[Antennaware] homemade coil

K9AY k9ay at k9ay.com
Thu Mar 15 09:09:08 EST 2007


You did the #1 best thing by using a large diameter. Any improvements with a 
neater winding will be small. Same goes for larger wire or tubing -- the 
theoretical improvement may be hard to see.

The only exception would be a coil with a lot of current flowing through it. 
In that case, a larger conductor and optimum length/diameter ratio for best 
Q would reduce the losses.

Actually, I'm a little surprised that you need inductance with a shunt 
feed -- is the tower short?

73, Gary

>I began work on shunt loading my tower for 80 and/or 160.  The initial
> reading on my MFJ 259 showed that the antenna was too short, and it
> needed a coil in series to get X=0.  I went to a plumbing shop and found
> solid #12 insulated wire, wrapped it around some 4-inch diameter PVC
> pipe, and lo and behold, I am in the ballpark.
> My question is: I intend to re-wrap the wire so it is neat, but what
> kind of problems should I expect from this kluge coil?  I tried moving
> the turns around, with the ends fixed in place, and there is almost no
> change in X on the 259.  Am I looking at low efficiency, potential
> arcing, other problems associated with such a cavalier method of
> creating a coil?
> Jan, KX2A
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