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Re: Need clarification on RF related concepts

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On 16.10.16 09:44, dakupoto@gmail.com wrote:
> Could some electronics guru please help ?
> I am a bit rusty on some RF concepts so I
> request some clarifications from the gurus
> here.
>
> By definition, a 4:1 balun has 4 times
> the impedance on the balamced side as the
> unbalanced side. For any inductor, the
> impedance is based on the reactance, which
> in turn is based on the frequency of
> operation.
>
> So, what frequency is being considered
> here ? The reason I ask is that a balun
> could be used as broadband impedance
> matching device. Thanks in advance for
> your help.

A balun is a matching element between a balanced and
an unbalanced transmission line. The 4:1 balun is
in its simplest form an auto-transformer (2 identical
windings connected in series). The center tap is connected
to the unbalanced side ground, one of the ends is
connected to both the unbalanced non-grounded wire and
one of the balanced wires. The remaining end of the transformer
is connected to the remaining balanced line wire.

There can be an impedance transformation of 4:1 using
a similar transformer, but connecting the center tap to
the unbalanced non-grounded line and connecting the
common end of the transformer to ground wires of both
low-impedance and high-impedance line. The non-grounded
high-impedance line it taken from the top end of the
auto-transformer.

A similar effect can be achieved using transmission lines.
If we have a feed of impedance Z0, we can connect it to
a pair of lines of impedance 2*Z0 in parallel. If the
other ends of the lines are connected in series, there
will be a connection of impedance 4*Z0, but there is
a requirement to prevent current flow outside the transmission
lines, to prevent part of the circuit being short-circuited.
This can be achieved by coiling the lines on a suitable magnetic
core, creating an auto-transformer on low frequencies and
a transmission-line transformer on high frequencies.

Google gave pretty good responses to 'trnasmission-line transformer'.

-- 

-TV

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Need clarification on RF related concepts dakupoto@gmail.com - 2016-10-15 23:44 -0700
  Re: Need clarification on RF related concepts amdx <nojunk@knology.net> - 2016-10-16 04:37 -0500
  Re: Need clarification on RF related concepts Phil Allison <pallison49@gmail.com> - 2016-10-16 05:14 -0700
    Re: Need clarification on RF related concepts amdx <nojunk@knology.net> - 2016-10-16 08:04 -0500
  Re: Need clarification on RF related concepts Tauno Voipio <tauno.voipio@notused.fi.invalid> - 2016-10-16 17:36 +0300
    Re: Need clarification on RF related concepts dakupoto@gmail.com - 2016-10-16 23:27 -0700
      Re: Need clarification on RF related concepts amdx <nojunk@knology.net> - 2016-10-18 08:44 -0500
        Re: Need clarification on RF related concepts Phil Hobbs <pcdhSpamMeSenseless@electrooptical.net> - 2016-10-18 11:06 -0400
        Re: Need clarification on RF related concepts "Michael A. Terrell" <mike.terrell@earthlink.net> - 2016-11-07 13:38 -0500
          Re: Need clarification on RF related concepts George Herold <gherold@teachspin.com> - 2016-11-07 11:00 -0800
            Re: Need clarification on RF related concepts "Michael A. Terrell" <mike.terrell@earthlink.net> - 2016-11-09 18:35 -0500
              Re: Need clarification on RF related concepts Jeff Liebermann <jeffl@cruzio.com> - 2016-11-09 19:59 -0800
                Re: Need clarification on RF related concepts "Michael A. Terrell" <mike.terrell@earthlink.net> - 2016-11-12 08:46 -0500
          Re: Need clarification on RF related concepts "nuny@bid.nes" <Alien8752@gmail.com> - 2016-11-07 11:09 -0800
            Re: Need clarification on RF related concepts "Michael A. Terrell" <mike.terrell@earthlink.net> - 2016-11-09 18:22 -0500
  Re: Need clarification on RF related concepts Tim Wescott <tim@seemywebsite.really> - 2016-10-16 14:28 -0500
  Re: Need clarification on RF related concepts rickman <gnuarm@gmail.com> - 2016-10-17 04:04 -0400
    Re: Need clarification on RF related concepts "Tim Williams" <tiwill@seventransistorlabs.com> - 2016-10-18 07:00 -0500
      Re: Need clarification on RF related concepts Jeroen Belleman <jeroen@nospam.please> - 2016-10-18 16:45 +0200
  Re: Need clarification on RF related concepts Jasen Betts <jasen@xnet.co.nz> - 2016-10-17 09:43 +0000

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