Shure Whiteboard Session: What is Intermodulation?

Welcome back, in this week’s whiteboard session, we’re going to tackle the often misunderstood concept of intermodulation.

Intermodulation is a product of two signals interacting with each other while on air simultaneously. It commonly occurs when two signals are in very close proximity to one another, and therefore, any intermodulation need to be avoided with careful frequency coordination.

Shure Whiteboard Sessions: Intermodulation

How Does Intermodulation Occur?

In theory, when we coordinate our wireless system we can avoid interference issues by ensuring each system is programmed onto its own operating frequency. We then switch both systems on, and they transmit happily on their own channel without interfering with each other, right? Well, sort of, but there’s a little more to it than that, as I’ll now explain:

When a wireless microphone is programmed to a given frequency, it does indeed transmit at the set frequency. At the same time, however, the transmitter also produces additional signal at given intervals, much in the same way as a musical note is made up of one fundamental frequency and lots of additional harmonics.

Intermodulation occurs when the harmonics of one wireless channel interact with the fundamental frequency of another wireless channel to create intermodulation products in the form of new signals on a different frequency. The first example in our video shows how this occurs when we take double the frequency of channel one, and we subtract frequency two; the result is a portion of spectrum that we can no longer use for the clean operation of wireless systems as the intermodulation product is now occupying this space.

The more systems we have online, the more intermodulation products are created, which makes coordination more difficult, but also critical. Check out the video below for a clear demonstration of intermodulation and how you can mitigate the risk of interference.

Signing Off

We hope you found our brief overview of intermodulation helpful. To learn more about how to successfully coordinate wireless systems, consider attending one of our Wireless Mastered or Wireless Workbench training sessions. To ensure you don’t miss our next whiteboard session video, please subscribe at LosingYourVoice.co.uk or simply enter your details below. If you missed last week’s video, check it out, here. See you next week!

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Marc Henshall

Marc forms part of our Pro Audio team at Shure UK and specialises in Digital Marketing. He also holds a BSc First Class Hons Degree in Music Technology. When not at work he enjoys playing the guitar, producing music, and dabbling in DIY (preferably with a good craft beer or two).

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2 Comments

  • Steve Caldwell says:

    Dont forget, Intermodulation can also occur as Receiver based IM, as well as transmitter based IM. In this instance, the Intermod product is actually generated inside the receivers’ (or antenna preamp, or distro) amplifier components. The IM product is not actually present in the air, only inside the receiver electronics. This occurs most often when too much preamp gain is used, or high power transmitters are used, regardless of their proximity to each other.

    • shureUK says:

      Thanks Steve, great point. It’s always tricky to know what to leave out in these sessions. We still need to talk about getting you set up as a contributor. A lot of our readers could really benefit from your knowledge on the subject 🙂 All the best!

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