Avoid Dropouts with wireless mics

Except for Diversity Fins—which have the added benefit of having co-located antennas, so the signal in both antennas is in the same phase period—antennas need to be a minimum of a quarter wavelength (6") apart from each other, though they are much better at two wavelengths (44”) apart. However, that is still not far enough away from each other to prevent interaction between the antennas. It may not seem intuitive, but some of the power received by your antenna gets reflected (VSWR or return loss) out from the receiver and back into the receiver’s antenna, where it now becomes a transmitter. If one antenna is within about 6" of another antenna, their signals will  imprint onto each other causing interference. This is the major reason “antenna farms” should be avoided at all costs.

Keeping Wireless On The Air  

Avoiding Antenna Farms

Loss of range is typically caused by competition from localized interference, such as that caused by TV stations, motors, LED lighting, anything with a computer chip, and now cell phone service in the 600 MHz band. These sources, added together, form your noise floor. Directional antennas and bandpass filters can work together with high-quality coax cables to help mitigate this problem.

Multipath interference is caused by reflections of your transmitter’s signal, primarily by metal objects in your venue and other boundaries. These reflections flip polarity and arrive out of phase which causes cancellations in your receiver’s antennas.

Cross-polarization fades (aka signal cancellation) happen when your direct signal and reflected multipath signals mix in your antennas. This can be somewhat mitigated by proper antenna positioning. However, since multiple antennas must be separated by distance to avoid interfering with each other, the signal in each antenna will not be in the same wave period (phase). Our patented Diversity Fin antenna solves the distance problem by being co-located, while orthogonally mounted elements eliminate cross-polarization fades. Not only is it more convenient, it is actually better than two “paddles”: It doesn’t drop out!

Keeping Wireless on the Air

Webinar – Why Mics Dropout

Antenna Polarization Basics

Bandpass Filter Basics

Diversity Fin Whitepaper

Proper antenna aiming can result in free benefits, so don’t ignore it. Omni antennas, such as the whips that are provided with a new wireless microphone, pick up in a 360° horizontal circle, so they cannot be aimed. They provide low gain and no rejection of local interference. Directional antennas (paddles and helicals) provide additional range and typically reject 50% or more of local interference.

The horizontal coverage angle of directional antennas is primarily what to consider when aiming antennas. Basically, the task is to visualize a triangle with the pattern of your antenna and lay that over your floorplan in a way that includes all the positions you need to cover for your performers. This can often be improved by connecting your RF scanner to your antenna and making relative measurements at a few positions. In some cases, signal improvements of up to 20 dB can be achieved by simply moving your antenna to a different position only a few feet away from its starting point.

Antenna Placement Webinar 

Scanning for Antenna Positioning

The range of any wireless system depends on a number of factors, of which antenna type is only one. Antenna placement, noise floor, and interfering signals are by far the most significant factors in determining range. Very few live sound applications exceed antenna to mic distances of 300’. The Diversity Fin will provide the same or slightly better range than paddle/shark fin antennas, under the same RF conditions - which is more than enough for most production scenarios. Those who need longer range should consider the CP Beam.

Only one Diversity Fin is required per diversity receiver. The Diversity Fin is a polarization diversity antenna system with two antenna outputs. Simply connect output one of the Diversity Fin’s outputs to channel “A,” and the other to channel “B” on your wireless microphone receiver or antenna distributor. Consider watching the video for a better mental picture. A single Diversity Fin can accommodate four or more receivers using a single or cascaded DISTRO4 antenna distributor.

Yes. The Diversity Fin provides superior signal dropout protection than a pair of matched paddle/shark fin antennas. The Diversity Fin eliminates multi-path interference and reduces switching noise using coincident placement of orthogonal elements. A technical description of the Diversity Fin’s benefits is found in our white paper.

The Diversity Fin was designed for receive applications in a diversity receiver system. Although it is technically possible to use one of the two antenna elements (LPDA or dipole) for a transmit application, like an in-ear monitor, none of the Diversity Fin’s benefits will carry over to a transmit scheme. In other words, it defeats the point. You’re better off purchasing a single standalone paddle or a helical antenna to use with your wireless monitor.

For extra protection use we recommend this acrylic dome

Check out this blog post for more information.