Electrical parameter coefficient of standing wave. On the antennas, coaxial cables and CWS, is simple about complex. What can lead to inaccurate balancing

When installing and configuring radio communication systems, it is often measured by a certain not all and not quite clear value called KSW. What is this characteristic, in addition to the frequency spectrum, indicated in the characteristics of the antennas?
We answer:
The coefficient of the standing wave (CWS), the beading wave coefficient (CBW), the inverse losses are the terms characterizing the degree of coordination of the radio frequency path.
In high-frequency transmission lines, the correspondence of the signal source resistance to the wave resistance of the line determines the conditions for passing the signal. With the equality of these resistances, the running wave mode arises in the line, in which all the power of the signal source is transmitted to the load.

The cable resistance measured on constant current will show either idling or a short circuit depending on this, which is connected to another end of the cable, and the wave resistance of the coaxial cable is determined by the ratio of the diameters of the internal and external cable conductor and the characteristics of the insulator between them. Wave resistance is a resistance that has a high-frequency running wave line. Wave resistance constantly along the line and does not depend on its length. For radio frequencies, the wave resistance line is considered unchanged and purely active. It is approximately equal:
where L and with the distributed container and the inductance of the line;




Where: D is the diameter of the external conductor, D is the diameter of the internal conductor, the dielectric constant of the insulator.
When calculating radio frequency cables, they strive to obtain an optimal design that provides high electrical characteristics with the lowest consumption of materials.
When using copper for internal and external radio frequency cable conductors, the ratio is true:
Minimal attenuation in the cable is achieved by diameter ratio

Maximum electrical strength is achieved with:

Maximum power transmitted with:

Based on these ratios, wave resistances of radio frequency cables manufactured by industry are selected.
The accuracy and stability of cable parameters depend on the accuracy of the manufacture of diameters of internal and external conductors and the stability of the parameters of the dielectric.
There is no reflection in the perfectly agreed line. When the load resistance is equal to the wave resistance of the transmission line, the incident wave is completely absorbed in the load, the reflected and standing waves are absent. This mode is called a running wave mode.
With a short circuit or idling, the line in the end of the line, the incident wave is completely reflected back. The reflected wave is folded with the falling, and the resulting amplitude in any section cross section is the sum of the amplitude of the incident and reflected waves. The voltage maximum is called the beaciousness, minimum voltage of the voltage node. Nodes and beacons do not move relative to the transmission line. This mode is called a standing wave mode.
If an arbitrary load is connected at the output of the transmission line, only a part of the incident wave is reflected back. Depending on the degree of mismatch, a reflected wave is increasing. The line simultaneously installs standing and running waves. This is a mode of mixed or combined waves.
The coefficient of standing wave (CWS) is a dimensionless value that characterizes the ratio of incident and reflected waves in the line, that is, the degree of approximation to the traveling wave mode:
; As can be seen by definition, the KSW can vary from 1 to infinity;
The CWW changes in proportion to the ratio of the load resistance to the wave resistance of the line:

Running wave coefficient This is the value of the reverse QCV:
CBW \u003d may vary from 0 to 1;

  • Return Loss is the ratio of power supply and reflected waves expressed in decibels.

or vice versa:
Reverse losses are convenient to use when evaluating the effectiveness of the feeder path when the cable loss expressed in dB / m can be simply summed up with feedback.
The magnitude of the mismatch loss depends on the KSV:
rapidly or in decibels.
Transmitted energy with inconsistent loads is less than when consistent. The transmitter operating on the inconsistent load does not give a line all the power that would be given to the agreed. In fact, it is not loss in line, but a reduction in the power given to the transmitter line. How much affects the KSV to reduce, can be seen from the table:

Power Fiting to Load

Feed losses
RL

It is important to understand that:

