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cliff wright · July 28th 07, 01:03 AM posted to rec.radio.amateur.antenna

wrote:
On Jul 26, 5:14 pm, Owen Duffy wrote:

wrote roups.com:

A 3/8 wave radiator is easily matched with a single variable cap..

Details?

Place cap at the feedpoint in series . Viola...
This is fairly common really.. IE: feeding "extended"
Inv L's where the length is appx 3/8 wave.
The usual reason for that is to raise the maximum current
point up off the ground a bit to lower ground losses..
BTW, once you find the best match, and find the cap value
needed, you could replace the variable with a fixed cap.
MK

G'Day!
Well I have tried the series cap idea of course first.
It is set up at the moment with a 500 pF TX type variable in the
matching box. However according to my SWR bridge it has quite a high
VSWR and varying the 500 pF had very little effect. And yes, the coax is
OK. 50 Ohm foam dielectric type which I have used up to 70 cM OK.
My phased verticals that I mentioned did use capacitive matching in this
case 1000 pF RX variables. But they were just a little too long.
Unfortunately because of space restrictions I am limited to 4 radials.
Thats one reason why I was trying for more than 1/4 wave.

73's Cliff wright ZL1BDA.