(And It’s Not Your Imagination)
By Dawie Nolte · Nolte Productions
If your wireless microphone has suddenly started dropping out, hissing or losing range — even though nothing has changed — you are definitely not alone. Here’s what’s really going on.
If you’ve been in this industry as long as I have, you’ll know the feeling. A wireless system that’s been rock solid for five, ten, sometimes even fifteen years suddenly starts dropping out, hissing, or picking up random interference — and nothing on your end has changed. Same venue, same setup, same gear you’ve trusted for years.
I get calls about this more and more, and I want to walk you through what’s actually going on, because understanding it can save you a lot of frustration (and a few embarrassing moments in the middle of an event).
It’s Not Your Gear. It’s The Airwaves Around It.
Wireless microphones don’t just make up their own frequencies — they operate in the UHF radio spectrum, sharing that space with television broadcasters and, increasingly, mobile phone networks.
Think of the radio spectrum as a giant parking area. For years there were plenty of open parking bays for wireless microphones to use. Then, almost overnight, most of those bays were reserved for someone else. Your car hasn’t changed, but suddenly it’s much harder to find a place to park.
That’s essentially what’s happened to wireless microphones in South Africa.
As the country moved from analogue television to digital television, a large portion of radio spectrum became available. Rather than leaving it unused, ICASA allocated much of that spectrum to mobile broadband services such as 4G and 5G. In 2022, these frequencies were auctioned to South Africa’s mobile network operators, and by 2023 broadcasters had moved out of much of the affected spectrum.
The result is that wireless microphones now have a much smaller section of spectrum available in which to operate.
Today, most wireless microphone systems operate in the lower UHF television band, roughly 470MHz to 694MHz, although certain licensed and specialised applications may legally use other portions of the spectrum depending on current ICASA regulations and the equipment involved.
Many older wireless systems, however, were designed to operate much higher in the spectrum. Those frequencies are now occupied by mobile networks, leaving older equipment with fewer clean frequencies to choose from.
So if your wireless system has suddenly become less reliable, it doesn’t necessarily mean it’s failing. In many cases, the radio environment around it has simply become a lot busier than it was when the system was first installed.
Why Some Brands and Models Feel It More Than Others
This is where I often get asked:
“But Dawie, my friend’s system works perfectly — why is mine acting up?”
It usually comes down to how frequency-agile your system actually is.
Older fixed-frequency or narrow-band systems — including some earlier Sennheiser EW and Shure UHF models — were designed around the spectrum available at the time. Their tuning range simply doesn’t extend far enough, or scan intelligently enough, to avoid today’s mobile network activity.
Newer frequency-agile systems (such as Sennheiser’s EW-DX and Digital series, Shure’s QLX-D, ULX-D and Axient ranges, along with more recent AKG and Samson digital systems) are generally much better at scanning the available spectrum, avoiding interference and selecting cleaner frequencies.
That doesn’t mean they’re immune to problems. They still need to be rescanned and properly coordinated for each venue instead of simply being switched on and expected to work.
Multi-channel systems are even more demanding. The more wireless channels you run in one venue, the more important proper frequency coordination becomes. Otherwise you can end up with intermodulation, where two or more frequencies interact and create a new “ghost” frequency that interferes with another channel.
With less spectrum available than there used to be, there’s also less room between channels. Frequency plans that worked perfectly five years ago may now cause problems in exactly the same venue.
If your system hasn’t been rescanned in the last year or two, that alone could be the cause of your problems.
The Basics Everyone Forgets: Line of Sight, Placement and Antennas
Spectrum congestion gets blamed for a lot of problems that are actually caused by basic RF setup.
UHF radio signals behave a lot like light — they travel best in a straight, unobstructed path. Every wall, LED screen, metal structure, flight case or even a crowd of people between the transmitter and receiver weakens the signal before interference even becomes a factor.
Line of sight matters more than most people realise. A performer walking behind a solid set piece, a pillar, or even through a dense crowd can cause dropouts that have nothing to do with frequencies at all. If the dropout happens in exactly the same place every time, first look at what’s physically blocking the signal before changing frequencies.
Receiver placement is another area where I regularly see avoidable mistakes.
Some simple guidelines I give every client are:
- Keep receivers up high and in the open — not buried in a rack at floor level, behind an LED wall or inside a closed flight case.
- Position receivers as close as practical to the performance area with the clearest possible line of sight.
- Keep receiver antennas away from Wi-Fi access points, intercom systems and other RF transmitting equipment.
- In larger venues, consider remote-mounted antennas and a proper antenna distribution system rather than trying to squeeze multiple receivers into one rack.
Antenna positioning is equally important. Most professional systems use diversity reception, where two antennas work together to minimise dropouts caused by signal reflections. For this to work properly, the antennas should be angled apart in a shallow “V” shape — roughly 45° to 90° — rather than sitting parallel to one another.
