[AMPS] SWR and line length, etc.

[Jon Ogden]

measures wrote:

>>>> I think that the indicated SWR minimum will always correspond to zero
>>>> reactance.
>>
>>No, that's not correct necessarily.  A 100 Ohm termination used in a 50 
>>Ohm system has no reactive components.  Adding a 1/8 wavelength of 50 Ohm 
>>transmission line will make that 100 Ohm real load look purely reactive.  
>
>€  Weird Science.  

How is that Weird Sceince, O Great One?

Or do you say that the Smith Chart is not correct and that all the people throughout the world who use it are wrong?

If I have a 50 Ohm piece of coax in a 50 Ohm system and my load is 100 Ohms, at a point 1/8 wavelength toward the exciter, the polar angle of my impedance vector is -90 degrees.  This indicates a purely reactive condition with no real component.  You end up with the impedance being 0 - j30 Ohms - capacitive.

Now if I am wrong, someone please point it out.  The Smith Chart is a mapping that you can overlay on an X-Y axis where the Y-axis is the imaginary or reactive component and the X-axis is the real component.  If the value of the X coordinate is zero at some particular point that therefore implies that it is a completely reactive point!

How is that weird science?

73,

Jon
KE9NA

--------------------------------------------------------------------------
The Second Amendment is NOT about duck hunting!


Jon Ogden

jono@enteract.com
www.qsl.net/ke9na

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


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