[ARC5] ARC5 Digest, Vol 105, Issue 155

Thu Oct 25 21:25:14 EDT 2012

Hi guys i had a 19set #2 M xyl and 3 cats were in the basement when i
sterted the dynamotor the cats took off to hide under a bed my xyl shook
her head as she left the basement owell      73    darryl    ve3cpo

On Thu, Oct 25, 2012 at 12:53 AM, <arc5-request at mailman.qth.net> wrote:

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> Today's Topics:
>
>    1. Re: Why an UNUN? (Neil)
>    2. Re: Why an UNUN? (Neil)
>    3. Re: Why an UNUN? (Mike Feher)
>    4. Re: Why an UNUN? (J. Forster)
>
>
> ----------------------------------------------------------------------
>
> Message: 1
> Date: Thu, 25 Oct 2012 15:58:21 +1300
> From: "Neil" <neilb at ihug.co.nz>
> Subject: Re: [ARC5] Why an UNUN?
> To: "arc5" <arc5 at mailman.qth.net>
> Message-ID: <338D1B49C9D640969376EEC1D3C96068 at neilb>
> Content-Type: text/plain;       charset="iso-8859-1"
>
> > The 13 seems a bit high. Is there a lower limit given also? I don't have
> > that manual to hand.
>
> I've seen a figure of 5 ohms, but I can't recall where.
> Most likely on this very forum.
>
> 73 de Neil ZL1ANM
>
>
> ------------------------------
>
> Message: 2
> Date: Thu, 25 Oct 2012 16:03:13 +1300
> From: "Neil" <neilb at ihug.co.nz>
> Subject: Re: [ARC5] Why an UNUN?
> To: "arc5" <arc5 at mailman.qth.net>
> Message-ID: <DDCC699C353D4EEFA36F27E37DD44CA0 at neilb>
> Content-Type: text/plain;       charset="iso-8859-1"
>
> > A transmitter does not present a "load" as such to the input end of a
> > transmission line.
>
> Actually it does, to the power reflected from a mismatch.
> And in the real world, there is ALWAYS reflected power,
> no matter how minute.
>
> 73 de Neil ZL1ANM
>
>
> ------------------------------
>
> Message: 3
> Date: Wed, 24 Oct 2012 23:38:11 -0400
> From: "Mike Feher" <n4fs at eozinc.com>
> Subject: Re: [ARC5] Why an UNUN?
> To: "'arc5'" <arc5 at mailman.qth.net>
> Message-ID: <[email protected]>
> Content-Type: text/plain;       charset="us-ascii"
>
> About 25 or more years ago I bought a mint WS-19 at the Vienna hamfest. I
> just had to put it on the air. Read up on it and I figured I at a minimum
> needed a 1to 4 matching transformer. So, I built one. A simple coaxial on a
> toroid and placed it in a small box. Right away I was able to load up my
> WS-19 and worked all over the place with it. Never used a series capacitor.
> When I got a BC-474A, I also used it with it with amazing results. Again,
> no
> capacitor. Then came a brand new TCS, and, same results. In my opinion it
> is
> the simplest, no mod, remedy to get a rig designed for a short antenna on
> the air.
>
> Mike B. Feher, N4FS
> 89 Arnold Blvd.
> Howell, NJ, 07731
> 732-886-5960
>
>
>
>
> ------------------------------
>
> Message: 4
> Date: Wed, 24 Oct 2012 21:51:50 -0700 (PDT)
> From: "J. Forster" <jfor at quikus.com>
> Subject: Re: [ARC5] Why an UNUN?
> To: "mac" <w7qho at aol.com>
> Cc: ARC-5 List <arc5 at mailman.qth.net>, Mike Hanz
>         <aaf-radio-1 at aafradio.org>
> Message-ID:
>         <1154.12.6.201.149.1351140710.squirrel at popaccts.quikus.com>
> Content-Type: text/plain;charset=iso-8859-1
>
> >
> >
> >
> >
> >
> > On Oct 24, 2012, at 6:45 PM, J. Forster wrote:
> >
> >>
> >> Not really.
> >
> >
> > Yes really
> >
> >
> >>
> >> A transmitter, like a battery or other power supply, can be modelled
> >> as a
> >> Thevinin Equivalenrt, an ideal Voltage Source in series with an Output
> >> Impedance.
> >
> >
> > The equivalent circuit of a class C amplifier would look like an AC
> > (RF) voltage source with a very low internal resistance.
> >
> >
> >
> >>
> >> There is a circuit theory theorem that, for maximum real power
> >> tranfer,
> >> the load impedance should be equal to Complex Conjugate of the source
> >> impedance.
> >
> > We're not talking about maximum power transfer here.  A Class C amp is
> > designed to provide a particular power output at a high efficiency,
> > not maximum power transfer which results in an efficiency of 50% .
> > You''re thinking of class A.
>
> The class of the amplifies has nothing to do with the conditions for
> maximum power transfer fron the transmitter tank to the antenna.
>
> -John
>
> ====================
>
> > This means equal to, if the source and load are purely resistive.
> >
> >>
> >> This means if one is inductive, the other must be capacitive, and the
> >
> >
> > We keep the load resistance seen by the PA tube purely resistive here
> > with our resonant tank circuit.   In practice we strive to present the
> > amplifier with a purely resistive load if possible. Small values of
> > reactance reflected into the tank circuit can be accommodated by
> > tuning adjustments.  In those cases where the reactive components are
> > too large external antenna 'tuners" are employed.
> >
> >
> >> inductive reactance equals the capacitive reactance.
> >>
> >> This means if the source is complex (resistive + inductive), the
> >> load must
> >> have a load where the resistive componants are equal and the
> >> capacitive
> >> reactance is equal, and opposite, to the source inductive reactance.
> >>
> >> ie:  The L & C are resonant at the operating frequency.
> >
> > See above
> >
> > Dennis D.  W7QHO
> > Glendale, CA
> >
> >
>
>
>
>
> ------------------------------
>
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> End of ARC5 Digest, Vol 105, Issue 155
> **************************************
>