|[AMRadio] 4-1000A Grounded Grid Class-C|
wa1qix at piesky.com
Thu Oct 3 10:22:03 EDT 2013
At 07:55 PM 10/2/2013 -0700, you wrote:
>Is it possible to run a 4-1000A in grounded gridS, cathode driven, biased
>for class-C and then plate modulate it and get 100% modulation? Has
>anybody tried this?
It is possible. The only important factor is how does the unmodulated feed
through power effect the linearity of the RF amplifier as a square law device.
As the modulation approaches 100% negative, the feed through power becomes
an increasing factor. It will not behave like a classic negative peak
limiter, which has no effect until it comes into conduction. So, there may
be some distortion, but how much is unknown having never actually done it.
Do you know how much feed through power you actually get? This will be an
important number to know. Because AM is a square law function, 1/10th the
unmodulated plate voltage (90% negative modulation) is 1/100th the
power. If you have, say, 5% feed through power, that is actually a lot
with respect to 100% negative modulation. I didn't figure it out, but it
may be 20% modulation... just something to consider.
If you do this arrangement, don't use the feed through as a negative peak
limiter (of sorts) without also protecting the modulation transformer (if
there is one). Implement a protection diode/resistor/power supply across
the transformer secondary to protect the transformer during the periods of
the modulation cycle where there is no current.
If it were me, I'd give it a try !! :-)
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