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Author Topic: New Wireman Folded Dipole product using ladder line as the radiator...  (Read 1830 times)
K9SRV
Member

Posts: 121




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« on: December 20, 2012, 11:07:21 AM »

The product is #804. It is a kit designed to use ladder linas as both the feeldine and the radiator.
My question is wos the 2 conductors be enough to work well? At 50 feet and a lenght 0f 200 feet, give or take 20 feet, do you guys think this antenna would work well, with the feedline run into a Matchbox?
Also, is it possible that someone may be able to rub an eznec analysis of this setup for me?
Since it is a new product, I am wary, and would appreciate any and all feeback.

Thank You,
John
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W9GB
Member

Posts: 2616




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« Reply #1 on: December 20, 2012, 01:06:48 PM »

Pres, W8UG -- The Wireman is just selling the insulator kit (#804)
This antenna design (folded dipole) is over 70 years old !!

You are aware that Folded dipole antenna at 300 ohm (Z) with twin lead feed line (ladder line)
was the predominate solution for TV and FM radio reception from 1946 to early 1980s ??

Folded Dipoles
http://www.buxcomm.com/foldedipole.htm

VK1OD thoughts
http://vk1od.net/transmissionline/LOLL/index.htm

Cecil, W5DXP -- Folded dipole fed with ladder line
http://www.w5dxp.com/ShortFD.htm

QRZ Discussion
http://forums.qrz.com/archive/index.php/t-339054.html

DX Engineering center insulator kit with photos and directions to follow.
http://static.dxengineering.com/global/images/instructions/dxe-uwa-kits_rev5b.pdf
« Last Edit: December 20, 2012, 01:17:52 PM by W9GB » Logged
WB6BYU
Member

Posts: 13174




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« Reply #2 on: December 20, 2012, 01:14:33 PM »

A folded dipole is just a half wave dipole with a higher feedpoint impedance.  Makes a
convenient match to 200 or 300 ohm feedlines.  There's no problem using the same
material for both the feedline and the radiator, though you could also use two lengths
of regular antenna wire for the radiator.

The problem with this approach, however, is when you want to use it as a multiband
antenna.  While a standard dipole/doublet has some gain on the second harmonic,
with a folded dipole most of the radiation cancels itself, and it doesn't work very
well at all.  So the recommended approach of simply making it as long as will
fit your supports is NOT a good idea.

That's not to say that there is anything wrong with the product:  it looks like
a perfectly servicable insulator for a folded dipole, or various other types of
antennas fed with ladder line.  But for multiband use you will get better
results using a single length of antenna wire rather than a folded dipole made
of ladder line for the radiator (not to mention that it would be lighter, cheaper,
and have less wind resistance.)


I make similar insulators by sawing up some old white PVC lattice and drilling
holes in it.  Works for all sorts of antennas.
« Last Edit: December 20, 2012, 01:23:26 PM by WB6BYU » Logged
AA4PB
Member

Posts: 12805




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« Reply #3 on: December 20, 2012, 02:38:59 PM »

A folded dipole needs to be 1/2 wavelength long on the band where it is used. It will not work well if you try to use a tuner to feed it on other bands.

A dipole (i.e. a single conductor antenna split in the middle) fed with ladder line can, with a tuner, be used on multiple bands as long as the dipole is at least 1/2 wavelength long on the lowest frequency band. For example, a 120 foot long dipole fed with ladder line is often used on 80M through 10M with a suitable balanced tuner.
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