From: Andy Griffith [w4uld@bmd.clis.com]
Sent: Tuesday, September 26, 2000 2:51 PM
To: 'fmederos@adinet.com.uy'; 'grbait@hotmail.com';
'kc1tf@sierrael.com'; 'Ken Ball'; 'Jerry and Moe'; 'ppagel@arrl.org';
'sch1103@aicon.net'; 'schwab.kl@gateway.net'; 'scotty@tonks.com';
'TEHatton@aol.com'
Subject: 2M/440 MHz. J-pole Feedback

Feedback

2M/445 J-Pole Modifications

To help answer a question from a reader of my article in October 2000 QST, I built another antenna according to the plans in the article. In my haste I drilled the 5/8 in. holes in the stand-off insulators at too high a speed and allowed the spade bit to wobble a little. This resulted in oversized holes in the stand-offs so that the 445 MHz. elements would not stay in place and the insulator was too loose on the upper and lower elements. I suspect that other builders will run into the same problem. To correct the problem I cemented small lengths of 1/2 in. PVC pipe adjacent to the holes in the stand-off insulator. The problem should not occur if 1/2 in. PVC pipe is used for the stand-offs. However, as pointed out in the article, a drill press and vise will be required to get accurate alignment of the holes.

Cut ten 3/8 in. long pieces of 1/2 in. PVC pipe (the same pipe used for the center insulator) and slit them with a hacksaw just like the center insulator. The pipe sections will be placed on each 445 MHz. element above and below each stand-off insulator, below the stand-off on the lower main element, and above the stand-off on the upper element. The one on the lower element must be installed at the same time as the lower stand-off during final assembly of the antenna. After soldering the feed point and placing the center insulator in its final position, place the 445 MHz. elements and the stand-offs in their proper position. Initially install each 3/8 in. piece of PVC about 1/2  in. away from the stand-offs. Swab the 1/2 in.. space between the 3/8 in. pieces of PVC and stand-offs with PVC cement. Swab around the holes in the stand-offs. A small cotton swab on a stick such as a Q-tipR  should be used. The swab that comes with the cement is too large and messy. Finally, push the 3/8 in. pieces into place tightly against the stand-offs. Make any needed adjustments quickly while the cement is liquid. Allow the assembly to cure for at least two hours. 

73, Andy - W4ULD
