[TowerTalk] Why did adding a radial make the input Z of my inverted L go ...

[Lee Buller]

I am not an expert in these matters, but I can give you my experience this past fall.  I have an Inverted-L going up the tower 60 feet and then over to a tree at around 132 feet.  I used a grid-dip meter (the only thing I have) and found the dip to be fairly high.  There was no ground to the "L" except for a ground rod.  Now, I live on a city lot of about 80 by 150 feet.  I took 650 feet of #14 stranded insulated wire and put 16 radials down that would fit on the lot.  The radials are in a half moon because of the house in the way.  The connection point is a stainless steel ring that was tapped for machine screws.  All of the radials were random length.  Some are long, some are short.  The ground plane field is not symetrical.  Well, nothing is perfect.  I would check the resonance of the antenna as I was adding radials and found the frequency lowering when I was putting on more and more radials.
 
I put the GDO back on the system and found that the resonance of the antenna came down from 2.0 Mhz to 1.8 Mhz.  Remember, the GDO is not a precision device, but neither is my antenna.  The GDO is an old Heathkit.
 
I am not sure what the radiation resistance is, but I think that is fairly low like the books say it should be.  I matched the "L" with a small cap and it had a fairly sharp tuning range as I expected it would.  I can get about 45 Khz between 2.0 to 1.  The center fequency was easily matched at 1850 Khz.
 
Since then, I've taken out the small cap and just match it with the Tuner.  Works OK that way as well.
 
It does radiate on 160.  Worked a lot of stations with 100 watts.  I just wish the horizontal end would be up in the air another 30 feet....but the "experts" say it will work with the horizontal leg drooping.
 
Just my experience...not a quantitative description at all.
 
Lee - K0WA