"Cecil Moore" wrote in message
...
Sal M. Onella wrote:
A non-linear junction mixes two or more signals ...

I once had a cracked/cold solder joint in a 40m downspout
vertical that seemed to partially rectify the source
signal generating undesirable harmonics on 15m detected
by another ham 1/2 mile away. A jumper across the bad
junction cured the problem.

Yup. Navy ships have from a few dozen to several hundred such jumpers,
depending on ship type. Many are welded but some are bolted, especially if
the object must be moved for use, etc.

I have heard that hams who use a tin roof as an HF ground plane are apt to
generate harmonics.

Sal