The APC is intended to be resistive (damps Q) at high freq and very
low reactance at operation freq. I should have mentioned that the 4R7
should be a carbon resistor (not wire wound).

I hope that the anode isolation inductor is mounted away, so can't
form part of the tuned circuit... What value is the inductor you are
using ?

Just for getting the anode tuning sorted out, have you considered
driving the grid with a crystal oscillator source and a suitable
buffer - this splits the problem in two. A few volts of drive should
be a good start, maybe a CMOS oscillator driving some paralleled
74AC04 buffers, that will give you 5V P-P drive into a 1:2 torridal
transformer, 10V P-P may be useful dive ?

Just out of interest, why haven't you gone for Grounded Grid
configuration ?

-Mark

On Jul 27, 1:15 am, wrote:
GHZ spectrum analyser would be a nice bit of kit to borrow, but I dont
know anyone with one - which is a pity. The scope is 40MHz so 25MHz is
pretty close to its max and the resolution is not the best. Waveform
is fairly symmetrical so I think the fundemental is right at 25MHz.

Ill do the APC tonight, what difference will it make?

As for 1.5kV - yup, I have had it cranked to full, 2.2kV, and no extra
power really (maybe a slight amount, but I am looking for 1kv swing
where I am only seeing 50v so its not even close). Underwear got
messy... makes the hair on the back of my neck stand up from fear to
be that close to a 10u cap charged to 2.2kv...!



Also... borrow a GHz Spectrum Analyser and chech that the unit is
running at the expected freq. What bandwidth is your scope ?

An anode APC is also a very good idea. A few turn of 16AWG around a 2W
4R7 maybe a good start.

Any chance of cranking Va up to 1500V just to see how much power
increases ?

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