Everybody loves the convenience of cutting the cord and going wireless with your microphones. But getting them to work can sometimes seem like black magic. I put together this handy guide for people who are having problems with their wireless systems. Keep in mind that most microphone problems (wired or wireless) are a direct result of user error. It's imperative to understand how to use a microphone if you want it to work properly.
Wireless dropouts are not usually caused by defective hardware, but by improper use or installation. Before you declare your system defective, make sure you are doing all of these things:
Here are a few "best practices" tips for wireless:
- The most common cause of RF dropouts is improper antenna placement. Line of sight should be maintained between the antennas and the transmitters. If that's not possible in your rack, the antennas should be mounted away from the receivers, possibly up on a wall, balcony rail, ceiling, etc.
- The antenna on the transmitter should not be covered. With handheld mics, take care not to cover the antenna with your hand. If you don't see an antenna, it's probably hidden inside the last couple of inches of the body. Hold the mic closer to its head.
- If you are using a beltpack with an external (wire) antenna, make sure that the antenna isn't wadded up or bent when wearing it. Not only is this bad for the antenna (bend a wire enough times, and it's sure to break), but it severely imparis its transmission. You'll get a lot shorter range and more dropouts with a wadded-up antenna.
- Only use systems that are true diversity (two antennas) and frequency agile (have the ability to change channels if there is interference).
- Signal strength and operating range tend to drop off as the battery dies, so it's generally best to change your batteries at the beginning of every show / service, even if they aren't completely dead.
- Use an antenna combiner if you have more than two wireless systems.
- Use one of the databases provided online by the FCC or wireless mic manufacturers to choose frequencies that won't get interference from licensed transmitters (TV stations, public safety etc) in your area.
- Frequencies of multiple wireless systems must be carefully coordinated to avoid interference with each other. Simply having different frequencies is not enough. Usually, the best way to do this is to use wireless systems from the same manufacturer and series (Shure SLX, or Audio Technica 3000-series, Sennheiser Evolution Wireless, etc.), and use frequencies that are already pre-coordinated not to interfere with each other. If you are mixing systems from different manufacturers or different series, consult an expert.
- True diversity (more than one antenna) is your best defense against dead spots and RF dropouts. In true diversity systems, both antennas must be connected for diversity to be achieved. They should be installed at least 9" apart, and at a 90-degree angle to each other. If they are remote-mounted, the cables connecting them to the receiver or antenna distro MUST be the same length.
- Also remember that human bodies are excellent absorbers of RF energy. Your wireless transmitter probably does not have enough "oomph" to power through an entire audience on their feet. If your antennas are in the back of a room, the middle of the pastor's back may not be the best place for the beltpack transmitter. That forces the signal to pass through the pastor's body on its way to the receiver.
- If you are having problems with clear reception, try reducing the distance between the transmitters and receivers by moving the receivers closer to the stage. If that's not practical, consider remote-mounting the antennas to be closer.
- If one must run long antenna cables, don't scrimp to save money - get the lowest loss cable that's available. RG-8 is recommended. If the cable run exceeds 25 ft, you may need an antenna booster. It's time to call an expert.
There are more, of course, particularly in large systems with a lot of units running at once, antenna distribution units, and remote-mounted antennas. If that's you, you would be wise to consult with a wireless expert (note: the salesman at your local guitar store likely does not qualify as a "wireless expert").