[TowerTalk] Re: 80 Meter Hybrid Triangle Loop

[Tom Rauch]

> * First...of all I kind of like loops. I have a 40
> meter vertical oriented n/s and fed at the bottom. Out
> plays the dipole hands down. So I thought I would try
> another one...that is 80 meter and orient it e/w. I
> have some nice 60 foot trees to work with in that
> orientation.

Liking an antenna is one thing. It's certainly OK to have a
favorite antenna.
On the other hand if there is a large difference between a
loop and a dipole at the same height with the same
polarization, it has to be because something is seriously
wrong with the reference dipole

On 80 you are in worse shape, because you really need the
lowest wire as high as possible above ground in terms of
wavelength.

> * 2nd...I am on a city lot so an antenna with
> multiband versatility, within range of the rigs
> internal tuner is a consideration. It is my
> understanding that from the antennas design frequency,
> you can go up 1 band (that is 80-160) and down 2-3
> (80-40-20) without 2 many problems.

I don't know why that would be true. A full wave loop,
unless you open the loop electrically opposite the
feedpoint, has a terrible impedance at 1/2 frequency. It is
true it presents a modest impedance at harmonics, as long as
those harmonics fall where you actually need them.

>I know that he who
> dies with the wire in the air wins...I do want to
> maximize my choices and limit the overall number of
> antennas.

Limiting the number of antennas is a good idea. The worse
thing in the world is having too many antennas in a confined
area.

> *  3rd...The configuration of this hybrid loop
> provided an easy feed point, laid out nicely in trees,
> and was vertical in nature. The feed point in the
> article allowed some vertical and horizontal
> polarization. Best of both worlds...which from your
> comments may be an impossibility.

It is impossible to have two polarizations at once without
having a rotating wave, and that antenna would not generate
such a wave. The nonsense about V and H polarization at the
same time permeates antenna advertising, so it's no wonder
we all believe it.  All you really have is a tilted field
who's tilt varies with azimuth and elevation, just as the
field from a dipole does (it is only perfectly horizontal
broadside to the dipole).

While it might fill in directions, it wouldn't help fading.
If you really could transmit a V and H wave, it would
typically have more fading than a single polarization on a
skywave path. It would fill in some directions, no surprise,
by reducing FS in other directions.

> * 5th...Gain with a loop at its fundamental frequency
> is basically equal to that of a dipole.

Bingo. Then why is your 40m loop stronger than your dipole?
It can only be because something is wrong with the dipole.

>A loop is
> quieter by nature and is readily seen when switching
> back and forth with the dipole.

There is no physical or electrical reason why a loop is any
quieter than any other antenna with a similar pattern.
Unless an antenna is involved in a weather situation where
corona is discharging from the antenna itself, it cannot be
any quieter than any other antenna at the same physical spot
with the same pattern.

Now this doesn't say your loop doesn't receive better than
your dipole, because we know from your transmitting report
of the loop being stronger than the dipole something is
wrong with how your dipole works.

>The data says that
> gain is achieved when you go to multiples of the
> fundamental frequency, but will be off the lobes.

Almost any single element antenna has that property.

> * 7th...Given the site, trees available, distance
> between endpoints, +/- 55' height, and location to
> house/shack, a vertical loop is do able. I have the
> thought process that anyone can put up a dipole, but
> not everyone can put up a loop (much less a vertical
> loop). If there is something else better suited for my
> situation...I am open to suggestions.

We all use what will fit into our property.

> * 8th...I can change the configuration to a rectangle
> loop, lets say 35' vertical ends by 106.5' top and
> bottom...fed vertically or horizontally. I also could
> configure a delta loop with apex down...112' top and
> 85.5' legs. I understand that these would be 100 ohm
> impedance and could be fed with 1/4 wave of 72 ohm
> coax.

75 ohm cable in a 1/4 wl Q section for 40 meters would only
work on 40 meters, because that's the only band where the
antenna is 100 ohms and the feedline an odd 1/4 wl long.
There goes your band agility. Maybe you'd be better off to
use 300 ohm transmitting feedline and a good tuner.

There is nothing wrong with rolling up our sleeves and
working, and certainly that helps us learn. I'm just puzzled
why your dipole is such a poor player. There's nothing wrong
with a loop, but it should be about the same as a dipole in
performance.

73 Tom