"David Forsyth" wrote in message
...
Would it be possible, though not necessarily practical, to make a reciever
for the modern FM broadcast band, using only pre-WWII tube technology? I
know they had FM on a lower frequency band at that time. What sorts of
tubes could one use from the 1930's to make a reciever that could tune in
the modern FM band? I'm sure I wont actually attempt such a thing,
especially any time soon, but just wondered how difficult it might be.
Are
there any schematics or construction articles from the late 30's about
making FM radios that might be adapted over to the new FM band?

just curious,

Dave

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).

73, Alan

"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.

"R J Carpenter" wrote in message
...


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.


My S-36 has two selectivity settings, sharp and broad. The broad
position is fine for FM broadcast. I don't know how sharp the sharp
position is.


[snip]

Frank Dresser

Hi,
Thanks for the correction. The S-37 doesn't have any choice of
selectivity, unlike the 36 which had tertiary windings in the IFs.

73, Alan

Hi,
Thanks for the correction. The S-37 doesn't have any choice of
selectivity, unlike the 36 which had tertiary windings in the IFs.

73, Alan

"R J Carpenter" wrote in message
...


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.


My S-36 has two selectivity settings, sharp and broad. The broad
position is fine for FM broadcast. I don't know how sharp the sharp
position is.


[snip]

Frank Dresser

"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.

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).

73, Alan