[Amps] peak voltage rating for load cap

[Vic Rosenthal]

The loading capacitor in a PI-L circuit is at an intermediate impedance point between the plate circuit impedance and 50 ohms. So the first step is to determine what the impedance is at that point, which depends on the circuit design.
Once you know that, you can use Ohm's law to figure out the voltage assuming, everything is tuned and SWR is unity. The voltage will be the square root of (the power in watts times the impedance in ohms).
To allow for mistuning, SWR, etc., you should probably use a capacitor rated at several times this.

Vic 4X6GP 

> On 19 Aug 2017, at 13:07, Conrad PA5Y <g0ruz at g0ruz.com> wrote:
> 
> Hello what is the rule of thumb for conservatively estimating the required ratings for a load capacitor when used with a mono band Pi-L tank circuit?
> 
> Anode voltage 2750V
> 
> Tube design RL = 2600 ohms
> 
> Q = 12
> 
> I have searched on the internet an I cannot find any really convincing info, I have something that will stand 1200V but that is marginal and will not survive a fault I expect.
> 
> Alternatively does anyone have a small vac variable around 40-60pF that is around 3 inches/76mm? That will obviously do the job.
> 
> Also where can I buy a couple of Ohmite Z-50 chokes in Europe? Anyone got one or two that they can spare?
> 
> Regards
> 
> Conrad PA5Y
> 
> 
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