calcuating tubular capacitance?

[tenchy]

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]

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]

thanks a lot for the reply and the info.

I'll seek out the app.

73 Steve