  • The KSW is the same in any section cross section and cannot be regulated by changing the length of the line. If the testimony of the KSV meter when moving along the line differ significantly, this may indicate the antenna effect of the feeder, caused by a current current on the outer side of the coaxial cable braid, and / or on the bad design of the meter, but not that the CWW changes along the line.
  • Reflected power does not fall back to the transmitter does not heat and does not damage it. Damage can be caused by the operation of the transmitter output cascade on the incidental load. Exit from the transmitter, since at its output may be in an unfavorable case, the output voltage and the reflected wave can occur due to exceeding the maximum allowable semiconductor transition voltage.
  • High CWW in a coaxial feeder caused by a significant mismatch of the characteristic resistance of the line and the input resistance of the antenna, in itself does not cause the appearance of the RF current on the outer surface of the cable braid and the emission of the feeder line.

The CWS is measured, for example, using two directed couplers included in the tract in opposite directions or the measuring bridge reflectometer, which allows you to obtain signals proportional to the incident and reflected signal.

Various devices can be used to measure the CWW. Complex devices are in their composition of the swinging frequency generator, which allows you to see the panoramic picture of the KSW. Simple devices consist of couplers and indicators, and the signal source is used external, for example, a radio station.

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


P4-11 served to measure the KSWH, the phase of the reflection coefficient, module and phase of the transmission coefficient in the range of 1-1250 MHz.
Imported devices for measuring KSV who have become classic from Bird and Telewave:

Or easier and cheaper:

Simple and inexpensive Panoramic meters from AEA:

The measurement of the CWC can be carried out both at a specific point of the spectrum and in panorama. In this case, the XV values \u200b\u200bcan be displayed on the analyzer screen in the specified spectrum, which is convenient for setting the specific antenna and eliminates the blundering when trimming an antenna.
To most system analyzers, there are Control Head - reflectometric bridges, allowing to measure the CWS with high accuracy at a frequency point or in panorama:

The practical measurement consists in connecting the meter to the connector of the test device or into the path breaks when using the passage instrument. The CWW value depends on many factors:

  • Beggars, defects, inhomogeneities, adhesions in cables.
  • Quality cutting cable in radio frequency connectors.
  • The presence of transition connectors
  • Moisture getting into cables.

When measuring the CWW antenna through a feeder with losses, the test signal in the line fades and the feeder will make an error corresponding to the losses in it. And falling, and reflected waves feel attenuation. In such cases, KSVN is calculated:
Where k. - The attenuation coefficient of the reflected wave, which is calculated: k \u003d 2bl; IN- specific attenuation, dB / m; L.- Cable length, m, while
factor 2 It takes into account that the signal is weakened twice - on the path 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 loosening on the length of the feeder of 40 meters will be 1.6 dB in each direction, only 3.2 dB. It means that instead of the actual value of the CSW \u003d 2.0, the device will show 1.38; When CMV \u003d 3.00, the device will show about 2.08.

For example, if you check the feeder path with a loss of 3DB, an antenna with KSV 1.9 and use a 10 W power transmitter as a signal source for passing meter, then the incident power measured by the instrument will be 10W. The filed signal will weaken the feeder 2 times, the antenna will reflect 0.9 the incident signal and, finally, the reflected signal on the way to the device will be aslaring 2 more times. The device honestly shows the ratio of falling and reflected signals. Falling power 10W and reflected 0.25W. KSV 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 be insufficient to create the desired voltage on the detector of the reflected wave and you will see the noise path.

In general, the efforts spent on the reduction of the KSW below 2: 1 in any coaxial line do not give results from the point of view of an increase in the efficiency of the antenna emission, and are appropriate in cases where the transmitter protection scheme is triggered, for example, when CWS\u003e 1.5 or Frequency-dependent chains connected to the feeder are upset.

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

The MFJ-259 XV meter is very compact, it can be used both with an external low voltage power supply and with an internal set of AA batteries.

MFJ-269.
CSW meter MFJ-269 Compacted combined device with autonomous power.
The indication of operation modes is carried out on a liquid crystal display, and measurement results - on the LCD and the shooting devices located on the front panel.
MFJ-269 allows you to produce a large number of additional antenna measurements: RF impedance, losses in cables and their electrical lengths to the breakdown or short circuit.


