Topband: T Vertical feed

[Jerry Keller (K3BZ)]

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: topband at contesting.com
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, ct1ilt at sapo.pt 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