Grid-Leak Detector Vacuum Tube Radio
YouTube videos for this project:
This is a variation of my earlier vacuum tube radio but operating with a low-voltage laptop power supply at 19V - it will work on 12-volts just as well.
This is constructed by using a soft pine board and using metal thump tacks as soldering points. The poster board on top of the wooden board is handy for drawing out component placement, noting voltages, etc. If the tacks bend going use a very small drill bit to make a pilot hole.
The above schematics uses a high gain 6HA5 triode or with a little more complexity a 6BA6. With the screen grid connected to a potentiometer this can act as a volume control by controlling the gain.
This will work with any number of vacuum tube triodes, etc. but high gain tubes give more volume. The two above designs are known as grid leak detectors and will measure a negative voltage on the grid when a station is present.
Selectivity (separating neighboring radio stations) and volume depend on the length of the external antenna and the quality of the homemade tuning coils. Coils for Highly Selective Crystal Radio
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