Topband: [Topband] Inverted "L" vs." T"

[Michael Tope]

Rick Karlquist wrote:

>>Why does NEC not confirm this statement?  An example: A T antenna and an
>>L, both with the same ground loss, the same vertical section length
>>(49.5 ft), and the same resonant frequency.  The T calculates as a
>>feepoint impedance of 18.1 ohms at 1.81 MHz.  The L calculates as 20.2
>>ohms at 1.81 MHz.  If you calculate the radiation resistance, the L will
>>be 1.5 to 2 ohms higher.
>>    
>>
>
>The higher radiation resistance and lower ground loss of the inverted
>L is illusory, because the additional radiation represents horizontallly
>polarized waves, which tend to be inefficient for communications purposes
>on 160 meters most of the time, especially at typical inverted L heights.
>
>If you do an NEC model with a second reference vertical, say 5
>wavelengths away, and look at the amount of vertical power received by
>the second reference vertical, then you will see that the horizontal
>section of the inverted L contributes nothing, whereas a T top actually
>increases received signal.
>
>Hope that clears up this persistent misconception.
>
>Rick N6RK
>
>  
>
Thanks for clairfying that, Rick. I also noticed that when modeling the 
inverted-L compared with a symmetrically top loaded vertical with the 
same vertical height. This inconsistency between the radiation 
resistance of the inverted-L compared to the pure vertical really bugged 
me, but I didn't know how to reconcile it (it seemed like you were 
getting something for nothing by using the inverted-L instead of the 
symmetrically top-loaded vertical). Your explanation makes a lot of sense.

73, Mike W4EF........