The problem with making the measurement with a LCR meter is that the
measurement requires 3 connections. You can connect the meter to the plate
and to the
cathode but what do you do with the grid between the two? You have to actually
measure the actual coupling between the plate and cathode with the grid
(Fariday Shield) between
them.
73
Bill wa4lav
At 07:21 AM 10/6/2010 -0400, you wrote:
>Date: Tue, 5 Oct 2010 01:44:58 -0400
>From: "Fuqua, Bill L" <wlfuqu00@uky.edu>
>Subject: [Amps] 833 plate cathode capacitance
>
>
>Finally got around to it and measured the plate to cathode capacitance.
>I was quite surprised. It was as high as stated in specs. I got about 20pF
>but that includes
>a few pF from setup wiring.
> I thought I'd try another tube that has similar dissipation and
> characteristics 304TL.
>Its plate to cathode capacitance was less than a pF.
>So even grounded grid operation with a 833A may not be stable with out
>some neutralization.
>
>Used spectrum analyzer and tracking generator. Measured feed thru signal
>level and calculated capacitance based on
>frequency and input Z of spectrum analyzer. The grid was grounded and
>signal fed to plate and cathode connected to
>spectrum analyzer.
>
>
>
>73
>Bill wa4lav
>
>## why not just use a digital LCR meter ? Factor in the test leads if
>required, depending on
>spacing between em.
>
>Jim VE7RF
>
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