-Don't expect anything for another month or so as I just arrived home after an extended vacation. I agree that most hams will have trouble handling even the most simple impedance matching information in the ARRL Antenna Book so when I can get something together on matching on the DB 224 I will submit it. AC
-- In Repeater-Builder@yahoogroups.com, "Chuck Kelsey" <wb2...@...> wrote: > > How about an article with examples to post at the Repeater Builder site? > > Chuck > WB2EDV > > > ----- Original Message ----- > From: "wa9zzu" <wa9...@...> > To: <Repeater-Builder@yahoogroups.com> > Sent: Friday, August 21, 2009 3:11 PM > Subject: [Repeater-Builder] Re: DB-224 Matching > > > > -Well guys, > > > > With all due respect to Jim and his tried and true dipole modifications in > > which he changes the load impedance presented to the cable harness which > > is in turn reflected to the 1st junction connected to the antenna pigtail, > > and all the others who do some sort of extensive dipole modification to > > get a resulting VSWR to their liking, I find that the simpliest and most > > rewarding, easiest, least labor intensive, not to mention least possible > > to create mechanical problems, is the addition of just two short lengths > > of 50 ohm coax at the antenna feed point coax, one in series and one in > > shunt, to a tee connector. This matching section has been done to several > > DB 224 antennas by my self with great success. > > > > No strain, no pain, and only a minimum of cost and time, with low VSWR > > over the 144-148 band. > > > > And I challenge any one to tell the difference in the gain of the DB224 > > using the original dipoles with my impedance matching section to the > > modified dipoles with the loss in the mismatch created in the antenna > > harness with the modified dipoles. > > > > All it takes is some effort with a Smith Chart and some simple coax cable > > construction after measuring the feed point impedance / VSWR at the band > > edge and the center frequencies from 144 to 148 MHz. All done at gound > > level. Simple matching stub design can be found and is well described in > > the ARRL Antenna Book, 13th edition on Pp. 122-126. > > > > I have done this same type of coaxial impedance matching on several of the > > DB 420 antennas as well with good results. > > > > 73 Allan Crites WA9ZZU >
