05-03-2026, 07:03 PM
Rod -
Yes, it has Major Armstrong's pre-WWII FM band from 42 to 50 MHz. The FM slide-rule dial is calibrated with channel numbers from 21 (42.1 MHz), 25 (42.5 MHz), and 29 (42.9 MHz), up to 93 (49.3 MHz), 97 (49.7 MHz), and 99 (49.9 MHz). As is the case in the current FM band, channels have 200 kHz spacing (center frequencies 42.1, 42.3, 42.5, 42.7, 42.9, and so on). As is still the case with FM in the US, carrier deviation was +/- 75 kHz, and pre-emphasis was 75 µs. I can generate a perfect signal using a modern stereo generator operating in mono (to provide pre-emphasis) into the external modulation input of my AN-URM-70 FM signal generator. Although its lowest band is 50-100 MHz, it will easily tune to 49.9 MHz. It will easily deviate 75 kHz in that band.
Dale H. Cook, Semi-retired AM/FM/TV Chief Engineer, Roanoke/Lynchburg, VA
https://plymouthcolony.net/starcityeng/index.html
Yes, it has Major Armstrong's pre-WWII FM band from 42 to 50 MHz. The FM slide-rule dial is calibrated with channel numbers from 21 (42.1 MHz), 25 (42.5 MHz), and 29 (42.9 MHz), up to 93 (49.3 MHz), 97 (49.7 MHz), and 99 (49.9 MHz). As is the case in the current FM band, channels have 200 kHz spacing (center frequencies 42.1, 42.3, 42.5, 42.7, 42.9, and so on). As is still the case with FM in the US, carrier deviation was +/- 75 kHz, and pre-emphasis was 75 µs. I can generate a perfect signal using a modern stereo generator operating in mono (to provide pre-emphasis) into the external modulation input of my AN-URM-70 FM signal generator. Although its lowest band is 50-100 MHz, it will easily tune to 49.9 MHz. It will easily deviate 75 kHz in that band.
Dale H. Cook, Semi-retired AM/FM/TV Chief Engineer, Roanoke/Lynchburg, VA
https://plymouthcolony.net/starcityeng/index.html
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