[Elecraft] RE: Attic Ant.-Closed Loop vs. Open Ends?

[Todd Fonstad]

Greetings,

It is interesting that this topic has arisen now, as I am wrestling with
some of the same challenges previously posted. I recently remarried and
moved across town to =91her house=92 I bought half of it =85 the north =
half :). I
put up a 110' long attic loop at about 25' above ground which is fed =
with a
short length of 300 ohm ladder line down through the ceiling to my =
shack. It
works very well from 40M on up, but although the K2's ATU will 'tune' =
itself
for 80M and even 160M duty, the loop is essentially a dummy load on =
those
low bands.=20

I would like to try to cut the loop at its center so as to have a
'convoluted doublet' (for lack of a better term) 55' long per side. I =
think
it would do relatively well on 80M but I have no idea what effect doing =
so
would have on noise levels and efficiency on the other bands.=20

I'm trying to avoid extensive experimentation. The low head room and the
thick insulation (I have to put plywood sheets down to avoid going down
through the ceiling) make negotiating the attic very difficult.=20

The main challenge is finding the exact center of the loop opposite the
feedpoint. There is no way this 63-year-old body is going to measure =
every
inch of the antenna to find this point where I would make the cut. Does
anyone have an 'elegantly-crafted' method of finding this point, perhaps
electronically?

Best regards,
Todd
N9NE
Oshkosh, WI



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