What is Intermodulation??? (017) 

Glad it was helpful! :-)

Boy, ya! I can see that happening! I just never thought of where the IM products would end up.

​@@eie_for_you I deal with this particular scenario all the time, from the perspective of the aeronautical radio that is. It can be PIM but it can also be poorly desgined or implemented transmitter combiner. Basically one TX is leaking over to another TX and mixes in the finals. Unless the combiner takes account of that possibility those products will get radiated.

First, intermodulation is the result of undesirable mixing/multiplication of signals. 😞 There is a desirable version of this mixing/multiplication of signals. 🙂 It is through this process of multiplication that we get the needed mixing products required by receivers. For instance, you are tuned to a 3 MHz signal on the front end of your receiver. By multiplying this 3 MHz signal with a 2.545 MHz local oscillator, you get a 455 KHz signal as one of the mixing products to send into the Intermediate Frequency (I.F.) stages where all of the filtering and signal processing takes place. Demodulation is at the end of the I.F. "pipeline" which is followed by your audio amplifier and speakers. Here is the mathematical expression for this multiplication/mixing process: If we have two signals, one of frequency A and another of Frequency B, then cos (A) * cos (B) = 0.5*cos (A-B) + 0.5*cos (A+B) So, if we have A = 3 MHz and B = 2.545 MHz, then the output of the perfect multiplier would be 3 + 2.545 = 5.545 MHz and 3 - 2.545 = 0.455 MHz The I.F. stages are tuned to only accept the 0.455 MHz signal. The 5.545 MHz signal is thrown away. Hope this helps to understand this.