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@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@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
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UR RST IS ... ... ..9 QSB QSB - hw? BK
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UR RST IS ... ... ..9 QSB QSB - hw? BK
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