Topband: (no subject)

[bobk8ia at aol.com]

>I have a K9AY that I would like to try at my mountain QTH. I am on the top
where there is little or no soil, just bare rock. I have seen references to
using the K9AY over rocky ground using 4 radials laid out on the ground.
What kind of performance should I expect in a situation like this? How long
radials should I use?

73 de Björn /SM0MDG

----
 
Bjorn;
 
Very rocky QTH here too, in Arizona USA. I used 4 radials about 25 ft in length each. I also use a choke at the feedpoint. However the key to this antenna playing well, for me, was careful selection of termination resisitor. I ended up with about 320 ohms, much less than recommended for "normal" ground. Mine is used strictly on 160.
 
It works as it should, very well for a small rx antenna. With the above arrangement, I see F/B in the 25+ db range most of the time and S/N improvements of 15+ db all the time, here.
 
The antenna is quite sensitive to being close to other conducting objects, transmitting antennas and/or any wires passing near it. Try to avoid that if you can. At one time I had a leg of an 80m inv vee that passed overhead maybe 40 ft above and 20 ft to the side of the loop centers and it reduced F/B significantly. Removal of that vee got the antenna playing properly again. Plus, a friend of mine has his only 50 ft from his 160 vert and was experiencing poor K9AY directivity until he detuned the transmitting vertical when receiving. All is well with his now too.
 
GL with your project.
 
73, Bob K8IA
Arizona USA


 
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