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Re: [TowerTalk] 80m dipole with open-sleeve parasitic

Subject: Re: [TowerTalk] 80m dipole with open-sleeve parasitic
From: jimlux <>
Date: Wed, 19 Jan 2011 14:28:36 -0800
List-post: <">>
On 1/19/11 12:36 PM, wrote:
> Hi, thanks for the comment
> In the antenna I described, the antenna is ordinary wire, and the feed is 
> ordinary coax.
> I'm planning on RG-6 actually (copper shield).
> The antenna I described doesn't have anything to do with bazooka designs? 
> It's just a dipole with a coupled parasitic.
> If you're saying a single wire with LC match can have same bandwidth and 
> lower loss, I guess I find that hard to believe?
> Am I missing a loss calculation in open sleeve designs?

When you say open sleeve, do you basically mean something where the 
apparent diameter of the conductor is larger (e.g. like cage dipoles, 
bowties, biconicals, and to a lesser extent, fan dipoles)?

In general, you can get pretty low loss in a lumped inductor, because 
you can use larger diameter wire and you can get more inductance for a 
given length of wire (i.e. a single turn has more L than a straight 
wire, and 2 turns has 4 times the inductance of a single turn, with only 
twice the resistance).  You can wind inductors with ribbons, tubes, etc, 

I think that Rick's comment is right on.. Doing a lumped network 
(because it's higher Q, lower loss) tends to be more challenging to 
construct and measure.  A "distributed loading" scheme has more loss and 
tends to be less construction picky.

For a builder with NO measurement tools other than a tape measure and 
the reflected power meter in their rig, a "build it to these dimensions" 
design has a lot of appeal (I know.. I've been there.. )


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