On Fri, 22 Jun 2007 05:32:11 GMT, "William R. Walsh"
<(E-Mail Removed) m> wrote:
>> Wanna build an antenna instead?
>You did mention that they're cheap to build, right? :-)
I'm practicing being subtle. I don't think it's working.
Omni antennas are incredibly difficult to build. That's because
there's nothing to support the driven elements. More specifically,
everything above the connector is part of the driven elements. There's
also nothing worse than building an omni antenna, testing it perfectly
on the bench, stuffing it into a plastic or fiberglass tube, and
finding that everything has moved down in frequency.
For example, here's an allegedly "easy" to build omni:
<http://wireless.gumph.org/articles/homemadeomni.html>
That's not my idea of easy (or a good antenna as the coax cable parts
have fairly high losses).
Here's a 5dBi vertical colinear kit, which is also not my idea of easy
to build:
<http://mobileaccess.de/wlan/download/arlx-om2400-all-inst.pdf>
Antennas double in size for every 3db gain, so a 12dBi will be about
4-6 times larger (and more complex).
On the other foot, the AMOS/Franklin sector antennas have the back
reflector to support the driven elements. Much easier to build, less
critical, fewer parts, and cheaper. Using a plastic rain gutter as a
radome has resulted in only a tiny frequency shift. Also, sector
antennas are much better for most applications as they can be tilted
downward, while omnis have an inherent uptilt.
>(sorry, couldn't resist...)
>William
My 80+ year old (at the time) piano teacher used to say "after a
certain age, it's not worth the effort resisting temptation". I think
I was about 12 years old at the time, and never forgot the line as a
great excuse to do what I damn well please.
--
# Jeff Liebermann 150 Felker St #D Santa Cruz CA 95060
# 831-336-2558
(E-Mail Removed)
#
http://802.11junk.com (E-Mail Removed)
#
http://www.LearnByDestroying.com AE6KS
Similar Threads
Linear Mode