Specifications

Frequency range, MHz

Measured characteristics
  • electrical length (in feet or degrees);
  • losses in feeder lines (dB);
  • capacity (PF);
  • impedance or value z (OM);
  • phase angle impedance (in degrees);
  • inductance (ICGN);
  • reactive resistance or x (Ohm);
  • active resistance or R (OM);
  • resonant frequency (MHz);
  • return loss (dB);
  • signal frequency (MHz);
  • KSV (Zo programmed).

200x100x65 mm

The range of operating frequencies of the KSV meter is divided into subbands: 1.8 ... 4 MHz, 27 ... 70 MHz, 415 ... 470 MHz, 4.0 ... 10 MHz, 70 ... 114 MHz, 10 ... 27 MHz, 114 ... 170 MHz

KSV and Power MetersComet.
A series of power meters and CMW COMET is represented by three models: CMX-200 (CWW and power meter, 1.8-200 MHz, 30/300/3 kW), CMX-1 (KSV and power meter, 1.8-60 MHz, 30/300/3 kW) and representing the greatest interest, CMX2300 T (KSV and power meter, 1.8-60 / 140-525 MHz, 30/300/3 kW, 20/50/200 W)
CMX2300 T.
The power meter and the CMX-2300 CMX-2300 consists of two independent ranges of the range of 1.8-200 MHz and the range of 140-525 MHz with the possibility of simultaneously measuring these ranges. The passage structure of the device and, as a result, the low loss of power allows measurements 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% (all scales)

CSW measurement area

from 1 to infinity

Resistance

Residual ksv

1.2 and less

Depository

0.2 dB or less

Minimum power for measuring KSV

Approximately 6W.

M-shaped

Nutrition for lighting lamps

11 - 15V DC, approximately 450 mA

Dimensions (data in brackets, taking into account protrusions)

250 (W) x 93 (98) (c) x 110 (135) (g)

Approximately 1540

Power meters and KSVNissen.
Often to work at the facility does not require a complex and giving full picture, but rather functional and easy to use the device. It is such "work horses" and is a series of power meters and NISSEN CWS.
The simple passage structure and the high limit value of power up to 200 W in conjunction with the frequency spectrum of 1.6-525 MHz make Nissen devices very valuable means where there is no integrated characteristic of the line A speed and measurement accuracy.
Nissei TX-502
The characteristic representative of the Nissen meter series can serve as Nissen TX-502. Measurement of direct and feed losses, measurement of the CWS, the arrow panel with a clearly visible graduation. Maximum functional with concise execution. And at the same time, during the configuration of the antennas, this is often quite enough for quick and operational deployment of the communication system and adjust the channel.

Coefficient of standing wave

Coefficient of standing wave - The ratio of the greatest value of the amplitude of the electric or magnetic field of the standing wave in the transmission line to the smallest.

It characterizes the degree of coordination of the antenna and the feeder (also talk about coordination of the output of the transmitter and the feeder) and is a frequency-dependent value. The reverse value of the KSW is called the CBW - the coefficient of the running wave. The values \u200b\u200bof the KSV and the KSVN should be distinguished (coefficient of standing wave voltage): the first is calculated by power, the second - voltage amplitude and in practice it is used more often; In general, these concepts are equivalent.

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

In the ideal case, KSVN \u003d 1, this means that the reflected wave is absent. When the reflected wave, the KSW increases in direct regulation on the degree of disagreement of the path and load. The permissible values \u200b\u200bof the KSWN at the operating frequency or in the frequency band for different devices are regulated in technical specifications and GOST. Typically, the acceptable values \u200b\u200bof the coefficient are in the range from 1.1 to 2.0.

The CWV value depends on many factors, for example:

  • Wave resistance of microwave cable and microwave source
  • Heterogeneity, spikes in cables or waveguides
  • Quality of cable cutting in microwave connectors (connectors)
  • The presence of transition connectors
  • Antenna Resistance at Cable Connection Point
  • The quality of manufacturing and setting the source of the signal and the consumer (antenna, etc.)

