The ARRL antenna book has a section on winding coils as you are looking for.
Depends on how far out the wire the coil will be needed. I suggest a coil
that traps 40 at the 1/2 wave point on 40 and loads 80 with the extra
length. So depending on where on 40 you are looking at out 66 feet or so.
As a sloper type wire there will be some directivity in the direction of the
slope. Be sure the feed line comes as close to right angles to the wire as
possible so not to mess up the pattern. Keep the opposite end off the
ground as far as possible so people or animals will not touch it.
I have two old Mor-Gain 80/40 dipoles almost vertical with the bottom
section of one sloping toward the NE and the second sloping toward the WSW.
But remember these are DX antennas with local skywave signals down 10 to 20
DB over the same antenna as a horizontal one.
Good luck. 73 Dave K4JRB
----- Original Message -----
From: "Dan" <email@example.com>
To: "Tower and HF antenna construction topics." <firstname.lastname@example.org>
Sent: Thursday, March 25, 2010 10:39 AM
Subject: Re: [TowerTalk] 40/80m dipole
>I should have mentioned that the 40/80 antenna for my son will be almost
> vertical. He has a single pulley in a tall tree to suspend the antenna.
> I agree that the fan dipole or bent full size dipoles would be good
> solutions but a single 2 band dipole is better suited to his needs.
> Thanks for all the comments. I was hoping to get an inductance value and
> location in a 90 ft dipole. Antennas of this type are widely available
> from suppliers but it is more fun to build it and he will be visiting in
> a week or so. It makes a nice educational project. I do have an
> instrument to measure inductance at those frequencies.
> 73, Dan
> Dan wrote:
>> I would like to build and send to my son a coil loaded dipole for
>> 80/40m. He has about 90 feet space to hang it in. Has anyone information
>> on loading coil values and placement in the 90 ft dipole?
>> Tnx, Dan, N5AR
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