Jon Noring wrote:

I recall last year a few people mention the NC-100. Is this radio
reputed to have excellent audio fidelity (I suppose when the variable
bandpass control is set wide) in addition to excellent selectivity and
sensitivity?

No - not at all - nor the point. What the NC-100 (and NC-120) have is a
"sliding catacomb" band change mechanism. This is a cast metal box with
three compartments front to back - duplicated five times left to right.
Each compartment (front to back) houses the frequency critical coils
(and trimmers); etc.) for each RF stage of the radio (the NC-120 has an
additional one compartment deep five-wide box appended to the rear of
the radio to add yet another tuned RF stage). Each compartment has five
contacts that stick "up" towards the radio's chassis (15 total; 20 in
the case of the NC-120). The band-change mechanism is a rack and pinion
affair that "slides" the entire box left and right - so that one set of
compartments (and their contact fingers) line up with the mating
contacts sticking down from the chassis. In this way - each band has
it's own complete set of RF coils completely isolated and brought into
the circuit as needed. Much like a strip TV tuner - but done linear
rather than turret style. The advantages are extreme shielding - and a
good bit of room in each compartment to put all of the frequency
determining components (note only the tuning cap and tubes are above
chassis - and are the only "shared" RF components).

I think Randy mentioned that the NC-100/120 have a product detector -
but that's not to imply that the fidelity is any good - just that many
usable parts and ideas are already in place (guess you could count the
power supply and amplifier as well). They are communications receivers -
first and foremost - but they do offer some intriguing possibilities for
TRF or multi-band BCB experimentation.

And can the circuitry be modernized (e.g., modern tubes),
etc.?

Nothing wrong with the tubes they have- you could go with miniature
equivalents - but since the copper plated chassis is already huge - why
bother? I don't believe any significant performance gains (in the BCB)
would be realized by "more modern" tubes.

The idea of making it a 5 band AM radio is certainly
interesting.

That's the point - whether it would be the BCB divided into 5
continuously tuned bands - each optimized as best fit in five segments -
or 5 specific BCB stations... each tweaked to "perfection" - the
foundation is all there.

--
Sherry