"Alan Douglas" adouglasatgis.net wrote in message
...
Hi,
Dave asked:

Would it be possible, though not necessarily practical, to make a
reciever
for the modern FM broadcast band, using only pre-WWII tube technology?

The Hallicrafters S-37 tunes 130 to 210 MHz and although it dates
from 1945, it uses 954 acorn tubes and could have been made with 1930s
technology. There's a front-panel selector for AM or FM (narrowband
most likely, but the manual doesn't say and I've never tried running
mine).

Wideband. I suspect that the S-37 and S-36 differed only in tuning range.
The S-36 had an IF bandwidth suitable for FM broadcast. The wouldn't have
been any narrow FM in that frequency range in 1945. Certainly no land
mobile, and wasn't land mobile about 20-30 kHz wide until post-WW2? Crystal
frequency stability didn't get good enough for NBFM at high VHF until the
hermetic holders like the HC-6, which are post-WW2, aren't they.

Even HC-6 and snap-action thermostat ovens could be pretty awful. Collins
built very special 400 MHz radios for an Air Force project I was on in the
early 1950s. Listening to their output frequency with BFO on you heard a kHz
or more of drift, with the fractional-minute cycling of the thermostat/oven.
Our digital modulation was 180-degree-shift PSK of the 400 MHz carrier, and
couldn't stand all that short-term drift. The solution was to disconnect
the oven's heater. We could stand slow drift.