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airborne radars
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airborne radars

airborne radars

 

Radiolakatsiey called radio engineering, is used to detect and determine the location of the air, surface and ground objects and phenomena of reflection of electromagnetic waves radiation these objects.

Methods radar

Pulsed light. With this method of periodically send brief signals with long pauses between them, and then receives the reflected signals from the object between regular sending signals (pulses).

The pulse method is characterized by: a pulse duration t; or a period T the pulse repetition frequency F; pulse energy; pulse power and average power.

 

Minimum range of detection radar

The energy carried by an impulse of radio waves, called a pulse energy. The power developed by the transmitter for the duration of the pulse is called a pulse power P.

The average power of the transmitter is the power that he developed would be working continuously, while maintaining the same power radio waves

Continuous light It is that the transmitter and receiver operates on frequency, and the degree of difference depends on the distance to the object. To reduce the effect of the transmitter to the receiver stations are used in suchtwo antennas, one for transmission and another for reception.

The phenomenon of the Doppler It lies in the fact that while moving relative to the receiver transmitter or receiver relative to the fixed transmitter receiver perceived by the oscillation frequency does not coincide with the frequency of the emitted radio waves.

The difference frequency

By measuring the detected object can be determined. With this method, you can only find moving objects, but it is impossible to determine the distance to the object and the amount of it are other smaller objects.

This principle is used in aircraft navigation station to determine ground speed and drift angle of the aircraft. The formula for determining the ground speed of the aircraft the Doppler frequency has the form:

Drift angle (DC) is determined by rotating an antenna device in a horizontal plane about a vertical axis at a constant angle between the left and right rays, achieving equality of the frequencies of the reflected signals.

 

Airborne radars allow all the tasks of piloting.

Recognizable landmarks it's best to work with the scale radars, close to the scale of the flight map. For example, if the radius of the screen mm zoom 55 1: 1 000 000 obtained by wide-range 55 km radius of the screen.

When using maps of scale 1: 2 000 000 most convenient to use the scale of the radar, if provided radar design, if not provided, then use the zoom 100 km.

With the selection of the contrast separate amplification of signals of high and low levels, the choice of the angle of the antenna beam scanning and brightness achieve the most precise selection of radar targets on the radar screen.

Place the plane (MS) is determined by radar with a rotating circular view scale bearing seal on the map bearing and distance from a reference point to the plane after adjusting for the convergence of the meridians, if the difference in longitude and MS significant landmark.

If the on-board radar is a sector review, the bearing of the aircraft is obtained by summing the yaw rate and the benchmark rate of the aircraft.

Since the radar does not measure the horizontal and slant range, at distances up to orientiroz less than five times the height of the flight, in the measure should be amended, AR. This correction is always negative. For these amendments recommended.

When the slant range equal to the flying height, the horizontal distance is zero. This explains the appearance in the center of the radar screen of dark spots with sharply defined boundaries, the removal of which from the center of the screen is equal to the true altitude aboveoverflown terrain. Therefore, this spot is called almimetralnym.

Onboard radar may serve directly to determine the origin ortodromichesknh MS. For this purpose, the bearing scale indicator should be set on the corner of preemption (W) with respect to the plane of its specified great circle track angle (PU).

Knowing the orthodromic coordinates of the landmark relative to the intermediate point of the MRP route), as well as the ground bearing and the distance from the aircraft to the landmark, the orthodromic coordinates of the aircraft relative to the last MRP can be calculated on the ruler. For this, the triangular index of the scale is combined with the range of the landmark from the aircraft R on the 5 scale. The suture line is aligned on the scale 3 with the value 90 ° - PP and on the scale 5 read the value of R sin (90 ° - PP); Then the sighting thread is combined with the value of the PP, reading the R sin sin value on the 5 scale. After that, the first value obtained is subtracted from the coordinate of the landmark by the choir, and the second from zop and obtained by x and z of the aircraft.

The same problem, but it is much easier and with greater accuracy is achieved when the beam span landmark.

This particular case of solving the problem is rare when using radar sector review.

When using the radar sector review to determine the great circle track the coordinates of the aircraft bearing a benchmark calculated by the formula, and the problem is solved as well as for the circular scan radar. It is recommended to endorse guidelines for greater exchange rate possible angles.

Most simply ground speed flight and aircraft drift angle may be determined by sequential MS, but this method is often not as fast enough to determine the CSS, as it requires substantial base for the measurements.

You can use several other ways, if the field of view are unidentified point sight buttons, do not give way to determine MS.

