Topband: Broadband Inverted L

[Jim Brown]

On Thu,11/20/2014 9:25 AM, Gene Smar wrote:
>   Don't ask questions and just enjoy the antenna's performance.

A low SWR is NOT an indicator of an antenna's performance. It only 
indicates a match to the transmission line.

In this case, the low SWR suggests that the antenna is highly resistive. 
The radiation resistance of an antenna of that height is less than ten 
Ohms. The rest of the 70 ohms or so of resistance it takes to produce 
that nice match is LOSS -- a bit in the wire resistance, the rest of it 
in the radial system.

A connection to earth is NOT an efficient part of an antenna -- the 
earth is lossy (a big resistor). The only reason for having a driven rod 
is for lightning protection. It's those radials that are providing a 
return for antenna current, and 2,000 ft of wire is not a lot on 160M. 
Over average soil, 2000 ft of wire typically provides a ground loss 
resistance on the order of 10 ohms; over poor soil, the loss resistance 
will be higher, over good soil, it will be less.

The high value of loss suggests that perhaps your radials might not be 
making a good connection to the coax shield, so all the antenna sees is 
those driven rods.

To understand this, and for some practical ideas for radial systems, study

http://k9yc.com/160MPacificon.pdf

73, Jim K9YC