[Amps] Input SWR revisited

[donroden at hiwaay.net]

Gerald,

I am not ignorant of transmission line theory.
I maintained high power UHF klystrons for many years, and fed  
kilowatts out of a 50 ohm transmitter into 70 ohm 6 inch lines.

Just don't make a blanket statement that line length doesn't matter  
without being VERY specific.

Don W4DNR



Quoting TexasRF at aol.com:

> Don, the swr at the 100 ohm end of the 75 ohm coax is 100/75=1.333.
>
> In the case the 75 ohm coax is 1/4 wavelength long the impedance at the
> other end is 75/1.333 or 56.26 ohms.
>
> The swr at the 56.26 ohm end of the 75 ohm coax 75/56.26=1.333.
>
> The swr anywhere along the 75 ohm coax is 1.333.
>
> The swr inside the coax matters because it determines the what the end
> impedance will be with a given source impedance.
>
> It is not so much that we "care" what the swr is, but knowing the swr just
> makes it easy to calculate what the load impedance will be with a given
> source  impedance. It gives us a chance to use a little science instead
> observing "the  magic".
>
> 73,
> Gerald K5GW
>
>
>
>
>
> In a message dated 1/14/2015 2:12:46 P.M. Pacific Standard Time,
> donroden at hiwaay.net writes:
>
>>  But, the swr inside the 75 ohm coax is still 1.333 at all points along
> the
>> cable.
>
> No, not at either end.
>
> Why does the swr  "inside" the coax even matter when we are discussing
> load and source  impedances ?
>
>
> Don  W4DNR
>
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