AV Receiver

An audio/video receiver (AVR) (also known as av receiver, wireless av receiver, Digireceiver, wireless tv receiver, video receiver) is a consumer electronics unit used in a home theater. Its primary purpose is to receive audio and video signals from a number of sources and process them to drive loudspeakers and a display. Possible displays include, television, monitor, or video projector while the inputs may come from, television, satellite receiver, radio, DVD players, Blu-ray Disc players, VCRs, and video game consoles. The AVR source signal and other settings, including volume, are normally set by a remote controller.And the wireless av receiver always works with the wireless av transmitter, multi receivers can receive signal from one transmitter.

Usage

The term receiver basically refers to an amplifier that has a built-in radio tuner. With AV receiver the basic functionality is to receive an audio signal, amplify the audio signal, and allow pass-through of the corresponding video signal to a display device such as a projector or a television.

As home entertainment options expanded, so did the role of the receiver. The ability to handle a variety of digital audio signals was added. More amplifiers were added for surround-sound playback. Video switching was added to simplify changing from one device to another. Within the last few years, video processing has been added to many receivers.

The term audio/video receiver (AVR) or Home Theater Receiver is used to distinguish the multi-channel audio video receiver (home theater receiver) from the simpler stereo receiver, though the primary function of both is amplification.

AV receiver may also be known as digital audio video receiver or digital media renderers.

The AV receiver is classified as an audio frequency electronic amplifier. But with the rapid addition of several features, AV receivers now generally have significant additional functionality.

Features

Channels

Stereo receivers have two channels of amplification, while AV receivers may have more than two. The standard for AV receivers is five channels of amplification. These are usually referred to as 5.1 receivers. This provides for a left, right, center, left surround and right surround speaker to be powered by the receiver. 7.1 receivers are becoming more common and provide for two additional surround channels, left rear surround and right rear surround. The ".1" refers to the LFE (low-frequency effects/bass) channel, the signal of which is usually sent to an amplified subwoofer unit. 5.1 and 7.1 receivers don't usually provide amplification for this channel. Instead, they provide a line level output.

Amplifier power

Audio amplifier power, normally specified in Watts, is not always as significant as it may seem from the specification. Due to the logarithmic nature of human hearing, audio power or sound pressure level (SPL), must be increased by ten times to sound twice as loud. This is why SPL is measured on a logarithmic scale in decibels (dBs). An increase of 10dBs results in a perceived doubling of loudness. Another complication with human hearing is that as the SPL decreases the perceived volume of the low and high frequencies decreases faster than the central frequencies around 2 kHz.

There are different standards for rating amplifier power depending on country, manufacturer, and model. Other factors also come into play: distortion, headroom, speaker efficiency. Thus, it is possible for an amplifier with a specified lower power to sound louder than an amplifier with a specified higher power.

Because of theses factors it is not easy to compare the perceived loudness of amplifiers solely from their specified power in Watts.

Decoders

AV receivers usually provide one or more decoders for sources with more than two channels of audio information. This is most common with movie soundtracks, which use one of a variety of different types of encoding formats.

The first common soundtrack format was Dolby Pro Logic, a surround sound processing technology. This format contains a center channel and a surround channel mixed into the left and right channels using a process called matrixing, providing a total of four channels. Receivers with Dolby Pro Logic decoders can separate out the center and surround channels from the left and right channels.

With the introduction of the DVD, the Dolby Digital format became a standard. Dolby Digital ready receivers included inputs and amplifiers for the additional channels. Most current AV receivers provide a Dolby Digital decoder and at least one digital S/PDIF input which can be connected to a source which provides a Dolby Digital output.

A somewhat less common surround sound decoder called DTS is standard on current AV receivers.

When Dolby Labs and DTS introduced technologies to add a rear center surround channel, these technologies found their way into AV Receivers. Receivers with six amplifiers (known as 6.1 receivers) will typically have both Dolby and DTS's technologies. These are Dolby Digital EX and DTS ES.

Dolby introduced Dolby Pro Logic II to allow stereo sources to play back as if they were encoded in surround sound. DTS introduced a similar technology, NEO:6. These decoders have become common on most current receivers.

As the number of playback channels were increased on receivers, other decoders have been added to some receivers. For example, Dolby Labs created Dolby Pro Logic IIx to take advantage of receivers with more than five channels of playback.

With the introduction of high definition players (e.g. Blu-ray Disc and HD DVD), yet more decoders have been added to some receivers. Dolby TrueHD and DTS-HD Master Audio decoders are available on many receivers.

