DIPOL Weekly Review - TV and SAT TV, CCTV, WLAN

Telecommunications airships instead of satellites?

The Thales Alenia Space company and HISPASAT satellite operator are designing stratospheric balloons for 4G/5G telecommunications services. The designers believe that they can be an alternative to geostationary satellites. An important advantage of the stratospheric solution is a greater operational flexibility - the airship can provide local broadband access to telecommunications services more quickly and easily, especially in areas of natural disasters.

Stratobus TM, the airship designed by Thales Alenia Space, is intended for both civilian and military purposes. The airship will operate at an altitude of 20 km, well above the level of airways. It will be observing for 5 years the surface of the earth, analyzing ship traffic, forest fires, coastline erosion, etc. To ensure continuous and reliable communication, the airship must remain stationary and withstand winds of up to 90 km/h. So, it will be equipped with special batteries and four electric motors allowing for stabilizing its position

Autonomic Stratobus, powered with solar panels

The batteries will be charged by solar panels occupying up to a quarter of the surface of the airship, 1000 m². Thales Alenia Space, in cooperation with the CEA LITEN scientific institute, has developed a photovoltaic technology whose advantages are: flexibility, competitive price, low weight (modules weigh less than 800 g/m²) and the amount of energy produced (over 200 W/m²). Tests have shown that the airship will be resistant to UV radiation, the presence of ozone and temperature changes in the stratosphere. The first object of this type is expected to appear in the sky in 2022.

MATV DVB-T system in a multifamily building.

One of Krakow's housing associations decided to modernize its MATV system for the reception of additional channels of DVB-T digital terrestrial television. So far, the installation received DVB-T broadcasts in the UHF band (ch. 21-60) and FM radio. Now the association wants to extend the range of channels by adding DVB-T MUX-8 and DAB+ radio multiplex, both transmitted in the VHF band (ch. 5-12). The four-story building has four staircases with 4 apartments on each floor .

All the broadcasts have to be received by one master antenna set and distributed to 64 antenna outlets located in the apartments. The extension of the system by the VHF band (174-230 MHz) requires the replacement of some components and application of new ones. One of the new components is the professional 7-element DAB / DVB-T Antenna DIPOL 7/5-12 A0710, shown in the diagram below. The antenna receives digital DVB-T and DAB broadcasts in the 174-230 MHz band (ch. 5-12).

The signals in the FM/VHF/UHF bands are distributed to 64 outlets
via a passive network composed of RF splitters and taps

The active components of the system include channel amplifiers TERRA at440 R82511 and at422 R82509, and broadband amplifier TERRA ma400 R82520. The at440 R82511 four-channel selective amplifier equalizes levels of 4 digital multiplexes in the UHF band (there could be used two twin-channel amplifiers TTERRA at420 R82510 instead). The TERRA at442 R82509 twin amplifier is a new component that filters and equalizes antenna signals in the VHF band. The multiband amplifier ma400 R82520 with three independent paths (FM, VHF&DAB, UHF) allows for final amplification of the signals in the UHF and VHF bands, as well as for the amplification and injection of radio signals broadcast in the FM band.

The signals are distributed in a passive network composed of RF splitters and taps. On each floor there is a 4-output tap connected directly with Signal R694130 subscriber outlets. The cabling is made of A-class coaxial cable RG-6 Tri-Shield DIPOLNET E1220_500.

Implementation of emergency power supply in a PoC system.

Power over Coax (PoC) is a new system allowing for transmission of power supply via the video coaxial cable. As the cabling carries power along with the video signals, the installation of the system is considerably simpler - each camera is connected with the system via a single coax or a twisted pair of wires from a minimum cat. 5e cable. In the latter case, the baluns have to support the PoC function (e.g. DS-1H18 M16641).

CCTV system with PoC power supply supported by a UPS

The power to the PoC cameras is distributed from the DVR with PoC functionality, so it is possible to use only one UPS that ensures power backpack for the whole system (the UPS can also be used for powering a monitor). In the event of a power outage, the built-in battery of the UPS allows the connected devices to continue work for some time. The average backup time depends on the UPS model (battery capacity) and power consumption. For example, the CyberPower UT850E-FR N9723 UPS with a load of 90 W can supply power for about 20 minutes, and with a load of 60 W for about 30 minutes.

Wireless access to the Internet in a school.

Wireless network in a school should provide access to the Internet throughout the school building and offer bandwidth sufficient for comfortable use of network services by students, teachers and administrative staff. The key factors in choosing the devices is their bandwidth and the maximum number of supported users. The Internet can provide easy and fast access to useful knowledge as well as to content that distracts the student's attention, so the school network should be subject to certain restrictions such as time windows, bandwidth, available content, etc.

The best practice for building this type of wireless network is to create several completely independent SSIDs (Service Set Identifiers) so that individual user groups connect to specific WiFi networks. Such networks should be created for:

The most important thing is that the wireless networks are to be isolated - devices connected to one network cannot be visible to devices in other networks.

TP-Link EAP access points can be highly recommended for creating reliable and efficient Wi-Fi networks in the demanding school environments. The modern devices can be easily mounted to walls or ceilings.

The Omada Cloud OC200 N2560 controller has been created to centrally manage a whole network of devices from the EAP series. Features such as real-time monitoring of traffic statistics and their analysis through built-in data visualization tools, guest authentication via the captive portal, system upgrading and restarting, and easy network scaling - will help manage the WiFi network. The device is an alternative to the EAP software controller - it has the same functions.

An example of deploying TP-Link EAP EAP225 N2567 units in a building

Integration of intelligent functions of IP cameras and PTZ camera via IP NVR.

Hikvision IP cameras, even from the budget series (without EasyIP Lite models), allow for intelligent image analysis in the form of detection of virtual line crossing and area intrusion. The functions can be activated and configured after logging in to the camera with the use of the iVMS-4200 client software or directly from a Hikvision NVR. The virtual line crossing and area intrusion detection can be used to detect people, vehicles and other objects. In response to the crossing of the line in a specified direction or intrusion into a defined area, the system can inform about the event, trigger video recording or alarm output, send an email, etc. These events can also be associated with a PTZ camera in order to trigger preset, patrol or route.

The system presented below employs 10 compact IP cameras Hikvision DS-2CD2023G0-I K17631 and one PTZ camera DS-2DE4225IW-DE K17912. The cameras are connected to the DS-7616NI-K2 K22165 NVR that allows for the video recording and integration of the intelligent functions of the IP cameras and the features of the PTZ camera. The PTZ camera has been mounted in the middle of the housing development, to enable detailed observation of any part of the inner area. The compact IP cameras installed inside the area have been setup so that they use the line crossing or area intrusion detection functions. Any of the events triggers a specific preset defined in the PTZ camera, i.e. monitoring of the corresponding part of the area, with defined parameters, including zoom. As a result, the PTZ camera can provide additional information with a wealth of detail necessary to identify the cause of the event. In the case of detecting several events in a short period of time, the PTZ camera handles the first one only. If the PTZ camera uses parking function, the camera will perform the actions specified after the programmed idle time. Without using this feature, the another violation will trigger the next preset.

IP video surveillance system using intelligent functions of compact cameras and special features of PTZ camera.
After intrusion detection by a fixed camera, the PTZ camera provides additional, detailed information.

Dead zones in OTDR measurements - the application of launch cables.

Correctly performed reflectometric measurements in fiber optic installations provide a lot of detailed information on the connections and irregularities occurring in optical paths. However, the specificity of Optical Time Domain Reflectometers (OTDRs) enforces the use of an additional fiber between the reflectometer and the measured optical fiber link. This spool of fiber is usually called a launch cable, or sometimes a leader cable, fiber ring, or dead zone box.

A reflectometer feeds into the optical fiber a pulse with user-specified length (the pulse duration can be e.g. 3 ns, 10 ns, 10 μs, etc). Of course, the reflectometer cannot take any measurements during that pulse. When the generated pulse (say 3 ns) encounters an event (splice, bend, connection etc.), it partially reflects and returns to the transmitter (reflectometer) blocking the measurement ability for the next 3 ns, necessary to receive the impulse, or even more, when the impulse is blurred. During that time, the impulse propagates further in the optical link, and any event encountered by it will remain invisible to the measurement system. To sum up: for one pulse with the duration of 3 ns, the reflectometer does not see any events during the time of the impulse emission and its return, i.e. 6 ns. Additional blurring of the pulse and switching times of the electronics add to that period.

Knowing the speed of light propagation in the optical fiber (usually the speed assumed for calculations is the same as in vacuum, i.e. 300,000,000 m/s), we can calculate the distance the light travels during the measurement pulse - it is about 0.3 m. After adding the reception and switching times of the electronics and possible blurring of the impulse, we can assume that the so-called dead (event) zone for such measurement impulse is 0.7 - 1 m. Within this section, the reflectometer is not able to identify events. Of course, the longer the pulse, the longer the corresponding dead zone, e.g. a strong impulse of 5 μs will generate a dead zone with a length of about 1000 m!

The first event in an optical path should be the first connector of the measured optical link. The dead zone should be estimated and the minimum length of the launch fiber determined for that place. Otherwise, without the suitable launch cable, the measurement will not detect events occurring in the dead zone, i.e. at the beginning of the optical fiber link.

DVB-T television and the Internet via one UTP cable. Low-voltage systems in office buildings often do not include TV antenna cables, but are usually fitted with structural cabling based on UTP cables. When some users want to connect televisions to watch DVB-T broadcasts, the lack of an RF distribution system may be a major obstacle (in many locations TV signals cannot be properly received using indoor antennas)... >>>more

Transmission of DVB-T and Ethernet signals over a single UTP cable with the use of R94200 baluns

Reliable 50 Ω connectors