Distance also plays a major role. Manufacturers often quote impressive maximum operating ranges, but those figures assume ideal open-air conditions. Once walls, people and other obstructions are introduced, practical working range is usually much shorter.
And yes — holding the antenna really does affect performance.
Whether it’s the antenna on a handheld microphone or a bodypack transmitter, wrapping your hand around it or hiding it under clothing changes the way it radiates the radio signal. It’s a small detail, but one I see causing unnecessary range problems surprisingly often.
Squelch: The Setting Everyone Has an Opinion On (And Few Set Correctly)
If there’s one setting I get asked about more than any other, it’s squelch — and it’s also one of the most misunderstood.
Squelch is simply a threshold. Your receiver is constantly listening for the transmitter. When that signal becomes too weak — because the performer has moved out of range, switched the transmitter off, or entered a dead spot — the receiver can either pass through bursts of static or mute the audio completely.
Squelch tells the receiver when to mute instead of amplifying noise.
Set it too high and the receiver starts muting perfectly usable signals, making the microphone cut out long before it should. Your operating range becomes unnecessarily smaller.
Set it too low and the receiver remains open even when the transmitter signal has disappeared, allowing bursts of hiss and RF noise through the PA.
The best place to start is always the manufacturer’s recommended setting. Modern digital systems often manage squelch automatically, leaving very little for the user to adjust.
On systems where it is adjustable, do a proper walk test. Turn the transmitter off while the receiver remains on and gradually increase the squelch until the unwanted noise disappears. Once it does, stop. Increasing it further only reduces your available range.
Finally, walk the entire performance area and make sure you’re not getting premature dropouts. If you are, you’ve probably set the squelch a little too aggressively.
Like frequency coordination, squelch isn’t really a “set and forget” setting. Different venues have different RF environments, so it’s worth checking whenever you’re working somewhere new.
Get it right and you’ll enjoy the maximum reliable range your system is capable of. Get it wrong and you can spend hours chasing a fault that doesn’t actually exist.
Batteries: The Other Silent Culprit
Spectrum issues get all the attention, but I’d say batteries cause just as many “mystery” dropouts and unexpected shutdowns — and it’s almost always avoidable.
| DO Use good quality alkaline batteries for critical, one-shot live events where you simply can’t risk a microphone dying halfway through a show — they discharge gradually and predictably. Use quality NiMH rechargeables (or the manufacturer’s dedicated system, e.g. Shure SB900 or Sennheiser BA packs) with a good smart charger. Choose the right capacity. 1900–2500mAh works well; 2000–2100mAh low self-discharge cells are the sweet spot for consistent runtime and charge retention. Replace or recharge batteries as a set to avoid uneven power delivery and unexpected shutdowns. Keep rechargeables in matched, labelled pairs so the same two cells are always charged and used together. Store and cycle batteries properly — months sitting fully charged or flat gradually reduces capacity. | DON’T Don’t rely on cheap, unbranded rechargeables. Poor cells drop voltage suddenly instead of gradually, giving little warning before switch-off. Don’t leave batteries inside mics or bodypacks during long-term storage — leakage can permanently damage contacts. Don’t assume rechargeables behave like alkalines. They hold voltage steady, then drop off fast — your indicator may not reflect true runtime. Don’t mix brands, capacities or ages. Small differences make one cell work harder, shortening the life of both. |
Good batteries won’t solve frequency problems — but poor batteries can certainly create problems that look very similar.
What I’d Recommend
If your wireless system has suddenly started acting up and nothing about your setup has physically changed, don’t assume the equipment is reaching the end of its life.
More often than not, it’s the environment around it that’s changed.
The available radio spectrum has become smaller, mobile network activity has increased, and venues are often filled with more wireless technology than ever before.
Before replacing expensive equipment, start with the basics:
- Perform a proper frequency scan.
- Check your antenna placement.
- Confirm your squelch settings.
- Review your battery routine.
You may be surprised how many “faulty” systems become completely reliable again after a little attention to these fundamentals.
If you’re still experiencing dropouts, hiss or unexplained interference, it may be time for a proper RF assessment. Every venue has its own unique radio environment, and what works perfectly in one location may not work at all in another.
A professional frequency scan and system coordination can often solve problems that changing channels — or replacing equipment — never will.
Wireless microphone technology hasn’t suddenly become unreliable. The world around it has changed.
Understanding that difference is often the first step towards getting your system performing reliably again.
Need A Hand Sorting This Out?
If you’re unsure whether your wireless microphone system is operating on suitable frequencies, or you’re struggling with persistent dropouts or interference, we’d be happy to help you get behind the cause and sorting it out. Get in touch with Nolte Productions.
— Dawie Nolte