I have converted quite a few DB-224 antennas that were originally used in the 155 mHz range down to the 146 mHz range by adding a folded aluminum tubing stub to the top and bottom of each element. Using the folded tubing from a defunct TV antenna I flatten about 3 inches on one end and then wrap it around the top and bottom loops of the antenna. A hole drilled through the flattened metal allows a screw and nut to be used to clamp the stub to the element. There is no dissimulator metal problem with this aluminum to aluminum connection.
After installation I cut the length of the stub to 2 inches. This has brought every antenna I have modified down to the 146 center frequency without having to modify the harness. SWR is not perfect without the harness mod, but is sure a lot less trouble. These antennas are perfectly usable with no modification at all in the ham band, but an improvement in the SWR can be had with this simple mod. This mod has been discussed on this forum several times. 73 - Jim W5ZIT --- On Fri, 1/15/10, [email protected] <[email protected]> wrote: From: [email protected] <[email protected]> Subject: [Repeater-Builder] Celwave/Sinclair, etc. antenna conversion to 2-Meters? To: [email protected] Date: Friday, January 15, 2010, 9:40 PM Several years ago, I found an article on the internet about converting the typical 150-174 MHz folded-dipole VHF antennas to 2-Meters. The article had each folded dipole element electrically "lengthened" by drilling a hole at the bottom and the top of each aluminum tubing element, and mounting a small bolt and nut - thus lengthening the overall electrical length of the element and lowering the resonant frequency. Possibly the coax harness was also rebuilt. The article I'm thinking of had nice color pictures and was a very well done web page article. I haven't been able to find this article, using Google and using the terms that I thought would be a good match. Does anyone remember this article and know what the url might be? These antennas often pop up surplus for cheap (often free), and they're very stout. I see in the catalogs that some versions are rated at 120 MPH wind velocity, and have a 6-year warranty! I've just been given one, too, and it appears to be almost brand-new. It would be a shame to just send it to the metal recyclers when I know there have been good conversion articles. Thanks and 73, Larry ____
