>Vic Rosenthal wrote:
>
>>>
>>> >What is the SWR as measured at the generator with a 50-ohm
>>> >characteristic-Z SWR meter?
>>>
>>> ? At the end of an any characteristic.-Z halfwave transmission line, the
>>> termination Z repeats itself -- with a reactance reversal. . Since
>>> there is no reactance in this termination, the Z at the end of the 93-ohm
>>> halfwave line is 50 +/- j0 ohms, the SWR is 1:1.
>>
>>No. It is correct that the impedance seen by the generator is 50 ohms but
the
>>SWR is unchanged, regardless of the line length. The SWR is entirely
>>determined by the impedances of the line and the load.
>
>This isn't correct, Vic.
>
>In a 93 Ohm system, the SWR is unchanged. However, we are attempting to
>measure a 50 Ohm load in a system where 50 Ohms is our base (the SWR meter
>has been specified as being 50 Ohms and the exciter is also assumed to be
>at 50 Ohms).
>
>At a half wavelength of coax, you rotate completely around the VSWR circle
>and thus see the impedance of the load at the input of the coax.
? indeed.
>In this
>case, the load is 50 Ohms. At the half wavelength of coax, the load is 50
>Ohms as well.
? ok
>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.
> 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.
>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.
- Rich..., 805.386.3734, www.vcnet.com/measures.
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