Topband: Broadband Inverted L

[Tom W8JI]

Joe posted,

>I moved my 160 inverted L to a tall tree in my backyard to get more 
>vertical height. The vertical leg is now about 65 feet and the rest 
>(65feet) is horizontal. I fed this one with about 125 feet of 75 ohm coax 
>just because I had lots of it laying around. No tuners, baluns, ununs or 
>chokes in the feed line. The ground is connected to the existing ground 
>system for the old L. I get a 1.1 SWR reading from 1.8 to 1.9 before it 
>moves up to 1.3 and slightly higher to 2.0. The antenna seems to be working 
>OK (relative to the old L). This seems awfully broad banded? Any feedback 
>would be great. Thanks -Joe N3HEE
>

and Joe added:

>The antenna feed point terminates at a four foot ground rod and then I am 
>running a number 14 wire from that ground rod to my existing radial field. 
>That run is about 40 feet. The radial field consists of 3 8 foot ground 
>rods and nearly 2000 feet of wire spread out over my entire front and back 
>yard. I didn't want to run "new" radials over top of the existing so that's 
>why I did what I did. I am measuring SWR from the shack end of the feed 
>line>>>

Unfortunately there is almost no radial system ground connection at all on 
the new inverted L, because there is almost 1/8th wave of a single thin wire 
between the real ground and the feedpoint.

That wire length, 40 ft, could add hundreds of ohms impedance to the ground 
path.

While bandwidth is a terrible way to guess efficiency, it is also obvious 
the ground radial connection really isn't a worthwhile connection at all.

73 Tom