[TowerTalk] 160m antenna ideas / suggestions
jim at audiosystemsgroup.com
Thu Jan 25 14:00:48 EST 2018
On 1/25/2018 8:52 AM, W1JCW John wrote:
> Thanks for all the replies.
> Now I'm determining the construction of a good inv L or T.
> Do you attach the coax at the base, center to the vertical piece shield to ground radials?
To radials or other counterpoise.
> How do you keep the wire away from the tower, use stand offs?
> I will have 100' of rohn 45 up so going vertical then horz out will work.
I wouldn't rig the vertical part of an inv-L or Tee next to a tower.
100 ft of tower with nothing on it will resonate in the range of 2.5
MHz. Aluminum on top (and a mast) that are electrically connected to the
tower will lower the resonant frequency. That frequency can be estimated
by using NEC, first with the tower itself, then adding the mast and Al
on top. With this height, I would be more inclined to either load the
tower or rig one or more sloping wires from the top of the tower.
The sloping wire will provide a few dB of gain, because the tower will
act either as a reflector (if it is longer than resonant) or director
(if it is shorter). The loaded tower will be omni. As described in my
email, the sloping wire is insulated from the tower, fed from the base
against radials or a counterpoise. Either way, the tower needs as many
radials as you can install.
> Would should the total length be? I've see a few that go up 60' then out 100'
You obviously didn't bother to study the slide show I posted, so I won't
bother to repeat what's in it.
73, Jim K9YC
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