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Topband: Inverted "L" vs." T"

Subject: Topband: Inverted "L" vs." T"
From: RK <>
Date: Wed, 8 Oct 2008 03:42:07 +0000
List-post: <">>
Hello Gary,

Regarding your question:

"Is there any advantage in using an Inverted-L if you have to run it up a 
tree where the vertical run is very close to the tree verses a "T" where 
the vertical portion would be in the clear between two trees for supports?"

Regardless of L or T format it is important to keep the vertical portion as 
far away from any metal or conducting objects. This would include trees. On 
160m the near field remains significant to at least 1/2 wavelength  where 
energy is absorbed and perhaps re-radiated. Which can be beneficial or 
detrimental to the desired effect.

In the T antenna which is traditionally called a Marconi, radiation from the 
two horizontal portions tends to cancel, leaving the mostly low angle 
vertical component. How much and how well is dependent upon the ground 
currents and uniformity.

In the L antenna the inverted horizontal portion radiates some in the 
horizontal plane. When that element slopes towards earth there is some small 
net gain in that direction.

I might add that if you have a vertical mast or wire,  the T portion can slope 
back towards the ground and still  cancel the horizontal component. However, 
the top loading wires must be equal in length and slope at the same angle 
back to earth to maintain balance. Further with the T portion as top loading 
the feed point radiation resistance will be greater for a given vertical 
height. This when coupled with an excellent ground system of 1/4 wave radials 
will make the antenna substantially more efficient than other types of 
loading. (Less Loss)

I hope this answers your question.



Bob Kile, W7RH
Linux is like living in a teepee. No Windows, No Gates,
Apache in charge.

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