All coils have loss so its a decision as to which one do you want? If the
coax loss is minimal and the amp loads into it thats the one Id take and
then add radials until there is no further meaningful change on the antenna
analyzer.
Carl
KM1H
----- Original Message -----
From: "Jerry Keller (K3BZ)" <k3bz@verizon.net>
To: "Dave Mueller" <daven2nl@gmail.com>; <topband@contesting.com>
Sent: Wednesday, January 25, 2012 9:56 PM
Subject: Re: Topband: T Vertical feed
> 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
>
> _______________________________________________
> UR RST IS ... ... ..9 QSB QSB - hw? BK
>
> _______________________________________________
> UR RST IS ... ... ..9 QSB QSB - hw? BK
>
>
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_______________________________________________
UR RST IS ... ... ..9 QSB QSB - hw? BK
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