[TowerTalk] 40 meter dipole

[jim.thom jim.thom@telus.net]

Subject: Re: [TowerTalk] 40 meter dipole

<The performance of an antenna will depend on the overall element size
(length).?
<Shorter elements will have a narrower usable SWR bandwidth.?

<Thanks n 73,James
  <  On Sunday, October 1, 2023 at 11:00:47 PM CDT, john at kk9a.com <
john at kk9a.com> wrote:

 <That depends on if you want a full size dipole or a shortened one. It also
<depends on your fabrication skills and available equipment and free time.
<It may also depend on how much aluminum tubing you have laying around.? In
<the past I designed and built a full size 40m beam. Full sized elements are
<massive, these days I am using commercially made 40m beams with shortened
<elements using High-Q loading coils.

<John KK9A

A simple DPST relay and 2 x coils in a nema box   will provide for 2 x
segments.  You can still buy the DPST kilovac vac relay from  MFJ.
 ($20.00, 12 vdc @ 100 ohm coil).   2 relays will provide for 4 x
segments.  Even 2 x segments will cover the entire 300 khz.

A 44'  to 50' shortened 40m ele is pretty straightforward to design and
fabricate. Tubing coils, and / or capacity hats are simple to fabricate.  I
used  DXE's  ' yagi mechanical'   software to design, or modify existing
eles.  Designing a shortened 40m ele to handle a 100 mph wind is a simple
task.  The solid fiberglass insulators come in various diameters..and
found at Max gain systems.  Mcmaster Carr has the rolls of aluminum tubing,
used for the coils.  A single overhead truss made from  5/16" dacron rope
is ample.

Jim   VE7RF