Tim Shoppa wrote:
Are the big old-fashioned IF transformers-in-a-can available
anywhere anymore? I want to make a receiver, probably double
conversion,
which would mean that I'd want several each of the 50kHz and some
higher frequency (455kHz likely).

Are these things that can be made from scratch without a lot of
difficutly? I can wind coils etc. but don't
have any transformer slug-tuned cores.

Tim KA0BTD

You can still find junk AA5 radios in the trash from time to time and
rip out their 455khz if cans. 85khz transformers from arc-5 radios are
STILL out there at hamfests, and the bc453 radios they came from show up
often on ebay. I think I have a few of these cans in my junk box. You
can pad them down to 50khz if you want, but there is nothing wrong with
the 85khz if frequency. The arc5 cans have a feature where the spacing
between the primary and seconday windings is variable. Remove the top
cap and pull up on the fiber rod to increase the spacing, push down on
it to move the windings together. With the windings spaced out you get
a nice sharp peaked bandwidth, with the windings together they are over-
coupled and you get a bandwidth well suited for ssb phone,
A Q multiplier and/or t-notch filter both work well at this frequency.

Some of the ARC-5 85khz cans had tapped windings to get better Q by
connecting the grid and plate of the tubes 'below' the high impedance
end of the coils by a few percent. If you exchange the hot and cold
ends of the coils, the taps might work out well for bipolar transistor
impedance matching connections!