RF Basics

The RF Basics series describe the fundamental building blocks of wireless systems. They are designed to be read in order. They should help if you are new to wireless systems, or to provide a refresher if you are experienced. However you use them we hope you feel more confident after reading them.

How RF gets audio signal from A to B?
All radio frequency (RF) systems have a transmitter (TX) and receiver (RX). Transmitters and receivers can take many forms including handheld, beltpack, rack mount or desktop.

Regardless of how they look, all audio RF systems take in an audio signal, attach it to an RF carrier wave at the transmitter, transmit the signal to the receiver where the RF carrier wave is detached from the audio allowing the audio to be sent to the audio output and into the audio system.

Form Factor
With RF microphones, the microphone (or beltpack the microphone connects to) is the transmitter and the receiver is, typically, a stationary unit with an audio output (Fig2a). With in- ear monitors (IEM), the transmitter is, typically, a stationary unit with an audio input and the beltpack the headphones connect to is the receiver (Fig2b). The notable exceptions to this rule are RF systems used in film and broadcast where, to save space and weight both the RX and TX units may be the size of a beltpack (Fig2c).

Antennas
All RF systems require an antenna. Depending on the size of the device these may be obvious or hidden. On handheld microphones the antenna is normally integrated into the handle. On beltpacks, whether a microphone TX or IEM RX, the antenna is normally a small piece of wire protruding from the device. On the normally stationary parts of the system, the antennas connect to the back or the front with BNC connectors (Fig3). BNC connectors are keyed so that the ring uses the pins to locate the connection, requiring a 90 degree turn to lock them in place.

 

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How RF gets audio signal from A to B?
All radio frequency (RF) systems have a transmitter (TX) and receiver (RX). Transmitters and receivers can take many forms including handheld, beltpack, rack mount or desktop.

Regardless of how they look, all audio RF systems take in an audio signal, attach it to an RF carrier wave at the transmitter, transmit the signal to the receiver where the RF carrier wave is detached from the audio allowing the audio to be sent to the audio output and into the audio system.

Form Factor
With RF microphones, the microphone (or beltpack the microphone connects to) is the transmitter and the receiver is, typically, a stationary unit with an audio output (Fig2a). With in- ear monitors (IEM), the transmitter is, typically, a stationary unit with an audio input and the beltpack the headphones connect to is the receiver (Fig2b). The notable exceptions to this rule are RF systems used in film and broadcast where, to save space and weight both the RX and TX units may be the size of a beltpack (Fig2c).

Antennas
All RF systems require an antenna. Depending on the size of the device these may be obvious or hidden. On handheld microphones the antenna is normally integrated into the handle. On beltpacks, whether a microphone TX or IEM RX, the antenna is normally a small piece of wire protruding from the device. On the normally stationary parts of the system, the antennas connect to the back or the front with BNC connectors (Fig3). BNC connectors are keyed so that the ring uses the pins to locate the connection, requiring a 90 degree turn to lock them in place.

 

Download full version

 

Tetris for RF signals.

You may have heard the phrase “frequency coordination” when reading and researching all things RF. Frequency Coordination is the process by which RF frequencies required for use by the user (that’s probably you) are made to fit into the larger RF environment created by TV stations in your location, any existing RF users nearby and any other constraints placed on the available RF spectrum.

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Almost all wireless devices, either microphone or IEM, have the ability to change the individual frequency that they broadcast on. Obviously, if the frequency on the TX is changed the frequency on the RX has to be changed to match otherwise nothing will be received. The vast majority of wireless devices offer functions that allow the device to scan the local RF environment and suggest the most open frequency for use. This scanning is a form of coordination but only if conducted in the following way.

Let’s say you want to have 4 wireless mics working together. The first unit is switched on and a scan initiated. Once the scan has finished, the system recommends a usable frequency and the RX and TX parts are changed to match. The system works and all is well with the world. This first unit should be left on while a scan is performed on the second unit. If the first unit is turned off, the second unit will find the most usable frequency, which is likely to be the same frequency unit one found. Turn both units on and battle ensues to use the frequency. This does not sound good. Leaving each unit turned on while performing a scan with subsequent units ensures that the scan always locates the next available best frequency, not just the best frequency.

For small systems in relatively remote locations, this scan and set may well be enough to ensure stable and usable RF in the system. However larger and more crowded RF environments require manual coordination of frequencies. This manual coordination uses software (such as IAS) and hardware to create a list of frequencies each device in the system should use. A manual coordination will not only balance available frequencies but also allows the RF tech to balance the use of the system with the RF spectrum available by using antenna placement, antenna gain, TX power, timing of simultaneous channels and relative positions to create the most stable RF signal possible.