Measure the KSWN, for example, using the two directional couplers included in the path in the opposite direction. In Space Technology, the KSWN is measured by the CWS sensors built into the waveguide paths. Modern chain analyzers also have built-in KSVN sensors.
When performing measurements of the KSWN, it is necessary to take into account that the attenuation of the signal in the cable leads to measurement errors. This is explained by the fact that both falling and reflected waves feel attenuation. In such cases, KSWN is calculated as follows:

Where TO - The attenuation coefficient of the reflected wave, which is calculated as follows:,
here IN - specific attenuation, dB / m;
L. - Cable length, m;
And multiplier 2 takes into account the fact that the signal is attenuating when transmitting from the source of the microwave signal to the antenna and on the way back. So, when using the cable PK50-7-15, the specific attenuation at the SI-bi frequencies (about 27 MHz) is 0.04 dB / m, then at a cable length of 40 m, the reflected signal will be tightened 0.04 2 40 \u003d 3.2 dB. This will lead to the fact that with the real value of KSVN, equal to 2.00, the device will show only 1.38; With a real value of the 3.00 device will show about 2.08.

The bad (high) value of the load (H) of the load leads not only to the deterioration of the efficiency due to the reduction of the useful power received in the load. Other consequences are possible:

  • The failure of a powerful amplifier or transistor, since at its output (collector) are summed up (at worst) the output voltage and the reflected wave, which may exceed the maximum allowable semiconductor transition voltage.
  • The deterioration of the unevenness of the frequency response.
  • The excitation of the mating cascades.

Protective valves or circulators can be used to eliminate this. But with continuous work on a bad load, they may fail. Matching attenuators can be used for low-power transmission lines.

Communication of KSVN with S-Parameters of the Quadruple

The coefficient of the standing wave can be unambiguously associated with the parameters of the transfer of a four-solubular (S-parameters):

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

KSV analogues in foreign publications

  • VSWR - full analog of KSVN
  • SWR - full analog of KSV

Notes


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What to choose an antenna on the car? There are many options. From the cheapest and most simple "rods" to very expensive and long. Obviously, it is necessary to choose what size the pin is not yet scary to put on the car. In general, the longer pin, the better the connection (provided that the antenna is agreed).

How to set up an antenna? To do this, you need a priest - KSW-METP. We must think that you can configure an antenna without it. The KSW meter costs about 1000 rubles. It is necessary to set the antenna in the nearest approximation at a minimum of the CWC (the coefficient of the standing wave), it is necessary to achieve the KSV less than 1.5; Usually the automotive can be brought to 1.1. It should be borne in mind that work in the CWS\u003e 3 may result in damage to the output cascade of the transmitter of imported Si-bi (in the radiation production of KB Berkut transmitters are less critical to the configuration of the antennas, no failure).

In general, the tincture and the choice of antenna is the case of a separate FAQ.

What should I remember when choosing an antenna? Antenna is the best amplifier.A good antenna will save on an amplifier. Especially since the amplifier can still be used without a fairly good antenna - he simply fails with a bad KSW (worse than 2, if the amplifier is quite powerful).

What is a feeder? Feeder, the feeder line is a line of station and antenna. In the general case, a coaxial cable with a wave resistance of 50 ohms. The feeder makes losses into the signal, so the cable with smaller losses is more expensive, but with a long time it can justify itself. The feeder feeding the antenna can work in several modes:

Unconfigured feeder Perfect matching (CWS \u003d 1) is obtained with the equality of the output resistance of the radio station, the feeder wave resistance (in the particular case of a coaxial cable) and an antenna input resistance. The frequency band in which a condition is performed sufficiently good matching is determined by the change in the complex output and input resistances of the transmitter and the antenna, respectively, when the operating frequency changes. When working in this mode, the feeder length may be arbitrary. Most of the modern radio stations and industrial antennas have in. / Out. Resistance (theoretically) 50 ohms and, when using a cable with a wave resistance of 50 ohms, not required with a configured antenna. Industrial KSV meters are also designed for 50 ohms.

Customized feeder. When using a feeder with a wave resistance other than the input and output resistances of the antenna and the passiostation can also be achieved by the ideal coordination (CWS \u003d 1). Sufficient conditions for this is the equality of the input and output resistances of the antenna and the index, and the feeder length, the multiple half of the wavelength in the feeder (i.e., taking into account the shortening coefficient). In this case, the feeder works in the (half-wave) repeater mode. Those. Regardless of the wave resistance of the feeder, it does not affect the approval of the antenna from P-st. This is associated with the well-known method of "settings" of the cable. To the exit of the P-ST (we consider the 50 Ohm) the KSV meter is connected, then the cable. By the end of the cable, the equivalent of the load is connected - a non-induction resistor of 50 ohms. Gradually shortening the cable, achieve the CWS \u003d 1. In this case, the cable length should turn out to be a multiple half-wave (which in the RG-58C / U cable with polyethylene insulation for CB is equal to the magical number of 3.62 meters). With a significant change in the working frequency, the coordination is broken (because the wavelength changes in the cable).

What types of cable and connections are used to connect antennas? When connecting an antenna to portables, the TNC connector is used (threaded, reliable) and BNC (domestic CP-50) - bayonet, somewhat less reliable, and the RG-58 type cable with different letters (by electrical properties).

On vehicles are used by the PL259 connector for a thin cable (RG-58) and this cable (RG-58).

Based on the PL259 connector for thick cable and the RG-213 cable (thick with low losses). There are adapters from any connectivity to any.

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

What is the antenna negotiation? Roughly speaking the efficiency of the system of the fide-antenna station, as well as the process of obtaining the maximum efficiency. Depends on the frequency, i.e. At one frequency, for example, in 20 channels of the C mesh, it is good, and in channels 1 and 40 of the same grid C it may be bad. Adjusts the length of the pin antenna or feeder cable, or a special matching device, in English - the Matcher. In the general case, the equivalent resistance on the antenna station connector (amplifier) \u200b\u200bof 50 ohms. The equivalent resistance of different antennas is essentially different, from 30 to several thousand ohms. In branded antennas, constructive approval has already been made, the homemade is better to connect through the menu, but since the antenna resistance also depends on local conditions, any antenna must be adjusted in place.

What is a match? In the simplest case of P-contout, consisting of inductor coil and two variable containers. By adjusting these containers, you can change the input and output complex resistance of this four-solid, and the coordination is achieved.

What is KSV? The coefficient of standing wave is a measure of coordination. It happens from 1 (ideal) to 3 (bad, but you can work), 4 ... 5 - it is not recommended to work, it may be more. It is measured by a special device - the KSW meter. They use it like this: the instrument is included between the antenna and the amplifier (station). ATTENTION: The device must allow work at your power !!! Switch to put in the FWD position (direct inclusion). Turn on the transmission, set the handle the arrow to the end of the scale, switch the device to the REF position, turn on the transmission, consider the CWS value.

Power loss:

KSV \u003d 1- loss 0%

KSV \u003d 1.3 - Losses 2%

KSV \u003d 1.5 - loss 3%

KSV \u003d 1.7 - 6% loss

KS \u003d 2 - Loss 11%

KSV \u003d 3 - Losses 25%

KSV \u003d 4 - loss 38%

KSV \u003d 10- loss 70%

But the increase in efficiency due to length - as a rule is much more significant in power losses - i.e. A longer antenna with the worst KSW is usually better than a short antenna with good CWS (in the formulas the range is proportional to the fourth degree from the power (with strong electromagnetic interference rather than the root square), i.e. power loss by 16% will reduce the range by 2 -four%). But the physical dimensions of the antenna, the height of the upper point above the earth - in all formulas of the communication range are included as a direct proportionality of the range, and not the roots of square or 4th degrees, i.e. Influence the range of radio communications is much stronger).

