[Antennas] Baluns and tuners

Fri, 7 Jun 2002 12:05:10 -0700

> -----Original Message-----
> From: Darryl J. Kelly [mailto:[email protected]]
> Sent: Thursday, June 06, 2002 5:51 PM
> To: Jan Reimers; Antennas Email Group (E-mail)
> Subject: Re: [Antennas] Baluns and tuners
> 
> 
> Jan,
> Don't know what kind of antenna you will be using, but if 
> it's a regular
> dipole, I would use a 1:1 balun. You can use coax from the 
> tuner to the
> balun, I have one in the attic, and then 300 ohm twinlead to 
> the antenna. 

OK that would be nice if I could use coax.  But there will be high SWR on
the line (multiband dipole) so I thought that in that case the coax would be
very lossy compared to for example home made AWG14 twin lead.

>I
> have used 300 ohm twinlead for several years with no 
> problems. I am using a
> better quality twinlead, Channel Master, I think. 

Do you run your antenna way off resonance?

> The 
> twinlead needs to be
> kept away from metal masses, and tensioned a little between 
> the antenna and
> place it leaves the building do it won't sway in the wind too 
> much. Max
> power here is 100+ watts. I also use a 4:1 balun at the 
> antenna with my
> off-center fed vee, but it is more of a tuned antenna than a 
> random length
> dipole that is used on different bands.

OK so it sounds like you don't run high SWR on the 300 Ohm twin lead then?

> Also my home brew 
> balanced tuner
> does a much better job feeding a balanced line than the 
> output of an MFJ T
> type tuner with a 4:1 toriod balun in the output. Like the recent QST
> article, almost no RF in the shack anymore with the balanced 
> tuner, and no
> bothering the computers. Hope this is of interest.
Sure is.  I might build a balanced tuner one day, but right now I only have
one roller inductor, so as a first go around I like to get on the air with
my unbalanced tuner.

73 Jan VA7JNR

> 73,
> Darryl, KK5IB
> 
> ----- Original Message -----
> From: "Jan Reimers" <[email protected]>
> To: "Antennas Email Group (E-mail)" <[email protected]>
> Sent: Thursday, June 06, 2002 5:07 PM
> Subject: [Antennas] Baluns and tuners
> 
> 
> >
> > Thanks again to everyone who helped out with my balanced 
> tuner question.
> The
> > Richard Measures article was very informative.
> >
> > I have managed to build a simple Pi network tuner (unbalanced) with
> > a roller inductor, and would like to use it to feed 
> parallel line going to
> > some sort of wire antenna (I suppose I'll start with a 40M 
> dipole).  So I
> > need a balun between the tuner and the feedline.  I have purchased a
> ferrite
> > core for this purpose (man these traditional parts are hard 
> to find!).  I
> > also have some 300 Ohm "radio shack special" flat line, but 
> I could also
> > make a higher impedance parallel line with thicker wire and 
> Plexiglas
> > spreaders.  I plan to run max 100W but with high SWR 
> between the tuner and
> > antenna. I have never done any of this before so here are 
> my novice level
> > questions:
> >
> > 1) Is the 300Ohm flat line suitable, or would I be much 
> better off making
> my
> > own (more manly) feedline?
> > 2) Should I wind the balun in a 4:1 arrangement, or do I 
> need to closely
> > match the resistance ratio of the antenna feed line and 
> tuner output (even
> > though the antenna Z will be jumping around depending on 
> what band I am
> on).
> > The only reason I prefer 4:1 is that the ARRL antenna book tells me
> exactly
> > how many turns to do for 4:1.
> > 3) Once I wind the balun how do I know it works?  i.e. How 
> do I know I
> have
> > the right number of winds and that the current on the 
> feedline is really
> > balanced.  (I am the proud owner of 1 voltmeter and 1 SWR 
> meter, not much
> > more!)
> >
> > Thanks
> > Jan (VA7JNR)
> > - - -
> >
> > Your moderator for this list is:
> > Larry Wilson KE1HZ [email protected]
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> 