Question: What are some common methods of remote mounting antennas?
Answer: In a previous blog we talked about when or why we would want to remote antennas for a wireless microphone system. Today, we will discuss several common methods for doing so, ranging from simple to more complex methods.
The simplest method is to move the antennas that are attached to a wireless receiver to the outside of an enclosed rack. In this case, the antennas are removed from the receiver and connected to the outside of the rack, using short 50 ohm cable and panel-mount BNC connectors. The ATW-BH1 Antenna Bulkhead Connector Kit provides everything necessary to do this. Sometimes it is necessary to move the antennas further away from the receiver and rack. To do this the antennas are removed from the receiver and mounted at the ends of longer 50 ohm cable (up to 100 feet is recommended). For cable runs under 15 feet, RG58 BNC-to-BNC cable, such as our AC12 RF Antenna Cable, is recommended because of cost as well as ease of installation, although RG8 can certainly be used as well. For cable runs between 15 and 100 feet, RG8 BNC-to-BNC cable, such as our AC100 RF Antenna Cable, is recommended.
If you are remote mounting ¼ wave antennas, they must be mounted perpendicular/parallel to a ground plane. A ground plane is a flat conducting surface (metal) that serves as part of an antenna. It reflects the radio waves from the other antenna elements. Note that the plane does not actually have to be connected to earth ground, but should be electrically connected to the coax ground. There are ways to calculate the requisite size of the ground plane for a given antenna, but a good rule of thumb is to use a plane that is the same size as the top of your wireless microphone receiver. If you are remote mounting ½ wave antennas, such as those on our 4000 Series wireless microphone system, a ground plane is not necessary because the ground element is embedded within the antenna assembly itself. Each ½ wave antenna can simply be connected to the end of a cable and mounted in whatever method best suits your application.
Certain applications call for remote mounting antennas other than those that come attached to the wireless receiver. For example, in a concert, theater or house of worship scenario, using LPDA (log periodic dipole array), such as our ATW-A49 UHF Wide-band Directional Antennas, might prove to be your best option. These are directional antennas, capable of focusing in on the transmitted signal. The same rules apply for cable runs (as listed above). Note that a ground plane is not necessary for these antennas, because it is integral to the LPDA assembly. It is quite common to see LPDA antennas mounted on microphone stands either at front of house or on stage for quick, portable use.
Similar to remote mounting LPDA antennas is remote mounting powered antennas like our ATW-A54P UHF Powered Dipole Antennas. These provide an internal gain switch that allows for a boost of 4 dB or 10 dB, which can be used to compensate for signal loss in long cable runs. These antennas are “active” devices and must receive antenna power from the receiver or distribution system. The required power for these antenna is 12V DC, provided via the antenna cable to power the antennas’ onboard electronics. Please note that these antennas will not only amplify the desired transmitted signal, but will also amplify other RF transmissions, so it is recommended not to use the 10 dB gain setting unless conditions warrant this setting. The same rules apply for cable runs as those listed above. Again, a separate ground plane is not necessary for these antennas.
There are many other types of antennas that may be used for various applications, such as a helical antenna, Yagi, ¾ wave and so on, but we have covered the most common types in this post.
Hopefully, you now have a better understanding of remote mounting options for antennas. Please stay tuned for a future related blog post on antenna distribution systems. As always, feel free to contact the Audio-Technica Audio Solutions Department for more information.