Does the cable length has impact on SWR measurement?

[puffo]

SWR measurement

I have an old HP SWR meter (those with changeable detector).
It is a passing SWR meter, it must be inserted in the trasmission line between generator and load.
The question is:
The lenght of cable between generator and meter, and between meter and load has impact on the result of the measure ??? (suppose that cable attenuation is trascurable)
Someone has saying to me that those cable must be lenght an entire multiple of lambda; is it true ??

 

[sergio mariotti]

Re: SWR measurement

The lenght of cable between generator and meter, Is LESS important
But the length of the line between meter and load is MORE important.
But it depend on what do you mean as DUT.

The DUT starts at the Meter connector and stop at the load. So you'll observe the VSWR of the ensemble cable+load.
As you certainly know, from the transmission lines theory, a line (cable) N*λ/2 long (N≥1, integer), and if the loss = 0 dB, so that cable is invisible. But it's true only for extremelly thin bandwidth.
If that cable has the same Zo of the meter and loss=0dB, once again the cable is invisible at all frequency.

But practically the cable is lossy and is mismatched.
So, for my opinion, the VSWR meter should be placed as close as possible to the DUT.