Diode Noise Source

A recent event reminded me of a VHF/UHF diode noise source I built many years ago.

I used it to optimize receiving converter performance. The circuit appeared in a 1972 ARRL V.H.F. Manual. It may have appeared in other's as well. I built this one in a slightly smaller minibox than the one shown in the ARRL publication. I also used a BNC connector unlike the ARRL version that used a PL 259.

The article suggested using a 1N21 microwave mixer diode as a noise source. At the time I did not have one so I used a 1N416G microwave mixer diode instead. This diode worked well but did not have as much noise output as the 1N21. The 1N416G may have been a better diode for it's original purpose and therefore did not produce as much noise when used in this application.

The device is powered by a 9 Volt battery. The pin jacks shown in the photo are used for monitoring diode current with an external meter. The higher the current the more noise is produced.

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