[AMRadio] Antenna experiments...


Bill Smith hbco2 at sbcglobal.net
Sat Mar 3 20:13:52 EST 2007


Hi Brett,

Generally, you can bend an antenna all over the place as long as you =
keep the center straight and in the air.  Don't bend the ends more than =
90 degrees or you will introduce cancellation with the other part of the =
antenna.  Bends introduce all sorts of funny patterns, but overall the =
antenna will work better than shorter antennas with coils.  If you can, =
keep the antenna somewhat symmetrical (bends on both ends). =20

Another way to take three or so feet off each end (that is, shorten the =
antenna) is to attach a copper toilet bowl float at each end of the =
antenna.  The floats act as giant capacitors.

Sometimes a delta-loop will fit where a dipole won't.  They are great =
antennas.  For 80 meters, the sides of the triangle need to be about 90' =
each.

Good stringing!

73 de Bill, AB6MT
hbco2 at sbcglobal.net

----- Original Message ----- 
From: Brett gazdzinski 
To: 'Discussion of AM Radio in the Amateur Service' 
Sent: Saturday, March 03, 2007 4:50 PM
Subject: RE: [AMRadio] Antenna experiments...


I received my new alpha delta dx-dd antenna, its for
80 and 40 meters, is about 82 feet long, has 2 coils at
about 35 feet from center, and then about 3 or 4 feet
of wire to the end insulator.
The way they get it to work is to make the coils have a lot
of inductance to separate the 40 meter from the 80 meter
section, but that makes the 80 meter section very short.
On 40 meters, it worked like a 40 meter resonant dipole,
and you can get the swr down very low, on 80 meters, you
can get the swr down, but I think it works like a 40 meter
dipole on 80 meters....

Band conditions have been poor, I heard nothing on 40
meters so I tuned in chu which is real far away and comes
in on the vertical antenna well, the home made g5rv well,
and the dx-dd a little less well.

Noise on the dx-dd seems high on both 40 and 80,
but it's a little lower then the g5rv and its over 
the house.

On 80 meters, the home brew g5rv is tops, the butternut vertical
seems worthless, and the dx-dd between the two.

I got the dx-dd mostly as an experiment, to see how the
home made g5rv compared noise wise to another antenna.

Now that its warming up outside, I can do more
antenna experiments...

What would happen if I made the g5rv about 120 feet long
by passing the wire through the trees and down, instead of ending
it at an insulator at the tree?

With about 35 feet of open wire line, then into coax, would
the swr be low on 80 without a tuner?


Brett
N2DTS 


 

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