[OKDXA] Dipole Antenna Question

[kd5gho]

Have a look at the top of the army C of E / IRS / FBI building located at
169 hwy and 44 hwy.
It is on the north west corner of the two.
You will see a folded dipole.
Their is one just like it (the dipole that is) in the top of the AA / MOC
building.
As far as the MOC one all i can find out is someone ie a company wes hiered
to install it.
It is used to comunicate with south Ameirica when phones
go out.
But it is brodside east west.
Okay with all of that?
I am useing a half wave dipole for 20 broad side north south.
This is the what the part.
Normaly i can hear east west way better than north south.
Okay south of us by the great I.C.B.M map says that allot of watter is out
their and south Ameiriac would look more east than south.
This is what is soo dang neet about amateur radio!
I call it the "Horton Hears a Who" effect.
Just when we think after the long journy for the answer has ended, We are
here!.
I love Amateur Radio.
Jim

----- Original Message -----
From: "Nelson Derks" <ac5up@vei.net>
To: <okdxa@mailman.qth.net>
Sent: Friday, November 01, 2002 8:53 PM
Subject: Re: [OKDXA] Dipole Antenna Question


> > Yes for a change I am glad I asked.
>
> Since it's going to be a cold and wet weekend, here's a web page you may
> want to spend some quality time with:
>
> http://www.cebik.com/radio.html
>
> > I have read about that type of tuneing, but not in that much detail.
> > The broad banded dipole is a wonderful idea.
> > Their are allot of antenna makers who claim that their product will do
> broad
> > band and don't.
> > The B&W adds a resister to the top of their folded dipole and sey its
like
> a
> > squashed rhombic. bull sh!#.
>
> And here's the analysis of a broadband folded dipole like the B&W:
>
> http://www.cebik.com/wbfd.html
>
> ...which introduces the related concepts of efficiency and gain.
>
> The most efficient antennas tend to be full-size resonant wires as they
can
> couple nearly 100% of the transmit power into the Ether. Throw in some
> tricks, like a loading coil, to make a big antenna more practical in size
> and the efficiency will be reduced. Same for multi-band trap verticals, or
> the terminated folded dipole which relies on a resistor to absorb
reflected
> power that would otherwise trip a newer rig into SWR shutdown. The B&W
> design trades efficiency for bandwidth utility, and that's not necessarily
a
> bad idea if your choice is between something like the B&W or a mono-band
> wire. Better to have a modest signal on several bands than a good signal
on
> one band if that band just happens to be closed tonight. The B&W looks
poor
> on paper when you realize it has no gain (and negative efficiency) over a
> Dipole, but every multi-band wire is a compromise of efficiency and gain.
>
> Which brings us to gain... There is no such thing as free power, but some
> folks think of it that way. Take a VHF Yagi with a rating of 10dB gain.
Put
> 50 watts in and it's like 500 watts out. Helluva' deal, but that's in one
> direction only. As long as you can rotate the antenna, and don't mind
> working the rotor box to catch a weak CQ off the back of the beam during a
> contest, you have a good thing going. On HF the antennas are often too
large
> to rotate, so you pick your favorite beam headings and build to match. In
my
> case, the back yard has a longest run that's true North-South. If it were
> East-West, my log would look much different or, I'd become a master of
> compact antenna design. You do your best with what you have to work with,
> and on a city lot with a bad orientation the B&W could be a very practical
> choice...
>
> - AC5UP
>
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