[Elecraft] Question for Wayne about your OCF Dipole

Don Sanders w4bws1 at gmail.com
Mon Sep 18 19:19:29 EDT 2017


So not much different than the G5RV with parallel feed line all the way to
the tuner, no coax.
Just fed off center at the 39% or 61% point instead of center fed.
I wonder about losses in the tuner due to the imbalance but not having
tested it I hold any judgement.
Several articles in the literature of similar OCF antennas fed with
parallel line.
Basically all are non-resonant, so no worries about resonance on higher
bands as with OCF , balun,coax fed antennas.

I used a 88 foot center fed with 2 lengths of RG 6 coax similar to what you
are using.
>From Ecuador I worked the world with QRP 40 to 10 meters and with 50 to 100
watts on 80.
Yes, a good antenna. I center fed it due to worries about loss in baluns
with OCF antennas and the lack of commercial balanced line. Just a little
loss from the RG6.

Dr. Don W4BWS
​SKCC 81C
K2 SN 163​


On Mon, Sep 18, 2017 at 6:02 PM, Wayne Burdick <n6kr at elecraft.com> wrote:

> Hi Marv,
>
> I didn’t measure the legs. My best guess, standing here by the shack
> window using an antique brass monocular, is 55’ on one side, 35’ on the
> other. This is the most satisfying thing about off-center-fed dipoles:
> length generally isn’t critical. Close your eyes and clip, knowing that,
> most likely, the ATU will do the rest.
>
> The installation was opportunistic, taking advantage of a back yard
> gazebo, a Home Depot telescoping pool-cleaning pole, and a huge white oak.
> Height at each end was determined by how high my son was able to climb
> without the neighbors noticing.
>
> The experimental feedline, running under the house for half its length,
> was more deliberate if not justified in the literature. At first I was
> using 300 ohm mystery twin-lead scavenged from an installation of yore. But
> given all the RFI sources I decided to try two lengths of LMR-400, taped
> together every few feet, forming a sortof-balanced-shielded feed. Purists I
> consulted ahead of time continue to be shocked at how well this works. At
> the mast, the grounds are left unterminated. In the shack, the two center
> conductors go to an Elecraft BL2 balun. The shields are soldered together
> and connected to the BL2’s ground lug.
>
> There you have it: Wide tuning range, low noise, low-loss, and
> theory-free. How it works is left as an exercise for the reader.
>
> Wayne
> N6KR
>
>
>
> > On Sep 18, 2017, at 2:31 PM, <marvwheeler at nwlink.com> <
> marvwheeler at nwlink.com> wrote:
> >
> > Wayne:
> >
> >
> >
> > In a previous post you mentioned your 90 feet long OCF dipole. Would you
> > please elaborate on your antenna? Balun, leg lengths, how fed?
> >
> >
> >
> > Thanks,
> >
> > Marv
> >
> > KG7V
>
>
>
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