Lectrosonics has developed a new method to deal with interference from vector diversity. Let’s take a look at what that means.
When it comes to improving wireless performance, manufacturers often use receivers Variety to improve the reception of RF signals.
Before diving into vector diversity, it is important that you familiarize yourself with the basics of wireless audio to better understand why diversity is essential to enhancing the overall signal of wireless audio.
What is a wireless audio system?
A wireless audio system generally consists of a transmitter and a receiver. Typically, a transmitter is connected to a Lav, microphone, or line level signal and sends audio to the receiver over a specific frequency channel. The receiver then typically sends the transmitted audio to a mixer, recorder, or even camera, where it can be recorded to a file or played live on the air.
One of the common wireless systems used in filmmaking is the Sennheiser G4, RØDE Wireless GO II, the Deity Connect System and many others from Lectrosonics, Wisycom, Audio-Technica and Zaxcom, to name a few.
While the most basic setup includes a single transmitter and receiver, larger wireless setups can include multiple transmitters and receivers. Regardless of the size of the setup, the radio signal is transmitted over a specific frequency channel. In the United States, this frequency spectrum is regulated by the federal government communication Commission (FCC).
The FCC licenses certain frequency channels to companies developing wireless audio systems for filmmakers. Over the years, the FCC has auctioned large portions of the available spectrum to wireless operators and cable companies. These auctions include the elimination of the 700 MHz and 600 MHz bands. As the number of frequencies available continues to decrease, the likelihood of radio interference increases when you are out and about. Wireless audio companies are looking for new ways to counter the shrinking spectrum, including developing wireless for the 900 MHz band and the unlicensed 2.4 GHz band.
Let’s stop at the frequency spectrum.
What is the frequency spectrum?
Wireless devices transmit signals in a frequency band. Generally, it will be in either the FM, UHF, or 2.4 GHz spectrum. Although the radio spectrum is much wider, the frequencies designated for radio microphones are generally as follows:
- Low-band FM 49-108 MHz
- High-band VHF 169-216 MHz
- Low-band UHF 450-806 MHz
- High-band UHF 900-960 MHz
- 2.4 GHz band 2.400 GHz – 2.483 GHz
With each frequency band, there are a certain number of channels over which a wireless system can transmit a signal. You will see some manufacturers say their wireless audio system is broadband, which means that it offers more of the available frequency spectrum on the model. Broadband radio systems are generally better because you get more frequency channels.
It’s also worth noting that 2.4GHz wireless audio systems are cheaper because they don’t have to go through the red tape to be approved by the FCC. Developing wireless in the UHF and VHF bands costs the company money, which can affect the overall price of the product.
If you’re wondering which of the FM, UHF or 2.4 GHz bands is better, you’ve come to the right place.
Is VHF, UHF, or 2.4 GHz better?
Although there are many technical details such as: B. wavelength properties, you need to know the following.
- The full spectrum is shared by different users and different devices
- All analog or digital signal types can be disturbed
Low-band FM 49-108 MHz
Do not consider this frequency band for serious wireless applications, except for assisted hearing aids and walkie-talkies. Among other things, it is very prone to failure. Devices like Comtek use the frequency band with great success.
High-band VHF 169-216 MHz
This frequency band is better than low-band FM because it has less interference. It’s great for small locations or when you have a good line of sight. It’s also able to penetrate thinner walls, and it’s good for auto work, but works best over shorter distances. Comtek systems also use 216 MHz here.
Low-band UHF 450-806 MHz
This is the best frequency band available for wireless systems. It has the longest range, most dynamic range, better performance over FM and most channels. The physical size of UHF radio can also be significantly smaller. While it is prone to failure, it suffers the least and can penetrate walls with the greatest efficiency.
Typical wireless microphones in the US operate between 470 and 600 MHz.
High-band UHF 900-960 MHz
This frequency band offers similar characteristics to low-band UHF, but the number of channels is limited. Typical radio in the US operates between 941 and 960 MHz.
2.4 GHz band 2.400 GHz – 2.483 GHz
This is a crowded spectrum. Bluetooth, internet, cordless phones, security systems and smartphones all have WiFi. The number of channels is usually limited, as is the range of the wireless network. The latency can also be slightly higher than with UHF systems. However, companies like Deity are changing the way 2.4 GHz radio systems work, offering better output and less interference. These systems are worth considering for less demanding applications.
Now that you know the basics of a wireless audio system and how it carries audio, let’s talk about the technology that enables better wireless performance.
What is a diversity receiver?
When it comes to enhancing the radio signal, wireless audio systems use diversity receivers. In its basic form, a diversity receiver uses two separate antenna systems. This allows the receiver to choose which signal coming from the transmitter is stronger and automatically switch to the more robust signal, preventing audio drop-off.
There are many ways a company can use a diversity system with two antennas in one receiver. Common techniques include antenna switching, phase switching, and true diversity. This is where Lectrosonics’ vector diversity comes in. This is a new way of optimizing receiver performance in order to generate fewer dropouts.
Let’s take a look at each diversity type.
Antenna switching variety
This diversity system, also known as space diversity or With the spatial diversity, one antenna is used in each case. With wireless audio, each antenna is set to a different interference environment. The receiver automatically switches to the other antenna if a fault occurs.
Phase switching diversity
When switching phases, the two antennas work together. The signal from the antennas is either out of phase or out of phase, depending on which combination provides the stronger signal. This is generally better than switching the antenna when it comes to wireless audio systems.
When it comes to diversity, true diversity, which can sometimes be referred to as ratio diversity or audio switching diversity, has become the de facto industry standard. A true diversity system has two independent receiver sections, each with its own antenna. That is, instead of two antennas and a single receiver, there are two receiver sections with their own antenna. This makes for a very stable signal, but it can add up the cost of the device.
Vector diversity is very similar to true diversity in that it uses two receiver channels and two antennas. However, according to Lectrosonics, the extra process of phase aligning the two signals is added before they are combined. This isn’t that important for analog RF sources, but it makes a big difference for digital ones because of the cliff effect.
With all digital systems, their signals do not gradually degrade. Instead, they perform great and then fall off a cliff. It’s like the end of Thelma & Louise. One minute they are driving on a dusty road, the next minute they are plunging into a ravine. Because of this, true diversity may not be the ultimate solution for digital wireless.
According to Lectrosonics, vector diversity works “by expressing the signal from each antenna in vector form (angle and size)”. According to Lectrosonics, this makes it possible “to mathematically rotate one of the vectors continuously so that the angles match and the signals can be combined constructively”. As a result, the energy from both antennas contributes to the receiver performance.
Lectro integrates two complete receivers that convert the signal from each antenna into a vector with an intermediate frequency in the digital range. These vectors are then rotated and optimally combined and then demodulated. And boom, you have vector diversity.
While users may not see a drastic change in performance in terms of vector diversity in analog wireless systems like Lectro’s Digital Hybrid System, in terms of digital technology, it can play the crucial role in enhancing audio drops. Vector diversity technology can be found in Lectro’s Digital Wireless range, including the new DCR822 receiver.
Have you had any experience with the new technology? Let us know what you think in the comments below.