What is the standing wave ratio? Voltage standing wave ratio (VSWR, vswr). Power delivered to the load

Often, a client, especially if he buys a walkie-talkie for the first time, is perplexed at the mention that in order to use the walkie-talkie, you need to adjust the antenna, namely, you need antenna SWR tuning. What is KSV? This term is incomprehensible to a person far from technical subtleties and sometimes even frightening. In fact, everything is simple.

What is KSV? The antenna is tuned using a special device - an SWR meter. It measures the standing wave ratio and shows the power loss in the antenna. The lower this value (SWR), the better. The ideal value is 1, but in practice it is unattainable due to signal losses in the cable and connectors, a value of 1.1 - 1.5 is considered to be working, values from 2 to 3 are acceptable. Why is it acceptable? Because if the SWR value is too high, your antenna starts not only to radiate a signal on the air, but to "drive" it back into the radio. What does this mean and why is it bad, you ask? First, you lose in communication range, because the efficiency of your radio-antenna system is reduced. Secondly, the output stages of the radio station overheat, up to a possible failure. That is why it is important adjusting the SWR of the antenna after it has been installed. One inexpensive SWR meter is the SWR-420 or SWR-430 from Optim. It can be used with 27MHz radios with transmitter output power up to 100W. The measurement error is no more than 5%. Using this device, you can achieve SWR values \u003d 1.1 - 1.3, depending on the type of antenna chosen (mortise or magnetic) and its installation location. But you don't need to dwell on it. 1.5 is a completely working and safe value.

How is it made tuning the SWR antenna of the SB range? The antenna is mounted on the car body, preferably at its highest point. The installation site should be chosen carefully, since the antenna will have to be in it all the time. When installing a mortise antenna, ensure normal contact of the antenna (or bracket) with the ground and carefully monitor that there are no short circuits in the cable and cable connection points to the antenna and radio. It is important to understand that the body of your car is also an antenna element, so the installation site and the quality of contact with the ground cannot be neglected.

The SWR meter should be connected to the radio via TX connector, connect the antenna to ANT connector and select the limit of the transmitted power level. To calibrate the device, you must set the switch to the position FWD, turn on the radio to transmit on the desired channel and set the indicator arrow SWR to the last division SET red scale. After that, the device is ready for measurements. To check the SWR on the current channel, move the switch to the position REF(the radio station continues to transmit) and look at the indicator readings on the upper scale, this will be the actual SWR value. If it lies in the range of 1-1.5, the setting can be considered complete and successful. If it goes beyond this value, then we begin to select the optimal value. To do this, we first find the minimum SWR value on various channels or even grids. We follow a simple rule: if the SWR increases with increasing frequency, then the antenna needs to be shortened; if it decreases, then lengthen. Having unscrewed the screws fixing the pin, we move it in the right direction, tighten the screws and again check the readings of the device. If the pin is inserted to the limit, and the SWR is still high, then you will have to shorten the pin physically by biting off. If the pin is extended to the maximum, then you will have to increase the length of the matching coil (in practice, in this case, the antenna is easier to change).

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Delivery of the SWR meter is possible to any settlements by Russian Post cash on delivery or EMS Post, for example: Alapaevsk, Artemovsky, Asbest, Astana, Aktobe, Aksu, Atyrau, Aksai, Almaty, Balkhash, Baikonur, Balakovo, Berezovsky, Bogdanovich, Verkhnyaya Pyshma, Zarechny, Ivdel, Irbit, Kamyshlov, Karpinsk, Karaganda, Kirovgrad, Kostanay, Kokshetau, Kyzylorda, Semey, Krasnoturinsk, Krasnoufimsk, Lesnoy, Nizhnyaya Salda, Nizhnyaya Tura, Novouralsk, Pervouralsk, Polevskoy, Revda, Severouralsk, Sysert, Clicker, Tavda, Vereshchagino, Nytva, Lysva, Krasnovishersk, Aleksandrovsk, Krasnokamsk, Ocher, Polazna, Chernushka, Gornozavodsk, Dobryanka, Gremyachinsk, Kudymkar, Gubakha, Yaiva, Vikulovo, Yarkovo, Nizhnyaya Tavda, Yalutorovsk, Kaskara, Kazanskoye, Borovsky, Petropavlosk, Romashevo, Golyshmanovo , Pavlodar, Tarmany, Taldykorgan, Zhezkazgan, Vinzili, Bolshoe Sorokino, Bogandinsky, Uporovo, Uralsk, Ust-Kamenogorsk, Shymkent, Taraz, Omutinskoye, Berdyugye, Abatskoye, Antipino, Isetskoye, Turtase, Norilsk, Salekhard, Vorkuta, Votkinsk, Ekibastuz.

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standing wave ratio

standing wave ratio- The ratio of the largest value of the amplitude of the electric or magnetic field strength of a standing wave in the transmission line to the smallest.

It characterizes the degree of matching of the antenna and the feeder (they also talk about matching the output of the transmitter and the feeder) and is a frequency-dependent quantity. The reciprocal value of the SWR is called KBV - the coefficient of the traveling wave. It is necessary to distinguish between the values of SWR and VSWR (standing wave ratio by voltage): the first is calculated by power, the second - by voltage amplitude and is used more often in practice; in general, these concepts are equivalent.

The voltage standing wave ratio is calculated by the formula: ,
Where U 1 And U 2 are the amplitudes of the incident and reflected waves, respectively.
You can establish a relationship between KCBH and the reflection coefficient Г:
Also, the value of the standing wave coefficient can be obtained from the expressions for the S-parameters (see below).

Ideally, VSWR = 1, which means that there is no reflected wave. When a reflected wave appears, the SWR increases in direct proportion to the degree of mismatch between the path and the load. Permissible VSWR values at the operating frequency or in the frequency band for various devices are regulated in technical specifications and GOSTs. Generally acceptable ratio values are between 1.1 and 2.0.

The SWR value depends on many factors, for example:

Wave impedance of microwave cable and microwave signal source
Irregularities, spikes in cables or waveguides
The quality of cable cutting in microwave connectors (sockets)
Presence of adapter connectors
Antenna impedance at cable connection point
The quality of manufacture and settings of the signal source and consumer (antennas, etc.)

VSWR is measured, for example, using two directional couplers included in the path in the opposite direction. In space technology, VSWR is measured by SWR sensors built into waveguide paths. Modern network analyzers also have built-in VSWR sensors.
When measuring VSWR, it must be taken into account that signal attenuation in the cable leads to measurement errors. This is because both the incident and reflected waves are attenuated. In such cases, the VSWR is calculated as follows:

Where TO is the attenuation coefficient of the reflected wave, which is calculated as follows: ,
Here IN- specific attenuation, dB/m;
L- cable length, m;
and the factor 2 takes into account the fact that the signal is attenuated during transmission from the microwave signal source to the antenna and on the way back. So, when using the PK50-7-15 cable, the specific attenuation at CB frequencies (about 27 MHz) is 0.04 dB / m, then with a cable length of 40 m, the reflected signal will attenuate 0.04 2 40 \u003d 3.2 db. This will result in an actual VSWR of 2.00 and the instrument will only read 1.38; with a real value of 3.00, the device will show about 2.08.

A poor (high) value of SWR (H) of the load leads not only to a deterioration in efficiency due to a decrease in the useful power delivered to the load. Other consequences are also possible:

Failure of a powerful amplifier or transistor, because at its output (collector) the output signal voltage and the reflected wave are summed (in the worst case), which may exceed the maximum allowable voltage of the semiconductor junction.
Deterioration of the uneven frequency response of the tract.
Excitation of conjugated cascades.

Safety valves or circulators can be used to eliminate this. But with prolonged work on a bad load, they can fail. For low power transmission lines, matching attenuators may be used.

Relationship of VSWR with S-parameters of a quadripole

The standing wave ratio can be unambiguously related to the transmission parameters of the four-terminal network (S-parameters):

where is the complex reflection coefficient of the signal from the input of the measured path;

SWR analogues in foreign publications

VSWR - a complete analogue of VSWR
SWR - full analogue of SWR

Notes

Wikimedia Foundation. 2010 .

So, here you bought a radio station, an antenna, and after screwing the kit to the car, you are surprised to find that you cannot be heard. Fools buy an amplifier, smart people tune an antenna. You are smart, right? Therefore, when you start to understand the reasons, the first thing you stumble upon is the words SWR or “Standing Wave Ratio”.

So what is SWR or “standing wave ratio”? This is such a number that characterizes the correctness of the setting. Less is better. There is no less than 1. What it means, you can read on the Internet: there are not just a lot of articles, but a lot.

How to measure it? Usually, in the same place where they sell radio stations and antennas, you can buy an SWR meter. You don’t need a professional one at all, take the cheapest one, it should cost 400-500 rubles maximum. As a display meter, it will be enough for the eyes.

The first step is to connect it. Usually everything is drawn in the pictures, but if anything, then in ANT or ANTENNA you need to screw the antenna, and in TRANSMITTER or RADIO - the output from the radio station.

We turn on the radio.

Now look at the SWR meter itself. There are REF-FWD and/or PWR/SWR switches. 1. We click in SWR and FWD.

2. Now we press “transmission” on the radio station’s tangent and use the knob on the SWR meter to bring the arrow to the maximum on the scale.

3. Click on REF.

4. Press “transmission” again and look at the scale, which is with the letters SWR. This is the desired SWR.

Well, we got a number. Let's say 2.5 or 3. And everywhere they write that the SWR should be 1! Otherwise bad. What to do?

Below is an exclusive picture from me.

As you can see, the SWR value graph is something that looks like a U or V. I must say right away that it is different for everyone! Some slopes are steep, while others are gentle. For someone, the left is steeper than the right, or vice versa ... For someone, the minimum of the graph passes through SWR = 1, and for someone, a deuce will be ideal. In general, yours - it is only yours!

Our task is to put a minimum schedule on the channel in which you communicate the most. Let's say the 15th, where the truckers talk.

The first thing to understand is on what “slope” everything is set up now. It's simple: put the station on the 1st channel, measure the SWR, then on the 15th, measure again, then on the 30th, measure again. Let's look at the numbers.

The numbers are falling - you are on the left. The antenna needs to be extended.

The numbers are growing - you are on the right slope. The antenna needs to be shortened.

Numbers in the spirit of “big-small-big” - your SWR graph is very narrow, reduce the step. Well, or you are very close to the target - enough to move the antenna in the holder.

Numbers in the spirit of “same-same-same” - your SWR graph is very wide. It is extremely unlikely to change the length of the antenna.

In my experience, most likely you will have to cut the antenna. The rest are very rare...

After lengthening or shortening the antenna, repeat the measurement process until the minimum SWR value on the desired channel is reached. I repeat, the minimum achievable level for each installation is different!

How to shorten? With any powerful wire cutters, bite off a centimeter from the top. The main thing here is not to overdo it, because lengthening is much more dreary than cutting.

How to lengthen? Here it is more difficult. If the adjustment range of the antenna itself is not enough, then they usually solder / screw / weld a piece to the top with a margin, which would then be cut ...

More advanced ones can do the same by changing the number of turns of the wire wound on the coil (the thickening is at the bottom of the antenna), but the advanced ones don’t need this story 🙂

Which SWR values are good and which are bad? Roughly speaking, anything over 2.5 is bad. 1.5-2.5 - pull. 1.1-1.5 is good. 1 is excellent.

Do you have a high SWR and does not decrease? 99% for the fact that there is a very poor contact somewhere in the chain “antenna ground - car body - radio station body”. Or in the antenna wire and connectors.

See how simple it is?

When installing and configuring radio communication systems, they often measure some not all and not entirely clear value called SWR. What is this characteristic, in addition to the frequency spectrum, indicated in the characteristics of the antennas?
We answer:
Standing wave ratio (SWR), traveling wave ratio (TWR), return loss are terms that characterize the degree of matching of the radio frequency path.
In high-frequency transmission lines, the correspondence of the signal source impedance to the wave impedance of the line determines the conditions for the signal to pass through. If these resistances are equal, a traveling wave mode occurs in the line, in which all the power of the signal source is transferred to the load.

The cable resistance measured at direct current by the tester will show either an idle or a short circuit, depending on what is connected to the other end of the cable, and the wave impedance of the coaxial cable is determined by the ratio of the diameters of the inner and outer conductors of the cable and the characteristics of the insulator between them. Characteristic impedance is the resistance that a line provides to a traveling wave of a high-frequency signal. Wave impedance is constant along the line and does not depend on its length. For radio frequencies, the wave impedance of the line is considered to be constant and purely active. It is approximately equal to:
where L and C are the distributed capacitance and inductance of the line;

Where: D is the diameter of the outer conductor, d is the diameter of the inner conductor, is the dielectric constant of the insulator.
When designing radio frequency cables, the goal is to obtain an optimal design that provides high electrical performance with the least consumption of materials.
When using copper for the inner and outer conductors of the RF cable, the following relations are valid:
the minimum attenuation in the cable is achieved with a ratio of diameters

maximum electrical strength is achieved at:

maximum transmitted power at:

Based on these ratios, the wave impedances of RF cables produced by the industry are selected.
The accuracy and stability of the cable parameters depend on the accuracy of manufacturing the diameters of the inner and outer conductors and the stability of the dielectric parameters.
There is no reflection in a perfectly matched line. When the load resistance is equal to the impedance of the transmission line, the incident wave is completely absorbed in the load, there are no reflected and standing waves. This mode is called the traveling wave mode.
In the event of a short circuit or open circuit at the end of the line, the incident wave is completely reflected back. The reflected wave is added to the incident one, and the resulting amplitude in any section of the line is the sum of the amplitudes of the incident and reflected waves. The maximum voltage is called the antinode, the minimum voltage is called the stress node. Nodes and antinodes do not move relative to the transmission line. This mode is called standing wave mode.
If an arbitrary load is connected at the output of the transmission line, only part of the incident wave is reflected back. Depending on the degree of mismatch, the reflected wave increases. Standing and traveling waves are simultaneously established in the line. This is a mixed or combined wave mode.
The standing wave ratio (SWR) is a dimensionless quantity that characterizes the ratio of the incident and reflected waves in the line, that is, the degree of approximation to the traveling wave mode:
; as seen by definition, SWR can vary from 1 to infinity;
The SWR changes in proportion to the ratio of the load resistance to the wave impedance of the line:

The traveling wave ratio is the reciprocal of the SWR:
KBV= can vary from 0 to 1;

Return loss is the ratio of the power of the incident and reflected waves, expressed in decibels.

or vice versa:
It is convenient to use return loss when evaluating the efficiency of a feeder path, when cable losses expressed in dB/m can simply be summed with return loss.
The amount of mismatch loss depends on the SWR:
in times or in decibels.
The transmitted energy with an uncoordinated load is always less than with a matched one. A transmitter operating on an inconsistent load does not give all the power to the line that it would give to a matched one. In fact, these are not losses in the line, but a decrease in the power delivered to the line by the transmitter. How SWR affects the reduction can be seen from the table:

	Power delivered to the load	Return Loss RL

It is important to understand that:

The SWR is the same in any line section and cannot be adjusted by changing the line length. If the SWR meter readings vary significantly across the line, this may indicate feeder antenna effect caused by current flowing through the outer side of the coaxial cable sheath and/or poor meter design, but not that the SWR varies along the line.
The reflected power does not get back into the transmitter and does not heat up or damage it. Damage can be caused by the operation of the transmitter output stage on a mismatched load. The output from the transmitter, since the output signal voltage and the reflected wave can develop at its output in an unfavorable case, can occur due to the excess of the maximum allowable voltage of the semiconductor junction.
High SWR in a coaxial feeder, caused by a significant mismatch between the characteristic impedance of the line and the input impedance of the antenna, does not in itself cause the appearance of RF current on the outer surface of the cable sheath and the radiation of the feeder line.

The SWR is measured, for example, using two directional couplers connected to the path in opposite directions or a measuring bridge reflectometer, which makes it possible to obtain signals proportional to the incident and reflected signal.

Various instruments can be used to measure SWR. Sophisticated devices include a sweeping frequency generator, which allows you to see a panoramic picture of the SWR. Simple devices consist of couplers and an indicator, and an external signal source is used, for example, a radio station.

For example, a two-block RK2-47, due to a broadband bridge reflectometer, provided measurements in the range of 0.5-1250 MHz.

P4-11 was used to measure the VSWR, the phase of the reflection coefficient, the modulus and the phase of the gain in the range of 1-1250 MHz.
Imported instruments for measuring SWR that have become classic from Bird and Telewave:

Or easier and cheaper:

Simple and inexpensive panoramic meters from AEA are popular:

SWR measurement can be carried out both at a specific point in the spectrum and in a panorama. In this case, the SWR values in the specified spectrum can be displayed on the analyzer screen, which is convenient for tuning a specific antenna and eliminates a miss when cutting the antenna.
Most system analyzers have control heads - reflectometric bridges that allow you to measure SWR at a frequency point or in a panorama with high accuracy:

A practical measurement is to connect the meter to the connector of the device under test or to a break in the path when using a through-type device. The SWR value depends on many factors:

Bends, defects, inhomogeneities, adhesions in cables.
Quality of cable termination in RF connectors.
Availability of adapter connectors
Moisture ingress into cables.

When measuring the SWR of an antenna through a lossy feeder, the test signal in the line is attenuated and the feeder will introduce an error corresponding to the losses in it. Both the incident and reflected waves experience attenuation. In such cases, the VSWR is calculated:
Where k is the attenuation coefficient of the reflected wave, which is calculated: k=2BL; IN- specific attenuation, dB/m; L- cable length, m, while
factor 2 takes into account that the signal is attenuated twice - on the way to the antenna and on the way from the antenna to the source, on the way back.
For example, using a cable with a specific attenuation of 0.04 dB / m, the signal attenuation over a feeder length of 40 meters will be 1.6 dB in each direction, a total of 3.2 dB. This means that instead of the actual value of SWR = 2.0, the device will show 1.38; with SWR = 3.00, the device will show about 2.08.

For example, if you are testing a feed path with a loss of 3dB, an antenna with an SWR of 1.9, and you are using a 10W transmitter as a signal source for a pass meter, then the incident power measured by the instrument will be 10W. The given signal will be attenuated by the feeder by 2 times, 0.9 of the incoming signal will be reflected from the antenna, and, finally, the reflected signal on the way to the device will be attenuated by another 2 times. The device will honestly show the ratio of the incident and reflected signals, the incident power is 10W and the reflected power is 0.25W. The SWR will be 1.37 instead of 1.9.

If a device with a built-in generator is used, then the power of this generator may not be enough to create the required voltage on the reflected wave detector and you will see a noise track.

In general, the effort expended to reduce the SWR below 2:1 in any coaxial line does not result in an increase in the radiation efficiency of the antenna, and is advisable in cases where the transmitter protection circuit is triggered, for example, at SWR> 1.5 or the frequency-dependent circuits connected to the feeder are detuned.

Our company offers a wide range of measuring equipment from various manufacturers. Let's briefly consider them:
MFJ
MFJ-259– a fairly easy-to-use device for complex measurement of parameters of systems operating in the range from 1 to 170 MHz.

The MFJ-259 SWR meter is very compact and can be used with either an external low voltage power supply or an internal AA battery pack.

MFJ-269
The MFJ-269 SWR meter is a compact self-powered combined instrument.
Indication of operating modes is carried out on the liquid crystal display, and the measurement results - on the LCD and pointer instruments located on the front panel.
The MFJ-269 allows you to make a large number of additional antenna measurements: RF impedance, cable loss and cable lengths to the point of open or short circuit.

Specifications
Frequency range, MHz
Measured characteristics	electrical length (in feet or degrees); feeder line losses (dB); capacitance (pF); impedance or Z value (ohm); impedance phase angle (in degrees); inductance (µH); reactance or X (ohm); active resistance or R (ohm); resonant frequency (MHz); return loss (dB); signal frequency (MHz); SWR (Zo programmable).
	200x100x65 mm

The operating frequency range of the SWR meter is divided into subranges: 1.8 ... 4 MHz, 27 ... 70 MHz, 415 ... 470 MHz, 4.0 ... 10 MHz, 70 ... 114 MHz, 10 ... 27 MHz, 114 ... 170 MHz

SWR and Power Meterscomet
The Comet power and SWR series is represented by three models: CMX-200 (SWR and power meter, 1.8-200 MHz, 30/300/3 kW), CMX-1 (SWR and power meter, 1.8-60 MHz, 30/300/3kW) and, of most interest, the CMX2300 T (SWR and Power Meter, 1.8-60/140-525MHz, 30/300/3kW, 20/50/200W)
CMX2300T
The CMX-2300 power and SWR meter consists of two independent systems in the 1.8-200MHz and 140-525MHz ranges, with the ability to simultaneously measure these ranges. The pass-through structure of the device and, as a result, a low power loss allows measurements to be carried out for a long time.

Specifications
	Range M1	Range M2
frequency range	1.8 - 200 MHz	140 - 525 MHz
Power measurement area	0 - 3KW (HF), 0 - 1KW (VHF)
Power measurement range
Power measurement error	±10% (full scale)
SWR measurement area	from 1 to infinity
Resistance
Residual SWR	1.2 or less
Insertion Loss	0.2 dB or less
Minimum power for SWR measurements	Approximately 6W.
	M-shaped
Power supply for backlights	11 - 15VDC, approximately 450mA
Dimensions (data in brackets including protrusions)	250(W) x 93 (98) (H) x 110 (135) (D)
	Approximately 1540

Power meters and SWRNissen
Often, on-site work does not require a complex and complete picture, but rather a functional and easy-to-use instrument. The Nissen series of power meters and SWR is precisely such "Workhorses".
The simple pass-through structure and high power limit up to 200 W, together with the frequency spectrum of 1.6-525 MHz, make Nissen devices a very valuable tool where not a complex line characteristic is needed, but speed and accuracy of measurement.
NISSEI TX-502
Nissen TX-502 can serve as a characteristic representative of the Nissen meter series. Measurement of direct and return losses, measurement of SWR, arrow panel with a clearly visible graduation. Maximum functionality with a concise design. And at the same time, in the process of tuning antennas, this is often quite enough for a quick and efficient deployment of a communication system and channel adjustment.

Which antenna to choose for a car? There are many options here. From the cheapest and simplest "fishing rods" to very expensive and long ones. Obviously, you need to choose what size pin is not scary to put on a car. In general, the longer the pin, the better the connection (assuming the antenna is matched).

How to set up an antenna? To do this, you need a device - an SWR meter. Do not think that you can tune the antenna without it. SWR meter costs about 1000 rubles. It is necessary to tune the antenna in the first approximation according to the minimum SWR (standing wave ratio), it is required to achieve SWR less than 1.5; usually the car can be brought to 1.1. It should be borne in mind that operation at SWR> 3 can lead to damage to the output stage of the transmitter of an imported CB radio (for radios manufactured by KB Berkut, transmitters are less critical to antenna tuning, they do not fail).

In general, the tincture and choice of antennas is a matter of a separate FAQ.

What should be kept in mind when choosing an antenna? The antenna is the best amplifier. A good antenna will save on the amplifier. Moreover, the amplifier still cannot be used without a sufficiently good antenna - it will simply fail with poor SWR (worse than 2 if the amplifier is powerful enough).

What is a feeder? Feeder, feeder line is the communication line of the station and antenna. In general, a coaxial cable with a characteristic impedance of 50 ohms. The feeder introduces losses into the signal, so a cable with lower losses is more expensive, but with a long length it can justify itself. The feeder that feeds the antenna can operate in several modes:

Unconfigured feeder Ideal matching (SWR = 1) is obtained when the output impedance of the radio station, the wave impedance of the feeder (in the particular case of a coaxial cable) and the input impedance of the antenna are equal. The frequency band in which the condition of sufficiently good matching is satisfied is determined by the change in the complex output and input impedances of the transmitter and antenna, respectively, with a change in the operating frequency. When operating in this mode, the length of the feeder can be arbitrary. Most modern radios and industrial antennas have input / output. resistance (theoretically) 50 ohms and, when using a cable with a characteristic impedance of 50 ohms, with a tuned antenna, additional matching is not required. Industrial SWR meters are also rated at 50 ohms.

