You say a 1:1 balun. What type is it and should it not be preventing
common mode currents? If not Id consider one that will rather than
adding a choke. I bought a commercial 1:1 Balun opened it up and found
it to be just a length of RG8X looped once inside the casing with half a
dozen ferrites around it. What I have done is have ground rods at the
base of the pole. I am using a 10-80 +warc fan dipole that looks a
little like a flattened spider web supported with guyed camouflage tent
poles to about 40 ft I have 6 ferrites on the coax at the feed the
ones I got out of the commercial balun. Then at the base I have several
5 ft copper pipes driven into the ground around the pole about 5 ft
apart all bonded together with 6 gauge bare copper that is also burred
a few inched below the surface safe from the lawn mower. I have a
barrel connector at the base that lets me connect the shield to this
ground I have no common mode issues. at least I have not experienced
any.
David VE3SD
On 10/20/2014 22:28, Dauer, Edward wrote:
I am thinking of adding a coiled coax common-mode choke to my system.
Presently it goes K3-KPA500-KAT500 then 100 ft coax to the base of an
inverted Vee¹s center support pole (collapsible fiberglass), then 30 feet
up the pole to a 1:1 balun feeding a fanned 10-15-20 Vee. The idea, for a
couple of reasons, is to put the choke at the base of the pole, something
I haven¹t seen discussed in the literature. Two questions I am wondering
about: 1. The choke would be 100 feet from the tuner and about 25 feet
from the antenna/balun. Probably not as good as having it right at the
Vee, but is that compromise worth while? 2. For appearance sake I am
thinking about winding the coax around the base of the support pole. It
is 2 inches in diameter but I could slip a 3 inch PVC over that section to
increase the diameter. Anyone know an algorithm for determining the
number of turns in the winding if I do that? I would be much obliged for
any thoughts and suggestions . . . Tnx!
Ted, KN1CBR
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