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[Amps] OFF TOPIC: Loop antenna question

To: amps@contesting.com
Subject: [Amps] OFF TOPIC: Loop antenna question
From: JimMoci@aol.com
Date: Sat, 25 Dec 2004 23:53:54 EST
List-post: <mailto:amps@contesting.com>
Happy holidays to all on the amps reflector. I have an off topic question 
about a loop antenna so if it is not appropriate please remove it or respond to 
me directly via email. I am asking here because there are so many experienced 
and knowledgeable people on this reflector and the info I receive will be very 
useful. 

My situation: I currently have a full sized 40 meter delta loop @ 30 ft and 
it is horizontal to the ground. I use it on 40 thru 10 with good results. The 
antenna exhibits a good SWR on 40 and an SWR less than 2.5:1 on 20 thru 10 
meters so the internal auto antenna tuner in my Icom solid state amp can handle 
the mismatch. What I would like to do is use it on 75 meters but dont have the 
room for a full sized 75mtr loop. The loop is to small for 75 and has an very 
high SWR, to much for the internal tuner to deal with. So far I have tried 
splitting it in the middle, essentially a full sized 75 meter dipole folded 
back 
on itself. It works ok, but not a stellar performer. It also lost the advantage 
of being a quiet receiving antenna, a characteristic loops are known for.

I have a couple ideas that I want to try but figured I would ask before I go 
climbing tress out in the cold. The first idea was to add another full turn to 
the loop, separated by a few inches. Essentially it would be a 2 turn loop, 
totalling about 260 feet, but only taking up the space of a 40 meter loop. The 
other idea was to add a large inductor in the middle of the loop. I have a 
large, silver plated, flat wound inductor from a broadcast transmitter that 
would 
do nicely. I also have a vacuum relay that I could use to short it out for 40 
thru 10 mtrs. 

My main question is will the two turn loop work? If so will it be better than 
the inductor?

I realize that I could use a large roller inductor tuner in the shack but 
that defeats the purpose of my lazy hams push button station. My solid state 
kilowatt is silent and automatic and it is my goal to keep the station totally 
push button. 

Thanks for any and all advice- It will save me many trips up the tree and 
there is snow in the forecast. Why didnt I do this in the summer?!?!?!

73, 
Jim W3ATV
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