"J. Laub" wrote in message
...
Tam/WB2TT wrote:
I took a quick look at the ARRL antenna book. Assuming your 3/4 pipe is
actually 1" OD, resonance will be off by quite a bit. About 6 - 7 inches
too long.

Tam
What page did u find that table on? This may explain why it tunes (with
transmatch) so much easier on 20 than 15.

I have the 19th edition. There is a graph on page 2 - 5. Kind of rough, but
I got k=.95 for 1" conductor at 21.3 MHz, which makes the real resonance
21.3x.95=20.235. I did not read the text, but they may give an equation
also.
If the SWR is lower at 21.0 than 21.4, the radiator is too long.

Tam