Input vs. Output

[Jeff Goldman]

Gordon,

You have the formula correct but your usage is not correct.

In your work to figure "p", you reversed the power forward and 
reflected.

p= 5/100, NOT 100/5

Therefore the formula should be SWR=(1+SQRT5/100)/(1-SQRT5/100)

SWR=(1+.223)/(1-.223)
SWR=1.57

73,
Jeff, K3DUA




On Dec 11, 2005, at 9:36 AM, GPBATEY wrote:

> Mel
>
> Most any handbook will have the info.  The following is from the
> 1988 ARRL handbook, page 16-2.
>
> VSWR = (1 + p) / (1 - p)
>
> where
>
> p = SQRT (Power reflected/ Power Forward)
>
> and SQRT is Square Root
>
> there fore if
>
> Power Forward = 100 watts
>
> and
>
> Power Reflected = 5 watts
>
> p= SQRT ( 100/5)  = SQRT(20) = 4.47
>
> and then
>
> VSWR= (1 + 4.47) / (1 - 4.47) = 5.47/-3.47 = -1.57
>
> The minus sign is neglected.
>
> thus the SWR is 1.57 to 1
>
> Hope that this helps.
>
> 73 Gordon WA4FJC
>
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