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Circuits for Crystal Diodes

The following circuits show uses for the crystal diode in an article written in 1959 for the Radio Constructor Magazine.
The first circuit (Fig 1) is for a simple Crystal diode receiver using 3 components (or 4 if you switch longwave) plus of course a crystal earpiece. The diode can be the currently availiable OA81. The variable capacitor can be the modern type which is readily availiable. For the coil(s) you can wind your own (which is the cheapest solution.
The second circuit (Fig 2) is for a crystal tuner, tuned to a single station with a fixed capacitor or again using the variable capacitor used in Fig 1.
Figure 3 is for a crystal receiver but with a transistor amplifier added. Using germanium transistors as the amplifier it uses more components than the other 2 circuits.
Remember this was 1959 and the valve was still very much in use so the next 2 circuits (Figs 4 and 5) are for crystal detectors driving valves.
These circuits use a high ht value so are not much use for today (Just supplying the HT will cost rather a lot, unless you have a spare ht transformer you can use.
Finally we reach Fig 6 which was to add a crystal diode to supply AVC (Automatic Volume Control) to a valve set.

If you need components have a look at Peters site or ask him.
Peter Roberts

Circuits for Crystal Diodes Page 1 Circuits for Crystal Diodes Page 2
Circuits for Crystal Diodes Page 3


Last updated 3.6.2005

2003-2005 © Maurice Woodhead