[Elecraft] KPA1500 Faulting for High SWR inappropriately

[David Woolley]

On 20/12/2022 01:38, Bob McGraw wrote:
> Use an antenna analyzer to determine the actual complex antenna 
> impedance.   I've always viewed SWR as more of a hocus pocus value, easy 
> value to obtain, but very broad in definition as it is a ratio between 
> two impedance, both usually unknown.

Whilst I'd agree that its usefulness is overstated, it is not the ratio 
of two impedances, and one of the impedances is generally known (unless 
you are measuring the the Lecher line way, by actually finding the 
voltage peaks and troughs on an open line, of unknown characteristic 
impedance).

I don't think the professionals have used for a very long time.  They 
prefer s parameters, or if they want a single number, they use return 
loss.  It is basically only heavily used in the amateur and CB communities.

Generally it is defined assuming an ideal transmission line, with a 
purely resistive impedance. and in that case, the only time that it 
equals a ratio is when the load impedance is also purely resistive.

The main advantage of SWR is that it can be physically measured without 
having to use anything other than the magnitude of the voltages read 
(i.e. no phase information).  But this means that the same SWR can be 
completely safe or destroy a PA, depending on the phase information.

-- 
David Woolley