I designed a full length 40 M dipole using old Telrex elements and some
added tubing. I did the stress analysis, etc. I had to double and triple
wall several places. It is broadbanded over the entire 40M band. Then I
suspended a #14 THHN stranded wire one foot above it, standing it off with
sawn sections of fiberglass electric fence posts, mounted with aluminum
angle. Holes drilled through the posts support the wire, some 46 feet and
change in length. There is no connection from the feed line at the center
of the 40 meter section. The result is a perfect SWR on both bands. And it
works.
The 40/30 is mounted at 105 feet on my rotating Rohn 55 tower. Above it at
145 feet and below at 75 feet are two, two element Moxons for 40 meters. I
can switch between the two antennas, Moxons and dipole, and see 7-10 dB
difference, in favor of the Moxons. It's cool to be able to see is stuff
work like is supposed to. I often can work a station off the dipole that
would be a the rear of the Moxons, saving the time and wear on the rotator.
Both antennas are fed with two core common mode RF chokes.
73,
Dave, K4TO
On Sat, Nov 9, 2019 at 11:48 AM Jim Thomson <jim.thom@telus.net> wrote:
> Date: Thu, 7 Nov 2019 12:50:54 -0800
> From: Elliott Lawrence <wa6tla@icloud.com>
> To: towertalk@contesting.com
> Subject: [TowerTalk] JK301 30M Dipole
>
> <I have a12 year old Force12 30M linearly loaded dipole. It works fine
> when the local sea air doesn?t cause the loading wire connections to
> corrode making the antenna unusable. I?m tried of needing to repair the
> antenna every few years!
>
> <Im considering a JK301 that uses loading coils and should be much more
> reliable. If someone has any experience with this antenna, I would
> appreciate any comments. The JK Antenna website doesn?t show any access to
> the assembly manual that I would like <to see before any purchase. I have
> made a request for the manual from JK Antenna but so far no response.
>
> <Thanks es 73,
> <Elliott WA6TLA
>
> ## How long is the F12 30m dipole....tip to tip ? How far
> out are the oem F12 insulators in each ele half ?
>
> ## another option is to toss all the LL wires, and wind hb
> coils.... strapped across the oem F12 insulators in each leg.
> Summitt racing and also Mc master carr sell AL tubing, 3003
> alloy, in rolls.
> Everything from 15-50 ft rolls. Any diam from .1875 up to .625
> .1875 od would be ample.
>
> ## Then use a single Dacron truss for each ele half. Inboard ends
> of each dacron truss can terminate on the mast.
>
> ## still another option is a hb full sized rotary dipole. Aprx
> 46-47 ft long. I already designed FS 30m eles using DXEs.....
> yagi mechanical. 1.75 inch OD down to .375 OD tips. Good for >
> 100 mph..... and .5 inch ice + 40 mph.
>
> ## 30m band is only 50 khz wide... that alone simplifies the
> ant. Then just a helical haipin across the feedpoint..... + CM
> choke.
>
> Jim VE7RF
>
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