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Proper frequency coordination should be performed with all RF systems and checked periodically to ensure it is still relevant. The need for proper frequency coordination will only increase over the next few years as the available RF spectrum decreases and the number of devices trying to use it increases.

page2image57007632

Tetris for RF signals.

You may have heard the phrase “frequency coordination” when reading and researching all things RF. Frequency Coordination is the process by which RF frequencies required for use by the user (that’s probably you) are made to fit into the larger RF environment created by TV stations in your location, any existing RF users nearby and any other constraints placed on the available RF spectrum.

page1image56772848 page1image56772640 page1image56773056 page1image56773264

1 of 2

Almost all wireless devices, either microphone or IEM, have the ability to change the individual frequency that they broadcast on. Obviously, if the frequency on the TX is changed the frequency on the RX has to be changed to match otherwise nothing will be received. The vast majority of wireless devices offer functions that allow the device to scan the local RF environment and suggest the most open frequency for use. This scanning is a form of coordination but only if conducted in the following way.

Let’s say you want to have 4 wireless mics working together. The first unit is switched on and a scan initiated. Once the scan has finished, the system recommends a usable frequency and the RX and TX parts are changed to match. The system works and all is well with the world. This first unit should be left on while a scan is performed on the second unit. If the first unit is turned off, the second unit will find the most usable frequency, which is likely to be the same frequency unit one found. Turn both units on and battle ensues to use the frequency. This does not sound good. Leaving each unit turned on while performing a scan with subsequent units ensures that the scan always locates the next available best frequency, not just the best frequency.

For small systems in relatively remote locations, this scan and set may well be enough to ensure stable and usable RF in the system. However larger and more crowded RF environments require manual coordination of frequencies. This manual coordination uses software (such as IAS) and hardware to create a list of frequencies each device in the system should use. A manual coordination will not only balance available frequencies but also allows the RF tech to balance the use of the system with the RF spectrum available by using antenna placement, antenna gain, TX power, timing of simultaneous channels and relative positions to create the most stable RF signal possible.

page2image57007424

Proper frequency coordination should be performed with all RF systems and checked periodically to ensure it is still relevant. The need for proper frequency coordination will only increase over the next few years as the available RF spectrum decreases and the number of devices trying to use it increases.

page2image57007632

Tetris for RF signals.

You may have heard the phrase “frequency coordination” when reading and researching all things RF. Frequency Coordination is the process by which RF frequencies required for use by the user (that’s probably you) are made to fit into the larger RF environment created by TV stations in your location, any existing RF users nearby and any other constraints placed on the available RF spectrum.

page1image56772848 page1image56772640 page1image56773056 page1image56773264

1 of 2

Almost all wireless devices, either microphone or IEM, have the ability to change the individual frequency that they broadcast on. Obviously, if the frequency on the TX is changed the frequency on the RX has to be changed to match otherwise nothing will be received. The vast majority of wireless devices offer functions that allow the device to scan the local RF environment and suggest the most open frequency for use. This scanning is a form of coordination but only if conducted in the following way.

Let’s say you want to have 4 wireless mics working together. The first unit is switched on and a scan initiated. Once the scan has finished, the system recommends a usable frequency and the RX and TX parts are changed to match. The system works and all is well with the world. This first unit should be left on while a scan is performed on the second unit. If the first unit is turned off, the second unit will find the most usable frequency, which is likely to be the same frequency unit one found. Turn both units on and battle ensues to use the frequency. This does not sound good. Leaving each unit turned on while performing a scan with subsequent units ensures that the scan always locates the next available best frequency, not just the best frequency.

For small systems in relatively remote locations, this scan and set may well be enough to ensure stable and usable RF in the system. However larger and more crowded RF environments require manual coordination of frequencies. This manual coordination uses software (such as IAS) and hardware to create a list of frequencies each device in the system should use. A manual coordination will not only balance available frequencies but also allows the RF tech to balance the use of the system with the RF spectrum available by using antenna placement, antenna gain, TX power, timing of simultaneous channels and relative positions to create the most stable RF signal possible.

page2image57007424

Proper frequency coordination should be performed with all RF systems and checked periodically to ensure it is still relevant. The need for proper frequency coordination will only increase over the next few years as the available RF spectrum decreases and the number of devices trying to use it increases.

page2image57007632