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[TowerTalk] Parallel dipoles

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Subject: [TowerTalk] Parallel dipoles
From: ik0hbn@libero.it (Sante - IK0HBN)
Date: Mon, 01 Oct 2001 20:18:42 +0200
Thanks to all answered my message. This is a GREAT reflector and answers 
never missed in 5 years...when asking help.

By the way, one afternoon job left me with 30 and 17 meters legs perfectly 
matched, but no way to have a SWR less than 2.1 on 12 meters legs. I must 
say that all the sistem is under a C3XL tribander and to achive a good 
match on 30, the boom must be turned perpendicular to the dipoles. Beside 
the little noise of turning beam to 90 degrees, now I must find the way to 
have even the 12 meters working. At moment, no way to add another 
balun/coax, so the stuff must share the same coax. MFJ read impedance of 26 
ohm and a Xs of 21, very high as I could see. As usual, any following hints 
will be greatly  appreciated.
TIA
Sante
At 09.25 01/10/01 -0600, you wrote:

>Hello Sante,
>
>As I recall from a triband wire vertical project, the higher
>band elements needed to be LONGER than normal due
>to interaction effects.
>
>One of my favorite WARC band antennas is a 20M dipole
>(34 ft total length) fed with ladderline and a balanced antenna
>tuner.  This provides a figure 8 pattern from 10 through 30M
>with beamwidths from 50 degrees on 10M where it acts as
>two half waves in phase to 90 degrees on 30M where it is a
>short dipole (2/3 size).
>
>Performance on 30M could be improved slightly by using a
>40 ft center fed dipole instead which will be two half waves
>on 12M (and 1.25 WL on 10M as a double extended Zepp).
>
>de  Tom  N4KG
>
>
>On Mon, 01 Oct 2001 Sante - IK0HBN <ik0hbn@libero.it> writes:
> >
> > Hi,
> > I need your help. I must redo 2 dipoles hanged down to the same
> > coax. They
> > got broken due to the age of wires, so I choice using thicker wire.
> > Involved bands were 30 and 17 meters. Having to do the job I have
> > thought
> > adding even the 12 meters band so to have that band running here. My
> >
> > questions are:
> > a) Is it possible sharing a single balun for 3 dipoles? I guess YES.
> >
> > b) Have I trying trimming them when ALL linked to the balun, or
> > should I
> > cut one dipole at time, removing it, and after putting up another to
> > be
> > trimmed?
> >
> > c) If the first option should be preferred, of course trimming one
> > band
> > legs, resonance on the other 2 bands will move, so  from which band
> > I have
> > to start trimming? IE. Do I begin bringing at resonance the 30
> > meters band
> > first with the other 2 at place (linked to balun) or should I start
> > from 12
> > meter? - My question take place from the evidence that cutting one
> > band,
> > the others two move enough.
> >
> > I have a MFJ-269 for the job.
> >  From the balun the 3 dipoles run slightly separated so to have them
> > at
> > ground about 1 meter between them.
> > Any possible help/hint will be greatly appreciated here.
> > TIA
> > Sante
> >
> > --
> >                                    \\||//
> > THIS MESSAGE WAS SENT BY:         (.)(.)
> >
>-----------------------------oOOo--(__)--oOOo----------------------------
> > Sante Lillo, IK0HBN                   | Home  telephone:
> > +39-0761-407543
> > Localita' Saineta, 3                  | Fax on request : as above
> > 01030 Bassano in Teverina (VT) Italy  | Cell. telephone:
> > +39-0338-6825052
> > E-Mail: ik0hbn@libero.it              | packet:
> > IK0HBN@IK0MIL.ILAZ.ITA.EU
> > Home Page: <http://www.qsl.net/ik0hbn>| DX cluster : IK0HBN >
> > I0JBL-6
> >
>-------------------------------------------------------------------------
> >
> >
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-- 
                                   \\||//
THIS MESSAGE WAS SENT BY:         (.)(.)
-----------------------------oOOo--(__)--oOOo----------------------------
Sante Lillo, IK0HBN                   | Home  telephone: +39-0761-407543
Localita' Saineta, 3                  | Fax on request : as above
01030 Bassano in Teverina (VT) Italy  | Cell. telephone: +39-0338-6825052
E-Mail: ik0hbn@libero.it              | packet: IK0HBN@IK0MIL.ILAZ.ITA.EU
Home Page: <http://www.qsl.net/ik0hbn>| DX cluster : IK0HBN > I0JBL-6
-------------------------------------------------------------------------


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