On Friday 24 May 2002 15:43, Steve Katz wrote:
> > If 1kW 'forward' results in 10W coming out of the 'forward' line, doesn't
> > 10W
> > also end up in the terminating resistor on the 'reverse' line?
>
> [Steve Katz] Isn't the reverse line termination power diminished by
> the return loss? That is, if VSWR = 2.0, then reverse line power would be
> 10W reduced by 10dB, or 1W?
The forward and reverse lines don't know which way round they are, they both
pick up forward and reverse power from the through line. The reverse output
delivers the coupled reverse power in isolation only because the coupled
forward power is absorbed by the terminating resistor on that line - the
accuracy of the match between that resistor and the pickup line Zo is a big
factor in determining the directivity of the coupler.
Looking at it another way, the reverse line has a 50 ohm termination on one
end, and a 50 ohm power meter on the other and it reads the reverse power. If
you swap the resistor and power meter round, it's the same as your forward
line - whatever the power meter reads is being dissipated in the resistor
normally (I think).
Steve
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