Hi Thomas.

Great text art!  Love the bicycle with the antenna.

And you're quite right.  I've done smith charts on the rubber duckies and
there is no way they are 50+j0.  At the high frequencies it's amazing how
hard it is to get rid of that j factor.  Best I was ever able to do was what
I've got posted at:

 http://www.autoartisans.com/images/WORM-433-2.03.jpg

John Dammeyer


> Subject: RE: [OT] What does 20+j10 mean?
> 
> 
> A "proper" antenna resonant is purely resistive...
> So 50+j0 would represent a 50 ohm antenna.
> 
> BTW MOST antennas are NOT 50 ohms!
> 
>   *
>   |  __O    Thomas C. Sefranek  WA1RHP@ARRL.NET
>   |_-\<,_   Amateur Radio Operator: WA1RHP
>   (*)/ (*)  Bicycle mobile on 145.41MHz PL74.4
>  
> ARRL Instructor, Technical Specialist, VE Contact.
> http://hamradio.cmcorp.com/inventory/Inventory.html
> http://www.harvardrepeater.org
> 
> -----Original Message-----
> From: piclist-bounces@mit.edu 
> [mailto:piclist-bounces@mit.edu] On Behalf Of
> John Dammeyer
> Sent: Thursday, February 01, 2007 3:54 PM
> To: 'Microcontroller discussion list - Public.'
> Subject: RE: [OT] What does 20+j10 mean?
> 
> Hi Marcel,
> 
> Brings up an interesting question.  Should an antenna that is 
> supposed to
> have a 50 Ohm impedance be 0+j50 or 50+j0 or 25+j25 or some 
> combination?
> Granted this is theoretical but I'm curious.
> 
> John Dammeyer
> 
> 
> > 
> > 
> > Paul,
> > yes, it is a complex number. j = sqrt(-1) (like 'i' in mathematics).
> > In the case of impedances, the imaginary component is the 
> reactance -
> > this is impedance contributed by inductive or capacitive elements,
> > whereas the real component is the resistance. So if you 
> have a 10 ohm
> > resistor and a 1 milli-Henry inductor in series, the impedance at a
> > frequency of 1KHz is R + j * w * L = R + j * (2 * Pi * 1K) 
> * 1m = 10 +
> > 6.29j .
> > 
> > On a Smith chart (since you're talking about matching), the 
> reactance
> > circles are the ones that all start on the right real axis and
> > intersect the outer circle. The ones in the positive half are
> > inductive, the ones in the negative half are capacitive.
> > 
> > Cheers,
> > - Marcel
> > 
> > On 2/1/07, Paul Anderson <wackyvorlon@gmail.com> wrote:
> > > This is a term I've seen when reading about impedance matching
> > > circuits, but thus far I haven't found an explanation of 
> > it's meaning.
> > >  It has to do with the impedance of the circuit, and it's 
> always of
> > > the form x+jy or x-jy.  Like 20+j10 or 20-j10.  Is it 
> reference to a
> > > complex number?  Any help is greatly appreciated.
> > >
> > > --
> > > Paul Anderson
> > > VE3HOP
> > > wackyvorlon@gmail.com
> > > http://www.oldschoolhacker.com
> > > "May the electromotive force be with you."
> > > --
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