Glidepath Antenna Design

The GP antenna comprises a lattice mast with three dipole antenna arrays A1, A2 and A3. The mast using the dimensions (W x D) 450 x 650 [mm] is rectangular and may be mounted by way of stirr ups.The mast is divided in sections of 3.50 m in length each, and can be adapted to satisfy nearby specifications.Each mast section comprises 4 bars connected collectively via struts and butt straps by indicates of rivets and screws. It's produced of aluminium ALMgSi, the metal parts are galvanized and all screw connections are created of metal V2A. The base frame is made of welded metal profiles. It consists of forked bolts which allow the mast to become tilted. The erected mast is fixed with supports. The mast suggestion is made of welded U-profiles. It includes two deflection rollers produced of polyamide for an auxiliary guy wire when installing the antenna dipoles, and 2 obstacle lights. The antenna mounting for the dipole array is really a buckled C-profile which permits a horizontal adjustment of the dipole array by about ±350 mm. The C-profile is mounted at a vertical tube 1 m long that is fixed to the mast by cross-strucks. With the vertical tube a fine vertical adjustment of the antenna array is possible. In addition the height of the complete body can be adjusted in actions of 500 mm. The mast is painted in red and white for 1.75 m alternately.The 3 dipole antenna arrays A1, A2 and A3 have a horizontal polarization and an identical design using the dimensions (H x W x D) 500 x 2000 x 250 [mm]; they're mounted over 1 an additional and somewhat offset. The antennas are protected against weathering exposure with a polyester glass fibre cover. They remain operational, even in case of substantial formation of ice. Atmospheric discharges are eradicated reliably, since all metal parts of the antenna are linked to floor.The reflector surface area in front of the GP antenna consists of a welded construction-steel internet which is embedded in gravel and which should be grounded. If preferred, the construction-steel web can also be embedded in asphalt, concrete or similar. The use of structural metal mesh isn't mandatory. Depending on the local conditons it may be established during website survey, if it is suggested or necessary.

LORAN-C

LORAN(Long Range Navigation) is a terrestrial radio navigation system using low frequency radio transmitters in numerous deployment to determine the location and pace of the receiver.The most recent version of LORAN in use is LORAN-C, which operates in the reduced frequency portion of the electromagnetic spectrum from 90 to 110 Kilohertz. Numerous nations have utilized the program, such as the us, Japan, and a number of European nations. Russia uses a nearly identical system within the same frequency range, called CHAYKA.
 

LORAN use continues to be in steep decline, using the satellite primarily based Global Positioning Program (GPS) being the primary substitute. However, there have been attempts to enhance and re-popularize LORAN, primarily to serve as being a backup and land-based alternative to GPS along with other International navigation satellite system (GNSS) techniques.The present LORAN program has been phased out in the Usa and Canada. The united states Coast Guard (USCG) and Canadian Coast Guard (CCG) ceased transmitting LORAN-C (and joint CHAYKA) indicators in 2010.

The navigational technique offered by LORAN is dependant on the key with the time distinction in between the receipt of indications from the set of radio transmitters.[6] A offered continuous time distinction in between the indications in the two stations might be symbolized with a hyperbolic type of place (LOP).When the positions with the two synchronized stations are recognized, then your place with the receiver might be established as becoming somewhere on the specific hyperbolic curve exactly where time distinction in between the acquired indications is continuous. In perfect conditions, this really is proportionally equal towards the distinction with the distances in the receiver to every with the two stations.

A LORAN network with only two stations can't offer significantsignificant navigation info because the 2-dimensional place with the receiver can't be fixed due to towards the stage ambiguities within the program and absence of the outdoorsoutdoors stage reference.A second software with the identical principle should be utilized, according to time distinction of the various set of stations. In apply, 1 with the stations within the second pair also might be-and frequently is-in the very first pair. In easy phrases, this suggests indications should be acquired from a minimum of 3 transmitters to target the receiver's place. By identifyingdetermining the intersection with the two hyperbolic curves recognizedrecognized with this technique, a geographic repair might be established.

