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#1
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"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 |
#2
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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 |
#3
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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 |
#4
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"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 |
#5
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"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. |
#6
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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 |
#7
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"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 The RCA 10T tombstone used the new metal tubes, and had an UltraShortwave band that reached to over 60 mc. Unfortunately, most of the RCAs had serious problems with the LO dropping off at about 50 mc orso, very few of the radios ever seemed to actually tune that high! I think I've seen one example that worked across the full tuning range without twiddling the circuitry to make it work. Bu, in 1936, probably no one even noticed, or cared. Pete |
#8
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"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 |
#9
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"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 The RCA 10T tombstone used the new metal tubes, and had an UltraShortwave band that reached to over 60 mc. Unfortunately, most of the RCAs had serious problems with the LO dropping off at about 50 mc orso, very few of the radios ever seemed to actually tune that high! I think I've seen one example that worked across the full tuning range without twiddling the circuitry to make it work. Bu, in 1936, probably no one even noticed, or cared. Pete |
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