How feed an extended half-square?
 

I have room to erect a "half square" (aka upside-down phased verticals?)
20-meter antenna to be fed at one corner (low-impedance location; attach
50-ohm coax) or at the bottom (high-impedance; use a matching network):

A B
+--------------+ 1/2wave long
| /| 1/4wave high
| / |
/ Matching Network
Coax

Unfortunately, I do NOT (because my house is in the way) have room
to make it a more-balanced curtain:

A B C
+--------------+--------------+
| /| |
| / | |
/
coax

However, if I extend the horizontal wire and leave out the middle
"vertical" (because it would dangle onto the roof), I have room for
four vertical sections in a space that should have five:

A B C D E
+--------------+--------------+--------------+--------------+
| | this part will be about | |
| | 10 feet above the peak | |
of my house

Observations:
* Line ABCDE will be about 28 feet above ground.
* There is almost no AC wiring in the roof part of the house.
* The incoming AC power line terminates reaches the house at about a
20-foot height (i.e., some 8 feet below the ABCDE line) about halfway
between points B and C and at about a 45-degree angle with line ABCDE
* A lot of tree- and ladder-climbing will be involved, so I'd like to
keep the "cut-and-try" to a minimum.

I've never done any antenna modeling, and I've never had any "feel" for
antenna phasing (EE degree notwithstanding), but I suspect feeding it
at the original corner (B) will result in somewhat unbalanced currents
almost everywhere.

QUESTION: Are there any suggestions on how to feed it (perhaps at
point C)?

What about, for example, substituting rope for the BCD wire (to maintain
the proper tension in AB and DE), connecting a coax to point B, another
to point C, then bringing both to a common point somewhere above ground
level (the shack is in the basement), and then connect them with a T to
the coax that goes through the wall to the rig? Should these two coaxes
be of any particular length?
--
--Myron A. Calhoun.
Five boxes preserve our freedoms: soap, ballot, witness, jury, and cartridge
PhD EE (retired). "Barbershop" tenor. CDL(PTXS). W0PBV. (785) 539-4448
NRA Life Member and Certified Instructor (Home Firearm Safety, Rifle, Pistol)