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Located at the Volcani Center campus in Bet-Dagan, near Tel-Aviv, Agricultural Research Organization (ARO) six institutes are responsible for Plant Sciences, Animal Science, Plant Protection, Soil, Water and Environmental Sciences, Agricultural Engineering, and Postharvest and Food Sciences. ARO also operates four research stations, in various parts of the country, and serves as a testing center for agricultural produce and equipment. Israel's Gene Bank For Agricultural Crops is also located on the ARO Volcani Center campus. While encompassing the full range of agricultural research activities, ARO focuses in particular on arid zone agriculture, enabling Israel - a country short of all the resources required for agriculture - to achieve among the highest levels of agricultural output in the world. As an agricultural research center of international standing, ARO each year attracts a large number of groups from abroad, as well as numerous individual visitors. These include academics, heads of experimental stations, representatives of private companies and public officials. ARO maintains particularly close relations with the various international, regional and national institutes involved in the promotion of good agricultural practice and in the increase of agricultural output, and in particular with the U.N. Food and Agriculture Organization (FAO). At Alpha Unmanned Systems we have always believed that our UAV, the SNIPER, could be useful in improving agriculture. From the Volcani Institute they have proven us correct and by buying two of our drone helicopters they have placed themself at the forefront of agricultural innovation. Equipped with a Flir SC-655 infrared camera plus an on-board processing computer, with a 2 hours autonomous flight and a 2.5 Kg payload; both SNIPER units will support the ARO in their precision agriculture researches, with main topics such as hydric stress, diseases detection or soil nutrients optimization. Also we want to emphasize that we will be pioneers in achieving certification for civilian use of unmanned helicopter. Once delivered, corrected and accepted by the Israeli authority all communication systems and manuals, Alpha gave a training program in Spain, Madrid for two pilots of the ARO and two pilots recognized by the Israel Civil Aviation Authority (ICAA) so they can mentor new pilots in their homeland. After making the handover protocol we travelled to Israel, Tel-Aviv to finish the ATP with our client and perform the first flight tests required to achieve certification by the ICAA. The flights were realized at Tel-Gezer which is a well known area due to it's natural park and past history. All both ATP & ICAA requirements were carried out succesfully.
The radio link range is one of the most important aspects in a UAV. How far can we go with a good radio link? What affects this distance? How to increase the link range? are usual questions that concerns to UAV developers and manufacturers. Well this are the main factors that will have influence while achieving the maximum possible distance: - Bandwidth: the rate of data transfer, bit rate or throughput, measured in bits per second (bit/s). - Transmitter power: is the actual amount of power (in watts) of radio frequency (RF) energy that a transmitter produces at its output. - Antenna gain: an antenna's power gain or simply gain is a key performance number which combines the antenna's directivity and electrical efficiency. Normally the higher the gain, the narrowest radiation patter, f.e. a omny antenna has typically 3 to 5 dBis while a patch antenna can have 9 to 18 dBi but the patch antenna like the used in the G-TRACK must be always aiming to the UAV to have good link quality. - Losses: connectors and cables reduces the final output power of the system as it has looses. - Receiver sensitivity: Is the minimum magnitud of input signal required for a good performance of the device. - Fade Margin: Is the minimum margin necessary to ensure a good communication link measured in dBi a desired fade margin is 20 dB. - Path Loss: The losses produced by the attenuation of the signal caused by the distance between the two radios. - System Gain: Final system transmiting power taking into consideration all the installation; is the sume of the following: Transmitter Power + (Transmitter Antenna Gain - Transmitter Cable and Connector Losses) + (Receiver Antenna Gain - Receiver Cable and Connector Losses) + | Receiver Sensitivity | The following example shows an estimation fo the distance that you can achieve using the PCM data link with both ground and air omny antennas: Tx power = 30dBm (equivalent to 1W) Tx antenna gain = 6dBi Tx cable/connector loss = 2dB (typical value for one meter coax cable) Rx antenna gain = 3dBi Rx cable/connector loss = 2dB Rx sensitivity = -108dBm System Gain = [30+(6-2)+(3-2)+108]dB = [30+4+1+108]dB = 143dB. Under this situation we can have maximum path loss of (System gain - Fade Margin) 143 - 20 = 123 dB that in the frequency of 2.4 Ghz is equivalent to 15 Km. A table that shows some Path Loss values can be found below. Distance (Km) Master Height (M) Remote Height (M) Path Loss (dB) 5 15 2.5 116.5 5 30 2.5 110.9 8 15 2.5 124.1 8 15 5 117.7 8 15 10 105 16 15 2.5 135.3 16 15 5 128.9 16 15 10 116.2 16 30 10 109.6 16 30 5 122.4 16 30 2.5 128.8