Good Morning Lloyd & All:
You have described my 160 & 80 meter antennas almost exactly. The
vertical part of my L is about 3 feet away from the tower at the top,
and approximately 2 feet away at the bottom. I also have a 80 meter
vertical wire on the other side of my tower. The 80 meter wire is
approximately 3 feet from the tower at both ends.
I modeled the Inverted L in EZ Nec, and determined that the Z at the
base is approximately 5 ohms. I built a T network to feed the antenna
and it works well. I'm not the biggest dog on the porch, but I work my
share of DX running 500 watts. I just have to stand in line a bit longer
than the big dogs. The same applies for the 80 meter vertical. I have
approximately 70 radials of varying length.
I'm confident that the farther you place the L from the tower, the
easier it would be to match, otherwise I believe it will perform well.
The trick appears being able to accurately determine the complex
impedance of the antenna. EZ Nec probably gets you in the neighborhood,
but there will probably still be some cut & try with the matching
network, If you can increase the number of radials to 65 - 70 you may
see better performance. I did a significant amount of reading on this
subject, and the consensus was that this number radials is near the
point of diminishing returns when you don't have the real estate to put
down a large number of full length radials.
73,
Mike, W5UC
On 4/27/2012 8:07 PM, Lloyd Korb wrote:
> Hello, I have used an Inverted L, on 160 meters, for many years and have
> always been curious if I am okay with my present spacing. The spacing
> between the vertical portion of the L and my 60 foot tower is 18 inches.
> The spacing was picked for the ease of feeding the wire at the base of my
> tower. The horizontal part, of the L, is around 85 feet and goes from the
> top of the tower to a pole that is 6 feet above the ground. Does anyone
> know of any studies done on the performance of the L versus the spacing of
> the vertical wire to the tower?
>
>
>
> I'm also wondering if I could run another wire, on the opposite side of the
> tower, for an L on 80 meters. It would be nice to be able to have two bands
> available. Will there be any interaction between the two wires? My present
> radial system is 24 wires of various lengths to fit in my yard.
>
>
>
> 73,
>
>
>
> Lloyd K8DIO
>
> _______________________________________________
> UR RST IS ... ... ..9 QSB QSB - hw? BK
>
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UR RST IS ... ... ..9 QSB QSB - hw? BK
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