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View Full Version : calcuating tubular capacitance?



tenchy
Tue 13th Apr 2010, 14:01
Hi,

I'm new here, didn't see a who are you intro section (hope I'm not blind!) so here goes straight in.

In the past I have made a capacitive match for a yagi using a rod soldered into an N-type socket, sleeved that with insulation and fitted a snug fitting ali tube which in turn got connected to my driven element.
It was a bit heath robinson, but it worked and I got a good match and antenna worked.

But what I would like to do now is make a smaller version, but calculating the capacitance value by design.

Is there an online calculator, or formula handy, where I can put my d1, d2, Er of dialetric, and length in to get a capacitance?
Also, I'd like to be able to calc the max power handling too.

Cheers.

5B4AJB
Tue 13th Apr 2010, 17:45
Funny this should come up today, yesterday I was planning a 500W capacitor for a top band magnetic loop...

It turned out two and a half feet long by one foot diameter :O

I found a program called Capcalc, by KI5GD. Not for tubular types, but if you work out the surface areas it will do the job.

Calculating capacitance is fairly easy if I remember correctly - can't find my college notes on AC theory however...

tenchy
Fri 16th Apr 2010, 06:55
thanks a lot for the reply and the info.

I'll seek out the app.

73 Steve