Radio DIY kit: Ultrashort wave (FM) radio receiver with a super-regenerative detector on 2 vacuum tubes

A two vacuum tubes super-regenerative ultrashort wave (FM) receiver provides a loud-speaking reception of the local FM radio stations with frequency modulation.

Frequency range: FM, 88 - 108 MHz.
Current consumption:
Anode 250V, not more than 30mA Attention! Danger to life!
Heater 6,3V, not more than 0,8A.
The board size: 131 x 91 mm.
The set is supplied as a printed circuit board and a kit of parts.
It is possible to purchase the set without the 6N14P (ECC84), 6J52P (E810F, 6J11P) vacuum tubes and/or the output transformer.

DIY kit Two vacuum tubes FM radio receiver with a super-regenerative detector Set of parts of DIY kit two vacuum tubes FM radio receiver with a super-regenerative detector
Attention! No matter how funny it may seem, make sure that there is an FM broadcasting in your region!

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Instructions for assembling and tuning the device:

By default, the tube 6J52P (6J11P) is supplied in the construction set but it is possible to use an E810F tube instead. To do this you need to remove the pin #6 from the tube panel in a way to exclude contact with the board.

Install the board and solder the details according to the concept and layout of the board. Keep the polarity in the right way while installing the electrolytic capacitors. The filter capacitors marked on the board as Ch are not indicated on the scheme but are recommended to be obligatorily installed in this radio constructor.

Circuit of DIY kit two vacuum tubes FM radio receiver with a super-regenerative detector

The superregen L2 coil is wound up with the 1mm diameter cable with 5,75 turns and a mandrel of 7mm in diameter that is included in the set.

After assembling the circuit, connect a piece of wire as an antenna to the "Ant" terminal, anode and heater voltage from the power supply. According to the experience of assembling a few radio constructors, a properly assembled radio constructor works at once, but it needs some tuning. It is recommended, during the first start-up, to check the current consumed by the anode circuits. It should not exceed 30mA. In case of exceeding this level of consumption pick denomination R12.

With the indicated ratings of parts, the covered range will be a bit bigger than 88-108 MHz. Therefore, it is enough to turn the shaft of variable capacitors to the far right and slightly extend the turns of the L2 coil and receive the highest frequency radio station in your area. The lower end range will be set automatically.

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