Robert wrote:
I have a slope antenna set up for 80/75 and getting a 40m run
> this evening while I wait on the new 238 tuner to show up on Tuesday to
> hook up this tangle of ladder-line...
Curious about your planned antenna, Robert. Is it a sloping, center
fed dipole, fed with ladderline?
A couple of thought to minimize RFI, telephone interference,
excessive pickup of Omni-generated birdies, encoder growl etc. If you
are center feeding your antenna with ladderline, you are using a
balanced feedline and you will want to maintain symmetry and thus
balance by keeping the dipole flat top reasonably parallel to the ground
in order to minimize imbalance. I suggest you utilize a true balanced
matching network such as the link-coupled Johnson Matchbox instead of
the unbalanced network/4:1 balun combo. The problem is that on some
bands and under various loads, the 4:1 balun does a relatively poor job
of providing balanced currents on the feeders. I refer you to Rich
Measure's (AG6K) article in the Feb. 1990 issue of QST for a discussion
of why this is so. Lastly, BE SURE you untangle that 450 ohm ladderline,
keep it away from metal objects, and make no sharp bends with it. Lead
it away from the antenna flat top at right angles to the plane of the
antenna to minimize feeder imablance. I use such an antenna and I
experience no RFI problems whatsoever. The feedline acts only as a
feedline, not as a radiating part of the antenna system. Just a thought.
Good luck!
Vince/K7NA
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