Towertalk
[Top] [All Lists]

Re: [TowerTalk] 80M Delta Loop (bobtail curtain)

To: towertalk@contesting.com
Subject: Re: [TowerTalk] 80M Delta Loop (bobtail curtain)
From: Jim Brown <jim@audiosystemsgroup.com>
Reply-to: jim@audiosystemsgroup.com
Date: Fri, 26 Jul 2024 23:23:54 -0700
List-post: <mailto:towertalk@contesting.com>
On 7/26/2024 8:48 PM, Jim W7RY wrote:
You guys need to investigate a bobtail curtain.

Thanks for pulling my coat about this one, Jim. Looks like a very useful antenna if you want something vertically polarized with a bi-directional +/-20 degree beamwidth, and that doesn't need radials! A bit more than 6 dB gain over a single vertical.

And if you have the space to rig it. It's three quarter-wave verticals in-line, spaced a half-wave, with a horizontal wire running between them at the top. The three verticals are in-phase, with current minima at the base. The outer verticals float from ground. So the beam is broadside to the array.

The center vertical is fed against ground, and it's a voltage maximum, so feed against ground with a tapped parallel resonant step-up inductor. Pretty easy to build and rig if you have the space and the skyhooks to hold the horizontal wire at the needed height and in the right places. Just drop the three verticals from the wire, with weights on the bottom of each.

This antenna would still work well with poor ground, and is that much better with good ground!

73, Jim K9YC

_______________________________________________



_______________________________________________
TowerTalk mailing list
TowerTalk@contesting.com
http://lists.contesting.com/mailman/listinfo/towertalk

<Prev in Thread] Current Thread [Next in Thread>