Wireless Microphone Technical Notes
Wireless Microphone Antennas Basics – Video Clip!
Wireless Microphone Cabling Notes:
- Use 50-ohm / RG8X/U type Coax Cable for Wireless Microphone Antenna Cables.
- Antenna cables can be run up to 50 feet, any antenna cable runs longer than 50 feet should be used with an “Antenna Amplifier” up to 100 feet (but not recommended to go any further).
- Don’t use 75-ohm / RG-59 cable. Wireless systems want to see 50-ohms not a 75-ohms mismatch. There is a possibility signals can “degrade” using 75-ohm cable – keep it matched at 50-ohms.
Receiver Related:
Diversity Receivers have two antennas. Each antenna “A and B” (see diagram on previous page) will connect to the same receiver. The way a Diversity Receiver works is that if the signal weakens or drops out on one of the antennas – the Receiver will shift to the other antenna automatically – so no signal is lost.
Antenna Placement:
- Antennas should be mounted as high as possible, and away from metal objects / components.
- As a guide to setting up Antennas – The performer using the transmitter should be able to “see” the receivers’ antennas at all times. This is referred to as “line of sight.”
- There are Bracket Mounting Kits that will allow you to mount the antennas away from the receiver, and in some cases – you may need to use an antenna booster to help with signal loss.
- The antenna’s tips should be pointed away from each other at a 45-degree angle.
Wireless Microphone Interference and Dropouts:
- Interference – Single System: Do a channel scan on the receiver and use the channel that the scan Auto-Selects. The “Group” does not usually need to be changed (but that also depends).
- Interference – Multiple systems: On the first receiver do a group scan, then channel scan. Then set the second receiver to the group used on the first receiver, and so on. It is recommended, in order to maximize system performance to set all receivers to the same group and set all the transmitters to different channels within that same group.
If you are experiencing any interference and / or dropouts you should reference the list below:
- Try a freshly charged or new battery.
- Try a different channel frequency.
- Try repositioning the Antennas so there is nothing obstructing the line of sight from transmitter to receiver. Also, make sure the antenna tips are pointed at a 45-degree angle from each other.
- Keep antennas away from large metal objects. Move the receiver out of the “metal” equipment rack if you haven’t done so already.
- Keep the transmitters more than 6 feet apart (as much as possible).
- Tip – You should identify any “trouble spots” during the initial system installation and / or during daily sound checks. Make sure to let the performers know to stay away from these areas.
Other Wireless Microphone Notes:
- The RF Indicator on the Receiver shows the signal strength from the transmitter.
- Balanced Receiver Outputs should be connected to a mixing console or another Pro-Audio input.
- Unbalanced should only be connected to “high impedance” inputs such as a Guitar amplifier.
- There will be a Mic / Line switch on the back of the receiver. Make sure that the switch is turned to “Line” not “Mic.” Line level will provide a stronger signal to the mixing board channel.
- Transmitter Gain – On both the Body Pack and Handheld Transmitters, there will be a “Gain Control” adjustment. Use caution when adjusting, stay out of the red with only occasional yellow LED flickering.
What is Antenna Distribution, and Antenna Boosters? Handout!
