INTRODUCTION AARF-RPA - ACTIVEHAMS AMATEUR RADIO FREQUENCY - RADIO PATH ANALYSER Why We Need a P2P RF Path / Propagation Path database of every District in India? As you know that we are research oriented scientific research society mentored and governed by radio amateurs.With our extensive real time experience in the communication field especially ,during a disaster time (we are not talking about the so called executive hams, who sits inside state office during a disaster or a natural calamity), we have found many difficulties to establish short range VHF P2P communication in affected area, especially during the Kerala flood 2018 and Cyclone Gaja. It would be a better idea if we collect all the possible point to point radio communication locations , which can provide the interference free wireless communication points ,inside and far away from the city or in district, local panchayat or even in every ward,to the district and local head quarters. If we have this database of every geographical locations along with the physical accessible paths ( way to the locations, normally hills or elevated places, where we can setup P2P or relay communication, would help the community to establish the communication with in s short span of time. The first step in determining the quality of the link between the endpoints is to conduct a radio path study. This study is done by specialists who use a variety of resources to accurately map the path between endpoints to determine the best path, the Fresnel Zone obstructions and their effect on propagation, the need for, and location of, any ancillary equipment such as repeaters, the required signal strength at the transmitter, and receiver sensitivity. The report typically contains visual depictions of the path on a topographic map and identifies any potential obstructions. When designing a link, it is advisable to contact the local building department to determine if any new high-rise buildings for other towers are being planned for the area within the path. Planning for a communication system cannot be done on the fly or by putting components together without a plan or professional guidance. Why we decided to build RF Line of Sight x Locations Database One of the most important factors in designing a wireless system is how the radio frequency (RF) signals will propagate between the transmitter and receiver. While this may seem obvious to many, real-life deployments often aren’t that simple. Ideally, a clear line of sight (LOS) between two end points is the desired goal, but this is impractical, particularly in an industrial setting, crowded urban environment, or even an office. Rural areas present unique seasonal problems that affect propagation. This can flummox even a seasoned technician. It is not always possible to provide a clear LOS transmission. This results in reflections, called
multipath propagation, which require specialized methods of transmission and reception. Non-LOS (NLOS) and beyond-LOS (BLOS) are other cases of propagation that can be successfully dealt with to provide a robust and secure link. Point to point communication. Point-to-Point (P2P) communication systems are used to establish a communication link between two points within line-of-sight, where at least one of the points is in motion. As such, antenna stabilization – even under harsh conditions – is critical for maintaining fast and reliable connectivity. P2P systems are commonly used between a ground station and a nearby oil rig or between two vessels that travel within line-of-sight at sea. Visible line of sight and Radio frequency line of sight ( RF LOC) Line of sight is exactly what it states; the transmitter can see the receiver, or at least, the antennas of each can see each other. It is the visual line of sight. This is, again, an ideal case. It is important to remember the shortest signal wavelength is several thousand times longer than the longest optical wavelength. This means a visually clear LOS does not necessarily translate into radio LOS, and vice-versa. To achieve a reliable RF link, careful planning, including a radio path study must be performed, along with an informed selection of equipment and antenna locations. The transmitter may use an omnidirectional antenna that is transmitting in all directions. The receiving antenna also may be an omni, but in many cases, and to increase the likelihood of receiving a usable signal, a directional antenna may be used. For a dedicated link between two points—a point-to-point link will use a directional antenna to narrow the beam-width to avoid interference and increase the effective strength of the signals. All of these factors must be considered prior to final system design. Designers also should be aware of several possible impairments. Fresnel Zone The first possible impairment is the Fresnel Zone (pronounced Fren-nel), which is a football-shaped area between the two tapered link end points that must be kept clear of obstructions to ensure a quality link. Area of concern here is the first Fresnel Zone (there are several); technically the area is a "prolate ellipsoid" that surrounds the transmitter and receiver and the area between them. Obstructions within the first Fresnel Zone are not necessarily in the LOS between the end points, but they will cause a degradation of the signal strength and intermittent impairment. Behavior of the signal will differ based upon antenna polarization: a vertically polarized signal encountering an object in the first Fresnel Zone will invert and arrive at the antenna out of phase, degrading the signal. The opposite will happen with a horizontally polarized signal. The distance between the link endpoints and the wavelength of the transmitted signal determines the area of the Fresnel Zone.
