[Amps] peak voltage rating for load cap

Manfred Mornhinweg manfred at ludens.cl
Sun Aug 20 10:42:22 EDT 2017

Hi Peter,

> The Russians doorknob capacitors do well.

At least they look pretty robust. Do you happen to know the ratings? A 
quick look on the web showed very high voltage ratings, but I couldn't 
find any current ratings. Probably the current handling is high enough, 
but it would be good to know for sure.

Mounting them with straps to the circuit board, as VK4AKV did, I would 
expect the series inductance in those connections to degrade the 
ultimate harmonic attenuation of the filters. Soldering the coils 
directly to small straps bolted to the top sides of the caps should be 

Anyway, do you know where to buy them at ham prices? The few online 
sources I could find sell them at prices that are quite similar to what 
ATC procelain capacitors cost, which are far easier to mount, and far 
better in terms of ESL. And those prices are simply too high, at $20 and 
more per capacitor, plus shipping, plus taxes. At those prices, the set 
of capacitors for the low pass filters would cost me about the full 
budget I have for my entire project!

My fallback solution is homemade copper-clad mica capacitors, which are 
inexpensive and effective, but not much smaller than those doorknobs, 
and take some time making for the correct capacitances.


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