[ARC5] Receiver input impedance.

[Leslie Smith]

Looking at the circuit for the BC-946 (similar to R23 etc) I see the
tank circuit is connected to the antenna (or the aerial if you live in
Australia) by a trimmer cap.  According to the theory (and working in
the ideal) the impedance of a parallel tank  circuit at resonance is
very high (infinite, for the idealist) and so the advantage in matching
an antenna to THIS load comes from stepping-up Z from 50 ohms to a
higher Z.  However, if the loop is also tuned to resonance, it will have
a similar high impedance (infinite for the idealist) and so there is no
need for a matching device.

This is why the signal "peaks" when the trimmer is adjusted.

That's my "teary" of how "de aerial" woiks.

So:   we have just seen "our" Sandy wreck havoc in New Jersey & co.
I invite group members to take the same approach with posting ....
To echo  the words of Paul Goebells,  "[Group] rise Up, and Let the
Storm Break Loose"

I wait, with anticipation, for the foist postings to appear  ...

Go for it ...

-- 
  Leslie Smith
  vk2bcu at operamail.com


On Wed, Oct 31, 2012, at 13:39, Richard Knoppow wrote:
> 
> ----- Original Message ----- 
> From: "Kenneth G. Gordon" <kgordon2006 at frontier.com>
> To: <Arc5 at mailman.qth.net>
> Sent: Tuesday, October 30, 2012 12:30 PM
> Subject: [ARC5] Receiver input impedance.
> 
> 
> > Does anyone have accurate data on the BC-453B receivers' 
> > antenna input
> > impedance?
> >
> > I need to build an UN-BAL to match my BC-453B to a 3 foot 
> > diameter
> > Stoddart loop which is fed with twin-ax.
> >
> > I have the Stoddart data, but need the other data.
> >
> > My particular BC-453B does not have the loop connections.
> >
> > Can anyone help?
> >
> > Kenneth G. Gordon W7EKB
> 
> 
>      If you know someone with an RF impedance bridge its 
> easy to measure the actual impedance at the antenna input. 
> Someone on this list may have the equipment and be within 
> reasonable distance. I suppose it could be calculated from 
> the values of the input tank but I can't tell you 
> specifically how.
> 
> 
> --
> Richard Knoppow
> Los Angeles
> WB6KBL
> dickburk at ix.netcom.com 
> 
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