What is transmitter noise interference?

Harmonic interference occurs when harmonics or multiples of a carrier frequency from the offending transmitter fall into the victim's band. The effects are similar to receiver desensitization. If the signal strength on the harmonic is high enough, it can either de-sense the receiver or in some cases completely drown out the intended signal. A spurious signal shows up on a spectrum analyzer as a spike. If this spike is strong enough, it can knock out the intended signal.