Valve Radio Home constructed

A few years ago a local historian was doing a project on the 1950's and asked me what lads in their early teens did in the way of hobbies and interests. I explained to her that many of us including myself built simple radio receivers from scrap parts that were given to us by understanding radio shops and dismantled obsolete receivers obtained from jumble and rummage sales. She was very surprised when I told her that we 'we plugged them into the mains'. In these times of health and safety with all its interest and brain deadening legislation it was inconceivable to her that this was allowed! I explained that we were well aware of the dangers and took the necessary precautions as we all have to do as we pass through life. To prove the point I constructed this simple receiver and loaned it to her for the duration of the project. It stimulated much interest at the time.
The receiver is a simple regenerative detector using the electron coupled circuit. The cathode of the detector valve [ EF39/6K7/G] is returned to earth via a few turns wound on the bottom end of the detector coil which is homewound. This allows some coupling between the control grid and cathode the degree of which is controlled by varying the valves screen voltage. [the reaction control] This arrangement sharpens the tuning and brings the valve into a very sensitive state. The circuit dates back to the very earliest days of radio and is reliable in operation. The signal is then passed to the second stage, a simple L.F. triode [L63/6J5/G] amplifier which then feeds the amplified signal to the output valve [6V6] and loudspeaker. The power supply consists of a mains transformer, 5Y3GT rectifer and conventional simple smoothing circuit. So there you have it, a simple radio receiver built from scrap parts that would have been constructed by a typical school lad around 13 years of age, A long way from todays cheap give away society!

Category:

Science & Technology

Tags:

• Valve
• radio
• homebuilt.
• Regenerative
• valve
• mains
• radio.
• Radio
• simple

[Hemingray]

You could omit the 6J5 and just use a 6F6, as they were meant to be driven directly from the detector.

[vinylseat]

Completely agree! This project was to use typical parts that a school lad would find in old television receivers etc. The

6F6 was a rare valve in the U.K. as such but the 6V6/6J5 were very common valves hence their use. J.

[NJPurling]

I have made this circuit in a smaller space.

I used a EFF39, EBC33 & a EL32.

I get HT with a Selenium rectifier directly off the mains & a small transformer runs the heaters.

The triode part of the EBC33 has more gain than a 6J5. An EL32 still makes 2 watts RMS. I guess you don't need the full power of the 6V6 anyhow.

The circuit here is probably safer, though the power the H&S guys have nowadays you probably wouldn't be allowed to take this into a school & demonstrate it.

[vinylseat]

Completely agrre with you. This was constructed to demonstate what could be done with components forced into service that were not ideal but would have been to hand to school lads. The EL32 is a very good valve but little used in domestic equipment unfortunately so was hard to find. All inspiration of the young has been killed off today hence the complete lack of basic engineering skills in teenagers. Its very sad but unfortunately degrees in 'media studies' [I want to be a pop star] count more.

[donnyab]

you won't be able to use it soon when it all goes digital

[felguid]

Ciao, è possibile avere lo schema del ricevitore .Sono molto interessato.Il mio call IK7XGD Email felguid@tiscali.it.Grazie

[n4120p]

Remarcable indeed ! I enjoy your electronics teaching,,your social observation clearly defines the decadence of our western culture,, well we are living nothing but what was propose by the ideology of the victorious party of WW2 liberty to all ideas, freedom to all as long as it makes money with a total social disregard for future,, I have always been intrigued how can the1000year old British culture can end up in such a self destructing proposition and followed by the world over

[eldorado303]

you can feel the nice tone coming from the set. really cool.

[rockangel1967]

hello. have a look at my homebrew FM radio :-) cheers

[MIKROWAVE1]

Very nice job and you have handled the hum situation, isolating the mains transformer well off to the side. This clearly demonstrates the benefits of using the ground plate on the front panel and a chassis. Excellent choice the 6K7.

[NJPurling]

This radio is successful, with no hum or feedback because the separate stages are well spaced out.

I have made a tuner & amp on separate chassis. You could listen to the radio feeder on high impedance headphones.

Maybe if you used a AF output transformer you could use 'Walkman' or IPOD earphones instead?

[AndyDaviesByTheSea]

Thank you for sharing this with everyone. It makes my want to go through the junk box and start constructing as you say just for the hell of it. Aren’t we lucky to have had the freedom to have done theses things? Mind you I can recall getting my first 300 Volt DC belt. Funny I should have chosen to go into high voltage electronics after that. May be that first belt gave me a healthy respect for the 8kV industrial valves I worked with.

Thanks again.

Kind Regards, Andy gw0jxm

[madamerotten]

Your radio sounds wonderful, and seems to have great selectivity. What's sad about modern electronics technology is that the parts are becoming too small to easily solder, deterring many potential hobbyists.

[WeaponsGradeMarmite]

Great stuff, brings back fond memories of jumble sales and rummaging about in the "Decca dustbins" on the way home from school.