Lane;
The inverted L with the vertical wire, I have found here, next to the
tower is fine. As the tower is less then a 1/4 wave. However, and
important consideration is for the horizontal wire of the inverted L to
be folded back on itself with spaces for about 60 to 65 feet thus
creating a 1/8 wave open stub. (Ladder line will work for this purpose.)
This method should limit the unwanted high angle radiation from the
horizontal section of the inverted L. You will end up with a feed
impedance of 30 to 40 ohms depending upon the ground system. This is
reasonable for a direct feed or a perfect match with a simple L network.
This method will also allow for the placement of radials at one
location, at the base of the tower. You can shunt feed the tower for 80
meters and end up with a super DX TX antenna for both bands.
Remember if you are interested in low angle take of try to cancel as
much of the horizontal radiation from an inverted L. Some may suggest
just shunt feeding the short tower. This will work but the matching of
a shunt or omega may be harder and the bandwidth may be more restricted.
Good luck in your project and let me know what works best for you.
Herb, NP2MJ
Lane Zeitler wrote:
> I have a 30 ft free standing Rohn 25G tower that I am extending to a
> total of 65 ft via the use of an old force-12 2" dia. boom from an old
> yagi. This will be clamped to the top of the tapered section vertically.
>
> I have enough tall trees to support either an Inverted L or a T for
> 160. Which will give me most bang for the buck or are they basically
> going to perform abt the same?
>
> My plan is to NOT actually feed the tower but to use it to support the
> L for the T.
>
> Ideas and thoughts?
>
> Lane
> Ku7i
>
> PS Or should I put up a T and shunt feed the tower? I have plenty of
> room for full size 1/4 radials to lay on the ground.
>
>
>
>
>
>
>
>
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