[AMPS] Re: The Worldwide, No Holds Barred, SWR Quiz.

Jon Ogden jono@enteract.com
Mon, 4 Oct 1999 23:27:37 -0500


measures wrote:

>>Not if the impedance of your transmission line is the same is the 
>>impedance of your source.  Draw it out on a Smith Chart, Rich.
>>
>€  In this case, the impedance of the source/generator is zero ohms, the 
>characteristic impedance of the half wavelength transmission line is 93 
>ohms, and the termination is 50-ohms. 
>
>>You move along a constant VSWR circle with 50 Ohms as the center of that 
>>circle.  The radius of the circle is the magnitude of the VSWR.  This 
>>assumes a 50 Ohms sytem and a Smith Chart normalized to 50 Ohms.
>>
>"This is assuredly not a 50 ohm system due to the presence of the half 
>wavelength 93-ohm coax."

Rich,

MUST you debate everything?  Even when somebody agrees with you?

It IS a 50 Ohm system because you are defining the measuring device as 50 
Ohms.  Therefore, you want to see what the SWR with a 50 Ohm device is.  
So you use the 50 Ohms as your characteristic impedance.

Now, you are correct in that it matters not what the impedance of your 
source is.  I thought more about this.  All that is being done in your 
example is using a 50 Ohm instrument to measure the VSWR.  And at the 1/2 
wavepoint in the 93 Ohm coax we have a 50 Ohm impedance, hence the 
instrument reads 1:1 SWR.  It matters not if the meter and the source are 
matched or not since the meter is only interested in what is after itself.

Please though, Rich.  I agree with you.  Enough debating on this!

73,

Jon
KE9NA

-------------------------------------
Jon Ogden
KE9NA

http://www.qsl.net/ke9na    <--- CHECK IT OUT!  It's been updated!!!!!


"A life lived in fear is a life half lived."


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