[TowerTalk] 80m dipole with open-sleeve parasitic

[knormoyle at surfnetusa.com]

okay Rick, thanks for the clarification.
I guess what I'm thinking is that there is no single LC match, even with two wires that gives equivalent bandwidth.

Things that I'm ruling out: switching the LC values for different frequencies.
Spreading the wire ends of the two wires up to 3 feet or more (I think that's unwieldy)

So while what you say sounds right, I don't think there's a pratical, single LC value, 80m, antenna that's equal.
If there is, I'd like to hear the exact dimensions so I can create a NEC simulation.

Again I'm ruling out very wide cage dipoles.

And when we talk about loss comparisons, just because loss numbers might be greater, that's not necessarily bad. 
It's all about magnitude of loss. So I'd really like to model any proposal that works better.

I don't know of one (if there's a link somewhere I should look at, I'd like to see it? I have the ARRL Antenna 
Book and believe I've absorbed most of the relevant info in it? If not, a pointer?

-kevin
ad6z


------- Original Message -------
>From    : Rick Karlquist[mailto:richard at karlquist.com]
Sent    : 1/19/2011 1:55:06 PM
To      : knormoyle at surfnetusa.com
Cc      : richard at karlquist.com; knormoyle at surfnetusa.com; towertalk at contesting.com
Subject : RE: Re: [TowerTalk] 80m dipole with open-sleeve parasitic

 knormoyle at surfnetusa.com wrote:
> 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?

That is not apples vs apples.

If you make the antenna out of two wires, but simply tie
them together to make a "fatter wire", then the LC network
wins.  It might still win with a single wire, because the
fatter wire doesn't help the bandwidth all that much.

The reason why a lumped element network is more broadband
that any sort of distributed structure is that the inductance
or capacitance of a distributed structure increases with frequency,
which decreases the bandwidth.  The inductance or capacitance
of a lumped element is constant, by definition.

> Am I missing a loss calculation in open sleeve designs?

Open sleeves, like linear loading, are not lossless, or even
necessarily less lossy than good lumped elements.  There is a
lot more lossy wire in a parasitic element than in a coil.

>
> -kevin
> ad6z

See:

QST Oct 1986 P27
QST Jun 1985 P42
QST Jul 1984 P45
QST Apr 1983 P22

available at arrl.org

Rick N6RK