You are correct that a 160 meter inverted vee at 60 ft is not a DX
antenna. Compared to a full size vertical with a good radial system, at
10 degrees elevation it should be down 7 to 10 dB, and if you are using
it for receiving it should be much noisier.
Without looking at what the balun does, and just assuming there is
coupling to the tower, consider what will happen to the current down the
tower. If your tower has guys, or no ground radials, the current goes
down the tower and into your tower grounding system and the cables
exiting from the tower. This is likely to have high loss due to large
ground currents. In order to first get any significant currrent in the
tower, you would have to have just the right lengths of cable to create
a low impedance point at the top of the tower. This is possible, but a
fairly low probability. Without the resonant point of the tower and
cables, the tower currents would be low and have very little effect on
the pattern. If the tower currents are significant, the antenna may
start showing some directivity due to the cables exiting the tower which
will radiate, but the system is lossy, so the gain is going to be low.
If your tower has no guys and a radial system it should be resonant
somewhere around 3 to 3.5 MHz. If this is the case, you would not be
able to get enough current into the tower to produce any significant
pattern change.
Another possibility: If you have a guyed tower, the guys could be acting
as a reflector for your inverted vee. This could give some directivity,
but this is also a lossy system, so the gain will be low.
A third possibility, it that you have other wires, or towers close by
that can act as a reflector which may slightly increase the gain.
Considering these possibilities (which is all I can think of at the
moment) I see no way to account for this antenna working well for DX.
Did you have it on the side of a mountain??
Jerry, K4SAV
RLVZ@aol.com wrote:
>Hi guys,
>
>Got a question I'd love to run by you:
>
>At another QTH I had a 160-m. inverted vee with apex at 60' on a Rohn 25
>tower. Had a Tribander mounted 3' up above it. Not much of an antenna on
>160
>but this particular antenna worked DX well ... much better than it should
>have. Such as, a KL7 told me that I typically was the first station East of
>the
>Mississippi he heard on 160.
>
>For a center insulator I was using a Unadilla 1:1 balun... the one with the
>ground strap attached for lightning protection. The ground strap was
>attached to one leg of the tower.
>I am wondering if somehow the DC ground strap was also coupling some RF into
>the tower?
>(it would appear possible as I was never able to get the SWR on that
>particular setup under 1.7 to 1 and usually it's quite easy to get a lower
>SWR than
>that) Or would everyone agree that if I had in-direct coupling taking place
>that it was via the top mounted tribander just a few feet above the apex of
>the Inv. V?
>
>With the way the low Inverted V worked so well on DX q's it would seem
>certain that somehow the Vee was getting indirectly coupled to the tower...
>thereby giving it some vertical polarization.
>
>Question: Are there any proven ways of mounting a Dipole or Inverted V on a
>tower so that some indirect coupling to the tower and therefore some
>vertical polarization can be derived from the tower?
>
>Thanks!
>
>73, Dick- K9OM
>_______________________________________________
>
>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.
>
>_______________________________________________
>TowerTalk mailing list
>TowerTalk@contesting.com
>http://lists.contesting.com/mailman/listinfo/towertalk
>
>
>
_______________________________________________
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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