By Becky Pell • April 26, 2019 A screenshot of Shure's Wireless Workbench RF coordination software – Starting with the IEM systems, I switch off the first transmitter and see if all RF signal disappears from the associated pack. If it does, happy days, it’s clear; I switch the transmitter back on and do the second one, and repeat the process for every transmit/receive pair. If any receiver is not completely “quiet” (i.e., interference and intermodulation free when its own transmitter is switched off and everything else is switched on), I set it to one side and come back to it at the end – if I have to retune anything then I’ll repeat this process until everything is quiet. – Next I do the same with the mic systems, switching off each transmitter in turn and making the sure the receiver goes quiet. This is the most time-consuming process of the day, but the time spent here reaps dividends later – it’s vital to not only be using clear frequencies, but that all of those frequencies play nicely together. (Some frequencies interfere with one another even though they are miles apart in the spectrum, in a phenomenon called intermodulation; and the more frequencies you use, the greater the potential for this to happen). – Once all of this is set, I send pink noise to the left then right of each bodypack in turn (shows up any patch boo-boos and lets me know that there are no hums on one side or the other) and line check the mics. Then it’s time to… – Walk the room. I test out the end user’s experience before I hand them their RF equipment – I walk the performance space with their pack (not a PFL pack on engineer mode – that won’t tell me if there’s anything wrong with their hardware) and talk to myself in the mic the whole time. This way I’ll experience any problems for myself and have time to fix them before the band walks on stage. Common Downfalls Be aware of the effect that LED screens have on RF. They transmit low-level interference, so you may need to play around with optimum antenna placement. If there’s just a single backdrop screen it shouldn’t be too bad, but if it’s an entire stage made from LED screen, as on one tour I worked, it may be time to enlist the help of an RF expert. Be aware that RF hates metal. Wireless gear does not play well with metal hardware, so keep packs off of metal belts, costume parts, and the like, and also make sure antennas aren’t resting on metal walls or truss – ideally they’re located at least 3 feet away from them. It’s all to do with an interesting phenomenon called the Faraday effect. Plan for the worst-case scenario. I always have a couple of spare bodypacks on dedicated frequencies ready to go, and I also carry several extra hardwired packs. A couple of them are always patched into the system, ready to go if needed. It’s imperfect if the performer needs to move around, but in an emergency it will get her/him through the gig. Another option when facing an unworkable RF nightmare is to go mono with the IEM systems – again, deeply imperfect, but a mono signal is much less susceptible to interference than stereo as well as throwing further, so if you’re truly stuck it can be a “the show must go on” option. Although this is a simple guide that is adequate for most monitor applications, RF is a highly complex and fascinating subject, and it’s always great to increase your knowledge. There’s a wealth of additional resources online at sites like ProSoundWeb, I also highly recommend attending the training offered by manufacturers like Sennheiser and Shure. As with everything about touring, be practical and systematic in your approach to wireless and you’re well on the way to having an enjoyable and trouble-free gig! Read the rest of this post 1 2 3 About Becky Becky Pell Becky Pell is a monitor engineer with more than 20 years of experience in live sound. She toured as a monitor and RF tech with Black Crowes, Travis and Kylie Minogue before moving behind the desk to mix monitors for artists such as Aha, Muse, Westlife, Anastacia and Take That. Read more from Becky at SoundGirls.org. http://SoundGirls.org Comments Have something to say about this PSW content? Leave a comment! Cancel reply Scroll past the ”Post Comment” button below to view any existing comments. Your email address will not be published. Required fields are marked *Comment Name * Email * Website This site uses Akismet to reduce spam. Learn how your comment data is processed. Tagged with: Becky Pell Bodypacks Diversity IEM Interference intermodulation LED Receivers RF Sennheiser Shure Transmitters Wireless Wireless Systems Manager Wireless Workbench · all topics Subscribe to Live Sound International Subscribe to Live Sound International magazine. Stay up-to-date, get the latest pro audio news, products and resources each month with Live Sound. Subscribe Today!