<div style="margin: 0in 0in 0pt"><span style="font-size: 18pt">Johnand Don,

You give a good explanation of mixing, but are slightly missing the 3IM point.

With transmitters, there is sometimes some undesirable power output at multiples of the frequency, which are referred to as harmonics. Sometimes in a receiver, this harmonic is mixed with a fundamental frequency, and produces a third order intermodulation distortion product, aka 3IM. The important point to stress, is that it is generated in the receiver. I have seen on more than one occasion, people using equipment trying to monitor for 3IM, and this is an invalid test. The only place to monitor is inside the receiver that is exhibiting 3IM symptoms, which is not practical in the field. </span></div><div style="margin: 0in 0in 0pt"></div><div style="margin: 0in 0in 0pt"><span style="font-size: 18pt">What can be done? Good quality transmitters, good quality receivers, and spacing are all good approaches. Receivers should be double conversion, or utilize DSP as in the Castle Creations receivers. </span></div><div style="margin: 0in 0in 0pt"></div><div style="margin: 0in 0in 0pt"><span style="font-size: 18pt">Attached is a 3IM spreadsheet that I created. Please note that for any 2 channels of operation, there are 2 possible 3IM products that may be generated. </span></div><div style="margin: 0in 0in 0pt"></div><div style="margin: 0in 0in 0pt"><span style="font-size: 18pt">Dave</span></div><div style="margin: 0in 0in 0pt"><span style="font-size: 18pt">

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