RadioBanter - View Single Post

March 22nd 06, 02:00 AM posted to rec.radio.amateur.antenna

wrote:
I picked up a Oct 1973 issue of 73 & noticed a interesting article on
a mast mounted rotatible very
hig gain 435mhz antenna, cheap and easy to built. Ive been trying to
build a high gain antenna to
recieve ATV in the 903-928 band & seems this maybe the one. The claims
for
this antenna seem streached abit, they claim 26dB gain from just wire
and a few resistors

You might try modeling the antenna or rading a textbook that covers
real Rhombic antennas.

Antennas and Transmission Lines by John (jack) Kuecken is a great
place to start.

I think what you will find is that gain figure is extremely inflated.
It is unobtainable in the real world. I'd expect more like 15dBd
maximum gain if you can do almost everything perfectly, and you might
squeek another 3dB with two Rhombics in optimum configuration.
At the old VOA installations, the very large Rhombic antennas had less
gain than curtain antennas that occupied much less space.

I have a 300 foot tall support. I've been trying to model an Inverted V
or V beam with useful gain over a small Yagi without success. If
anyone has sucessfully modeled one, please let me know.

73 Tom

I've been