Tuner (radio)
A tuner (English to tune, tune, tune ') is the receiving part in televisions or radios.
- 2.1 radio reception
- 2.2 TV reception
- 2.3 Digital Tuner
- 2.4 tuner device
Function
Stations transmit television and radio signals simultaneously, but at different frequencies. The tuner is connected downstream of the antenna input and selected, i.e., to filter out the desired signal. Often referred to so that only the high frequency part, which is usually realized as a separate assembly because of the required high gain and the necessary freedom from interference. In virtually all common today tuners, as in a superheterodyne receiver, implemented through a mixing stage, this high frequency is independent of the frequency of the transmitter intermediate frequency. In the classic television technology here ends the jurisdiction of the tuner.
The term tuner is used for:
- High frequency tuning and selection part: an assembly that generates the intermediate frequency, for example, in a television receiver.
- High frequency tuning and selection section, and the demodulator: a module that provides, for example, in a radio tuner, or as an autonomous device which sent the selected audio and video signals or audio transmitter.
Receiver
As a receiver is defined as the combination of the amplifier and tuner components, the actual radio reception part.
Types according to signal
There are different types of tuners for different signals:
- Analog TV via aerial or cable connection
- Digital television: via satellite ( DVB-S)
- (DVB -T)
- Over cable (DVB -C)
Construction
Radio reception
The predecessor of the AM tuner was on the radio from a coil set with wave switch for range selection of radio receivers for the long, medium and short waveband ( AM, short for amplitude modulation). The typical solution contained an oscillator circuit and only one input circuit. The two groups were matched with a dual variable capacitor. Later, it was possible to produce variable capacitance diodes with sufficiently high capacity and quality, so that the double - variable capacitor could be omitted.
For the FM band, there was a temporary attachments, advanced a normal LMS radio to an FM receiver. Because of the frequency modulation used in the VHF range these accessories had the IF amplifier and demodulator contain. The radio device only served as a low-frequency amplifier with speaker.
The entire assembly of input circuit, prepress, oscillator circuit and mixer stage including the first IF filter was also summarized in later, installed modules to the FM tuner. First solutions often contain an inductive tuning ( variometer ), in which two cores via cables are moved by a shaft. Later they used multi - variable capacitors.
Combined tuner for radio can also be on a common shaft two variable capacitor pairs of different capacities for LMK (AM) on the one hand and FM have the other. With advent of varactor diodes succeeded to realize the AFC function and later the FM tuning electronically.
Television reception
For television receivers only first tuner for VHF ( VHF band I and VHF band III) were needed. They were built in the shape of the drum channel selector. The for each receive channel (channels 1 to 12) coils necessary ( and capacitors) were as so-called channel strips on the circumference of a drum. These channel strips were adjusted during manufacture or in the workshop. The user had to fine-tune the oscillator in each channel. To an eccentric, consisting of a dielectric disc has been rotated, which was isolated between a capacitor surface, and a metal bracket on the housing, their effective area is altered. Often individual channel strips were also not equipped. This concerned in the former GDR as the "West " channels. There was also the television receiver with a tuner, which is only allowed to switch between two channels ( Alex).
With the development of the UHF range UHF tuner and UHF converters were built. The difference was that the tuner was built into the receiver and the intermediate frequency gave as the converter was an accessory that the received signal into a free channel (channel 3) followed it. The devices had multiple variable capacitors, later tuners then capacitance diodes for voting.
First electronically tunable tuner then novel capacitance diodes go back to work from the 1960s by Karl -Heinz copper at the company Philips. Ensure that televisions could be built that could be completely controlled via a remote control, including the tuning.
TV tuner modules are now smaller than a cigarette or even matchbox and cost in producing a few euros. For the tuner modules there are various manufacturers.
Digital tuner
Digital technology led first to the fact that a digital (numerical ) Reception frequency display could be realized: the assemblies generated the tuning to a digital - to-analog converter. Later devices synthesized frequency oscillator with a PLL circuit of a frequency reference ( oscillator quartz ). The receiving frequency display was now very precisely possible ( frequency count and subtracting the intermediate frequency ).
Today's digital tuner can largely dispense with inductive and tuning components by digital signal processing (DSP) and are also involved in the digital demodulation. Other functions that simplify the fact are automatic station search, numerical input of the frequency or the automatic assignment of the presets with the air channels.
Tuner device
The designation tuner later went on to stand-alone devices for radio reception, at whose output the demodulated AF signal was delivered with a level as well as on a turntable or other audio signal source. The tuner and amplifier (if the turntable included) were creatively adapted to each other and were together with the speakers a complete radio receiver.
In the studio technical high-class devices were designated according to type such as a tuner ball receiver. Television relay receivers were used together with small transmitters to supply by shading receiving weak areas ( valleys ). See also converters ( wireless technology ). Of course, the ball receiver contained a module tuner.