I see in the Wikipeadia entry for SWR meters the following:

"When not actually measuring VSWR, it is best to remove the ordinary type
of passive SWR meter from the line. This is because the internal diodes of
such meters can generate harmonics when transmitting, and intermodulation
products when receiving. Because active SWR meters do not usually suffer
from this effect, they can normally be left in without causing such
problems."

I have seen this advice from time to time, and having done some back of the
envelope calcs, I wonder at the accuracy of it.

Has anyone seen reports of measurements of the level of harmonics and IMD
products in the main line caused by the diodes of VSWR meters?

Owen