The WB3AYW MULTIELEMENT COLLINEAR ANTENNA

 

This is an introduction to a high gain VHF/UHF vertical collinear antenna program and project that can be an asset to many of you that are looking for more gain in a vertical antenna for base or repeater use. An added bonus is an extremely low angle of radiation!
The approximate gain is 9dbd+....not dbi!
WB3AYW uses this antenna in repeater operation.
The calculator program available for download to design this antenna is in xls spread sheet format and requires that you have a program that will read xls spread sheet files.

Instructions are included below for building the antenna in an example for 147.09Mhz. The antenna has about 4Mhz bandwidth so the measurements are not extremely critical except for the phasing coils.
The xls spread sheet comes with 2 program "sheets", each containing a different calculator program.
Sheet 1 (2) is used for building the antenna with a PVC housing covering the antenna.Sheet 1      is used for building the antenna without a housing. It uses fiberglass rods.

5 Element Design shown below is about 23 feet tall from the base!

(This antenna can be built with as many elements as desired. If want to build a 10 element design, it has about 13DBD gain at the horizon.

According to radiation coverage programs on the internet the phasing coil's actually add about 1DB extra gain for each coil to the antenna gain.)

Above typical non operating "graphic" from "Sheet 1"
 of the spread sheet xls calculator program.
DO NOT USE THE LENGTHS FROM THE GRAPIC ABOVE!
See building instructions below. They have been updated from an older version.

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Building instructions for the WB3AYW Collinear This instructions below have been updated from an older version for Two meters only.  147.09Mhz- 
The other bands and frequencies are similar.
Do not use the lengths from the graphic above! Download and Use the spread sheet calculator
 for other frequencies within the 2 meter band.

 

Get water pipe, (PVC) for hot/cold water at your building supply store, it is tanish / White.

 

Cut to 26 inches long for all coils assemblies.

 

Measure in on each end 3 1/4 inches and mark.

 

Measure the spacing between these marks and make sure they are 20 inches apart or per the program.

 

Drill a 1/8 inch hole through each mark all the way through the PVC pipe.

 

Measure out 3/8 inches from each hole and drill the same as the first set of holes. These are not as critical as for measurement as the first set of holes you drilled.  There will be a modification later to these holes.

 

Cut your #14 solid bare wire 80 inches long, one for each coil. Bend first end slightly and insert in first hole, then bend over more.

 

Measure 73 inches and mark or bend slightly as a stopping point on the wire for the length on the coils.

 

Wind 73 inches of #14 solid wire (per the program) on coil form tightly and stop, if using the correct tubing (as I use) the number of turns are 32.

 

Pull coil wire towards the other end of the PVC form letting it slide threw your fingers.

 

Feed the second end threw the inside hole on the other end and PULL TIGHT with pliers.

 

Bend over like you did on the other end; this keeps the coils the correct length.

 

If you do not pull the coil wire tight it will vary the length by about 1/2 inch and vary the frequency / phasing.

 

Trim the wire ends, to the length of the outside holes.

 

Make up all of your coil assembly's,  2, 4, 9 or what ever you want. It takes 4 coil assemblies for a 5 element design.

 

IN the PVC coil assemblies the outer holes; re-drill the hole at a slope next to the wire ends so your wire will slide through from the inside, out. 

 

Top radiator, bare 3 inches and make a small loop with your #12 stranded wire and solder the loop good, this will have all of the weight of the antenna on it.

 

Measure and cut  top element to 36 inches length (or per the program), this element is the only one, with end effect on it.

 

Bare about 3/8 inch and feed threw the center of the PVC and out threw the modified hole, and solder securely to the coil wire.

 

Cut all other (#12) wire elements to 36 1/2 inches long, or (to the program length).

Bare the #12 Stranded wires (3/8 inches) on both ends.

 

Feed through the center of the PVC and out through the modified hole that you re-drilled, making shure that it goes to the inter hole and solder to the coil wire.

 

Solder all connections as you go.

Do the same to all other elements.

 

Cut another piece of PVC 28 inches long.

 

Slide the 28 inch piece of PVC over the matching network or element above.

 

The matching section is made from 300 OHM Ladder Line, I use the Wireman's Ladder Line.

Cut Ladder Line to 18 1/2 inches, bare and bend the bottom to short it, solder the end shorting it.

 

Measure up, 1 7/8 inches from the short and bare the 2 wires of the Ladder Line about 1/2 inch.

 

This is the 50 OHM feed point. Use 4 feet of RG8X for pigtale section, it will fit inside of the PVC tubing.

 

Prepare your RG8X coax and solder to Ladder Line, feed point at the 2 inch point you bared.

The length of the Ladder Line needs trimming to length  17 1/2 inches.

 

Slide 28 inch piece of PVC up over the lower element or down over the matching section.

Solder the bottom radiator to the side with the coax center attached on the matching section.

 

RECHECK! and make sure the side of the ladder line connection, to the element is correct.

Put antenna up horizontally about 5 feet above ground and check VSWR, you should be lower in frequency than you want to be.

 

If the frequency is Low, then slide the 28 inch piece of PVC up over the matching network and trim opposite side (Short side) of the 300 ohm Ladder Line 1/8 inch at the time, to bring it up to frequency, putting the Ladder Line sleve back on each time. The sleve will change the frequency about 2 Megs.

 

Be careful as you cut only 1/8 th of an inch at a time. Then recheck VSWR.

 

When tuned the short side should now be about 17 inches long.

 

Seal all open wire connections for moisture. Seal up top and bottom of all elements sleves. The bottom sleve needs to be weathertight at the top to keep moisture out of the matching section.

 

Bees like to build nests, if not partly sealed on both ends.

 

Leave the 1/8 inch holes open on the side of the coils for water drainage.

 

The gain of the 5 element is about 9.46 DBD's (not DBI's).  Per my antenna program.

 

I am using a 8 element on my repeater in Blairsville, Ga. 147.09 +  PL100 at the present time.

Any problems or questions call me, 8AM till 4PM EST.  1 706 745 7099

My thanks to KK1CW for the original spreadsheet; without him this program would not be possible!

 

Leonard Shick    WB3AYW
Editors note: If any of these instructions are unclear to you, please contact the author of the article at: wwwb3ayw@windstream.net for questions.DOWNLOAD Spread Sheet Calculator

NOTE: The above Calculator program is an XLS file. You must be familiar with using this type of file. You will need a computer program that can open and read the file. It is suggested that you download the Open Office Org program called "Open Office". This is a free program that substitutes for the Microsoft Office program which is required to read the spreadsheet file and make the calculator work. Do a search on Google for Open Office.....if you need a very nice free office type program for reading and using xls files.

Instructions for using the spreed sheet calculator:
Download the xls spread sheet file here. Open it in your desired spread sheet program like Open Office mentioned above. Plug in your desisered center frequency where instructed and press Enter on your keyboard. The calculator will do the rest.

Typical Elevation Plots and Patterns

5 Element