Topband: Loop question

[Larry Molitor]

Jim, 
 
Having suffered through a similar situation, I may be able to offer some useable suggestions. I spent almost two years experimenting with various RX antennas placed close to the TX antenna and found that the "Flag" configuration had the best isolation / lowest interaction of any common RX antennas I tried.
 
Remember, TANSTASFL, "there ain't no such thing as a free lunch". If you are serious about better RX, you are going to have to work at it. 
 
The flag is much more difficut to construct than a K9AY loop, but in your situation I believe that it would show a distinct advantage over the K9AY. The problem is that you would need to build four flags to do what one K9AY would do.
 
You would need to point one in each direction, placed as far away from the TX antenna as practical and pointing directly away from the TX antenna. Assuming you don't have elevated radials running next to the flags, this configuration would have practically no interaction between the TX and RX antennas. 
 
At the old AZ QTH, I had a shunt fed tower for 160 and a shunt fed tower for 80 placed about 70 feet apart. I successfully operated a flag directly in between those towers, with no tower de-tuning, and no measureable interaction, provided the flag was not pointed at either tower!
 
It's a lot more work to use four flags, but I promise it will be worth it when you are trying to dig the weak ones out of the noise.
 
73,
 
Larry - W7IUV

KJ0M <kj0m at mchsi.com> wrote:
What I'm wondering is this. Would the loops make good listening 
antennas even though they wouldn't have the nice cardioid pattern 
shown by the K9AY loop? What I am looking for is a nice quiet 
listening antenna to go along with the BC trapper and loops seem to 
be the way to go on a small lot except for the interaction problems 
throwing the pattern off.

With a preamp, will the K9AY loop, or any type of loop for that 
matter, be a good listening antenna in my case or am I better off 
just suffering with the noise on the vertical?


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