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@kk9a.com <
john@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
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