I disagree.
I prefer a 270 foot lazy loop, fed with openwire.
It is quieter, and has more gain.
: -)
The 135' openwire fed dipole is #2 on my list.
73
Rick, DJ0IP
-----Original Message-----
From: TenTec [mailto:tentec-bounces@contesting.com] On Behalf Of Carl
Moreschi
Sent: Wednesday, July 10, 2013 10:32 PM
To: Discussion of Ten-Tec Equipment
Subject: Re: [TenTec] OCF antennas evolution
I totally agree with you Stuart, the 135 foot dipole fed with open wire line
and a balanced tuner is the best all band antenna I can think of.
Carl Moreschi N4PY
121 Little Bell Dr.
Hays, NC 28635
www.n4py.com
On 7/10/2013 4:11 PM, Stuart Rohre wrote:
> Many hams have used some form of OCF antenna. Not all are horizontal.
>
> For example, My Gap Titan vertical is technically an OCF antenna,
> since electrically it is longer on one side of the feedpoint than the
other.
>
> The original OCF was probably the "Windom", which was fed with one
> wire to the rig. Balance was not a concern as most rigs had single
> wire feeds against Earth. Enough power was used to radiate some and work
stations.
>
> Later in the application of the antenna, coax was adapted to feed the OCF.
>
> Well, the first problem was Windom was an out of balance antenna in
> that, unequal currents would be found in the differing length
> (resistance) radiators.
>
> To feed with coax, you had to step up to the impedance of the tap
> point which was considered to be about 300 ohms, or that was the line
> used to feed an OCF converted from Windom feed of single wire to
> parallel feed in the 50's.
>
> Now, using balanced 300 ohm line, you had still, unequal currents in
> each radiator leg. (The legs were differing impedances with more
> copper on one side).
>
> Later, coax became popular. Attempts to feed the OCF dipole with coax
> and step up transformers, (balun), still faced the unequal length
> radiators and hence unequal currents. Coax feeding a balanced antenna
> will have some added radiation on the shield which encloses the center
> conductor. The shield can be shown to consist of two conductors, the
> outside of the shield and the inside of the shield. Mismatching at
> some frequencies resulted in radiation from the outer shield, but also
> pick up of vertically polarized local noise.
>
> To further "fix" the OCF, cable chokes were added (also called coax
> isolators), usually cores applied to the outside of the coax. Finally,
> the OCF might become quiet in an urban noise environments. But, it
> still might radiate a little vertical component, and still was feeding
> an inherently unbalanced point having unequal currents in the dipole
> wires of unequal length.
>
> I just like the inherent simplicity of the equal legs dipoles of 135
> feet total, fed with parallel line, and a tuner; hopefully a balanced
> tuner like a double PI Net, which would finally afford the chance to
> have equal currents in all parts of the antenna. These have given good
> accounts on all bands, and are simple for home construction, with less
> weight, typically, than an OCF with its added matching and choking
> components.
>
> I would expect an OCF to have some directionality toward one end vs.
> the other, but have never seen this written up. Refined versions like
> the "Carolina Windom" (which is not single wire feed, and hence not a
> "Windom"), do work well for many folks, but you seem to have to spend
> more money and have more weight issues to support the OCF version of
> dipoles.
>
> Stuart Rohre
> K5KVH
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>
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