Tune Around!

CQ-Calling All Hams!
About Hamuniverse
Antenna Design
Antenna Safety!
Ask Elmer
About Batteries
Code Practice
Computer Help
FCC Information
Ham Hints 
Ham Radio News!
Post Reviews 
Product Reviews
Ham Radio Videos!
HF & Shortwave

License Study
Midi Music
Reading Room
Repeater Basics
Repeater Builders
RFI Tips and Tricks
Ham Satellites
Shortwave Listening
Support The Site
Vhf and Up
Site Map
Privacy Policy
Legal Stuff

Advertising Info



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

Download the updated and easier to build (12-08) version
It is a pdf file and is under 1 meg file size. Adobe Reader required.
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:


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.

I wasn't completely satisfied, leaning toward the side of perfection, so I did take it back down, took some pictures and added another 1/2 wave element and ran the coax thru the ferrite beads 3 times at 38" as per the calculator on the other collinear site linked earlier in this article, and then tied down the coax firmly. I won't make any other adjustments. The photo you should see above is of the antenna with 4 sealed joints, 1/4 wave at top and bottom, and 3 X 1/2 wave elements in the middle (14ft.total).

The Lime mountain repeater is 100 miles away from my QTH and my ham friend says my signal is full quieting on 5 watts!

I was honestly pleasantly surprised by the performance of this antenna.
Resonant on 6 meters too! Really!
It has very low swr on 6! Cool eh? My ham partner lives about 10 miles away and with the power all the way down we talked thru the repeater and simplex on 6 meters. Cool!
So you might call this project "The 2 Meter / 440 / Magic Band / Surprise Antenna" HI!
Further testing on 6 meters in progress! More to come?

Final comments:
There's something about the simplicity of alternating thin wire and large tubing which goes together so easily with good results. One thing I've learned is the greater the difference between the sizes of tubing vs. the wire, the better the SWR and broader the bandwidth.

This appears to be a truly high-gain home-brew project well within the abilities of the average home-brew tinkerer and the surprising ability to also be used on 6 meters was certainly an unexpected plus!

I like the fact that it is easily expandable, and a relatively simple design and each time you add another 1/2 wave section....more gain!

Editors Note: Upon doing some math, it appears that the entire length (14 feet) is acting as a (near) 3/4 wavelength antenna on 6 meters! Further testing in progress!
Radiation pattern and gain on 6 meters unknown,
but it works!

Have FUN!
Rick W7LPN



Hamuniverse.com uses Green Geeks Web Hosting!