Ground, water RF reflections The next impairment to LOS are the reflections from the ground or water local to the transmitter. Without getting too far into the weeds of antenna theory, the reflections from what is essentially a ground plane cause multipath interference and degrade the signal. In short range microwave transmission, the multipath phenomenon is dealt with by using diversity antennas and complex algorithms to combine or reject signals based on whether they are received in or out of phase (constructive and destructive multipath). For longer-range links, raising the height of the antenna is the most common way to deal with reflections from the ground plane. The improvement in signal quality is called "height gain." Earth, atmosphere One other parameter affecting LOS propagation is the earth’s curvature. The rule of thumb is a transmitter at sea level has a LOS of seven miles if unobstructed, which is referred to as an "earth bulge." Another factor is the effect of atmosphere on propagation. Since the signal does not travel at a uniform height above the earth, the effects of varying atmospheric conditions will affect LOS. The most pronounced effect of declining atmospheric pressure is the signal will be bent towards the earth, effectively increasing propagation by a factor of around 4/3, or about 15%. Wireless obstructions NLOS describes a link without a clear line-of-sight. Obstructions are either in the path of the link or within the first Fresnel Zone. The effect of an obstruction in a NLOS situation can range from negligible to complete obstruction. Radio waves are considered "plane waves" in that the magnetic and electric fields propagate in two distinct planes perpendicular to each other. Plane waves are affected by obstructions in several ways and the effect is dependent upon wavelength. Obstructions fall into three broad categories: Smaller than the incident wavelength, the same size as the incident wavelength and larger than the incident wavelength. When an obstruction is smaller than the incident wavelength, there is negligible, if any, interference. When an obstruction is the same size as the incident wavelength, the plane wave will diffract around and through it with minor attenuation. If an obstruction is larger than the incident wavelength, the signal will be obstructed to varying degrees depending upon the obstruction’s materials and their electrical characteristics. BLOS, beyond NLOS Beyond-line-of-sight (BLOS) propagation is a special case of NLOS often encountered in very long-distance communication links blocked by earth bulge, terrain, or other obstructions. BLOS and NLOS are virtually identical conditions with BLOS being used by the military to describe much the same conditions as NLOS. Methods for overcoming these conditions use the same technology to achieve stable
communication links. The most common method for medium to long-range links are passive and active repeaters, which receive the signal from the originating transmitter and repeat it to increase range. Passive repeaters do not amplify the signal; they reflect it into the desired area. Passive repeaters are used to beam signals into areas isolated by terrain such as a community in a valley or a hollow surrounded by hills or mountains. A passive repeater is useful if the original signal is strong enough to sustain the loss of transmission (propagation loss), the propagated signal diminishes according to the "inverse square rule," which states the signal strength is inversely proportional to the square of the distance from the transmitter-the signal attenuates by a factor of four as the distance from the transmitter doubles. Active repeaters receive, amplify, and then re-transmit the signal. In most cases of NLOS propagation mitigation. Active repeaters are more commonly used to increase range while preserving signal quality. Other methods of dealing with NLOS/BLOS are troposphere scatter (troposcatter) ionospheric propagation, which use the earth’s atmosphere as a reflector to propagate RF over the horizon. Troposcatter can increase range up to 300 miles; ionospheric propagation can cover more than 2,000 miles. Both methods are vulnerable to atmospheric conditions and suffer greatly during magnetic storms, such as CMEs. A radio path study is must and state should posses the database. You may think that why we need a real time data of P2P RF line of Sight geographical Details. Software Details Software based RF path Study Samples - Scadacore ,AARF-RPA and others AARS-KL RADIO PATH STUDY(RPS TX/RX) RX/TX LOCATIONS AND THE FORMATIONS OF THE EARTH TO LINE-OF-SIGHT OF A RADIO PATH
TOPOGRAPHICAL CALCULATE THE
Scadacore has a web based interface and it is easy to as long as the service provider support. But very basic details are provided in the output. The RF Line-of-Sight tool allows users to
easily drag-and-drop locations and obtain point-to-point line-of-sight information anywhere using Google Maps. This free online tool takes antenna height and the topographical formations of the earth to calculate the line-of-sight of a radio path. This RF Line-of-Sight tool is exceptionally helpful in mapping long distance radio communications for remote monitoring applications such remote shutdowns and data acquisition.
