Actually the open wire lines at medium wave BC stations exciting
verticals are all, as far as I know, unbalanced. See for example the
line shown here at KFBK, operating phased Franklins:
(A genuine Franklin is a sectionalized tower consisting of two stacked
half wave sections fed at the center. Yes, this is the true 160 meter
dream tx antenna. You will wish KFBK were a daytimer and you worked
at the tx site, but alas, no to both.)
http://www.fybush.com/sites/2005/site-051028.html
So, you _could_ in theory, feed your _unbalanced_ 160 m. vertical with
_unbalanced_ open wire feed, which by the way means using wires to
simulate the coaxial solid center/shield by using one or more center
wires with (usually) four wires equidistant from each other and the
center, but making spacers for this might be tough. Then there's what
might be too much loss for 2000 feet on 160 for your power level.
Until a few years ago WSM Nashville used this feed on 650 KHz but for
less distance, more power, and they eventually went with Heliax
so.....
At 2000 feet I'd start giving thought to constructing some sort of wx
proof dog house at the base of the tower and putting the tx out there
and operating it remotely from the shack. We have hams now operating
their stations from thousands of miles away via the internet so it
must be easier to set something like that up these days. : )
73,
rob / k5uj
<<<<I believe it is standard for AM broadcast stations to match the tower to the
feedline right at the base of each tower, even with their monster coax or
when they had balanced open feedline. (I worked at one that still had some
remnants of their old open feedline runs.)
Work out a loss budget to see how much power you lose by having a high
feedline SWR.
>> Almost everyone recommends matching in the shack as well as at the
>> antenna feedpoint.
You shouldn't need any special matching in the shack if you match correctly
at the antenna feedpoint. Just a balun with the right ratio.>>>>
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