[TenTec] ~ 1/4 wave 160 doublet

[Larry Rockfield]

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 at verizon.net>
To: <tentec at 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
>
>
>
> _______________________________________________
> TenTec mailing list
> TenTec at contesting.com
> http://lists.contesting.com/mailman/listinfo/tentec
>