[TowerTalk] 40-30m dipole design

[john at kk9a.com]

I think that most shorty 40's have the loading around 1/3 out from the
center. I prefer a Hi-Q loading coil over linear loading. A while back I
did some modeling trying to make a shortened 80m vertical and in my model
the actual shortening varied with the placement of the coil. The antenna
needed to be longer as I moved the coil towards the element tip. I am not
sure what placement gives the most efficiently, perhaps 1/3 from the feed
point is a good compromise between efficiency and element shortening
effect. N6BT is currently manufacturing multiband beams using switchable
loading coils at the feed point.

John KK9A


To:	towertalk at contesting.com
Subject:	Re: [TowerTalk] 40-30m dipole design
From:	jimlux <jimlux at earthlink.net>


There's no big advantage to linear loading: you might as well use a good
low loss inductor at the feed (the "shorty 40" does this).

I don't think the voltage will be all that extreme. A 30 m dipole, on 40m,
has a feed point impedance of 30-300j ohms. You can use one of the antenna
tuner apps to figure out what hte voltage is.