At 05:09 PM 2008-11-24, Gary Smith KA1J wrote:
>Well... it was supposed to be an inverted L on 160 but as it worked
>out, the terminal end is absolutely vertical and is 25' from the
>ground. so if you look at the antenna from a relief view, it looks
>more like a fish hook with a short shank. Here's my ascii art...
>
> - -
> / \
> / \
> / \
> | |
> | |
> | |
> | * <-Insulator @ end of wire
> |
> |
>__|__radials____
>
>Wire is the about 168' in total length and the apex is as high as the
>highest tree. There is some horizontal at the top but it does come
>straight down.
>
>Seeing as I am aiming for DX, would I be better to shoot an arrow
>over a neighboring tree and elevate the terminal as to make it as
>flat as can be done or will this "fish hook" be perhaps better a
>configuration for vertical polarization & DX?
This shape will have a lower feedpoint resistance than an inverted
L. My quick EZNEC model shows 32 ohms for the U vs 62 ohms for the
L, including 5 ohms of ground loss, with the open end 15 feet away
from the rising vertical wire. The L will have more signal (+5 dB or
so) at high angles and a little more signal (+0.5 dB or so) away from
the open end of the L at low angles. The L has about a 90 kHz 2:1
bandwidth vs. 57 kHz for the U.
The edge in efficiency for the inverted-L will increase if the ground
loss is higher than what I assumed.
Pulling the open end of the wire farther away from the rising
vertical wire will get you somewhere in between in performance.
73, Terry N6RY
_______________________________________________
Topband mailing list
Topband@contesting.com
http://lists.contesting.com/mailman/listinfo/topband
|