DSP effects

Most receivers offer specialized Digital Signal Processors (DSP) made for handling various presets and audio effects. Some may offer simple equalizers and balance adjustments to complex DSP audio field simulations such as "Hall", "Arena", "Opera", etc. that simulate or attempt to replicate as if the audio were being played in the places through use of surround sound and echo effects.

AV inputs/outputs

There are a variety of possible connections on an AV receiver. Standard connectors include:

Analog audio (RCA connector, or occasionally XLR connector)

Digital audio (S/PDIF; TOSLINK or RCA terminated coaxial cable)

Composite video (RCA connector)

S-Video

SCART video (primarily used in Europe and very uncommon in many other parts of the world)

Component video

HDMI

USB (usually involves special computer circuitry to read video formats from a file system)

Analog audio connections usually use RCA plugs in stereo pairs. Inputs and outputs are both common. Outputs are provided mainly for cassette tape decks.

Analog audio connections using XLR(Balanced) connectors are uncommon, and usually found on more expensive receivers.

Digital connections allow for the transmission of PCM, Dolby Digital or DTS audio. Common devices include CD players, DVD players, or satellite receivers.

Composite video connections use a single RCA plug on each end. Composite video is standard on all AV receivers allowing for the switching of video devices such as VHS players, cable boxes, and game consoles. DVD players may be connected via composite video connectors although a higher bandwidth connection is recommended.

S-Video connections offer better quality than composite video. It uses a DIN jack.

SCART connections generally offer the best quality video at standard-definition, due to the use of pure RGB signalling (although composite and S-Video may alternatively be offered over a SCART connector). SCART provides video and audio in one connection.

Component video has become the best connection for analog video as higher definitions such as 720p have become common. The YPbPr signalling provides a good compromise between resolution and colour definition.

HDMI is becoming common on AV receivers. It provides for the transmission of both audio and video. HDMI is relatively new technology and there are reported issues with devices not properly working with each other (referred to as hand-shake issues between devices), especially cable/satellite boxes connected to a display through an AV receiver. Different levels of support are provided by receivers with HDMI connections. Some will only switch video and not provide for audio processing. Some will not handle multi-channel LPCM. Multi-channel LPCM is a common way for Blu-ray Disc and HD DVD players to transmit the best possible audio.

PAKITE hdmi wireless transmitter with hdmi jack is coming soon, and the hdmi sender is used for the TV device with hdmi port, RX (Receiver) HDMI output resolution is 576I. Waiting for your inquiry about the wireless hdmi transmitter and receiver. Inquiry URL: http://www.pakite.net/products/5-8ghz-hdmi-transmitter-receiver.html

Video conversion and upscaling

Some AV Receivers can convert from one video format to another. This is commonly called upconversion or transcoding. A smaller number of receivers provide for de-interlacing of video signals. For example, a receiver with upconversion, deinterlacing and upscaling can take an interlaced composite signal at 480i (480 lines per frame sent as a field of 240 even numbered lines 0,2,4,8...478 followed by a field of 240 odd numbered lines 1,3,5,...479) and convert it to component video while also deinterlacing and upscaling it to a higher resolution such as 720p (720 lines per frame with all lines in normal sequence 0,1,2...719).

Radio on AVRs

AV receivers though primarily used for amplification may or may not have an inbuilt AM/FM radio tuner among other features such as LAN connectivity for various Internet applications and some with multi-room audio solutions.

Even though some AVRs may have an AM/FM tuner it is not a primary or mandatory function as an AVR still remains an amplifier.

Some models have HD Radio tuners.

Some models have Internet radio and PC streaming access capabilities with an Ethernet port.

Artical from Wiki: https://en.wikipedia.org/wiki/AV_receiver


recommend reading:
Analysis of Multimedia Video Conferencing
Reviews of PAT-556 Wireless AV Transmitter Receiver
Deep research about Wireless Audio/Video Sender

Transfer a Wireless TV Signal | PAKITE

How to Transfer a Wireless TV Signal ?

A television signal can be transferred from one TV to another video display, providing that both have video inputs and outputs. A wireless Audio/video transmission system(wireless av sender) can transfer the signal and is available from an electronics store or the TV accessories section of a department store. Audio/video cables found in most households, but which can be acquired from the same stores as the wireless Audio/ Video transmission system, must be used as well.

Place the wireless tv transmitter next to the television(By the way, if your Television has HDMI port, you should use HDMI wireless transmitter with hdmi jack). Plug its power cord into an outlet. Insert one end of a video cable into the video output on the back panel of the TV (labeled "Composite" on some sets). Insert the other end of the video cable into the video input on the av transmitter. Repeat this procedure with an audio cable, only plugging the red and white plugs at one end into the red and white outputs on the TV and the red and white inputs on the av transmitter.

