Slightly off topic but germane I hope, I have been operating portable from a
mountaintop location and the inverted vees do not seem to be effective, I
would think a true dipole would be a fine performer, but with only one
available high support, would I not be better with a delta loop? I know I'm
ignoring the ground underneath, but I have what I have. Ground slopes away
very rapidly so I am thinking my effective height is quite good, I was
thinking to try deltas for 80 and 40 next trip, with vertical polarization.
Would a horizontal feed be any better? Any other suggestions with one high
support? Thanks, great information so far.
Dave NT6AA
----- Original Message -----
From: "Tom Rauch" <w8ji@contesting.com>
To: "K0PYK" <k0pyk@yahoo.com>; "Tower Talk" <towertalk@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
>
>
> _______________________________________________
>
> See: http://www.mscomputer.com for "Self Supporting Towers", "Wireless
Weather Stations", and lot's more. Call Toll Free, 1-800-333-9041 with any
questions and ask for Sherman, W2FLA.
>
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>
_______________________________________________
See: http://www.mscomputer.com for "Self Supporting Towers", "Wireless Weather
Stations", and lot's more. Call Toll Free, 1-800-333-9041 with any questions
and ask for Sherman, W2FLA.
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