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

To: <amps@contesting.com>
Subject: [AMPS] Re: The Worldwide, No Holds Barred, SWR Quiz.
From: measures@vcnet.com (measures)
Date: Tue, 5 Oct 1999 03:38:02 -0700
>
>measures wrote:
>
>>>The SWR in a 50 Ohm system then is 1:1.  In a 93 Ohm system 
>>>you would have the SWR mismatch of 1.86:1, 
>>
>>?  Even though there is a half wavelength of 93 ohm coax between the gen. 
>>and the termination, the system is not 93 ohms.  It is 50-ohms at both 
>>ends of the half wavelength albeit-mismatched transmission line.
>
>Correct.  I wrote the statement above yours and in my entire post 
>specified the system as a 50 Ohm system.  
>>
>>> but in a 50 Ohm system, our 
>>>VSWR is 1:1.
>>>
>>?  If the termination were changed from 50 to 100-ohms, it would look 
>>like 100-ohms at the generator and there would be no reflection at the 
>>halfwave point. 
>
>Not exactly, Rich.  If the load impedance is 100 Ohms and the transmission 
>line impedance is 93 Ohms and the source is at 50 Ohms you can't say this.
>
?  The generator Z was never stated.  It is zero ohms.  

>If the source is 100 Ohms and the load is 100 Ohms, then you are correct.  
>There would be no reflection.
>>
>>>So the bottom line is that if you have a 50 Ohm load and a 1/2 wavelength 
>>>of coax that it matters not what the impedance of that coax is!  It's 
>>>inherently narrow band, but that's the case.
>>
>>?  Agreed.  However, above you claimed that the SWR is 1.86:1.
>
>I never did.  I always claimed the SWR is 1:1 at the halfwave point in 
>this 50 Ohm system.  

?  sorry for the blunder. 

>If I define my characteristic impedance (system 
>impedance) as 93 Ohms, then I do have a 1.86:1 SWR.  But your original 
>question revolved around a 50 Ohm system.
>
?  The original questions:  

"Questions 1 and 2:  

A 50-ohm termination is connected to a generator through a one-half 
wavelength, 93 ohm characteristic-Z  coaxial cable.  

What is the SWR as measured at the generator with a 50-ohm 
characteristic-Z  SWR meter?  

What is the SWR with a 93-ohm characteristic-Z  SWR meter?"
--------
You gotta get yo' ducks lined up.  

-  Rich..., 805.386.3734, www.vcnet.com/measures.  


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