(RADAR) Radio Detection and Ranging

           Radar radio detection and ranging is definitely an object-detection system which utilizes electromagnetic waves-specifically radio waves-to figure out the range, altitude, direction, or pace of both moving and fixed objects this kind of as aircraft, ships, spacecraft, guided missiles, motor autos, weather formations, and terrain. The radar dish, or antenna, transmits pulses of radio waves or microwaves which bounce off any object within their path. The object returns a small part of the wave's energy to a dish or antenna which is generally situated at the same site because the transmitter.The military programs of radar were created in secret in nations across the world during World War II. 
            
             The term RADAR was coined in 1940 by the U.S. Navy as an acronym for radio detection and ranging.The phrase radar has been use in English and other languages as the typical noun radar, losing all capitalization. In the Uk, the technologies was initially known as RDF (range and direction Finder), utilizing the same initials utilized for radio direction finding to hide its ranging capability.The contemporary uses of radar are extremely diverse, such as air visitors manage, radar astronomy, air-defense systems, antimissile techniques; nautical radars to locate landmarks and other ships; aircraft anticollision systems; ocean-surveillance systems, outer-space surveillance and rendezvous systems; meteorological precipitation monitoring; altimetry and flight-control systems; guided-missile target-locating techniques; and ground-penetrating radar for geological observations. High tech radar techniques are associated with digital signal processing and are capable of extracting objects from extremely higher noise levels.Other systems comparable to radar have already been utilized in other parts of the electromagnetic spectrum. One example is "lidar", which utilizes visible mild from lasers rather than radio waves.A radar program has a transmitter that emits radio waves known as radar indicators in predetermined instructions. When these arrive into contact with an object they are usually reflected and/or scattered in lots of instructions. 

              Radar signals are reflected particularly well by supplies of substantial electrical conductivity-especially by most metals, by seawater, by wet land, and by wetlands. Some of these make the use of radar altimeters feasible. The radar signals which are mirrored back again in the direction of the transmitter are the desirable ones that make radar function. When the object is shifting either nearer or farther away, there is a slight alter within the frequency with the radio waves, because of the Doppler impact.Radar receivers are often, but not usually, within the exact same location as the transmitter. Although the mirrored radar indicators captured through the getting antenna are often very weak, these signals can be strengthened by the electronic amplifiers that all radar sets include. Much more advanced methods of signal processing are also nearly usually used to be able to recuperate useful radar indicators.The weak absorption of radio waves by the medium through which it passes is what allows radar sets to detect objects at relatively-long ranges-ranges at which other electromagnetic wavelengths, such as visible mild, infrared mild, and ultraviolet mild, are too strongly attenuated. Such things as fog, clouds, rain, falling snow, and sleet that block visible mild are usually transparent to radio waves. Certain, particular radio frequencies which are absorbed or scattered by water vapor, raindrops, or atmospheric gases (especially oxygen) are prevented in creating radars other than when detection of those is meant.Lastly, radar relies on its own transmissions, rather than light from the Sun or the Moon, or from electromagnetic waves emitted by the objects themselves, this kind of as infrared wavelengths (heat). This process of directing artificial radio waves in the direction of objects is called illumination, no matter the fact that radio waves are completely invisible towards the human eye or cameras.