Place the wireless tv receiver next to a video display on which you want to watch the TV signal being transmitted wirelessly, for example, another TV. Plug the av receiver's power cord into an outlet. Insert one end of a video cable into the video input on the back panel of the video display device. Insert the other end of the video cable into the video output on the receiver. Repeat this procedure with an audio cable, only plugging the red and white plugs at one end into the red and white outputs on the av receiver and the red and white plugs on the other end into the red and white inputs on the video display device.

Turn on the TV to which the wireless tv transmitter is connected. Turn on the video display device to which the wireless tv receiver is connected. Press "Menu" on the remote that controls the video display device.

Navigate through the settings until you come to the "Video input" or similarly named menu. Select this menu. Highlight the video input to which the video cable is connected. Press the "Enter" or "OK" button, depending on the make of the remote. Press "Menu" to exit the settings so that you can watch the TV signal being transferred to the video display device.

Artical from: Transfer a Wireless TV Signal

Good news: PAKITE wireless hdmi transmitter and receiver with hdmi jack is coming soon, and the hdmi sender is used for the TV device with hdmi port. Waiting for your inquiry about the hdmi wireless transmitter.

recommend reading:

Typical program of wireless meeting rooms
How to improve the sense of experience?
PAT-260 Wireless Strong Penetration A/V Transmitter from PAKITE

List of 2.4 GHz radio use

There are several uses of the 2.4 GHz band. Interference may occur between devices operating at 2.4 GHz. This article details the different users of the 2.4 GHz band, how they cause interference to other users and how they are prone to interference from other users.

Phone

Many cordless telephones and baby monitors in the United States and Canada use the 2.4 GHz frequency, the same frequency at which Wi-Fi standards 802.11b, 802.11g and 802.11n operate. This can cause a significant decrease in speed, or sometimes the total blocking of the Wi-Fi signal when a conversation on the phone takes place. There are several ways to avoid this however, some simple, and some more complicated.

Using wired phones, which do not transmit.

Using cordless phones that do not use the 2.4 GHz band.

Using the 5 GHz band.

DECT 6.0 (1.9 GHz), 5.8 GHz or 900 MHz phones, commonly available today, do not use the 2.4 GHz band and thus do not interfere.

VoIP/Wi-Fi phones share the Wi-Fi base stations and participate in the Wi-Fi contention protocols.

Several different Wi-Fi channels are available and it is possible to avoid the phone channels.

The last will sometimes not be successful, as numerous cordless phones use a feature called Digital Spread Spectrum. This technology was designed to ward off eavesdroppers, but the phone will change channels at random, leaving no Wi-Fi channel safe from phone interference.

Bluetooth

Bluetooth devices intended for use in short-range personal area networks operate from 2.4 to 2.4835 GHz. To reduce interference with other protocols that use the 2.45 GHz band, the Bluetooth protocol divides the band into 79 channels (each 1 MHz wide) and changes channels up to 1600 times per second. Newer Bluetooth versions also feature Adaptive Frequency Hopping which attempts to detect existing signals in the ISM band, such as Wi-Fi channels, and avoid them by negotiating a channel map between the communicating Bluetooth devices.

The USB 3.0 computer cable standard has been proven to generate significant amounts of Electromagnetic interference that can interfere with any Bluetooth devices a user has connected to the same computer.[1] Various strategies can be applied to resolve the problem, ranging from simple solutions such as increasing the distance of USB 3.0 devices from any Bluetooth devices to purchasing better shielded USB cables.

Car alarm

Certain car manufacturers use the 2.4 GHz frequency for their car alarm internal movement sensors. These devices transmit on 2.45 GHz (between channels 8 and 9) at a strength of 500 mW. Because of channel overlap, this will cause problems for channels 6 and 11, which are commonly used default channels for Wi-Fi connections. Because the signal is transmitted as a continuous tone, it causes particular problems for Wi-Fi traffic. This can be clearly seen with spectrum analysers. These devices, due to their short range and high power, are typically not susceptible to interference from other devices on the 2.4 GHz band.

Microwave oven

Microwave ovens operate by emitting a very high power signal in the 2.4 GHz band. Older devices have poor shielding[citation needed], and often emit a very "dirty" signal over the entire 2.4 GHz band.

This can cause considerable difficulties to Wi-Fi and video[citation needed] transmission, resulting in reduced range or complete blocking of the signal.

