How about an article with examples to post at the Repeater Builder site? Chuck WB2EDV
----- Original Message ----- From: "wa9zzu" <[email protected]> To: <[email protected]> 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
