Jim, I think you will be better served going a different route. Most
likely, your feed point R will be around 2 Ohms with a jX ranging from 0 to
300 Ohms, assuming your feeder is between 50 and 100 feet in length. Not so
good. Tell us more about the height of the flat-top, the length of your
feeder, and how the feeder hangs with respect to the flat-top.
Consider joining the transmission line conductors together at the feed point
and loading the antenna as a vertical with a T-top hat. This configuration
would require some radials. I am sure you will notice an improvement in
performance. Your tuner will be happier.
Larry W6UB
----- Original Message -----
From: "Jim Reid" <jimr.reid@verizon.net>
To: <tentec@contesting.com>
Sent: Tuesday, October 21, 2003 12:16 AM
Subject: [TenTec] ~ 1/4 wave 160 doublet
> Aloha,
>
> I posted the following on the Top Band reflector hours
> ago; so far it has not appeared there nor in their archives.
> Strange reflector that one; puts out what appears to be
> some kind of digest every several hours!
>
> Anyway, here is my questions:
>
> Longest wire I can get up here is my 80/40 meter
> W7FG doublet about 125 feet long; center fed via
> 600 ohm ladder line. So, it is about 1/4 wave on
> 160 metes.
>
> Using my tuner, with extra capacity
> switched in at the output capacitor to yield about
> 450 pf at the output, I can reach an indicated
> vswr of about 1.7:1.
>
> However, it seems to me that feeding a 1/4 wave
> antenna at the center is not the right thing to do!
>
> So, given the achieved vswr here at the input of the
> tuner, is it "safe" to use, feed the set up some power?
> Seems that a LOT of voltage may sit at the tuner.....?
> Capacitors in the tuner are rated at 6kv. Tuner inductor
> is rated at 5kv, 30 amps.
>
> For use with balanced ladder line, this particular
> tuner uses a 1:1 current type, Ferrite core balun
> at the tuner input, not as is usual at the output.
>
> A a few years ago I was invited to take down my very
> long wires I was using on 160; the wires happened to
> cross plantation land leased by someone else!
>
> Should I try this set up? After thinking about this for
> a time, it seems that maybe the maximum current area
> will be in the balanced ladder line feed, and thus, my
> rigs power will be canceled in the far field! But at least,
> some signal would be getting out on 160 from Kauai.
>
> 73, Jim KH7M
>
>
>
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