5 ms·

And the spectrum RCA wanted between 42 and 50 MHz for television was only reserved. It was removed from the allocation table before it was ever used. With that

And the spectrum RCA wanted between 42 and 50 MHz for television was only reserved. It was removed from the allocation table before it was ever used. With that said, 88 to 108 MHz fits a lot more stations than 42 to 50 MHz would have. The 42-50 would have had to expand somehow.

lucas_membrane 4y ago
The 200 khz bandwidth of an FM broadcast signal might have been narrowed to allocate more channels. It is wide enough to carry all that additional info such as the stereo signal (not much of an issue in the 1940's, as nobody had stereo speakers or amplifiers at home), and the additional services (e.g. talking books for the blind, foreign language broadcasts, etc that have been multiplexed on top of the FM signal during the decades since). Now it also can carry the hierarchical digital (some of the comments to the original article apparently accept hierarchical-digital as high-definition, which it isn't) signals. The quality of music received by FM now is not so good as it used to be before all that other stuff started freeloading on the carrier. Most FM broadcast tuners and receivers are supposed to suppress the unwanted content by approximately 70 to 80 db. I don't know if the receivers go out of spec over the years, but when listening to classical music broadcasts medium loud, I often hear a soft garbled chatter during the quiet passages and silences between movements. From my POV, FM is fine for casual music listening but dead as a preferred medium for high-fidelity music. I am too discouraged by the poor S/N ratio that I now hear on FM to dare to spend much for for a better receiver that may not be significantly superior.
ac29 4y ago
They could have used 100kHz spacing in 42-50 MHz instead of the 200kHz spacing they use for 88-108 MHz. Wouldn't have sounded quite as good most likely, but still a substantial improvement from AM's 10 kHz channels.
- RF_Enthusiast 4y ago
  Oh, I agree. Definitely an improvement over AM. With the 100kHz spacing, it would still only fit about 80% of the channels we currently have. If they stuck with 42-50 MHz, they'd probably have to be creative, like have New York City use horizontal polarization and Philadelphia use vertical polarization (although now we know that doesn't make a huge reduction of interference). If they expanded it downward, it would touch what's now the high end of the shortwave bands. Might have been some interesting propagation. Sometimes when the conditions are right, a 25 MHz signal can travel the globe during the daytime.
  - drmpeg 4y ago
    A 42-50 MHz FM band would have been an interference nightmare. During the summer months, Sporadic E propagation is very prevalent on those frequencies (with high signal strengths). And during large sunspot cycles, regular F2 layer propagation is possible during the fall and spring months. During the peak of sunspot cycle 22 in 1989-91, a great F2 layer propagation indicator here on the west coast US was New Zealand TV channel 1 audio on 50.75 MHz (+/- 10 kHz). If you could hear the wideband FM audio on 50.75 MHz, it was almost guaranteed you could make a ham radio contact with New Zealand at 50.110 MHz.

lucas_membrane 4y ago

The 200 khz bandwidth of an FM broadcast signal might have been narrowed to allocate more channels. It is wide enough to carry all that additional info such as the stereo signal (not much of an issue in the 1940's, as nobody had stereo speakers or amplifiers at home), and the additional services (e.g. talking books for the blind, foreign language broadcasts, etc that have been multiplexed on top of the FM signal during the decades since). Now it also can carry the hierarchical digital (some of the comments to the original article apparently accept hierarchical-digital as high-definition, which it isn't) signals. The quality of music received by FM now is not so good as it used to be before all that other stuff started freeloading on the carrier. Most FM broadcast tuners and receivers are supposed to suppress the unwanted content by approximately 70 to 80 db. I don't know if the receivers go out of spec over the years, but when listening to classical music broadcasts medium loud, I often hear a soft garbled chatter during the quiet passages and silences between movements. From my POV, FM is fine for casual music listening but dead as a preferred medium for high-fidelity music. I am too discouraged by the poor S/N ratio that I now hear on FM to dare to spend much for for a better receiver that may not be significantly superior.

ac29 4y ago

They could have used 100kHz spacing in 42-50 MHz instead of the 200kHz spacing they use for 88-108 MHz. Wouldn't have sounded quite as good most likely, but still a substantial improvement from AM's 10 kHz channels.

RF_Enthusiast 4y ago
Oh, I agree. Definitely an improvement over AM. With the 100kHz spacing, it would still only fit about 80% of the channels we currently have. If they stuck with 42-50 MHz, they'd probably have to be creative, like have New York City use horizontal polarization and Philadelphia use vertical polarization (although now we know that doesn't make a huge reduction of interference). If they expanded it downward, it would touch what's now the high end of the shortwave bands. Might have been some interesting propagation. Sometimes when the conditions are right, a 25 MHz signal can travel the globe during the daytime.
- drmpeg 4y ago
  A 42-50 MHz FM band would have been an interference nightmare. During the summer months, Sporadic E propagation is very prevalent on those frequencies (with high signal strengths). And during large sunspot cycles, regular F2 layer propagation is possible during the fall and spring months. During the peak of sunspot cycle 22 in 1989-91, a great F2 layer propagation indicator here on the west coast US was New Zealand TV channel 1 audio on 50.75 MHz (+/- 10 kHz). If you could hear the wideband FM audio on 50.75 MHz, it was almost guaranteed you could make a ham radio contact with New Zealand at 50.110 MHz.