Topband: Inverted L Lengths

[GeorgeWallner]

On Sat, 12 Nov 2011 20:54:02 -0000
  "Doug Turnbull" <turnbull at net1.ie> wrote:
>...some use inverted L antennas of 160 feet 
>plus in length and
> others like myself have them closer to a quarter wave 

Doug,

You had a great signal here in Miami the other night, so 
 I think your antenna works well (enough). So don't rush 
out to lengthen your inverted L just yet :-)... But...some 
believe that a longer antenna will move the current 
maximum higher, away from the lossy ground.

As others on this reflector have pointed out, when a 
buried, or on the ground, radial field is insufficiently 
dense to shield the antenna's H field from the ground, the 
resulting eddy currents through the (less then perfect) 
ground will result in losses. The less of the field is 
intercepted by the ground, the lower these losses. Hence 
the idea of moving the current maximum -- and thus the 
field maximum -- up.

I have done some informal testing comparing a 1/4 wave 
vertical with an almost 1/2 wave vertical and found that 
the longer antenna put out a stronger signal. So there may 
be something to this theory... Of course, with an inverted 
L you do not want to move the current maximum into the 
horizontal section, so the antenna should not be too long.

73,

George, AA7JV