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Old 5th Jan 2005, 6:20 pm   #1
McIntyre
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Question Early FM tuners

Does anyone know the history of seperataly housed and powered FM tuners? I was going through my local charity SPCA shop and came across three "Comet FM tuners" - all valved - Using an EZ81, 2x EF89 and a ECC85 covering the usual frequencies froom 88 to 108 - chassis' only, in various states of decomposition.

I never knew that seperate tuners where available : What was the purpose of a seperate tuner - most radio stations of the 50's ran parallel BC, SW and FM transmissions? I imagine that by the mid 60's most receivers feautured a seperate FM band? Where these tuners home construction kits? One is marked "made in Denmark". When would something like this have been manurfactured, I'm guessing late 50's?

The tuners are absolutely fascinating as the are so simplistic in their construction - I bought the two "better" condition sets as the look like an easy fun project to repair (all "IF" type cans are still sealed with their original wax so it doesn't appear a nasty surprise awaits there).
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Old 5th Jan 2005, 6:49 pm   #2
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Default Re: Early FM tuners

Just as with separate tuners today, these were used with hifi systems, though some people plugged them into the 'gram' socket of existing AM radios. This was obviously a very small part of the market then, and as you imply most people carried on using MW and LW even if their radios covered FM, since they'd got used to the 'warm tone' of AM radio.

Some tuners were kits made by enthusiasts, but companies like Quad and Leak made commercial products. As often as not these didn't contain a power supply and were supposed to take HT and LT from the power amp or preamp.

HTH, Paul

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Old 5th Jan 2005, 6:56 pm   #3
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Default Re: Early FM tuners

Yes, in the 1950s there was a developing interest in hifi stuff, and given the expense of equipment and components at the time many people started off with a record deck and a good quality stereo amp, but did not want the AM bands, so a 'stand-alone' FM unit or one which took its power from the amp had a ready market. I have one of the latter units, which according to it's legend was made by Goodsell of Brighton, but I suspect was a revamped Jason unit. It used similar types of valves, an ECC85, 2 x EF85 and an EB91, a rectifier not being needed.
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Old 5th Jan 2005, 7:01 pm   #4
high_vacuum_house
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Smile Re: Early FM tuners

Hello there,
I think that the main idea of a seperate FM tuner unit with a power supply is that you diddn't need to buy a completely new radio reciever when FM was introduced. You connected the output to the gram connection on your existing set and then used the gram setting for FM. An output stage, volume/tone controls were not required on the tuner unit as these were on your existing radio. Without these components plus a smaller cabinet and power supply the tuners were fairly cheap compared to a new radio.
There were quite a few DIY kits avaliable, the best known one being by Jason kit. I have 2 of these bought at the same time at a radio rally. They are very simple to build and use a small quantity of components. I think a metal rectifier is used for HT and 2 semiconductor diodes are used in the discriminator circuit.
Thanks,
Christopher Capener
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Old 5th Jan 2005, 7:07 pm   #5
jim_beacon
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Default Re: Early FM tuners

The popular kit tuners in the UK were from JasonKit and Haethkit.

Jason produced at least three different models, starting with a kit to build the "Wireless World" design, which used four Z77 (EF91) valves, with a fifth in the fringe version. This kit was placed on the market during the FM trials, when there was omly one experimental station. Later a booklet was produced, detailing the tuner construction, and also the construction of the Osram 912 Hi-Fi amplifier. I have one of these early kits, and it works, though it is difficult to tune, and the slightest cold draft will cause it to go off frequency! Jason later produced a much better fully tuneable unit, and a four station preset unit.

Heathkit produced some nice tuners, the one I have works very well (I forget the model number), but has EF80s in it, so it is a reasonably early design.

There were also a number of construction articles in "Wireless World", "Practical Wireless" and "Radio Constructor", for both switch tuned, and variable tuning designs, and one or two for the conversion of Government Surplus units - I know there is one based on the VHF Gee unit, and I think one based around the R1132, but I don't think you would get away with an R1132 in the front room!

Jim.
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Old 5th Jan 2005, 7:08 pm   #6
radiogammon
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Default Re: Early FM tuners

I remember buying a couple of such tuners back in the early 60's when I had an interest in building valve amplifiers and large corner enclosures using 15in Wharfdale speakers. The main problem with them was drift as this was before the days of AFC. One of them used a turret pre-set tuning arrangement like the old TV's but it was forever giving trouble because of dirty contacts, in spite of contact cleaner. The cores of the coils on the turret were also inclined to move because of vibration, sending them out of tune. O those were the days!!
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Old 5th Jan 2005, 7:33 pm   #7
McIntyre
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Default Re: Early FM tuners

I had a quick look at the tuner I've got and it seems to have to outputs - one for the "gram socket" and another which I can't identify - it is defintely not a phono input. The other 2 jacks on the chassis are for the the FM aerial. Is there any particular length the two pieces of aerial needs to be?
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Old 5th Jan 2005, 7:43 pm   #8
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Default Re: Early FM tuners

Some early FM tuners were designed as an add-on rather than for "hi-fi" purposes; the oft-seen HMV model comes to mind here. Also, if you look at the KB FB10FM (the FM "Toaster") what would be the wavechange switch on the AM model now reads IIRC "Radio" and "Adaptor". Again, usually designed to go in the pick-up sockets.

We didn't do what the Germans did - make our sets adaptable for FM reception via an internal add-on adaptor- but then and again, we didn't get screwed over in the Copenhagen Plan like they did. Another case of the "spoils to the victor".

I recommend a visit to Andrew Mitz's FM Only website for further reading. Although Andrew is American, his site encompasses the world.

As for your aerial - it needs to be 1.5m across from end to end as a simple dipole. Ordinary twin lighting flex or loudspeaker cable will do.
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Old 5th Jan 2005, 8:15 pm   #9
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Default Re: Early FM tuners

Everyone seems to have summed up the situation pretty well. The take up of FM was slow in this country and many people didn't want to spend money on a new set at the start of FM transmissions. FM tuners were a great help here because as stated earlier, they could be connected to the gram socket. In the late fifties, my brother was in the radio trade and we had an FM tuner (home-built Jason job I understand) which he used to record Top of the Pops on Sundays. Years later I also aquired a Jason tuner (four EF91's) and used it through a home-built Hi Fi system. I even tried building a stereo decoder for it but it was never really very successful. So separate tuners have always been of great use as far as I am concerned.


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