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No. 11/2022 (March 14, 2022)
Electricity from air.
Researchers at the University of South Florida have developed an antenna that could be an important step in the development of processes for recovering energy from radio waves generated in cell phone networks or Bluetooth transmissions. This technology could potentially provide wireless power to sensors, LEDs and other simple devices with low energy requirements.In the Optical Materials Express journal, the researchers report that lab tests of the new antenna show that it can "harvest" 100 microwatts of power. Such power is sufficient to power simple devices. This was possible because the metamaterial the antenna is made of absorbs radio waves perfectly.
Scientists have been trying to capture energy from radio waves for a long time, but it has been difficult to get enough energy to be useful. This is changing thanks to the development of metamaterials and the ever-increasing number of available external sources of radio frequency energy, such as cell phone networks, Wi-Fi, GPS, and Bluetooth signals.
Antenna design with embedded diodes in slots
A 16 cm by 16 cm device was tested in the laboratory. During the tests, the power and frequency of the radio source were varied from 0.7 to 2.0 GHz. The researchers demonstrated the antenna's ability to process 100 microwatts of power from radio waves with an intensity of only 0.4 microwatts per square centimeter (such a value occurs, for example, when the operator's BTS is 100 meters away). Also, a cell phone located very close to the antennas delivers enough energy to, for example, power an LED.
Since the antenna in the current version is much larger than most of the devices it could potentially power, the researchers are working on making it smaller. They would also like to create a version that could collect energy from multiple types of radio waves simultaneously so that even more energy can be gained.
DVB-T2/HEVC signal measurement in TV systems.
The first European country to begin official DVB-T2 broadcasting was the UK. A test with a TV transmitter was carried out by BBC Research & Development in June 2008. Currently, in the European Union, DVB-T2 signal is broadcast in Austria, Czech Republic, Germany, Belgium, Croatia, Romania and France (DVB-T broadcasting is planned to be switched off only in 2024). TV broadcasts in both, DVB-T and DVB-T2 standards are available from broadcasters in the United Kingdom, Italy and the Scandinavian countries. In these countries, no cut-off date has been set for the DVB-T signal. In Poland, the transition from DVB-T to DVB-T2 is to take place by 30 June 2022.Polish TVN station and the operator Emitel are testing television broadcasting in the DVB-T2/HEVC standard. Therefore, it was possible to measure this signal and test the capabilities of the Signal ST-5150 R10842 meter.
The video above shows measurements of DVB-T2/HEVC signal with the ST-5150 R10842 meter
Setting up opening codes for wickets in Hikvision modular IP video intercom system.
After connecting the DS-KD-KP G73668 code lock to the DS-KD8003-IME1 G73652 or DS-KD8003-IME2 G73644 modular door station, it is possible to control the first relay in the door station using the pre-programmed codes. Using the iVMS-4200 application, up to 16 public codes of 4-6 digits and 1 private code of 6 digits can be set directly at the door station and at each monitor. To open the wicket using the programmed code, enter the #set code # sequence with the keypad. For a private code set with the indoor station, the wicket is opened by entering the sequence: # apartment number, set code #. When devices are added to iVMS-4200, codes are established at the following locations:- door/gate station: Remote configuration -> Access Control -> Password Settings
- monitor: Remote configuration -> Permission Password, and for Password type, select Unlocking password
View of the public password setting window in the gate station
View of the private password setting window in a monitor
Recommended method of signal measurement in optical TV/SAT systems.
Checking the optical signal level at different points of a fiber optic TV antenna system is essential to eliminate a number of potential problems when starting up the system. A distinctive feature of the systems using optical transmitters with DVB-S/S2 and DVB-T inputs is the existence of two wavelengths in the fiber optic link: 1310 nm and 1550 nm. It has a direct impact on the way the measurements are performed and interpreted by typical signal level meters, such as GRANDWAY FHP2B04 L5822.
Connecting the meter directly (e.g. via a short patch cable) to the transmitter shown in the picture above, the screen readings close to 9 dBm are obtained regardless of whether the measurement is set at 1310 nm or 1550 nm. This is because typical signal level meters are based on broadband detectors and are not equipped with additional filters. At the same time, of course, they are calibrated in such a way that when a given wavelength is selected in the options, the correct indication is given as far as the light of this wavelength reaches the detector. Such design of the devices has its consequences:
- in systems where the signal is generated at a single wavelength (e.g. 1310 nm), by setting the meter to measure a different transmission window, such as 1550 nm, the installer will be able to see the measurement result on the screen. However, it will not be correct. The correct one will be obtained only when the meter is set to measure 1310 nm;
- in systems where two wavelengths are used, setting the meter to measure one of them actually measures both, and the result is the sum of both measurements, both, the correct and incorrect ones. Therefore, in the above example, system with a 6 dBm transmitter, regardless of the chosen wavelength, 9 dBm will be read on the screen, the signal is 2x stronger (or otherwise stronger by 3 dB) than expected.
