[Lowfer] Musical capacitors and dissipation loss

Fri, 14 Nov 2003 18:12:56 -0600

Hi Lisa...err Paul,
I built a pipe cap last winter out of 1/2" and 3/4th" copper pipe and
wrapped it with clear poly sheeting. I don't remember what it measured for
capacitance, but I took it to work and did some hi-pot tests on it and it
handled 5000v DC and AC without anything going wrong. There wasn't even any
ozone created. The cap is about 2 feet long. I was working with the idea so
I could eliminate the mechanical problems with the air variable caps brushes
and bearings.

Mike>WE0H

-----Original Message-----
From: [email protected] [mailto:[email protected]]
On Behalf Of Lisa Cianciolo
Sent: Friday, November 14, 2003 3:40 PM
To: [email protected]
Subject: [Lowfer] Musical capacitors and dissipation loss

Hello Again,

Anyone ever hear of a trombone capacitor?  Basically 2 pieces of copper
tubing that are slipped inside each other, isolated with a dielectric such
as teflon.

Why should you care, well maybe you shouldn't but in an effort to rid myself
of mechnical connections, I anm looking at this method of tuning my MEDFER
loop.

With 2 pieces of brass tubing about .5" dia and 10" long and a slip fit, I
was able to make a very stable 230 Pf capacitor that was very stable.
Stable, as in all the compression types I made changed capacitance over time
(minutes) as the dielectric changed shaped or flattened out. The only teflon
I used was at the very outer ends of t he tuning so really it was used more
as a bushing then a dielectric.90% of the tubing was air space.

Has anyone ever tried these before?  I only need 520 Pf or for the MEDFER
loop.  So this  method may and work tuning was very smooth.

The other question I have is my LCR meter tests at 1 Khz, not really
adequate for measuring dissapation factor at 1700Khz.

Does anyone know of a test that I could perform, even a relative test, to
compare the air against say a silver mica?

Any help would be appreciated.  Thank you

PaulC

W1VLF

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