Tactical Air Navigation (TACAN)

A tactical air navigation technique, generally referred to through the acronym TACAN, is actually a navigation method used by military aircraft. It provides the person with bearing and distance (slant-range) into a ground or ship-borne station. It is just a much more precise model with the VOR/DME technique that gives bearing and variety data for civil aviation. The DME portion from the TACAN method is available for civil use; at VORTAC amenities wherever a VOR is combined with a TACAN, civil plane can receive VOR/DME readings. Aircraft equipped with TACAN avionics can use this system for enroute navigation too as non-precision approaches to landing fields. The room shuttle is one such automobile which was built to use TACAN navigation[citation needed despite the fact that it has since been upgraded with GPS like a substitute. The common TACAN onboard consumer panel has handle switches for setting the channel, the operation mode for both Transmit/Receive (T/R, to have both bearing and array) or Receive Only (REC, to acquire bearing although not assortment). Capability was later upgraded to incorporate an Air-to-Air mode (A/A) where two airborne customers can get relative slant-range information. Based on the installation, Air-to-Air mode could supply assortment, closure (relative velocity with the other unit), and bearing,  however an air-to-air bearing is noticeably less precise than a ground-to-air bearing.TACAN on the whole might be described as the army edition from the VOR/DME method. It operates from the frequency band 960-1215 MHz. The bearing unit of TACAN is much more correct than a standard VOR since it makes usage of a two frequency principle, with 15 Hz and 135 Hz parts.The gap measurement part of TACAN operates with all the identical specifications as civil DMEs. Therefore to cut back the quantity of necessary stations, TACAN stations are often co-located with VOR services. These co-located stations are known as VORTACs. This is a station composed of a VOR for civil bearing information along with a TACAN for army bearing information and military/civil length measuring information. The TACAN transponder performs the operate of the DME with no the require to get a separate, co-located DME. As the rotation of the antenna produces a big portion in the azimuth signal, should the antenna fails, the azimuth component is no longer obtainable as well as the TACAN downgrades to a DME only mode.

Remote Maintenance Monitoring

The Remote Maintenance and Monitoring Configuration (RMMC) is used for remote monitoring, operation and maintenance of all the connected navigation systems. The network has a radially configured architecture based on communication between the system components via switched or private lines in the public network and dedicated lines in private networks. Optionally a connection to a LAN via Ethernet line is possible.The remote control instruments allow all the networked navigation systems to be operated optionally from central points, from normal operation of the dual systems with automatic changeover in the event of a fault through manual operation to measurement and setting of all the possible signal parameters, as well as detailed fault analyses on the basis of a wide range of measured values. They facilitate new maintenance strategies, whereby primary importance is placed on concentrating logistics and qualified personnel, and then on responding to specific failures with systematic maintenance activities rather than relying on periodic precautionary measures. This considerably improves both maintenance efficiency and the economic efficiency of the systems throughout their service life.

Glidepath

Glide slope / Glide Path

Is a portion of the ILS that provides the pilot with vertical guidance to the touchdown point of the runway. The GP generates an RF−Signal at frequency range of 328 to 336 MHz and is amplitude modulated with 90 and 150 Hz. The transmitter of GP can be a 2F system or 1F system and both produce 5 W of power. The glide path signal is receivable up to a distance of 10 nautical miles within an azimuthal sector of ±8°relative to the localizer course line with the touch down point as reference and between the elevations 0.30 to 1.75 nominal glide path angle.The GP antenna is installed approximately 286 to 344 m beyond the runway threshold and 120 to180m from the runway centre line. An optional nearfield dipole is installed in the GP radiation sector for monitoring the course position of the GP signal. The position of the dipole depends on the type of installation and on the local conditions as regards the glide angle. The GP transmitter shelter is installed in the vicinity of the GP antenna.

Glidepath or Glideslope also radiates two modulating signal, the 90Hz and 150 Hz. Above the path angle 90Hz is predominant than 150Hz. Below, the 150Hz is predominant than 90Hz, and at path angle the two are equal.

LOCALIZER

LOCALIZER

 

Localizer is a part of ILS that provides the pilot with horizontal guidance towards the airport runway center line.

Operating Frequency Band

  108 – 111.975 MHz

Modulation Frequency

  90 Hz and 150 Hz

DDM

  20% (90 Hz and 150 Hz) Nominal

  18% - 21% allowed for Cat. I and Cat. II

  19% - 21% allowed for  Cat. III

Voice Modulation

  Optional

Identification Signal

  1020 Hz with 5% - 15% Modulation

  keyed 2 – 3 Characters of International Morse Code (audio of 1020 Hz) e.g. I-CIA

Monitoring

  Automatic Monitoring System to designated control locations.

