from FB group Building Transistor Radios 2018-11-19
IMPORTANT
I used to work for a guy who did radio engineering and would
troubleshoot problems such as this ‘bleedover’. For convenience some
radio stations colocate their transmitters near or at the same site.
Because the signal strengths are very high, the two stations can cross
modulate their signals and give sum and difference signals. This can be
caused by rust and/or corrosion on metals especially if they are
dissimilar metals. Copper oxide was once used for rectifiers. So if
the interference is heard on more than one receiver, it could be the
radio stations or something nearby is causing the problem. This has
been called the Rusty Bolt Effect. If this can be verified, the radio
stations should be notified so they can take remedial action.
