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Rob Orland
Historic Coventry
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121 of 130  Sat 25th Apr 2020 10:16am  
Webmaster: Joined Jan 2010  Total posts:1575

On 24th Apr 2020 9:36pm, JohnnieWalker said: My dad came home one day from work at the GEC, with a bit of copper wire, a crystal, a variable condenser, an antique pair of headphones - and a toilet roll. He assembled all these bit and pieces (excuse me if I've missed or misnamed some component - probably should be a battery?)....
Amazingly to many, it probably wouldn't have required a battery. What you've described is a crystal set, and there's enough voltage induced in the aerial (usually just a very, very long piece of wire for Long or Medium Wave) to power a pair of high impedance headphones. In more recent years I made an equivalent (but using germanium diodes instead of a crystal) to demonstrate a battery-less radio to our children. We used our aluminium ladders an an "aerial" and they were amazed at being able to tune into local stations quite clearly!
Music memories
scrutiny
coventry
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122 of 130  Sat 25th Apr 2020 10:52am  
Member: Joined Feb 2010  Total posts:706

It has been a long time since I built a crystal set. Used one of my dad’s tobacco tins and a set of earphones from the Army Navy stores. Circa 1961. Memories? Oh my
Music memories
Slim
Another Coventry kid
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123 of 130  Sun 17th May 2020 10:09pm  
Member: Joined Mar 2013  Total posts:660

My first attempt at a crystal set was from my dad's old Hobbies Manual, dated 1930 something. It used a galena crystal with a "cat's whisker", a bit of pointed wire where you had to keep fiddling to get the right spot on the crystal. It didn't work very well.. didn't work period to be honest. An older mate at school, who was into electronics in a much bigger way than I - well his dad was one of the brothers who owned Electronic Services in the City Arcade - suggested I use a modern germanium diode. So I went down to his dad's shop and bought one - an OA85 IIRC. It worked! After a while, I realised that, there being no active components - it consisted solely of the ferrite aerial I had wound, tuning cap, diode, small rf bypass cap (probably 1nF) - it could only power my old ex-military/surplus stores high impedance (2k ohms) headphones, so the volume was very limited. Hungry for power, I set about designing a bolt-on amplifier for a small speaker. This consisted of a few more components, fed off a 9V battery (PP6 in those days). The magic active components were two "red spot" transistors (courtesy of Electronic Services and my paper round earnings). One was a preamplifier, followed by the output transformer driver. I was chuffed that it worked quite well, and I had built in a volume control pot too. Looking back, I'm amazed it worked at all. The transistors were germanium - silicon wasn't freely about then. In addition, I later learned that the "red spot" marking, devoid of part numbers like OC44, AF115, meant that those highly prized transistors were actually manufacturers' rejects which really should have gone into the bin!
Music memories
Rob Orland
Historic Coventry
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124 of 130  Mon 18th May 2020 10:23am  
Webmaster: Joined Jan 2010  Total posts:1575

Ah, Electronic Services - what a wonderful Aladdin's cave that was - I do miss places like that. There's was virtually nothing they couldn't find for you in those thousands of little drawers behind them, and the old chap and his staff were so knowledgeable. When I worked at the GEC in Spon Street in the 80s, it was so convenient to just wander into there - sometimes to buy something I'd not even thought about when I went in! I also used some 2kohm headphones (which I still have) for the germanium "crystal" set - and I managed to modify the original design by using multiple diodes effectively as a bridge rectifier for a slightly increased volume. I was pleasantly surprised that it worked!
Music memories
Annewiggy
Tamworth
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125 of 130  Mon 18th May 2020 10:40am  
Member: Joined Jan 2013  Total posts:1714

I spent quite a lot of time standing outside that shop while Roy bought stuff. The shop was not big enough for more than a couple of people. The only place he can get stuff now is on the internet. Good job at the moment though. The postman must be fed up of the little packets we get!
Music memories
Kaga simpson
Peacehaven, East Sussex
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126 of 130  Mon 18th May 2020 11:06am  
Member: Joined Sep 2014  Total posts:3559

Yes, well, you have all hit on the craze of the era, 1930 wireless. All the hobby manuals had ways of making your own. The word DIY was not known. Radio made big name, didn't really happen in the Victorian age. The broadcasts in the twenties were from primitive equipment. 1923 saw the first election results broadcast, 1927 the first automatic telephone exchange, and first cable laid from UK to USA. The BBC moved from Savoy Hill to its new abode in Portland Place. By the thirties it was the new model craze, I believe crystal sets could be bought and were in nearly every house.
Music memories
Slim
Another Coventry kid
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127 of 130  Mon 18th May 2020 11:13am  
Member: Joined Mar 2013  Total posts:660

But does anyone remember the original ES shop, pre-City Arcade? An even tinier shop, and the RS (Radio Spares in those days) catalogue was half a dozen sheets of loose paper stapled together. The building was demolished to make way for the ring road.
Music memories
Midland Red
Cherwell
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128 of 130  Mon 18th May 2020 12:06pm  
Moderator: Joined Jan 2010  Total posts:5582

If you type “electronic services” into the search box (posts), you’ll find plenty of mention of them in various threads and a photo of their previous shop Thumbs up
Music memories
Old Lincolnian
Coventry
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129 of 130  Mon 18th May 2020 4:51pm  
Member: Joined Sep 2012  Total posts:519

My father had Hobby's Weeklys going back to the 1930s, so I built my first crystal set from the plans in one of them (as well as lots of other things). You could improve reception by running a length of copper wire down the garden. A metal bed frame would improve it as well and the bed frame also worked for both vhf radio and television.
Music memories
Slim
Another Coventry kid
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130 of 130  Mon 18th May 2020 6:37pm  
Member: Joined Mar 2013  Total posts:660

Those were the days when there was no tv, so the radio was very important, there often being only one in the house. No fm radio, just medium and long wave stations. Every design in the hobbies books was safe - i.e. batteries only. After the war, my dad built a professional looking mw/lw four valve set from a kit purchased from a London company called the Clyne Radio Company. He used an old copper iron heated on the stove to solder, and did an excellent job. That was our main radio for many years, and I remember listening to music on it in bed at weekends as a little boy. I'm surprised there weren't more explosions or electrocutions. Earth: "wrap a wire round the nearest pipe", whether water or gas. Our Clyne radio had a "live chassis" (cheaper than a safety transformer). One of the three Bakelite knobs got brittle, and a piece came off its middle, exposing a potentially live brass shaft to the touch. When we moved, I had the thing in the kitchen, and decided the cast iron fireplace might make a good aerial. I was amazed that touching the aerial wire onto the metalwork caused quite bright sparks and a loud spitting noise that soon burned the end of the thin wire away. Of course, the fireplace metal was effectively earthed through the damp in the brick work and floor. I later learned that for safety, there was an aerial isolating capacitor (about 500pF) inside the set, but one of its connexion lugs had snapped off flush, so to get the set working, the aerial lead had been stripped back and wrapped around the other lug, bypassing this safety component!
Music memories

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