 

Localizer radiates two modulating signals 150Hz and 90Hz. It produce a predominance of 150Hz to the right of the runway centerline as seen by the aircraft and a predominance of 90Hz modulated RF to the left of runway centerline. At centerline the two modulated RF are equal.

Defective Associated Facility Interface (AFI) module of DME

The AFI module is used as interface between the DME ground beacon and an associated VHF equipment to make the emission of the identity code expressed in international Morse code synchronous.This module allows the identification signals to be correctly exchanged between the DME and associated equipment (e.g. VOR, ILS, and MLS equipment). If any, as far as the identity code and the status signals are concerned.

 figure of Defective AFI

We experienced this trouble when the DME equipment shuts down on both system. We checked the system and it found that AFI is defective because of burned out module and LED's in front doesnt blinking at all. The remedy is only buying a new module since all individual components of AFI are surface mounted.

DVOR Trouble

Last year we encountered a DVOR problem in which the Nearfield position RF level is too low that caused an alarm on our two monitors. It shutdowns both system of DVOR. We bypassed the two monitors and check the actual RF level by using a DVOR portable receiver. All the actual reading of data in aerial is the same as per recorded normally in our logbook. We concluded that the equipment is operating normally and the problem is in the monitor dipole section.Through analysis and at the same time reading the equipment manual we decided to troubleshoot at the dipole section of the DVOR. We loosened and tightened back the transmission cable and clean all connectors for possible contamination of rust. The problem still existed, and we then checked the 3dB attenuator if its the caused of the problem. We found available attenuator and changed the existing one and still the problem is just the same. After all the possibility we decided to focused on antenna itself. We brought down the antenna of monitor and we found out that it had made by ants as its habitat and all its holes were contaminated with dirt's. We disassembled the antenna and by used of pressure washer we cleaned thoroughly all the contamination.After cleaning we assembled again the antenna and brought up and all data on RF nearfield level goes back again into normal state.

        figure of Antenna  monitor dipole

Distance Measuring Equipment DME

DME

DME (Distance Measuring Equipment) is a radio aid for short and medium distance navigation. It can allows 100 aircrafts simultaneously to measure their distance from a ground reference (DME transponder). The distance is determined by measuring the propagation delay of a gaussian pulse, which is emitted by the aircraft transmitter and returned by the ground station after reception.DME operates in the frequency range of(960 to 1215 MHz).

Aircraft's airborne interrogator transmit encoded interrogating  pulse pairs on the ground station. The DME station in turn, transmits encoded reply pulse pairs on the air-borne equipment, The real distance information is the time interval between interrogation emission and reply reception. Aircraft's equipped with DME transmit encoded interrogating RF pulse pairs about the beacon's obtaining channel. The beacon, consequently, emits encoded reply pulse pairs about the receiving channel with the air-borne tools, that is 63 MHz apart from the transmitter frequency former.

Time interval among interrogation emission and reply reception provides the aircraft with all the real
distance data through the ground station; this info could be go through from the pilot or even the navigator straight around the airborne indicator. The ground transponder is capable to reply approximately about 200 interrogators at a time (i.e. 4800 pulse pairs/s). Generates random pulse pairs ("squitter") to take care of a minimum PRF of 800 to 2700 pulse pairs per
2nd (programmable) whenever the amount of decoded interrogations is decrease than that.
This reply is obtained and decoded by the airborne receiver, where unique timing circuits automatically measure the lapse between interrogation and reply and convert this measurement into electrical output indicators. The beacon introduces a fixed delay, known as reply delay, among the reception of each encoded interrogating pulse pair and also the transmission of the corresponding reply.

