[Antennas] End-fed half-wave religion

Thu, 18 Jul 2002 07:24:56 -0400 (Eastern Daylight Time)

I saw (have) a diagram of this "end-fed" dipole in a
book on QRP that I have. The book has to be
ten years old.

73,

Bill KA8VIT

-------Original Message-------

From: Mike J Maloney
Date: Wednesday, July 17, 2002 09:26:04 PM
To: [email protected]
Cc: [email protected]
Subject: Re: [Antennas] End-fed half-wave religion

There was an interesting trick presented for "end" feeding a half-wave
dipole some time back in QST and republished in ARRL's Antenna
Compendium, Vol.2. It involved using the coax shield outer surface
"skin" as one leg with the center conductor spliced to a quarter-wave
unshielded wire at the center of the dipole. To create a high impedance
virtual "insulator" the feedline was coiled into a several turn choke
approximately 1/4 wave back from the center. By adjusting the position
of the coil turns up and down, the antenna could be tuned to provide a
good match to the rig. 

I saw another simular article in another ham magazine more than 20 years
ago, that actually used a variable capacitor to resonate the coil to the
desired freq. of opertation. He called it a "Tuned Transmission Line
Trap" or T2LT. 

Both authors reported very good results with their respective methods. 
Though electrically the dipole is center fed, physically the feedline
comes away from the end and is in line with the twopole (DIE-POLE)
elements. The antenna could be strung horizontal, vertical or
diagonally, but still the feedline comes off the end. 

Now regarding the WWVH antenna. I have a 2M ground plane that has 4
sloping radials that works quite well and presents a very good match to
the rig. I cant help but think that an HF model would work well,
without radials, if the feedpoint were elevated a half wave-length or
more above ground. Has anyone modeled this and compared to a ground
plane with horizontal radials at the same height?
- - - 

Your moderator for this list is:
Larry Wilson KE1HZ [email protected]
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