[TowerTalk] Re: 80 Meter Hybrid Triangle Loop

[Bob]

In my exprience, on 75 meters a half wave dipole and a full wave sloping
delta loop play quite differently.  I have both and have done countless A -
B tests between the two.  The apex height for both is about fifty feet.

I have found that early in the evening the dipole is the better of the two.
Later in the evening as the band starts to lengthen out, the sloping delta
loop definately is the best.  The loop seems to be a very effective dx
antenna.  The feed point at one of the bottom corners is the key.

Of course, YMMV...

Bob W7KD


----- Original Message ----- 
From: "Tom Rauch" <w8ji at contesting.com>
To: "K0PYK" <k0pyk at yahoo.com>; "Tower Talk" <towertalk at contesting.com>
Sent: Sunday, November 07, 2004 8:54 AM
Subject: Re: [TowerTalk] Re: 80 Meter Hybrid Triangle Loop


> > * 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
>
>
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