Doppler Very High Frequency Omnidirectional Radio Range (DVOR)

DVOR

DVOR- is a navigational aid equipment designed to provide bearing information to aircraft.VOR Systems composed of a transmitting station on the ground and receiving station on the aircraft.

VOR Stations:

a.En-route -112MHz-118Mhz

b.Terminal -108MHz-112MHz

The DVOR radiates a radio frequency carrier with which are associated two separate 30 Hz modulations.
One of these modulations is such that its phase is independent of the azimuth of the point of
observation (reference phase). The other modulation (variable phase) is such that its phase at the
point of observation differs from that of the reference phase by an angle equal to the bearing of the
point of observation with respect to the DVOR. Compared to a CVOR station for the DVOR system
both 30 Hz modulations are reversed. The conventional VOR is more sensitive for multipath reflections
from fixed object, near and distant, such as trees, power lines, buildings and mountains which
rise the bearing errors. The improved radio navigation beacon DVOR relies on the Doppler change
in frequency which would result if a radiation antenna is moved around a large diameter circle. If the
antenna is rotated 30 times a second, the signal at a distant observation point will be frequency modulated
at a 30 Hz rate. The modulation index is determined by the diameter of the circle.

Azimuth angle between aircraft and ground station

The effect of a rotating antenna is simulated by using a ring of antennas and switching the RF signal to each in turn. Provided sufficient antennas are used and the pulse RF energy is suitable shaped, the simulation is good. The shape of the modulation envelope is called the ’blending function’. The azimuth−dependent information is contained in the phase of the frequency modulation.The reference phase of the 30 Hz amplitude modulated carrier signal is radiated from a single antenna at the center of the ring. The aperture of the Doppler VOR antenna is much more greater than in conventional equipments. By virtue of the resulting ’space diversity’, effects due to reflections are greatly reduced. The bearing information is inherently determined by the geometry of the antenna array and since the Doppler VOR array is large it can be made very stable and accurate. The DVOR 432 is a Double Sideband DVOR system (DSB DVOR) and is full compatible with all existing airborne VOR receivers. In a DSB DVOR system signals 9960 Hz above and below carrier frequency (Upper Sideband →USB / Lower Sideband → LSB) are radiated simultaneously from 48 sideband antennas diametrically opposed to the ring. Both sidebands are commutated at 30 Hz in the same direction.

INSTRUMENT LANDING SYSTEM (ILS)

An  (ILS)  Instrument Landing System is a ground-based equipment that radiates guidance information to be received by an aircraft during final approach for correct and safe landing. It is composed of ground based equipments such as transmitter, combining/dividing network, antenna and monitors systems.

ILS have three subsytem: Localizer, Glidepath/Glideslope and Marker Beacons.

 

A.The vertical plane containing the runway centerline is defined by VHF transmitter called Localizer.

B.The horizontal plane of 2 to 4º of vertical angle above the horizontal plane is defined by a UHF transmitter called the Glide slope.

C.Distance information installed on a fixed distance reference points are provided by markers.

MARKER BEACONS

Beacons are AM transmitters operating at 75 MHz located at specific points along the landing path used to designate distance away from the threshold.

Operating  Radio Frequency

  75 MHz  ± 0.01%

Modulating Frequency

  Inner  Marker (when installed) : 3000Hz

  Middle Marker: 1300 Hz

  Outer Marker: 400 Hz

Coverage

  Inner Marker (when installed) 150 m ± 50 m

  Middle Marker : 300 m ± 100 m

  Outer Marker : 600 m ± 200 m

Identification Signal

  Inner Marker (when installed): 6 dots per second continuously

  Middle Marker: Series of dots and dashes

  a. dashes keyed at a rate of 2 dashes/sec

  b. dots keyed at a rate of 6 dots/sec

  Outer Marker: 2 dashes/sec continuously

Monitoring

  Automatic Monitoring System that transmit a warning signals to  a control point    during

  a.  Failure of modulation or keying

  b. Reduction of Power output to less than 50%