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M17 (amateur Radio)
M17 is a digital radio modulation mode developed by Wojciech Kaczmarski ( amateur radio call sign SP5WWP) et al. M17 is primarily designed for voice communications on VHF amateur radio band and above. The project received a grant from the Amateur Radio Digital Communications in 2021 and 2022. The protocol has been integrated into several hardware and software projects. Overview M17 utilizes 4800 symbols per second 4FSK with a root Nyquist filter applied to the bitstream. Radio channels are 9 kHz wide, with channel spacing of 12.5 kHz. The gross data rate is 9600 bits per second, with the actual data transfer at 3200. Protocol allows for low-speed data transfer (along with voice), e.g. GNSS position data. The mode has been successfully transmitted through EchoStar XXI and QO-100 geostationary satellites. In 2021, Kaczmarski received the ARRL Technical Innovation Award for developing an open-source digital radio communication protocol, leading to further advancements in amate ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
M17 Spectrum
M17 or M-17 may refer to: Roads * M17 road (Ireland) * M17 road (Bosnia and Herzegovina) * Highway M17 (Ukraine) * M-17 (Michigan highway) * M17 (East London), a Metropolitan Route in East London, South Africa * M17 (Cape Town), a Metropolitan Route in Cape Town, South Africa * M17 (Johannesburg), a Metropolitan Route in Johannesburg, South Africa * M17 (Pretoria), a Metropolitan Route in Pretoria, South Africa * M17 (Durban), a Metropolitan Route in Durban, South Africa * M17 (Port Elizabeth), a Metropolitan Route in Port Elizabeth, South Africa Aircraft * Myasishchev M-17 Stratosphera (NATO reporting name Mystic-A), an early version of the Myasishchev M-55 reconnaissance aircraft * Miles M.17 Monarch, a 1936 British, light, touring aeroplane * ''M.17'', a German World War 1 prototype aircraft, the basis for one of the two Fokker B.II (1916) Military Equipment * M17 Half-Track, an anti-aircraft variant of the M5 Half-track * M17 rifle grenade used by the United States dur ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Convolutional Code
In telecommunication, a convolutional code is a type of error-correcting code that generates parity symbols via the sliding application of a boolean polynomial function to a data stream. The sliding application represents the 'convolution' of the encoder over the data, which gives rise to the term 'convolutional coding'. The sliding nature of the convolutional codes facilitates trellis decoding using a time-invariant trellis. Time invariant trellis decoding allows convolutional codes to be maximum-likelihood soft-decision decoded with reasonable complexity. The ability to perform economical maximum likelihood soft decision decoding is one of the major benefits of convolutional codes. This is in contrast to classic block codes, which are generally represented by a time-variant trellis and therefore are typically hard-decision decoded. Convolutional codes are often characterized by the base code rate and the depth (or memory) of the encoder ,k,K/math>. The base code rate is ty ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Speech Coding
Speech coding is an application of data compression of digital audio signals containing speech. Speech coding uses speech-specific parameter estimation using audio signal processing techniques to model the speech signal, combined with generic data compression algorithms to represent the resulting modeled parameters in a compact bitstream. Some applications of speech coding are mobile telephony and voice over IP (VoIP). The most widely used speech coding technique in mobile telephony is linear predictive coding (LPC), while the most widely used in VoIP applications are the LPC and modified discrete cosine transform (MDCT) techniques. The techniques employed in speech coding are similar to those used in audio data compression and audio coding where knowledge in psychoacoustics is used to transmit only data that is relevant to the human auditory system. For example, in voiceband speech coding, only information in the frequency band 400 to 3500 Hz is transmitted but the reconst ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
D-STAR
D-STAR (Digital Smart Technologies for Amateur Radio) is a digital voice and data protocol specification for amateur radio. The system was developed in the late 1990s by the Japan Amateur Radio League and uses minimum-shift keying in its packet-based standard. There are other digital modes that have been adapted for use by amateurs, but D-STAR was the first that was designed specifically for amateur radio. Several advantages of using digital voice modes are that it uses less bandwidth than older analog voice modes such as amplitude modulation and frequency modulation. The quality of the data received is also better than an analog signal at the same signal strength, as long as the signal is above a minimum threshold and as long as there is no multipath propagation. D-STAR compatible radios are available for HF, VHF, UHF, and microwave amateur radio bands. In addition to the over-the-air protocol, D-STAR also provides specifications for network connectivity, enabling D-STAR radio ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
NXDN
NXDN stands for Next Generation Digital Narrowband, and is an open standard for public land mobile radio systems; that is, systems of two-way radios (transceivers) for bidirectional person-to-person voice communication. It was developed jointly by Icom Incorporated and Kenwood Corporation as an advanced digital system using FSK modulation that supports encrypted transmission and data as well as voice transmission. Like other land mobile systems, NXDN systems use the VHF and UHF frequency bands. It is also used as a niche mode in amateur radio. NXDN is implemented by Icom in their IDAS system and by Kenwood as NEXEDGE; both Kenwood and Icom now offer dual-standard equipment which supports the European dPMR standard. History Icom and Kenwood began their collaboration in 2003. The NXDN protocol was announced in 2005, and NXDN-compatible products first appeared in 2006. The NXDN Common Air Interface (CAI) was accepted at the Study Group 5 (SG5) meeting of the International Tele ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Android (operating System)
