Re: Eugene Radio Happenings

Andy Brown

Normally referred to as 2A-B IMD.

This is the second most common form of third order intermodulation distortion. (second page down)

Receiver intermodulation occurs as the results of two or more high-level off-channel signals overloading the receiver’s RF amplifier causing it to operate in it’s nonlinear region thus acting as a mixer. Older radios may not employ an RF amp and go straight into the first mixer.

It may be difficult to determine where intermodulation is occurring because the new frequencies being generated are precisely the same whether they are generated in the receiver front end, transmitter PA or some other non-linearity. Inserting a 6 db. attenuator in the receiver front-end will attenuate “transmitter” intermod by 6 db. “Receiver” intermod will be attenuated more rapidly because both signals A & B are simultaneously reduced by 6 db each.

Are the 103.7 and 102.3 transmitters close to each other? See: