Antenna tuner

tunerpi networkantenna couplingantenna coupling networkantenna tuningantenna-tuning unitATUequipmenttransmatchtuned
Antenna tuner, matchbox, transmatch, antenna tuning unit (ATU), antenna coupler, and feedline coupler are all equivalent names for a device connected between a radio and its antenna to improve power transfer between them by matching the impedance of the radio to the combined impedance of the antenna and feedline.wikipedia
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Antenna (radio)

antennaantennasradio antenna
Antenna tuner, matchbox, transmatch, antenna tuning unit (ATU), antenna coupler, and feedline coupler are all equivalent names for a device connected between a radio and its antenna to improve power transfer between them by matching the impedance of the radio to the combined impedance of the antenna and feedline.
An antenna coupling network is a passive network (generally a combination of inductive and capacitive circuit elements) used for impedance matching in between the antenna and the transmitter or receiver.

Feed line

feedlinefeeder linefeeding line
In transmitting systems with an antenna separated from the transmitter and connected to it by a transmission line (feedline), there may be another matching network (or ATU) at the antenna that matches the transmission line’s impedance to the antenna.
This adjustment is done with a device called an antenna tuner in the transmitter, and sometimes a matching network at the antenna.

Impedance matching

matching networkimpedance matchmatching
Antenna tuner, matchbox, transmatch, antenna tuning unit (ATU), antenna coupler, and feedline coupler are all equivalent names for a device connected between a radio and its antenna to improve power transfer between them by matching the impedance of the radio to the combined impedance of the antenna and feedline. In transmitting systems with an antenna separated from the transmitter and connected to it by a transmission line (feedline), there may be another matching network (or ATU) at the antenna that matches the transmission line’s impedance to the antenna.
These passive (and active) impedance-matching devices are optimized for different applications and include baluns, antenna tuners (sometimes called ATUs or roller-coasters, because of their appearance), acoustic horns, matching networks, and terminators.

Standing wave ratio

SWRvoltage standing wave ratioVSWR
If there is still a high standing wave ratio (SWR) in the feedline beyond the ATU, any loss in the feedline is multiplied several times by the transmitted waves reflecting back and forth between the tuner and the antenna, heating the wire instead of sending out a signal.
Matching the impedance of the antenna to the impedance of the feed line can sometimes be accomplished through adjusting the antenna itself, but otherwise is possible using an antenna tuner, an impedance matching device.

Electrical length

electrically shortelectrical lengtheningelectrical lengthing
Electrical lengthening
Since resonant antennas are usually specified in terms of the electrical length of their conductors (such as the half wave dipole), the attainment of such an electrical length is loosely equated with electrical resonance, that is, a purely resistive impedance at the antenna's input, as is usually desired. An antenna that has been made slightly too long, for instance, will present an inductive reactance, which can be corrected by physically shortening the antenna. Based on this understanding, a common jargon in the antenna trade refers to the achievement of resonance (cancellation of reactance) at the antenna terminals as electrically shortening that too-long antenna (or electrically lengthening a too-short antenna) when an electrical matching network (or antenna tuner) has performed that task without physically altering the antenna's length. Although a very inexact use of terminology, this usage is widespread, especially as applied to the use of a loading coil at the bottom of a short monopole (a vertical, or whip antenna) to "electrically lengthen" it and achieve electrical resonance as seen through the loading coil.

R. L. Drake Company

DrakeR.L. Drake
This circuit was used in tuners covering 1.8 to 30 MHz made by the R. L. Drake Company.
Along with transceivers and separates, the 4-Line included a set of matching accessories including the L-4 linear amplifier, C-4 control console, W-4 and WV-4 power meters, transmit and receive converters for the 50 MHz (6 meter) and 144 MHz (2 meter) bands, and antenna impedance matching networks (tuners), the MN-4 and MN-2000.

Transmitter

radio transmittertransmittersradio transmitters
Antenna tuner, matchbox, transmatch, antenna tuning unit (ATU), antenna coupler, and feedline coupler are all equivalent names for a device connected between a radio and its antenna to improve power transfer between them by matching the impedance of the radio to the combined impedance of the antenna and feedline.
An impedance matching (antenna tuner) circuit to match the impedance of the transmitter to the impedance of the antenna (or the transmission line to the antenna), to transfer power efficiently to the antenna. If these impedances are not equal, it causes a condition called standing waves, in which the power is reflected back from the antenna toward the transmitter, wasting power and sometimes overheating the transmitter.

Inductor

inductorscoilinductive
Here the inherent capacitance of a short, random wire antenna is so high that the L-network is best realized with two inductors, instead of aggravating the problem by using a capacitor.
It is used in antenna tuners and matching circuits to match low frequency transmitters to their antennas.

Dipole antenna

dipolehalf-wave dipoledipoles
The antenna feedpoint is usually high in the air (for example, a dipole antenna) or far away (for example, a ground-mounted monopole antenna used for receiving as well as transmitting).
Not being close to 3⁄2 wavelengths, this antenna's impedance has a large (negative) reactance and can only be used with an impedance matching network (or "antenna tuner").

Preselector

The Series Parallel Capacitor or SPC tuner can serve both as an antenna coupler and as a preselector.
Although a preselector is placed in the same location as an antenna tuner, it serves a different purpose: An antenna tuner or “transmatch” connects two signal lines with different signal impedances and only blocks out-of-tune frequencies incidentally (if it blocks any at all).

Loading coil

load coilloaded cableloading coils
Loading coil
Antenna tuner

Electrical impedance

impedanceimpedancescomplex impedance
Antenna tuner, matchbox, transmatch, antenna tuning unit (ATU), antenna coupler, and feedline coupler are all equivalent names for a device connected between a radio and its antenna to improve power transfer between them by matching the impedance of the radio to the combined impedance of the antenna and feedline. If the impedance seen by the transmitter departs from this design value, the output power can be reflected back towards the transmitter, creating a condition called "standing waves".

Load pull

load
Transmitters are designed to feed power into a resistive load of a specific value, very often 50 Ohms.

Ohm

Ωohms
Transmitters are designed to feed power into a resistive load of a specific value, very often 50 Ohms.

Standing wave

standing wavesstationary wavestationary waves
If the impedance seen by the transmitter departs from this design value, the output power can be reflected back towards the transmitter, creating a condition called "standing waves".

Electrical network

circuitelectrical circuitelectric circuit
They may be a circuit incorporated into the transmitter itself, or a separate piece of equipment connected between the transmitter and the antenna.

Transmission line

transmission linestransmissionbalanced transmission line
In transmitting systems with an antenna separated from the transmitter and connected to it by a transmission line (feedline), there may be another matching network (or ATU) at the antenna that matches the transmission line’s impedance to the antenna.

Mobile phone

cell phonemobilemobile phones
Transmitters with built-in antennas that only cover a narrow frequency band, such as cell phones and walkie-talkies, have an ATU circuit inside permanently set to work with the installed antenna.

Walkie-talkie

walkie talkiewalkie-talkiesradio
Transmitters with built-in antennas that only cover a narrow frequency band, such as cell phones and walkie-talkies, have an ATU circuit inside permanently set to work with the installed antenna.

Amateur radio

ham radioamateur radio licenseamateur
In communication stations like amateur radio stations and high power transmitters like radio broadcasting stations, the ATU is adjustable to accommodate changes in the frequency, antenna, or transmitter, and adjusting the ATU to match the transmitter to the antenna is an important procedure which is done after any work on the transmitter or antenna occurs.

Radio broadcasting

radio stationsradio stationradio
In communication stations like amateur radio stations and high power transmitters like radio broadcasting stations, the ATU is adjustable to accommodate changes in the frequency, antenna, or transmitter, and adjusting the ATU to match the transmitter to the antenna is an important procedure which is done after any work on the transmitter or antenna occurs.

Radio station

stationradio stationsradio
In communication stations like amateur radio stations and high power transmitters like radio broadcasting stations, the ATU is adjustable to accommodate changes in the frequency, antenna, or transmitter, and adjusting the ATU to match the transmitter to the antenna is an important procedure which is done after any work on the transmitter or antenna occurs.

SWR meter

This adjustment is typically made using an instrument called an SWR meter, which measures the amount of power reflected back toward the transmitter.

Electrical resonance

resonanceresonateResonant
However, in practical systems feedline losses limit the ability of the antenna ‘tuner’ to match the antenna or change its resonant frequency.

Coaxial cable

coaxialcoax cablecable
But with lossy, low-impedance feedlines like the commonly used 50 Ohm coaxial cable, maximum power transfer only occurs if matching is done at both ends of the line.