configured feeder. When using a feeder with a wave impedance different from the input and output impedances of the antenna and the radio station, perfect matching (SWR=1) can also be achieved. Sufficient conditions for this are the equality of the input and output impedances of the antenna and the radio, and the length of the feeder, a multiple of half the wavelength in the feeder (ie, taking into account the shortening factor). In this case, the feeder operates in the (half-wave) follower mode. Those. regardless of the wave impedance of the feeder, it does not affect the matching of the antenna with the p-st. A well-known method of "tuning" the cable is associated with this. An SWR meter is connected to the p-st output (we consider 50 ohms), then a cable. A load equivalent is connected to the end of the cable - a 50 Ohm non-inductive resistor. Gradually shortening the cable, achieve SWR = 1. In this case, the cable length should be a multiple of half a wave (which in the RG-58c / u cable with polyethylene insulation for CB is equal to the magic number of 3.62 meters). with a significant change in the operating frequency, the coordination is violated (because the wavelength in the cable changes).

What types of cable and connectors are used to connect the antennas? When connecting the antenna to portable devices, they use a TNC connector (threaded, reliable) and BNC (domestic СР-50) - bayonet, somewhat less reliable, and an RG-58 type cable with different letters (according to electrical properties).

Cars use the PL259 thin cable connector (RG-58) and this cable (RG-58).

The base uses a PL259 connector for a thick cable and an RG-213 cable (thick with reduced loss). There are adapters from any connector to any.

Domestic cable is mainly used RK-50-2 (thin) and RK-50-7 (thick) for the base.

What is antenna matching? Roughly speaking, the efficiency of the station-feeder-antenna system, as well as the process of obtaining maximum efficiency. Frequency dependent, i.e. at one frequency, for example, in channel 20 of grid C, it is good, but in channels 1 and 40 of the same grid C, it can be bad. It is adjusted by the length of the whip antenna or feeder cable, or by a special matching device, in English - a matcher. In general, the equivalent resistance at the antenna connector of the station (amplifier) is 50 ohms. The equivalent resistance of different antennas is significantly different, from 30 to several thousand ohms. Constructive coordination has already been made in branded antennas, it is better to connect home-made products through a matcher, but since the antenna resistance also depends on local conditions, any antenna must be adjusted on the spot.

What is a matcher? In the simplest case, a P-loop, consisting of an inductor and two variable capacitances. By adjusting these capacitances, it is possible to change the input and output complex resistance of this four-terminal network, and this is how matching is achieved.

What is KSV? The standing wave ratio is a measure of matching. It happens from 1 (ideal) to 3 (bad, but you can work), 4 ... 5 - it is not recommended to work, it may turn out to be more. It is measured with a special device - an SWR meter. They use it like this: turn on the device between the antenna and the amplifier (station). Attention: the device must allow operation at your power!!! Set the switch to the FWD (direct on) position. Turn on the gear, set the arrow to the end of the scale with the pen, switch the device to the REF position, turn on the gear, read the SWR value.

Power loss:

SWR=1- loss 0%

SWR \u003d 1.3 - loss of 2%

SWR \u003d 1.5 - loss of 3%

SWR=1.7 - loss 6%

KS=2 - loss 11%

SWR=3 - loss 25%

SWR=4 - loss 38%

SWR \u003d 10 - loss 70%

But the increase in efficiency due to length - as a rule - is much more significant than the loss in power - i.e. a longer antenna with a worse SWR is usually better than a short antenna with a good SWR (in the formulas, the range is proportional to the fourth root of the power (in strong electromagnetic interference, more likely to the square root), i.e. a loss of power by 16% will lead to a decrease in range by 2 -4%). But the physical dimensions of the antenna, the height of the upper point above the ground - all formulas for the communication range are included as a direct proportionality to the range, and by no means square or 4th roots, i.e. affect the radio range much more strongly).