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

Twisted metamaterial rods as energy storage.

An international research team from the oldest German technical university, the Karlsruhe Institute of Technology (KIT), has developed mechanical metamaterials with exceptional properties. Thanks to the use of highly twisted rods that deform in a helical manner, these materials have gained high rigidity and the ability to store and release large amounts of elastic energy. The results of this research have been published in the prestigious journal Nature. Mechanical energy storage plays a key role in technology, being used in areas such as energy-damping springs, flexible robotics components, and energy-efficient machines. Kinetic energy (energy of motion) is converted into elastic energy, which can be fully recovered again if necessary. The key challenge in this process is to achieve maximum enthalpy, i.e. the material's ability to store and recover energy.

Professor Peter Gumbsch from KIT explains that the biggest difficulty was to combine contradictory properties such as high rigidity, strength and flexibility. The solution turned out to be the precise arrangement of helically twisted rods in the metamaterial structure. This design ensures that stresses are evenly distributed, which increases the strength of the material. Metamaterials are artificially designed structures with characteristics that are impossible to achieve in nature. They are made up of individually designed units; this allows for the optimization of their properties. In the research described, a team of scientists from China, the USA and Germany took full advantage of the potential of such structures, creating materials with an enthalpy 2 to 160 times greater than in previously known solutions. An example is the classic bending spring, in which tensile and compressive stresses on the surface limit its maximum deformation. In helically twisted rods, a significant portion of the internal stresses are limited, allowing for larger and more complex deformations.

The newly developed metamaterials have great potential for application. They can be used in shock absorption technologies, flexible connections in robotics or energy-efficient machine structures. Moreover, their elastic energy storage capacity opens up new possibilities in the design of lightweight, efficient and reliable mechanical components.

Incorrect cleaver height as a reason for bad optical fiber cleft.

Proper preparation of the ends of optical fibers is the basis for successful fiber splicing. Even the best and most expensive splicer will not be able to properly connect dirty or improperly cut fibers. For this reason, care for the cleanliness of fiber optic tools is extremely important. A good, clean and well-adjusted fiber optic cleaver guarantees correct and precise cleaving of fibers.

Before proceeding with the adjustment of the cleaver height, it is good to find out whether the blade in the tool is set too high or too low. Of course, it may happen that the installer is not able to determine that during the initial assessment. A good practice then is to deliberately lower or raise the blade to the extreme positions. After reaching one of the extreme positions, gradually lower/raise the blade to set the optimal position. The effect of each change in height should be checked on the splicer display. It is important to do that for two fibers. It may also happen that the fiber looks good on one side and on the other not. It is also important to tighten all stabilizing bolts after changing the height. They also have a slight but still noticeable effect on the blade position.

More tips on how to properly position the blade can be found in the article Cleaving optical fibers without secrets – blade adjustment.

RG-6 75 Ohm Trishield coaxial cables.

Trishield type RG-6 75 Ohm coaxial cables are a coaxial cables characterized by triple shielding. This design gives the cable a range of benefits that make it the perfect choice for systems that require high-quality signal transmission.

With these advantages, 75 Ohm Trishield RG-6 coaxial cables are the ideal solution for applications requiring reliability, high-quality transmission, and resistance to interference. DIPOL offers a family of 75 Ohm Trishield RG-6 cables of the TRISET 302 brand.

Controlling the second relay with a password in Hikvision's modular IP video door stations.

If a keypad is connected to the door stations of the modular IP video door phone system (DS-KD8003-IME1(B) G73652) or 2-Wire (DS-KD8003Y-IME2 G73646) is connected to the keypad, it is possible to control the first or second relay built into the door station with a password. In order to control the second relay, the door station must be updated to 2.2.62 or higher firmware version. After entering the settings of the door station from the iVMS-4200 application, go to Door phone → Settings and select the option to add a password. During the adding process, it will be possible to assign a password and select the relay that will be triggered when it is used. Up to 16 public passwords can be added directly at the door station.

Fresnel zone.

Wireless network range depends on many propagation factors, some of which can be controlled (e.g. transmission power, antenna height, terrain obstacles), while others remain unknown or are difficult to predict (e.g. weather conditions, interference). One of the key issues in radio link planning is the Fresnel zone. This is the area of space between the transmitter and receiver in which radio waves actively participate in the transmission of signal energy. In a longitudinal section, the Fresnel zone has the shape of a rotating ellipsoid, while it has the shape of a circle in a cross-section, with the radius changing along the signal propagation axis. The radius of the first Fresnel zone reaches its maximum value halfway between the antennas. The first zone is the most important in practical terms, as it is responsible for transmitting the majority of the signal energy. Partial obstruction of this zone can lead to a significant reduction in signal strength due to interference from direct and reflected waves.

Objects (hills, trees, buildings, etc.) located in Fresnel zones have a big impact on wave propagation (especially if they are in the first zone). The more of them and the larger they are, the worse the conditions for signal transmission. For links with improved operational reliability, the entire area of the first Fresnel zone should be free of obstructions. In practice, ensuring the purity of 60% of the 1st Fresnel zone guarantees minimal power loss.

PTV satellite signal in IP standard. IPTV is a method of delivering TV content which, instead of traditional ways, based on coaxial cable, uses technologies used in computer networks. DIPOL now offers an IP streamer that enables distribution and management of DVB-S2X/S2/S satellite TV offerings through an Ethernet network (LAN), based on a twisted-pair cable...>>>more