[Antennas] Loop vs Dipole

[George, W5YR]

Ron, two things:

1. "perfect resonance" has little or nothing to do with radiation efficiency
or how well your antenna works. It can be convenient in some line/antenna
matching situations, but like a low SWR, it has little to do with how well
you get out.

2. the 1:4 transformer you are using may in fact be worsening your
performance. I use a full-wave horizontal loop on 80 meters which I feed
with ladder line, a bead balun to coax, and a tuner. Works great on 80-10
and really gets out. But my 20 meter EDZ antenna equals or outperforms it on
75 meters, proving that resonance has little to do with performance.

I suggest that you forego the transformer and feed the loop at any point
with ladderline and see if that doesn't make things better. Plus, it buys
you multiband operation.

I hope that you don't think I am taking you to task, as I am not, but a
perfect SWR and perfect resonance do not at all ensure a good working
antenna system. My EDZ antennas are non-resonant on all ham bands and are
fed with a line having an SWR of as much as 15:1 - I usually work anything I
can hear and on 75 meters, I keep up with the boys with the big amps running
my 100 watts.

Another classic rule about antennas is that performance does not lie. If
your inverted Vee is working better, then that is the antenna to use,
regardless of the supposed theoretical merits of loops. Again, my loop
outperforms my EDZs many times on various bands, but the opposite is true as
well. Plus my vertical outperforms them all on occasion. No single antenna
can be expected to be optimum for all conditions and all bands.

Happiness is lots of different antennas and a good coax switch!

73/72, George
Amateur Radio W5YR -  the Yellow Rose of Texas
Fairview, TX 30 mi NE of Dallas in Collin county EM13QE
"Starting the 58th year and it just keeps getting better!"
w5yr@att.net

----- Original Message ----- 
From: "Ron & Madhavi" <mchilkuri@kasnet.com>
To: <antennas@mailman.qth.net>
Sent: Tuesday, September 30, 2003 12:13 PM
Subject: [Antennas] Loop vs Dipole


> Here's a tough one....or is it?!
>
> I live in a townhouse in Kingston - the backyard is no more than 32' long
> and 10' wide, with a concrete parapet wall at the back.
>
> I have a 25' tall aluminum pole clamped to the wall and ran an inverted
vee
> on 20m (25' at the apex). Results were fair and with my 850S, I worked
into
> Asia and more consistently into Europe.
>
> Wanting to improve on it, I replaced the vee with a full wave loop and
> expected it to outperform the inverted vee. The loop has perfect resonance
> (a nice 1.1 SWR). The matching is done with a  1/4 75 ohm transformer.
> HOWEVER, even though I have tried to move the feed to a corner, 1/4 from a
> corner, center, apex etc., nothing seems to make it outperform the
inverted
> vee. I know that this does not confirm theory -- as the loop is larger,
has
> a lower take off angle (at least so they say!) and better SWR etc.
> Adddmitedly, the base of the delta is a FEW feet lower off the ground than
> the ends of the vee, but I expected the claimed superiority of a full wave
> loop to offset that.
>
> Used many 40/80m lops in the past, but never compared them to dipoles and
> vees at the same height! The results however were quite pleasing. First
time
> I am running comparisons on  loops and dipoles on  20m . Is the
superiority
> of the loop greatly exaggerated or am I missing something here?  I have
> written articles encouraging people to use lops instead of dipoles and now
> wonder if I lead them astray!!!!
>
> Again...perfect resonance (checked witha  RF1 at the feed point, end of a
> half wave section of coax and after matching with the 1/4 transformer too!
I
> can't see I have made any mistakes here! If its the height......how come
the
> inverted vee works MUCH better?
>
> Any thoughts. comments, advise?
>
> 73,
> Ron, 6Y5/4S7RO
>
>