"Buck" wrote in message
...
On 15 Aug 2006 04:39:27 -0700, "Denny" wrote:

Another way would be two aluminum tubes that just fit inside each other
with Teflon insulator... Sliding these in and out like a trombone will
change the tuning... I have actually done this.. Keeping the internal
spacing even is difficult and the insulator seems to want to bunch
up... Probably a pile of plates is better...


I know the spacing will be wider, but can two pipes with a PVC pipe
between make a usable capacitor? i.e. 1/4 od metal pipe inside 1/2 od
pvc, inside 3/4 id metal pipe. (numbers are fictitious, but you get
the idea.)

Buck
N4pgw
PVC is not a great dielectric. Polystyrene, polyethylene or teflon are far
better.

Dale W4OP