Sight a point near the course line. If clearly visible on the radar screen ^ sighting point moves near the course line, then W and CM can be measured by the sight of running this point. Such a sight is recommended to perform within a range of up to 60 30 km altitude to avoid errors.

At the moment of crossing-point mark 60 km range and note the time scale bearing point «0» set against the course features a viewfinder thread - parallel movement of the point. When the point crosses mark 30 km distance, time and again intersect counttransit time base, then define W, adding to the length of the base correction for altitude range for 30 km. The corners of the demolition is ticking on the bearing scale, and negative angles are taken as an addition to 360 °.

This method is accurate enough to measure the angles of the demolition. Ground speed due to too short base measurement determined by large errors. For example, when the flight speed 900 km / h the error in measuring the time of flight base 4 seconds gives an error in the measurement of W until 30 km / h.

The method of a right triangle. This method is more accurate and convenient than the sight of a point near the course features, and gives more opportunities to select targets for the sight. Landmarks are not necessarily close to the course line.

Having set zero on the bearing scale against the heading line and having measured with the help of the sight a heading of the landmark, and along the ring marks - its range, you should turn on the stopwatch. After this, without changing the position of the sighting device, it is necessary to follow the movement of the landmark on the screen until this perpendicular strand of the visor intersects with this landmark. At this point, the stopwatch is stopped and the range of the landmark is again determined by the ring marks. After that, by entering the corrections for the height of the flight from the table into both measured oblique ranges, calculate the angle a between the position of the sighting line and the direction of movement of the landmark, and also the length of the measurement base S; A and S can also be calculated from the formulas:

In this case, the drift angle is defined as the difference between the first reference point and the azimuth angle of the ground speed as the ratio of the length of the base at the time of her flight

The double direction finding sighting points at equal distances inclined. This method is the most accurate in determining the FF and W by sight, but time-consuming than the previous ones.

With the passage of highly visible sighting point any range rings in front of the screen, a stopwatch and measure the heading angle of the point.

At the time of this sighting secondary crossing point of the same range rings in the rear of the field of vision of the stopwatch is turned off and the second determining the course angle of sight point.

After the introduction of sloping distance correction for altitude measurements of the length of the base is determined by the formula, and ground speed W - in the usual way on the NL-10.

Determination of the US for the secondary Doppler effect by the "stopped antenna" method. With some experience in the selection of the gain of the receiver and the angle of inclination of the US antenna, this method can be measured in a few seconds, especially since some airborne radars of the sector review have a special mode and an additional indication for this purpose. The essence of this method is that with circular rotation of the antenna, the beating frequencies are not noticeable for the eye, since each luminous point is quickly traversed by a scanning beam and is displayed on the screen with a single flash followed by afterglow. A weak visual impression of the secondary Doppler effect remains even with a fixed radar antenna in the case of a significant mismatch in the direction of its radiation with the direction of motion of the aircraft. In this case, the flickering of the points occurs at a high frequency and is smoothed out by the afterglow of the screen. But if you slowly approach the direction of the antenna to the direction of the aircraft, the luminous points beginall flashing at the frequency with increasing amplitude.

Thus, the slowest, but the bright points of light flashing on the screen indicates the direction of the antenna pa coincidence with the direction of movement of the aircraft.

Drift angle is defined as the angle between the position of the scan lines on the screen at maximumsecondary Doppler effect and exchange feature.

Note. In determining the CSS any of the four methods discussed herein bearing scale can be installed not zero, and the rate of the aircraft. In this case, all calculations TEM replaced bearing targets and the resulting solutions will not FF. and the actual track angle (FPA) of the aircraft (for example, the great circle of the aircraft FPA, if the scale set by great circle bearing the rate of the aircraft).

 

To replace vacuum tubes in blocks Radar

  • When replacing the radio tubes in blocks should be guided by the following:
  • to replace vacuum tubes begin only after checking the condition of the fuses;
  • the nature of the defect determine which unit should be replaced vacuum tubes;
  • unscrew the lock mounting block; pull the unit over and open the top cover;
  • from the emission filaments in glass vacuum tubes to make sure that the filament intact; be sure to touch the metal radio tube heat;
  • check the reliability of the installation of tubes in tube panels;
  • When replacing the radio tubes it is necessary to carefully pull out of the panel and insert the new bulb, making sure that the key lights got in a groove.

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Replace the picture with the article!
The picture depicts the respondent of the secondary radar system SO-96. It has nothing to do with airborne radars.
As an example, Buran-A200 - weather radar, is intended for installation on Be-200.

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