W2I - COLLINEAR WIFI OMNI ANTENA 2010

• Coil wire diameter: 1.5mm
• Coil OD: 6mm
• Coil pitch: 3.5mm center to center
• Tube diameter: 3mm
• Tube length: 56.5mm

PARTS LIST:
Below is the complete parts list with prices I paid:

• (2) 12" long 3/64" diameter brass rod 2x$.59
• (2) 12" long 3/32" diameter brass tube 2x$1.09
• (1) 12" long 11/32" diameter brass tube $1.99
• (1) 2ft long 1/2" diameter PVC pipe $0.10
• (1) 1/2" diameter PVC end cap $0.29
• (1) N-female panel jack $4.50

CONSTRUCTION:

Below is my assembly procedure:

NOTE: Try to be as accurate as possible in cutting the parts and spacing them during assembly. .5mm accuracy is difficult but at least try to get within 1mm of what's specified. Otherwise, you may be sorely disappointed with the performance of your finished product. I used a pair of vernier calipers extensively during the construction of this antenna.

1. Hold a piece of 3/64" brass wire against 9/64" drill bit and wind 4 turns, each turn separated by about 3.5mm. Leave about 10mm of straight wire before the turns and 24mm after the turns. Adjust the spacing of the turns with needle nose pliers while the coil is still on the drill bit. Bend the ends neatly with the needle nose pliers. Repeat until you have 4 coils.
2. Cut four 57mm long pieces of 3/32" tubing and one 91.5mm long piece. I used the cutter on a pair of needle-nosed pliers to cut them; this flattened them, which is not bad because the hole in the tubing is actually a loose fit. Next, I used the needle-nosed pliers to squeeze the tubing until the hole opened up large enough to pass the wire into it. Finally, I filed the tubing smooth, which took off about .5mm off its length.
3. Cut a 30mm piece of 11/32" brass tubing. I used a hacksaw and mitre box.
4. Solder the 91.5mm long tube to the center pin of the N-jack. This is the feedline
5. Slip the 30mm tube over the 91.5mm tube, and solder to the N-jack. This tube is the decoupler. The feedline must be supported in order to keep it from shorting on the decoupler; I slid a piece of rubber hose over the feedline.
6. Solder a coil to the feedline, leaving about 3mm of wire between the feedline and the start of the coil.
7. Solder a piece of 3/32" tubing to the other end of the coil, leaving 22mm of straight wire between the last turn and the tubing.
8. Repeat until you get to the top of the antenna.
9. Cut the PVC pipe to the proper length to enclose the antenna and glue on the end cap.
10. Cut pieces of foam to support the antenna inside the PVC pipe - I stuffed the foam into the coils - and carefully slide the antenna into the pipe.
11. Attach the N-jack to the other end of the pipe. You can screw it onto a flat end cap if you can find that style. I chose to just tack the N-jack directly to the pipe with hot glue. Then, I used epoxy over the hot glue for strength and heat resistance.

DONE:

W2I-2010