Dave, Filipe, anyone..... my helix-wound vertical has a couple of elevated radials, which are not grounded. Everything sits above "ground", fed direct with 50 ohm coax, about 20 ohms R at feedpoint. I have a 2.5 : 1 SWR in the shack over about 60 KHz of the band. I haven't had it up very long so not much history with it yet. It seems to pretty well, but I'd like to see how it does if I can raise the feedpoint closer to 50 ohms. I'd like to try the hairpin coil, connected across the coax at the feedpoint. What's your opinion.... worth trying? Or should I be putting in a ground rod at the feedpoint to ground the radials and running the hairpin to that? (I could just try it but thought I'd get opinions first)
73, Jerry K3BZ -----Original Message----- From: Dave Mueller Sent: Wednesday, January 25, 2012 8:40 PM To: [email protected] Subject: Re: Topband: T Vertical feed Fil, My 80/160m antenna is configured identically to yours on 160m. Same dimensions. In my case, with 90 radials of various lengths, I measured an Rr of 16 ohms at the feed point. The SWR exceeded 2:1 in the shack. I use a hairpin coil recommended by K2KW (Team Vertical) to bring the impedance up to 50 ohms. Approximately 6 turns on a 10cm form between the feed point and ground does the trick nicely. Adjust turn spacing for minimum SWR. 73, Dave KH2/N2NL (/KH6 at the moment) On 1/26/2012 5:27 AM, [email protected] wrote: > Hi Everyone, > > just finishing puting up a T Vertical (exactly in T shape) using 2 > supports at the ends. > > The vertical portion is 18m and the T is 17m to each side (34m total). > > I am laying radials from 20m - 40m (have about 20 right now). > > My question is regarding the feeding of the antenna, should it be > straight with 50 Ohm cable? Should I make some impedance transformer? > (I have FT240-61) that I could use. > > Thanks for help, getting ready here for CQ WW cw 160M. > > 73's Filipe CT1ILT aka CR6K > > _______________________________________________ > UR RST IS ... ... ..9 QSB QSB - hw? BK _______________________________________________ UR RST IS ... ... ..9 QSB QSB - hw? BK _______________________________________________ UR RST IS ... ... ..9 QSB QSB - hw? BK
