I can't seem to get any work done so I'd better describe this beast and
get it out of my system.

The ZL-Special I built is also known as a Field-Day Special.  You may
find (better) instructions in some antenna books by looking for it under
that name.

The entire antenna is made of 300-ohm twinlead.  I used the cheap white
plastic stuff that comes in 40-foot rolls from Radio Shack (if the
antenna doesn't work, you haven't spent a bundle).  One roll for the
front element, one for the back, and then you need 8.5 feet more, which
unfortunately you DON'T have left over from these rolls, so you might
have to buy a third.  Total cost of antenna is around $10.

Electrical connections:

                    Front element
|----------------------------------------------------------|
|---------------------------F F----------------------------|
                            | |
                            | |
                            | |
                            | | <-- phaseline
                            | |
           /^\              | |
         /  |  \             X  <--- twist in phaseline-- important!
            |               | |
            |               | |
         forward            | |
                            | |
                            | |
                            | |
                            | |
|---------------------------| |----------------------------|
|----------------------------------------------------------|
                       Rear element

--Antenna is made from three lengths of 300-ohm twinlead.  
--The front and rear elements are approximately 1/2 wavelength long and
the two wires in each element ARE SHORTED TOGETER at the ends (making them
folded-dipoles). 
--The middle piece is the phaseline and is approximately 1/8 wavelength
long, and MUST have a single twist in it.

F = the feedpoints (note that it feeds in front)

I took the dimensions from the article by L.B. Cebik (W4RNL) (frequent
QRP-L contributor) in the Winter 1997 Communications Quarterly, which
were for 10m, and I doubled everything for 20m.  This gave:

front element length    32.46 feet
phaseline length         8.55 feet
rear element length     32.68 feet

I drilled holes in the rear element and the back end of the phaseline
and just used a 4/40 screw and nut to hold them together (be careful
your hole doesn't hit either wire of the twinlead).

For the front element and the front end of the phaseline, I again
drilled 4/40 holes in both twinleads.  I then took a SO-239 chassis
mount connector, and put its center soldering stub through the two
holes.  I oriented the SO-239 so its 4 mounting holes lined up with the
two lengths of twinlead, i.e. like a diamond in the above diagram (I let
the phaseline stick out the front end about 1/8 inch), and marked the
four spots on the twinleads above the mounting holes.  I then drilled
these four holes in the twinlead and used 4/40 screws and nuts to secure
both lengths to the SO-239.  This means the electrical connections
have no stress on them.   I dunno I think this arrangement is rather
clever:


       | _______ |  <-- phaseline
       |   / \   |
_______| /__S__\ |_______
/      /         \       /  <-- front element
/    / S    X    S \     /
/    \ |         | /     /      X = soldering stub of SO-239 sticking
/______\_________/_______/          through holes in both twinleads
       | \  S  / |              S = 4/40 screws through twinleads
       |   \ /   |                  and SO-239
       |         |
       |         |
       / / / / / /
           (to rear element)

NOTE:  This diagram is the mechanical assembly ONLY!  You must make the
electrical connections in the top diagram.  Before mechanical assembly
cut the back wire of the front element (at the center-point) and the
front wire of the rear element, and strip about 1/4 inch of the
insulation. I used a solder lug over the stub on the SO-239, soldered so
it lay flat.  I was then able to stick the (+) wire into the tube-part
of the solder lug. For the (-) wire I put a solder lug on one of the
four screws and soldered to it.

I ran clothesline from behind the rear element, along the phaseline, to
out in front of the front element.  The SO-239 and the rear junction are
tied to the clothesline.  This keeps the phaseline nice and taught.  I
then tied 50-lb fishing line through little holes in the four ends of the
front and rear elements, and tied them reasonably tight, as parallel as
I could manage.

My RG58 feedline runs vertically up to the feedpoint.  I tied it around
the SO-239, to take tension off the conector and to form a rain-loop.  The
impedance at the feedpoint is right for 50-ohm coax. 

If you have room for a 20m dipole, you have room for one of these!  For
other bands, just remember, the elements are 1/2 wavelength, the phaseline
is 1/8th. I'd really like to hear from anyone who builds one of these, and
let me know if anyone has questions.  My thanks to W4RNL for his article
and all the work he put into it. 

-- Tim N1PAZ