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From: legg <legg@nospam.magma.ca>
Newsgroups: sci.electronics.design
Subject: Re: Valve frequency multipliers
Date: Tue, 04 Feb 2025 09:02:01 -0500
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On Sat, 01 Feb 2025 07:23:57 -0800, john larkin <JL@gct.com> wrote:

>On Sat, 1 Feb 2025 10:50:22 +0000, liz@poppyrecords.invalid.invalid
>(Liz Tuddenham) wrote:
>
>>john larkin <jl@glen--canyon.com> wrote:
>>
>>> On Fri, 31 Jan 2025 23:50:56 +0000, Cursitor Doom <cd@notformail.com>
>>> wrote:
>>[...]
>>
>>> >    Operating Point:
>>> >        Grid Voltage: Adjusting the grid voltage to operate closer to
>>> >cutoff can increase harmonic distortion since the tube's response
>>> >becomes more non-linear near cutoff.
>>> 
>>> Operate it deep in cutoff, off most of the time. A high amplitude
>>> drive and grid-leak bias would be good.
>>
>>That is exactly what I am doing and it doesn't appear to be working.
>>With 100v on the anode,  15 Mc/s at 25v pk/pk on the grid and a 22k grid
>>leak, the peak current for one triode of an ECC91 is around 20 - 30 mA
>>at the positive peak of the grid swing.  The average anode current is
>>around 2.5 mA, so the conduction period is about 10%.
>>
>>A 75 Mc/s parallel-tuned circuit in the anode circuit is giving so
>>little drive to the following stage that I can't see any change in the
>>average grid voltage of that stage caused by the drive.
>
>Spice it!
>
>LT Spice has tube models.

If Spice was of any use in RF ham gear, the amateur radio guys 
would have been all over it three decades ago.

I've modeled known-good valve power cctry only as a curiosity, to 
see if spice could come anywhere close to practical results. 
Curiously the nowhere-near-common valves used already had models, 
so I'm pretty sure somebody else had already made a run at the 
identical application. (Tek HV oscillator).

RL