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Test: VR tube impedance wrt frequency.
















This is something I have wanted to know about for some time, so I designed and then built the circuit, then measured for half amplitude drop (equal wave-forms when x=1:y=2 setting on the oscilloscope).

Impedance therefore is equal to Xc plus DCR of the rheostat.

28mADC through the VR tube, sinusoidal 10vp-p waveform,

With and without 0.056uF bypass cap across the VR tube. (in this case 0A2). The table header is misleading in the second column it should follow the first.

The oscillogram is 10vp-p at 100kHz, one trace across the signal generator, the other across the VR tube.

The VR tube emits an audible sound which was prevalent between 3 and 7kHz, which came as a surprise.

This is tribute to my father who left this plane just a few days ago.

Thanks for the interest.


Shane


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Topic - Test: VR tube impedance wrt frequency. - shane. 21:36:34 05/3/17 (1)

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