"Frank" wrote in message
...
I need a cheap and simple analog receiver for some experiments I'm
doing and the old Realistic DX-100 will seemingly fit the bill as long
as it's reasonably drift stable over a few minutes (+/- 150 Hz or so).


My DX 100 has a huge warm up drift. It will easily drift 5kc on the top
of the AM BC band in the first half hour or so, more drift on the higher
bands. It's better after the warm up. I can listen to SSB without
riding the tuning, but it never really stops drifting. It might be
something like 150 Hz over a few minutes, or a litte better.


What is the dial drive mechanism (knob to varicap) and the resolution
of the fine tuning.

Knob to indicator drum to a dragging plastic dielectric variable
capacitor is good old dial cord. Although the original cord seems kinda
slick and can slip.

The fine tuning control is a simple pot. The resolution is arbitrary.
It's marked off 100 - 0 - 100 with a number indication every twenty.
Twenty what? I dunno. It takes six indicator lines to go from one
twenty whatever to the next twenty whatever. The fine tuning knob is so
thin, it's almost useless.

If you start at 3.9 MHz with the fine tuning control at 0 turning it
fully clockwise (100) brings the frequency to 3.942 MHz . Turning the
fine tuning control from the same zero counterclockwise brings the
frequency from 3.9 to 3.865.

It's 7.231(100cw) - 7.2(0) - 7164(100ccw)

I checked these frequencies listening to the local oscillator radiation
with my DX 440. I assumed the IF frequency is 455 kHz.

It seems as if the fine tuning control tunes only the oscillator, and
not the antenna stage.


It will be used in the CW mode. Any pro and con
comments will be appreciated.

Thanks,

Frank

Are you going to make a huff 'n puff oscillator stabilizer? That seem
like a useful mod.

Woven cover fishing line might make a good dial cord replacement, if
needed. I have some real fiberglass core dial cord, but it's too thick
for this radio. I'd avoid the nylon stuff.

I don't like the tuning feel of the DX 100. A small knob and it has
alot of rubbery backlash. I was thinking what a nice radio it would be
if it had a air dielectric cap with a real bandspread. It might even
drift less.

Frank Dresser