[Synchrodyne]

There did appear to have been a spike in setmaker interest in FM reception in the late 1949-early 1950 period. As well as the Decca and English Electric TV-FM receivers, HMV offered the 1250 FM receiver, and Kolster Brandes (KB) offered both an FM receiver and an FM adaptor (the RF section of the receiver). And Mullard also offered its GFR520 communications receiver that had FM band coverage.

At the time, the BBC experimental transmissions from Alexandra Palace were ongoing, with a planned change to the Wrotham high-powered transmitter. (The AP transmissions were originally in the 40 MHz band, then were moved up to the 90 MHz band.)

The Region I (including Europe) Band II limits had been set at 87.5 to 100 MHz at the ITU 1947 Atlantic City meeting. In the UK case, that was footnoted to say that 94.5 to 85 MHz was assigned for meteorological aids purposes, and that 95 to 100 MHz was for fixed and land mobile services. That left a net 87.5 to 94.5 MHz, which was in fact the tuning range for the HMV 1250 FM receiver. The KB receiver had a crystal controlled oscillator, and covered 90 to 94 MHz. Elsewhere in the world, Band II spanned 88 to 108 MHz in Region 2 (deriving from the 1945 FCC allocation) and 87 to 108 MHz in Region 3.

One might say that in choosing the 88 to 110 MHz range for its Decola TV-FM model, Decca was taking few chances, although perhaps surprisingly it was 0.5 MHz short at the bottom end. The Mullard GFR520 covered 540 kHz to 110 MHz, with FM reception available from 27 to 110 MHz. Curiously, from the modicum of information available, this receiver appears to have had essentially the same basic parameters as the Hallicrafters SX-42 and SX-62 models.

Returning to the UK FM band, I suspect that the 94.5 to 95 MHz section was cleared for broadcasting use fairly early on. I understand that the BBC slot aerial radiator system included in the Sutton Coldfield mast in 1949 and first “used in anger” at Wrotham was designed for the 87.5 to 95 MHz band. Also, the BBC VHF AM-FM comparator receiver (designed and built by Fitton (Ambassador) to BBC specifications, with design work starting in 1949) tuned the 87.5 to 95 MHz range. The UK submission to the ITU 1952 Stockholm included Band II assignments from 88.1 to 97.3 MHz, indicating that some clearance of the 95 to 100 MHz sub-band of other services was already in view.

Possibly that early peak of setmaker interest in FM passed when it was seen that the decision to “reinvent the wheel” by revisiting the FM vs AM issue would cause further delay and carried the risk of a perverse outcome. A small number of Band II tuners from the small hi-fi makers appeared around 1952-53, but these catered for VHF-AM as well as VHF-FM. The setmakers though waited until FM was a certainty before returning to TV-FM and FM receiver activities.


Cheers,