[Antennas] Baluns and tuners

Thu, 6 Jun 2002 19:50:56 -0500

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