Return losses, reflection coefficient and coefficient of standing waves serve to assess the consistency / coincidence of complex resistance (electrical impedances) of the source, load and transmission line. Consider the physical meaning of these parameters and their relationship.

Definitions

Return losses (feedback, Return Loss) are power loss in a signal returned / reflected from heterogeneity in the transmission line or fiber. This value is usually expressed in decibels (dB):

  • RL dB - return losses in decibels;
  • P PAD - Falling power;
  • P OTP - reflected power.

The reflection coefficient of voltage, γ is the ratio of complex amplitudes of stresses of reflected and incident waves.

\\ [Γ \u003d (u_ (OTR) \\ OVER U_ (PAD)) \\]

The reflection coefficient is determined by complex load resistances Z Narch and the source of Z East:

\\ [Γ \u003d ((z_ (nurts) - z_ (IST)) \\ OVER (Z_ (Narr) + Z_ (East))) \\]

Note that the negative reflection coefficient means that the reflected wave is shifted by a phase by 180 °.

The coefficient of the standing wave (CWS, KSWN, the standing wave coefficient, SWR, VSWR) - the ratio of the greatest value of the amplitude of the standing wave voltage to the smallest.

\\ [КСВ \u003d (u_ (st .max) \\ OVER U_ (st .mill)) \\]

Since the uneven distribution of the amplitude of the standing wave along the line is due to the interference ("addition and subtraction") of the incident and reflected waves, the greatest value of the amplitude U Art. Max waves along the line (that is, the amplitude value in the beacon) is:

U Pad + U Otr

and the smallest value of amplitude (i.e., the value of amplitude in the node) is

U Pad - U Ot

Hence

\\ [CWS \u003d ((U_ (PAD) + U_ (OTP)) \\ OVER (U_ (PAD) - U_ (OTP))) \\]

Relationship between KSW, return loss and reflection coefficient

With the help of the substitution in the formula below, and their simple conversion can be obtained as follows:

\\ [Γ \u003d ((KSW-1) \\ OVER (KSV + 1)) \\]

\\ [KSV \u003d ((1 + γ) \\ OVER (1-γ)) \\]

\\ [Γ \u003d 10 ^ ((- RL) \\ OVER 20) \\]

\\ [KSV \u003d ((1 + 10 ^ ((- RL) \\ OVER 20)) \\ OVER (1 - 10 ^ ((- RL) \\ OVER 20))) \\]

Table conversion of KSV values, return loss and reflection coefficient
Reflection coefficient | γ | in %Return losses, dBCoefficient of standing wave
100,0000 0 ∞
89,1251 1 17,3910
79,4328 2 8,7242
70,7946 3 5,8480
63,0957 4 4,4194
56,2341 5 3,5698
50,1187 6 3,0095
44,6684 7 2,6146
39,8107 8 2,3229
35,4813 9 2,0999
31,6228 10 1,9250
28,1838 11 1,7849
25,1189 12 1,6709
22,3872 13 1,5769
19,9526 14 1,4985
17,7828 15 1,4326
15,8489 16 1,3767
14,1254 17 1,3290
12,5893 18 1,2880
11,2202 19 1,2528
10,0000 20 1,2222
8,9125 21 1,1957
7,9433 22 1,1726
7,0795 23 1,1524
6,3096 24 1,1347
5,6234 25 1,1192
5,0119 26 1,1055
4,4668 27 1,0935
3,9811 28 1,0829
3,5481 29 1,0736
3,1623 30 1,0653
2,8184 31 1,0580
2,5119 32 1,0515
2,2387 33 1,0458
1,9953 34 1,0407
1,7783 35 1,0362
1,5849 36 1,0322
1,4125 37 1,0287
1,2589 38 1,0255
1,1220 39 1,0227
1,0000 40 1,0202
0,8913 41 1,0180
0,7943 42 1,0160
0,7079 43 1,0143
0,6310 44 1,0127
0,5623 45 1,0113
0,5012 46 1,0101

Have you become a happy owner of a portable or automotive radio station? Now there is a turn to prepare a walkie-talkie to work. The mechanical part of the work described by the manufacturer in the instructions does not cause problems - for this you need a minimum set of tools and a bit of intelligence. But with the antenna setting is not so simple.

