Minimizing RF Problems When Using Digital Wireless Audio
Minimizing RF interference is essential to achieve the best wireless audio possible. Several common issues which result in dropouts and short range include:
- Interference from other RF sources (RFI). This includes DTV broadcast television, gigantic video walls, and RF video links. RF video systems can be the source of interference, even though most of these systems operate outside the UHF band at 5.8 GHz. From our experience, wireless video links can interfere with any UHF-band audio system by any manufacturer, whether analog or digital. Solution: when possible, work away from, or turn off, other RF sources. Look for other possible sources of interference.
- Transmitters are too close to the receiver. With digital systems in particular, it is recommended to keep at least ten feet/three meters between all transmit and receive antennas. Transmitters placed too close to receiving antennas can overload the receiver’s front end, rendering the system unstable and prone to dropouts. Solution: Reducing transmitter output power can improve performance in close-proximity situations.
- Camera, IFB transmitters, and walkie-talkies are in close proximity to receivers. This is a variation of the issue above. A transmitter in close proximity to a receiver can desensitize it, reducing range. Solution: Maximize the distance between receiver antennas and transmitter antenna in a bag with both wireless receivers and transmitters (for camera hops or IFB).
- Too much RF gain in the system. Directional antennas inherently add “passive gain.” A typical shark fin reduces the pickup pattern to 120 degrees and adds 7 dB of gain. Active antenna amplifiers are great tools, but are only intended to compensate for cable loss: adding 12 dB of amplifier gain to overcome 6 dB of cable loss does not give 6 dB of range in addition. A directional antenna plus an antenna amplifier can be particularly problematic, and overload the system if the transmitters get too close to the antenna. RF gain applied when the system already has sufficient gain can overload the receiver front end and cause dropouts. Solution: reduce RF gain and avoid antenna amplifiers when unnecessary.
- Antenna frequency mismatch. Antennas operate most efficiently at a specific frequency. Mismatching frequencies negatively impacts range. Solution: Make certain to use both transmit and receive antennas that are the correct length, or tuning.
Part 2: Picking the Right Antenna for Digital Wireless Audio
Part 3: Minimizing RF Problems When Using Digital Wireless Audio
Part 4: Maximizing Wireless Range When Using a Production Bag