The IEEE 802.11 committee that developed the Wi-Fi specification conducted an extensive investigation into the interference potential of microwave ovens. A typical microwave oven uses a self-oscillating vacuum power tube called a magnetron and a high voltage power supply with a half wave rectifier (often with voltage doubling) and no DC filtering. This produces an RF pulse train with a duty cycle below 50% as the tube is completely off for half of every AC mains cycle: 8.33 ms in 60 Hz countries and 10 ms in 50 Hz countries.

This property gave rise to a Wi-Fi "microwave oven interference robustness" mode that segments larger data frames into fragments each small enough to fit into the oven's "off" periods.

The 802.11 committee also found that although the instantaneous frequency of a microwave oven magnetron varies widely over each half AC cycle with the instantaneous supply voltage, at any instant it is relatively coherent, i.e., it occupies only a narrow bandwidth.[3] The 802.11a/g signal is inherently robust against such interference because it uses OFDM with error correction information interleaved across the carriers; as long as only a few carriers are wiped out by strong narrow band interference, the information in them can be regenerated by the error correcting code from the carriers that do get through.

Video devices

AV senders typically operate using an FM carrier to carry a video signal from one room to another (for example, satellite TV or closed-circuit television). These devices typically operate continuously but have low (10 mW) transmit power. However, some devices, especially wireless cameras, operate with (often unauthorized) high power levels, and have high-gain antennas.

Amateur Radio operators can transmit two-way Amateur television (and voice) in the 2.4 GHz band - and all ISM frequencies above 902 MHz - with maximum power of 1500 watts in the US if the transmission mode does not include spread spectrum techniques.[4][5] Other power levels apply per regions. In the UK, maximum power level for a full privileged license is 400 watts.[6] In other countries, maximum power level for non - spread spectrum emissions are set by local legistration.

Although the transmitter of some video cameras appears to be fixed on one frequency, it has been found in several models that the cameras are actually frequency agile, and can have their frequency changed by disassembling the product and moving solder links or dip switches inside the camera.

These devices are prone to interference from other 2.4 GHz devices, due to the nature of an analog video signal showing up interference very easily. A carrier to noise ratio of some 20 dB is required to give a "clean" picture.

Continuous transmissions interfere with these, causing "patterning" on the picture, sometimes a dark or light shift, or complete blocking of the signal.

Non-continuous transmissions, such as Wi-Fi, cause horizontal noise bars to appear on the screen, and can cause "popping" or "clicking" to be heard in the audio.

Wi-Fi networks

AV senders are a big problem for Wi-Fi networks. Unlike Wi-Fi they operate continuously, and are typically only 10 MHz in bandwidth. This causes a very intense signal as viewed on a spectrum analyser, and completely obliterates over half a channel. The result of this, typically in a Wireless Internet service provider-type environment, is that clients (who cannot hear the AV sender due to the "hidden node" effect) can hear the Wi-Fi without any issues, but the receiver on the WISP's access point is completely obliterated by the AV sender, so is extremely deaf. Furthermore, due to the nature of AV senders, they are not interfered with by Wi-Fi easily, since the receiver and transmitter are typically located very close together, so the capture effect is very high. Wi-Fi also has a very wide spectrum, so only typically 30% of the peak power of the Wi-Fi actually affects the AV sender. Wi-Fi is not continuous transmit, so the Wi-Fi signal interferes only intermittently with the AV sender. A combination of these factors - low power output of the Wi-Fi compared to the AV sender, the fact that typically the AV sender is far closer to the receiver than the Wi-Fi transmitter and the FM capture effect means that a wireless AV sender may cause problems to Wi-Fi over a wide area, but the Wi-Fi unit causes few problems to the AV sender.

802.11n Wi-Fi networks are proving to be a source of interference for other wireless data networks operating at 2.4 GHz.

EIRP

Many AV senders on the market in the UK advertise a 100 mW equivalent isotropically radiated power (EIRP). However, the UK market only permits a 10 mW EIRP limit. These devices cause far more interference across a far wider area, due to their excessive power. Furthermore, UK AV senders are required to operate across a 20 MHz bandwidth (not to be confused with 20 MHz deviation). This means that some foreign imported AV senders are not legal since they operate on a 15 MHz bandwidth or lower, which causes a higher spectral power density, increasing the interference. Furthermore, most other countries permit 100 mW EIRP for AV senders, meaning a lot of AV senders in the UK have excessive power outputs.

From wiki: List of 2.4 GHz radio use



recommend reading:
Smart Home Appliance
HDMI Wireless Transmission System
How to make it simple but effective?