Fw: [AMPS] tuning capacitor & insulator

[Steve Thompson]

In message <B0000442420@alpha.futurenet.co.za>, John Fielding
<johnf@futurenet.co.za> writes
>

BIG SNIP

>
>As a final thought:
>
>Consider the anode impedance of an amplifier.  One tunes up with maximum
>drive.  In this case for the anode voltage/curent in use the tube now
>"sees" its correct load impedance and transfers the maximum power to the
>load (antenna).  Under low drive conditions the tube "sees" an impedance
>which is many times higher than what it was set up for.

I think not - the impedance the tube sees is set by the matching
components between the tube and the antenna. When you drive at lower
power than max, the load is lower impedance than ideal for maximum power
transfer and the tube runs at lower efficiency.

>  Can some genious
>devise an automatic tuning mechanism that will provide the correct anode
>impedance for any condition of drive level, to ensure the best efficiency
>under all drive conditons?

Didn't Collins do a lot of work on this?

Steve

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