If, following the scheme, mechanically connect the wires, then, most likely you will not be heard. We begin to understand, and the question arises: what is the coefficient of the standing wave antenna, or SWR, if the instruction in English.

This is a coefficient that shows which part of the energy of radio waves goes to the antenna, and which part returns back to the feeder. Without the correct setup of the KSW, your wagon will not work correctly and will not provide comfortable communication.

Coefficient standing wave antenna

If it is completely simple, this is a digit on the measuring device, which characterizes the correctness of the settings of your radio station. We'll figure it out in the physical essence of the KSV.

Radio waves apply to the waveguide - the antenna-feeder path. That is, the signal coming from the transmitter falls on the antenna by means of a cable fider. Not delighting the theory of waves, the radio station user needs to be understood that there are falling and reflected waves in any waveguide. Falling waves come directly on the antenna, and the reflected returns back to the feeder and nothing but heating the surrounding atmosphere are not engaged. All waves have a property to develop. As a result of the addition of the amplitudes of reflected and falling waves, it creates an uneven field along the entire length of the feeder cable. Thus, the inverse losses of the KSW are formed. Than they are more, the weaker the signal of your radio station and the worse the subscribers will hear you.

Experts distinguish the coefficients of standing waves on the voltage (KSVN) and in power (CWS). Practically, these concepts are observed that for the user who makes the configuration of its radio station, there is no difference.

Standing wave coefficient: calculation formula

The KSV coefficient when setting up the radio station is not calculated by formulas, but is determined using a special device. What is a KSV meter? This is an easy-to-use electronic device that shows the difference in the amplitude of oscillations, and this is the coefficient of standing wave.

The CCV formula is not the most difficult:

KSV \u003d umax / umin

In it in the numerator and denominator, the maximum and minimum amplitudes:

  • Umax - the sum of the capacities of the falling and reflected wave;
  • Umin is the difference between the flow rate of the incident and reflected signal.

It is easy to conclude that with the equality of Umax and UMIN KSV will be equal to one and this is ideal conditions for the effective operation of your radio station. But, since there are no ideal conditions in nature, then when configuring the CWW antenna, you will have to try to tighten the KSW to one.

What could be the cause of increased CWS? Factors set:

  • wave resistance of the cable and radio source;
  • incorrect spike, inhomogeneity of waveguides;
  • poor-quality cable cutting in the lines of connectors;
  • adapters;
  • increased resistance at the cable connection site with an antenna;
  • poor-quality assembly of the transmitter and the KSVN antenna.

If you do not go into the formula for calculating the CWS, which for the owner of the automotive radio station represent little interest, we will proceed to the practical aspect of the antenna setting.

How to measure KSW

First of all, you need a CWW meter. It can be bought or rent. Then:

  • turn on the radio and install its switch to the SWR position;
  • click the Tangent transmission and the KSV meter regulator, output the arrow to the maximum;
  • click Ref and click on the tangent again;
  • see what shows the shooter on the SWR scale is your KSW.

He, of course, will be far from the ideal unit, but you now have something to do. By the way, with an indicator within:

  • 1.1-1.5 can work;
  • 1.5-2.5 - in principle satisfactory;
  • more than 2.5 - you need to work.

What to do? This is the subject of a separate big article or a reason to turn to the master, who knows what the KSV is and how to work with it.

You can buy an instrument for defining the KSV right now on our website. In the catalog, your attention is presented by professional and amateur modifications of VEGA and OPTIM brands, which can be used not only when installing antenna, but also for continuous monitoring of the radio station.