Intermod Support Forums

Intermod is an application that uses Visual Basic with an MSExcel front-end. It calculates possible intermodulation products within wireless microphone systems. Intermod includes tools to help the audio engineer drill down the massive amount of data, to a smaller set of most significant results, allowing better selection or elimination of elements in a given system.

Please take a look at the screenshots and the online instructions.

For futher information please contact: intermod “@” brightandloud.com

Screenshots:

Frequency input and filter setup page

All Results Display

Worst Case Display

Intermod theory

Calculating intermods for a set of numbers is described by the formula:

M
--

IM product = /  a[i] * f[i]
--
i=o

Jim Brown explains this in plain English like this:

Let the frequency of signal #1 be A, the frequency of signal #2 be B, the frequency of signal #3 be C. For any combination of signals A and B, you have the potential for beats at all combinations of the sum and difference of their fundamentals and harmonics. The most common combinations which give us grief are A+B, A-B, 2A-B, 2B-A, 3A-2B, 2A-3B, and so on. For three signals, you can have beats at A+B-C, A-B+C, and B+C-A.

As you can imagine, large numbers of frequencies or large numbers of Orders produce a very large number of calculations that need to be performed and checked. For instance, checking 24 frequencies to 5th order produces over 2 million results.

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