TERRA optical TV systems have one unique feature. The receivers used in them have WDM diplexers whose connectors are located outside the housing. This allows the installer to properly measure the level of the optical signal at the input of the receiver (only about 0.5 dB attenuation of the diplexer has to be taken into account) for each of the two wavelengths: 1310 nm and 1550 nm.
OR501W TERRA A9877 optical receiver. 2 diplexer connectors outside the housing, allowing to measure 1310 nm and 1550 nm signals with a broadband meter.
DynDNS service.
To run a server, e.g. with a website or for viewing CCTV cameras, to be available from anywhere on the Internet, and if you do not have a fixed IP address, but you only receive it (public address) dynamically from a DHCP server, you have to use the DDNS (Dynamic Domain Name System), i.e. the dynamic name server service.Subscribers connected to the Internet often do not have a fixed public IP, but it changes from time to time. In this case, the user unable to directly connect remotely to such a location. Here, the DDNS service comes to the rescue, which, like the DNS, has a database of entries of the domain and numeric address relationships, but it can be updated at any time by the domain owner (a dedicated service/application installed on user hardware notifies the DDNS server of the address change). Thanks to that, the server can be reached under one fixed name, regardless of what IP address it currently has. For that reason, you can communicate with the server only using the domain address translated by the DDNS server (unless the current numeric server address is known, but you never know how long it will be valid).
Here is a diagram of a one-cycle communication between the client and server without a fixed IP address via DDNS. It will be repeated the next time the address is changed.
| 1. Your IP is 83.17.30.134 2. IP changed to: dipol.no-ip.org so now 83.17.30.134 3. What is the current IP address for dipol.no-ip.org? 4. dipol.no-ip.org is now 83.17.30.134 5. Hello, 83.17.30.134, send me your website 6. Here is my website | |
Note that it may take a short while, after the DHCP server changes the IP address, before the program or router detects that, and then it may take about a minute for the update information to be sent to the DDNS server, before the server writes the data to the DNS server. You have to bear in mind that the server may be unavailable for several minutes when the IP address changes.
 | The FORSCHER FS-8117 N7051 cable tester can be used for measuring cable continuity, cable length, pair attenuation, PoE voltage measurement and cable fault distance measurement. It allows to detect connection faults in UTP/STP, telephone and coaxial cables. Additionally, the FS8117 tester is equipped with advanced cable pair locator. It is based on a unique technique that combines the generation of both analog and digital tones , allowing for significantly increased accuracy in locating cable bundles. High sensitivity allows searching for cables even under plaster up to the depth of 100 cm. | |
 | The TP-Link TL-SG1048 48xGE N299391 switch is perfect for small and medium community computer networks. It has Auto MDI/MDIX function that allows the installer to forget about the problem of "straight" or "cross" connections. The switching capacity is 96Gbps so that maximum link bandwidth is utilized. MAC address table of 16000 addresses provides scalability even in large networks. | |
 | TP-Link TL-SG1210MP 10xGE (8xPoE) 802.3af/at PoE switch N29932 is a desktop device ensuring smooth network transmission. in 10/100/1000 Mbps Ethernet networks. It has 8 10/100/1000 Mbps ports that support Power over Ethernet (PoE+ 802.3af/at). The switch automatically detects PD devices compliant with IEEE 802.3af or IEEE 802.3at standard and supplies them. In addition, the device has a 1000 (combo) Mbps SFP slot and two 10/100/1000 Mbps Ethernet ports. | |
Worth reading
Signal Fire – FTTH splicing. splicers prove to be perfect in fiber optic connections in the last mile systems, i.e. at end customer connection. These splicers are particularly widely used by installers performing fiber optic cabling in multi-family housing, which consists in connecting each apartment with a telecommunication room by means of a double-fiber single-mode fiber optic cable... >>>more
The diagram above shows a hybrid multiswitch system
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Coaxial cable for emergency exits
