The W7LPN 2 - 440 Vertical Collinear Antenna Project
with a 6 Meter Surprise!
by W7LPN ~ Rick Frazier


I would like to share with you my findings and my design of the well known vertical collinear antenna, by looking at the work of two other hams:

http://www.repeater-builder.com/antenna/n1bug-construction.html

And: http://home.comcast.net/~ross_anderson/sc.htm 

I morphed these two ideas and came up with a truly commercial grade antenna you can build at home.

The simple colinear antenna is honestly too long, gangly and tall to be practical.

You may immediately see the possibilities of combining these two projects or meeting them in the middle.

The more common coax collinear requires a PVC radome to give it rigidity and weather proofing, and assembly can be difficult.
The "Simple Collinear" is very long, gangly, and heavy, requires several guys, and is difficult to raise. ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
The 2 - 440 Collinear vertical in this project is simple to build and expand, semi rigid, self supporting, water tight, electrically sound, and a professional appearance when completed.
 
Getting Started:

First look at my drawing below, and decide how long an antenna you want to have up, approximately. Then sketch it out. Start at the bottom with a 1/4 wave 19" section and a 1/2 wave 38" section separated by the feed point.
Keep in mind that each 1/2 WL section adds approximately 2.14dB.

Note in picture above, the outer most portion of the antenna is the aluminum tubing.

I started with 3/4" and 1/2" fiberglass tubing from Max-Gain and 0.79" and 0.59" aluminum antenna stock from MFJ.

Assemble 0.79" fiberglass tubing sections with 2 part epoxy (not putty), with short sections of 1/2" fiberglass inserted to reinforce the joints.

Run a long #22 wire inside the entire length of fiberglass while assembling. It is much more difficult to thread afterwards if you don't. When soldering or attaching #22 wire ends, remove any coating down to bare wire.

Leave plenty extra length at each end for pulling and attaching at each section. Too much epoxy can gum up your project and hang up the thin wire.

NOTE: Element sections are numbered starting at bottom of antenna.
A 12" section of 1" PVC glued over the bottom end of the fiberglass flush with the end acts as a good mounting stub.

Directly above that, place #1 element, a 19" X 0.79" aluminum tubing (1/4 wl) section. Directly above this, drill a hole in the fiberglass large enough to pull the shield and center conductor of your coax through.

Then place #2 element a 38" X 0.79" section directly above this, allowing access to the drilled whole.

Use Ox-Guard or Penetrox and rivets or screws to secure the shield to the lower element pulling it laterally and down.
 
Then pull the center conductor through the hole using caution to separate them, pulling up and away from the shield connection.

As in the drawing, pull the thin wire through the hole with a hemostat, or tweezers and pull out a little working length.
 
Cut a strip at both ends, attach by soldering to the shielding near the connection you just made.
 
Drill another hole between #2 & #3 elements, pull the wire snug and attach the wire to the bottom end of #3 with screw or rivet.
Repeat the process between #2 and #3 elements.

Attach a wire at top end of #2.
Pull it through a whole between #3 & #4 elements.
Cut an trim and repeat this process and finish with 1/4 wl X 0.59" aluminum connected only to the thin wire.

Thus you can see #1 skips to #3, #2 skips to #4 etc, until you terminate at the 19" end stub.

Some final construction notes:
Start with 1/4wl -19" at the bottom and end with 1/4 wl -19" at the top, the middle is expandable. I placed ferrite beads over the coax about 38" below the base of the antenna, adjust distance for best SWR.
Keep in mind, the greater the difference between the diameter of the
tubing and the size of the thin wire, and the larger the tubing, the lower the SWR, broader the bandwidth, and the easier the tuning.
 
Sealing each joint.
I used hot glue and shrink tubing. The tip:
I filled with hot glue and pulled a short piece of heat shrink inside itself and to the side, then shrunk it over the end.

Finished antenna in picture above works fine... about 6.5 dB.