A Futuristic TV with FM Radio

[Mikey405]

Hi all.

I decided that as I could probably never afford the real thing, I'd buy the manual for the rather futuristic and extremely comprehensive TV / radio set called the Decca Decola.

This particular Decola (there were several large radios / grams with the same name) is a combined projection-TV and 8-band radio from 1949 / 1950; it has 48(!) valves, 8 of those (including two PX25s) are in the audio amplifier. The set is huge and built in the grand-manner - and probably cost an absolute bloddy fortune too. I've seen them listed on eBay from time to time but I wonder how many have survived with their amplifiers intact.

Anyway, the reason that they are so futuristic (to my mind at least) is that the set has an FM radio band (5/6 years before I thought the BBC started broadcasting) and the manual states that the FM range "used by the BBC" is 88-110MHz. And this in 1949/1950.

Does anyone have any memories of these and what might have been available on the FM band for your great cash outlay in 1950?

Thanks all.

Kind regards.

From Mike.
PS. I realise that this is straying into "Radio" territory but as it was foremost a TV, hopefully it could be excused.

[FERNSEH]

Hi Mikey,
Made in 1950 the English Electric model 1550 also has FM radio facilities.

There's one languishing in the back of the workshop.

With regard to the Decca Decola projection TV set. I'm sure I saw one or something like it in a 1950s film shown on Talking Pictures TV.
Whatever it was it was huge!

DFWB.

[Restoration73]

Not in my living memory, but this may be of interest;

http://www.async.org.uk/Tony.Davies/...rt_handout.pdf

[Nuvistor]

BBC research papers, lots of information about early VHF FM, there are more available than these if you are interested.
http://downloads.bbc.co.uk/rd/pubs/reports/1946-05.pdf
http://downloads.bbc.co.uk/rd/pubs/reports/1946-19.pdf
http://downloads.bbc.co.uk/rd/pubs/reports/1946-05.pdf
http://downloads.bbc.co.uk/rd/pubs/reports/1947-33.pdf
http://downloads.bbc.co.uk/rd/pubs/reports/1948-34.pdf
http://downloads.bbc.co.uk/rd/pubs/reports/1949-08.pdf
http://downloads.bbc.co.uk/rd/pubs/reports/1951-03.pdf

[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,

[Heatercathodeshort]

Interesting one Mike. I have seen a picture of that massive Decca projection receiver. I seem to remember that the solid projection screen folded down behind the cabinet. It's amazing there was a demand for such luxury models but I suppose there always has been in the UK.

We were very late with FM, understandably considering the terrible state of Britain after WW2.

It was a different state of affairs in the USA. This is the radio chassis from a Stromberg Carlson radiogram circa 1941. It covers 42-50mc/s Band 1. At the end of WW2 in the USA the FM band was changed to the familiar 88-108mc/s.The FM unit is mounted on the top and clearly an afterthought adding it to the AM chassis by the makers.

As David has stated, English Electric produced a television in 1950 that incorporated FM. I may be wrong but I think they also produced a version with AM radio or could that have been Emmerson? Regards, John.

[Restoration73]

John, does that chassis use slope detection for FM ? The 42-50 MHz Armstrong band is
a development of the earlier Apex AM band, with many stations effecting the change;
https://en.wikipedia.org/wiki/Apex_(radio_band)

[Heatercathodeshort]

Sorry I don't know. I have attempted to obtain a service manual for this model for a long time without success. It uses a 6H6 [EB34] double diode and as far as I can make out, a standard ratio detector. As it's not TV connected, better we not go OT. regards, John.