but one would have hoped for a varactor
tuned preselector

It's completely unlikely that it doesn't have a tuned front end.
Because the whole notion of "tracking" came about when early on
it was realized that images were a bad side effect of the superheterodyne
receiver, and it they didn't set it up so the front end tuning
wasn't tuned with the same knob as the oscillator, it would be too easy
to mistune to the image.

The bad image rejection is a reflection of the low cost. Any cheap receiver
from forty years ago would likewise suffer bad image rejection. There really
is no real difference between a front end tuned with a mechanical
variable capacitor and a front end tuned with a varactor.

IN order to be cheap, such reacievers would skimp in the design. So there'd
be one or two tuned circuits before the mixer, and that wasn't enough
the higher you went in frequency with a 455KHz IF to get rid of the images.

On the other hand, a top end receiver like the HRO-60 was said to be pretty
good at image rejection, even getting up there close to 30MHz. The difference
was that it had more tuned circuits between the antenna and the mixer, so it
was far better able to reject the image.

Michael