Added on Sep 17, 2010

Length: 05:34 | Comments: 0

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 ...

Channels: Hobbies & Interests  

Tags: Tech  Valve  radio  homebuilt.  Regenerative  mains  radio.  simple