TopBand: antenna changes

[jim funk]

Greetings, all....
        In the category of "never change a working antenna within 24 hours 
of a contest":
        My inverted L is coax-fed at the base of a 75' Rohn 25 tower.  The 
shield is grounded at the tower base and the center conductor is simply 
hooked to a wire that goes up alongside the tower (only 8" away from the 
tower) to the top and then ties off to a tree.  The horizantal portion is 
approximately 75' long as well.  There are 3 resonant radials elevated 4' 
that go off at about 30, 90 and 180 degrees.
        Simple.  SWR 2:1 bandwidth was 1800 to 1860.  No tuner anywhere.  
Work about anyone I can hear, including EU w/ 5 watts (but not lately!!).
        So, what did I do?  I decided that the vertical portion must be too 
close to the tower, so I pulled it out about 3' from the tower.  No other 
changes.  Now the SWR doesn't go below 2:1 ANYWHERE and the antenna is 
resonant at about 1780 khz.  I could shorten it to raise the resonant 
frequency, but I don't see that solving my problem.  What did I do wrong?  
Was my assumption that 8" separation between the vertical portion and the 
tower was not a good idea correct or not?  Is 3' still too close?  I can use 
a tuner in the shack and get by for this event.  I can change it back but 
thought I'd solicit the advice of the group first.

        TIA and 73, Jim N9JF

Quote of the year:
"Umpires are like dairy cows. The bottom 20% should be culled each year."
Al Oppendal, Ruthven, IA in Nov. 16, 1998 _Sports Illustrated_


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