On Wed, 03 Sep 2008 03:06:01 GMT, "Spin"
wrote:

I would like to make/experiment with a longwire antenna
specifically for the two meter fm band. Is there an optimum length to try &
still keep an omnidirectional pattern? Also the optimum amount of radials
and will i need a matching unit?

The nice things about VHF and UHF wire antennas is that they can be
easily built and easily modeled with one of the numerous NEC2 programs
available. The short wavelength means that you can generally ignore
ground effects. However, you do have to consider the mounting
structure (i.e. tower) in your calculations. I have no way to answer
your questions as you didn't specify what you're trying to accomplish
or what you have to work with. Optimum for what? VSWR, gain,
radiation angle, pattern, what? Not enough info.

As penitence for this capital crime, you are sentenced to download and
install EZNEC, 4NEC2, or other NEC2 modeling program:
http://www.eznec.com (Free demo is good for simple antennas)
http://home.ict.nl/~arivoors/ (lots of good examples included)
http://www.si-list.net/swindex.html (old list but still useful)
Plug your proposed antenna into these programs, and see what it will
do in the way of pattern, VSWR, radiation efficiency, bandwidth, etc.
Incidentally, the 3D antenna patterns are cool. Yes, you will have to
learn a bit about antennas, learn how to run the program, and learn a
few new profane incantations to get it working. However, I assure you
that it's worth the effort. Once you get something reasonable on the
computah, then built it and do some measuring.


--
# Jeff Liebermann 150 Felker St #D Santa Cruz CA 95060
# 831-336-2558
# http://802.11junk.com
# http://www.LearnByDestroying.com AE6KS

On Tue, 02 Sep 2008 20:38:12 -0700, Jeff Liebermann
wrote:

As penitence for this capital crime, you are sentenced to download and
install EZNEC, 4NEC2, or other NEC2 modeling program:
http://www.eznec.com (Free demo is good for simple antennas)
http://home.ict.nl/~arivoors/ (lots of good examples included)
http://www.si-list.net/swindex.html (old list but still useful)

One more free antenna modeling program.
MMANA-GAL:
http://mmhamsoft.amateur-radio.ca/mmana/
I just blundered across this one. Plenty of examples to plagerize.
Optional NEC2 interface using engine from 4NEC2. Looks nice so far.

--
Jeff Liebermann
150 Felker St #D http://www.LearnByDestroying.com
Santa Cruz CA 95060 http://802.11junk.com
Skype: JeffLiebermann AE6KS 831-336-2558