Hi Jim, That's what I was looking for!
Do you have any oxidation/connection issues where the tubing is wrapped around & screwed together? Perhaps drilling a hole through the original element for connection might be better. Just wondering. Thanks for the tip!! Tim W5FN --- In Repeater-Builder@yahoogroups.com, Jim Brown <w5...@...> wrote: > > I have modified several of the 155 mHz center frequency DB-224 antennas to > the ham band. I found that it takes a 2 inch extension to each end of each > dipole to move them down. My mod was done empirically by taking a single > dipole and hooking it to an analyzer and finding the original center > frequency to be ~ 155 mHz. With the 2 inch extension added to each end, the > center frequency moved down to 146 mHz. I did not have to modify the harness. > > I make the extension out of a scrapped TV antenna with rolled tubing > elements. I flatten the tubing so that it can be wrapped around the dipole > at the center point of each end and put a single screw through the wrapped > flat portion of the TV tubing to clamp it to the dipole. When all assembled, > I measure the distance to the end of the tubing from the 224 dipole and cut > the extension to 2 inches. This moves the center frequency of the completed > DB-224 mod down to 146 mHz from 155 mHz. > > 73 - Jim W5ZIT > > --- On Wed, 8/19/09, tahrens301 <tahr...@...> wrote: > > From: tahrens301 <tahr...@...> > Subject: [Repeater-Builder] DB-224 Matching > To: Repeater-Builder@yahoogroups.com > Date: Wednesday, August 19, 2009, 8:40 AM > > > > > > > > > > > > > In my quest to get rid of desense with > > the Quantar, someone mentioned that having > > the 'wrong' antenna could make the desense > > worse. > > > > I've got a DB-224 - not the 'ham' version, > > but the 150-160 MHz version, and there is > > a bit of a mismatch. > > > > Has anyone ever had any desense that they > > could attribute to less than perfect matching? > > (I'm not talking about a gross problem, like > > one of the elements broken, etc) > > > > Has anyone built a 'tuner' for that version > > of the 224, so that the transmitter/ duplexer > > pair would see a better SWR? > > > > If this thing ever gets up, it's gonna be > > perfect! :-) > > > > Thanks, > > > > Tim W5FN >