Software based RF path Study Samples - AARF-RPA and SPLAT
AARF-RPA (Activehams Amateur Radio frequency - Radio Path Analayser V.01) is a powerful terrestrial RF propagation and terrain analysis tool built on QT/QML for the spectrum between 20 MHz and 20 GHz. AAARF-RPA built based on another command based tool, and is designed for operation on Linux-based workstations. The UI based application has developed in QT and QML.The software was designed by Biju Gopi Thilaka, Founder of Activehams Amateur radio Society and Linux Club, you can contact him by sending a mail to root [at] linuxclub [.] org. AARF-RPA include the UI based visualization, design, and link budget analysis of wireless Wide Area Networks (WANs), commercial and amateur radio communication systems above 20 MHz, microwave links, frequency coordination and interference studies, and the prediction of analog and digital terrestrial radio and television contour regions AARF-RPA provides RF site engineering data such as great circle distances and bearings between sites, antenna elevation angles (uptilt), depression angles (downtilt), antenna height above mean sea level, antenna height above average terrain, bearings, distances, and elevations to known obstructions, Irregular Terrain Model path attenuation, and received signal strength. In addition, the minimum antenna height requirements needed to clear terrain, the first Fresnel zone, and any user-definable percentage of the first Fresnel zone are
also provided.
AARF-RPA using splat command line interfaces in background, splat is a command-line driven application and reads input data through a number of data files. Some files are mandatory for successful execution of the program, while others are optional. Mandatory files include digital elevation topography models in the form of splat Data Files (SDF files), site location files (QTH files), and Irregular Terrain Model parameter files (LRP files). Optional files include city location files, cartographic boundary files, user-defined terrain files, path loss input files, antenna radiation pattern files, and color definition files.In the UI based application you can directly input the QTH (location details of a Ham radio operator or Radio station Geo-location co-ordinates, other data from the user Interface. Optionally you can set to physical files ( which may contain multiple locations (point A to B to C, and A to C etc)
AARF-RPA produces reports, graphs, and high resolution topographic maps that depict line-of-sight paths, and regional path loss and signal strength contours through which expected coverage areas of transmitters and repeater systems can be obtained. When performing line-of-sight and Irregular Terrain Model analyses in situations where multiple transmitter or repeater sites are employed, AARF-RPA determines individual and mutual areas of coverage within the network specified.
ACTIVEHAMS AMATEUR RADIO SOCIETY AARS-KL A Scientific Research Society.
AARL-KL President : Rajasekharan Nair (VU2RJR +91 99958 28660) | Secretory : Nishath AK (VU3MOE - +91 70124 14506) | Vice President : Biju Gopi Thilaka (VU2HBI - +91 944745 1144)
Govt Reg No : KLM/TC/196/2018 Email qso@aars.in Web www.aars.in
We Are“ACTIVE HAMS AMATEUR RADIO SOCIETY (AARS-KL)”, a Govt registered society founded by a group of radio amateurs from Kerala, The Southern State of India. During this flood disaster we have contributed our technical support and volunteer service In association with Fire & Rescue Services Kollam. We formally adopted our constitution on 2nd of May 2018. We assure the timely support to TRACKS during disaster. We can provide timely wireless communication assistance during disaster along with TRACKS as per the order from district collector. We can provide ASOC exam and effective communication process / procedure to handle emergency situation or any disaster like Oakhi cyclone for TRACKS members. We Provide emergency rescue volunteer services during floods, landslides, tsunamis, earthquakes, cyclones, accidents (Rail / Road / Air). Whenever 'normal' communications go out, we are ready to use our radios to provide emergency communication services to their communities. Ham Radio possesses a vast potential to serve as an alternative communication channel, should the mainstream channels breakdown during disasters.
For Active Hams, Biju Gopi Thilaka Founder AARS-KL
