Piston Attenuator?

Feb 24, 2010 3 Replies

I'm seeking tutorial and /or building instructions for a piston attenuator which is a short waveguide operating well below cut-off and is capable of an easily calibrated (by mechanical vernier) attenuation factor.


AIUI, these were commonly used in valved signal generators. Any info anywhere?


Somebody Inscribed thus:

Some of the "Marconi" sig gens used those attenuators.

Best Regards: Baron.

Answering my own question ...

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Years ago we used a microwave attenuator for changing the coupling into a cavity. It was a piece of waveguide that was below cut-off. There was a Teflon slug that could be moved within the waveguide to change the coupling. With the Teflon fully inserted the waveguide was above cut-off. One end of the slug was tapered. I assume to reduce reflections.

George H.

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