On 5/31/2011 4:26 PM, Dave Platt wrote:
In , John wrote:

So, I had this idea. The usual monopole (or ground plane) has about
30-35 ohms resistance. To get 50 ohms it is common practice to droop the
radials about 45 degrees. Since that raises the feedpoint resistance,
would raising the radials lower the feedpoint resistance of the folded
unipole and, if so, what effect would it have on the pattern?

EZNEC said to raise the radials of the folded unipole about 23 or so
degrees to get 50 ohms and the pattern would not be affected.

So I built one and it works swimmingly. I had to make some minor
adjustments in element lengths but that was fairly easy with the vector
voltmeter. Hooray for modeling.

Slick... and I bet that the appearance of it raises the occasional
question and/or eyebrow!

I use it at home. Nobody in the area knows enough to even blink an eye.

The matching approach I've usually seen for folded monopoles, is to
use a quarter-wave transformer made out of (e.g.) RG-6 or another
75-ohm coax... this brings the impedance down to something not too far
from 50 ohms. Your method avoids the need for this.

I am aware of that method. I think the challenge for me was to have it
all inherent.

If I were to build one I think I'd stick a fat cap over the end of
each raised radial... just to reassure myself that I wasn't setting up
an "automated pigeon-skewering device" of sorts :-)


Hmmmm. I didn't think of that.