G0CWA Crystal Tester

Firstly although this is my build of a go / no go crystal tester the actual design came from the excellent book “Solid state design for the radio amateur” published by the ARRL. The circuit is a Pierce oscillator to which the crystal under test is plugged into. The circuit includes switchable feedback settings using the centre off switch sw2 for different crystals.

Unusually for my projects I have not included a PCB design as building “dead bug” style was far more convenient.

The diodes used were 1N34A’s but any small signal diode will do, the transistor was a BC108. The meter movement I used was a small battery test meter but any meter from 50 micro-A to 1mA FSD can probably be used. The crystal holder was “made” from a turned pin i.c. socket, a lot cheaper than a standard crystal socket. The final feature being an output socket so the output can be monitored on a scope etc., or even used as a simple signal source or BFO etc.

The crystal activity is monitored on a simple RF detector and analogue meter arrangement. This enables measurements of relative crystal performance amongst similar crystals.

Please note overtone crystals can be checked but due to the lack of tuned circuits they will operate in their fundamental mode. Sorry this one is so short and sweet a project but I am sure you will find it a very useful addition, and a very cheap almost “junk box” piece of test equipment.

I will be following this with other similar useful but cheap items of test equipment not the least of which will be a realistically priced simple GDO with AM modulation option.

If you are into solid state radio home brew, the book mentioned is, to my mind, a must have. I apologise if this write up is not to my usual standard but I have had a major relapse in my health but I can still be contacted with any problems via either the Radio board or QRZ forums (G0CWA) or by E-mail shown at the bottom of this page. Please be patient for replies as I am not back to my normal self and won’t be for quite a while.

Please only contact me via these routes if you have any questions, I can’t guarantee to reply otherwise as I can’t see every reference to my sets.

Enjoy the design 73 for now Nick G0CWA

Crystal Activity Tester Schematic

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