Topband: R: Inverted L Directivity

[Tom Rauch]

>The last 25% of the horizontal portion would be over the house.
>I know this would change directivity but how would it effect ones
>health?

The only study linking non-ionizing radiation to health risks was 
based on fraudulent data. Everything else shows unless you actually 
heat the cells nothing happens. It takes an extreme amount of power 
on low frequencies to heat someones tissues. The exposure guidelines 
are VERY conservative, and you would be nowhere near safe limits with 
that antenna.  

> system. If you plan to use an inverted L antenna, I suggest to study
> an antenna with two parallel horizontal wires, one at the top of it
> and one at its base, even one meter above ground. Feed the antenna at
> the center of the vertical section.... and even if the vertical
> radiator is very small, I think you get a good radiator.

The idea elevating a feedpoint improves performance was probably 
popularized by an antenna company who claims their elevated feedpoint 
makes super performance. Unfortunately it is one of the worse 
antennas available for low bands. 

You can move the feedpoint around all you like, and efficiency will 
not change unless you make a bad or poor feedpoint connection. It is 
the distribution of current that can change efficiency, and that only 
changes when you change the system's structure....not when you move a 
feedpoint around.

For good efficiency an antenna either requires many radials or 
counterpoise wires, very salty water, or to move the antenna at least 
1/8 to 1/4 wl or more above earth at the closest point to earth. This 
is even true for dipoles, and is especially true for any vertically 
polarized antenna. Install a reasonable ground, and be done with it. 

73, Tom W8JI
W8JI@contesting.com