[TowerTalk] 80m dipole with open-sleeve parasitic

[jimlux]

On 1/19/11 12:36 PM, knormoyle at surfnetusa.com 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, 
too.

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.. )