Android is a mobile operating system based on a modified version of the Linux kernel and other open-source software, designed primarily for touchscreen mobile devices such as smartphones and tablets. Android is developed by a consortium of developers known as the Open Handset Alliance and commercially sponsored by Google. It was unveiled in November 2007, with the first commercial Android device, the HTC Dream, being launched in September 2008. Most versions of Android are proprietary. The core components are taken from the Android Open Source Project (AOSP), which is free and open-source software (FOSS) primarily licensed under the Apache License. When Android is installed on devices, the ability to modify the otherwise free and open-source software is usually restricted, either by not providing the corresponding source code or by preventing reinstallation through technical measures, thus rendering the installed version proprietary. Most Android devices ship with additional ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Terrestrial Trunked Radio
Terrestrial Trunked Radio (TETRA; formerly known as Trans-European Trunked Radio), a European standard for a trunked radio system, is a professional mobile radio and two-way transceiver specification. TETRA was specifically designed for use by government agencies, emergency services, (police forces, fire departments, ambulance) for public safety networks, rail transport staff for train radios, transport services and the military. TETRA is the European version of trunked radio, similar to Project 25. TETRA is a European Telecommunications Standards Institute (ETSI) standard, first version published 1995; it is mentioned by the European Radiocommunications Committee (ERC). Description TETRA uses time-division multiple access (TDMA) with four user channels on one radio carrier and 25 kHz spacing between carriers. Both point-to-point and point-to-multipoint transfer can be used. Digital data transmission is also included in the standard though at a low data rate. TETRA Mob ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Poland
Poland, officially the Republic of Poland, is a country in Central Europe. It is divided into 16 administrative provinces called voivodeships, covering an area of . Poland has a population of over 38 million and is the fifth-most populous member state of the European Union. Warsaw is the nation's capital and largest metropolis. Other major cities include Kraków, Wrocław, Łódź, Poznań, Gdańsk, and Szczecin. Poland has a temperate transitional climate and its territory traverses the Central European Plain, extending from Baltic Sea in the north to Sudeten and Carpathian Mountains in the south. The longest Polish river is the Vistula, and Poland's highest point is Mount Rysy, situated in the Tatra mountain range of the Carpathians. The country is bordered by Lithuania and Russia to the northeast, Belarus and Ukraine to the east, Slovakia and the Czech Republic to the south, and Germany to the west. It also shares maritime boundaries with Denmark and Sweden. ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Warsaw
Warsaw ( pl, Warszawa, ), officially the Capital City of Warsaw,, abbreviation: ''m.st. Warszawa'' is the capital and largest city of Poland. The metropolis stands on the River Vistula in east-central Poland, and its population is officially estimated at 1.86 million residents within a greater metropolitan area of 3.1 million residents, which makes Warsaw the 7th most-populous city in the European Union. The city area measures and comprises 18 districts, while the metropolitan area covers . Warsaw is an Alpha global city, a major cultural, political and economic hub, and the country's seat of government. Warsaw traces its origins to a small fishing town in Masovia. The city rose to prominence in the late 16th century, when Sigismund III decided to move the Polish capital and his royal court from Kraków. Warsaw served as the de facto capital of the Polish–Lithuanian Commonwealth until 1795, and subsequently as the seat of Napoleon's Duchy of Warsaw. Th ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Digital Mobile Radio
Digital mobile radio (DMR) is a specification for commercial products so they can interoperate. It is defined by a standard created by the European Telecommunications Standards Institute (ETSI), and is designed to be low-cost and easy to use. DMR, along with P25 phase II and NXDN are the main competitor technologies in achieving 6.25 kHz equivalent bandwidth using the proprietary AMBE+2 vocoder. DMR and P25 II both use two-slot TDMA in a 12.5 kHz channel, while NXDN uses discrete 6.25 kHz channels using frequency division and TETRA uses a four-slot TDMA in a 25 kHz channel. DMR was designed with three tiers. DMR tiers I and II (conventional) were first published in 2005, and DMR III (Trunked version) was published in 2012, with manufacturers producing products within a few years of each publication. The primary goal of the standard is to specify a digital system with low complexity, low cost and interoperability across brands, so radio communications purchasers a ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Baseband
In telecommunications and signal processing, baseband is the range of frequencies occupied by a signal that has not been modulated to higher frequencies. Baseband signals typically originate from transducers, converting some other variable into an electrical signal. For example, the output of a microphone is a baseband signal that is an analog of the applied voice audio. In conventional analog radio broadcasting the baseband audio signal is used to modulate an RF carrier signal of a much higher frequency. A baseband signal may have frequency components going all the way down to DC, or at least it will have a high ratio bandwidth. A modulated baseband signal is called a passband signal. This occupies a higher range of frequencies and has a lower ratio and fractional bandwidth. Various uses Baseband signal A ''baseband signal'' or ''lowpass signal'' is a signal that can include frequencies that are very near zero, by comparison with its highest frequency (for example, a s ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Exclusive OR
Exclusive or or exclusive disjunction is a logical operation that is true if and only if its arguments differ (one is true, the other is false). It is symbolized by the prefix operator J and by the infix operators XOR ( or ), EOR, EXOR, , , , , , and . The negation of XOR is the logical biconditional, which yields true if and only if the two inputs are the same. It gains the name "exclusive or" because the meaning of "or" is ambiguous when both operands are true; the exclusive or operator ''excludes'' that case. This is sometimes thought of as "one or the other but not both". This could be written as "A or B, but not, A and B". Since it is associative, it may be considered to be an ''n''-ary operator which is true if and only if an odd number of arguments are true. That is, ''a'' XOR ''b'' XOR ... may be treated as XOR(''a'',''b'',...). Truth table The truth table of A XOR B shows that it outputs true whenever the inputs differ: Equivalences, elimination, and introduc ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
