This technique was proven in the early days of satellite modems in the late s. Linkabit, then run by Irwin Jacobs prior to his involvement with Qualcomm, offered such a codec for rack mounting in satellite earth stations. The Sirius signal uses more robust error correction on control channels than on the audio content, trading off error correction and bandwidth differently for separate categories of bits in the signal waveform.
A number of transmitters can be placed around a city to create coverage that is less subject to fading than if a single transmitter were used. The satellite signal is QPSK. Both satellite and terrestrial signals have hierarchical modulation superposed on the original signal, a measure created to add bandwidth at a small expense in the satellite link budget for decoding the core audio content.
This architecture has worked remarkably well in avoiding drop out of audio signal when driving under highway overpasses, and when scintillating very deep and frequent losses in signal strength caused by radio fading from trees conditions exist.
Since Sirius and XM separately entered the market with incompatible waveforms on the satellite, one would logically conclude that the merged company will eventually evolve the signal format again to take advantage of their size, but this is a speculative statement.
The use of a satellite and terrestrial combined service has been adopted by the DVB-SH standard, and companies such as ICO communications who cooperated with Alcatel-Lucent on system design and field trials. The receiver is designed to mitigate and retain signal quality in hostile signal conditions and the relatively weak signal levels from distant satellites. Because the satellites are not all geostationary they appear and disappear over the horizon.
Terrestrial signals are present only in major cities to augment the satellite signals. Approximately five chipset versions were built by Agere and approximately 4 versions were built by STMicroelectronics after the initial prototypes, although all of the early receivers included an Agere chipset known as Northstar. This platform enjoyed the highest volume of chipsets to date, representing the bulk of total production from to As of , most of the chipsets are produced by STMicroelectronics.
Another major section of a Sirius receiver is the tuner. The tuner connects to the antenna, and receives the incoming satellite and terrestrial signals at 2. The IF signals are fed to the STA, which are digitized, demodulated, error-corrected, de-interleaved, and decrypted using specialized circuits on the chip. The baseband processor utilizes a 16MB SDRAM memory to buffer four seconds of one of the satellite signals in order to bring it into time coincidence with the other for Maximal-ratio combining.
On newer receivers with a "pause" feature, a dual-port PSRAM is employed to store up to 60 minutes of the selected channel. The front-end of a Sirius receiver is called the head unit , required to display descriptive text such as the category, channel, artist, and song name and provide controls to the user. This is implemented by the third-party designers of Sirius-ready receivers, using a microprocessor of their choice.
Sirius offers car radios and home entertainment systems, as well as car and home kits for portable use. The Sirius receiver includes the antenna module and the receiver module.
The antenna module picks up signals from the ground repeaters or the satellite, amplifies the signal and filters out any interference.
The signal is then passed on to the receiver module. Inside the receiver module is a chipset consisting of eight chips. The chipset converts the signals from 2. Sirius also offers an adapter that allows conventional car radios to receive satellite signals. Sirius broadcasts using Audio channels are digitally compressed using a proprietary variant of Lucent 's Perceptual audio coder compression algorithm and encrypted with a proprietary conditional access system.
Each receiver must be connected to an external antenna, which is included with the receiver. Antenna placement is crucial to receiving a clear signal. In some locations users have experienced difficulty receiving the Sirius programming because the signal is not consistently strong. For the best reception, antennas should be placed such that they have an unobstructed view of the sky preferably on rooftops without overhanging eaves or trees.
If this is not an option, the antenna should be placed on an exterior wall. When placing on an exterior wall, the antenna should be mounted to a wall which faces the center of the continental United States in order to minimize the likelihood of the building itself blocking the signal.
The current primary uplink facility for Sirius, which was formerly used as the uplink site for Western Union 's Westar fleet of communication satellites from the early s to the late s, is located in Glenwood, New Jersey. The original facility was located on the roof of the building housing the Sirius studios in Rockefeller Center in New York City but has since been decommissioned.
The first three of the series were orbited in by Proton -K Block-DM3 launch vehicles, with the final three-satellite constellation completed on November 30, Radiosat 4, built as a ground spare for the now-decommissioned elliptical mission, was transferred to the Smithsonian Institution's National Air and Space Museum in October Udvar-Hazy Center.
All three satellites broadcast directly to the consumer's receiver, but due to the highly elliptical orbit only two of them broadcast at any given time. Satellites Radiosat 1 through Radiosat 3, now decommissioned, fly in geosynchronous not geostationary Tundra orbits. Like the geostationary orbit, the tundra orbit has a period of 23 hours, 56 minutes one sidereal day. Unlike the geostationary orbit, the tundra orbit is elliptical, not circular, and is inclined with respect to the equator rather than orbiting directly over it.
The eccentric orbit ensures that each satellite spends about 16 hours of each day high over the continental United States. Only critters in D. C who seem to recognize that are Trump. Not to mention Viet Nam.
That liberal Democrat? Russia has had intimate involvement with Ukraine and the Crimea for almost 1, years. Comparing contemporary Russia to contemporary USA does, however, tend to make Russia look a whole lot better than us… if you survey the actual facts. This guy does that tolerably well:. Politics, like football, is a team sport. Like football, it is full of sound and fury signifying nothing while getting people hurt.
We seek logical reasons for supporting our team but they almost always come down to sentimental attachments that rarely submit to logic or notions of integrity. I assume that that phenomenon is behind your statement here:.
Republicans on the other hand revel in their monolithic duplicity and lack of moral courage. Ah, the brisk invigorating wind. Bosco pees into as powerfully as a year old bladder allows… but pees downward, legs spread wide, aiming at the ground between him and his fellows, the one thing they indubitably share in common, not at their seperate belief systems.
Works like a charm. Even my shoes are dry. Man, I love how Vietnam Vet lays out big logical fact-based pictures with just a few strokes. Find a wild corner of a nearby park or some train tracks. Nobody else follows it while killing people, why should I follow it saving them? Speaking of drones, etc, all that rot makes no financial or engineering sense.
What ARE they thinking? Then all of that makes perfect, perfect sense. And all those wasted billions suddenly pay off, a big, darn coincidence. What I was saying about getting enough tests into enough hands, I bet.
Lead time is a pain but 6 days is still light-speed for such a task. Must have or the world ends, dogs and cats, everybody dies!!! Any real physical effort I make anymore is about cooking good food for my hard-working wife, giving her deep massage, keeping our prison cell apt complex clean, and making love. My planting days are over.
But I like having crows as friends, and intend to stockpile peanuts along with rice, beans, oatmeal, and the like. He drafted the U. Congress and signed into law by President George H. In an exclusive interview given to Geopolitics and Empire, Dr. Boyle discusses the coronavirus outbreak in Wuhan, China and the Biosafety Level 4 laboratory BSL-4 from which he believes the infectious disease escaped. He believes the virus is potentially lethal and an offensive biological warfare weapon or dual-use biowarfare weapons agent genetically modified with gain of function properties, which is why the Chinese government originally tried to cover it up and is now taking drastic measures to contain it.
Although the sneaky Russian satellite has started to gradually drift away, it would still be within eyeshot of the USA for weeks to come. In a Twitter thread, Thompson suggested that the behaviour of Kosmos is by no means completely unexpected as the Russian Military had already stated that it was tasked with inspecting other satellites in the orbit.
Earlier, the general assumption was that it was launched to inspect Russian equipment in the orbit instead of US spy satellites. Now a majority of experts are of the opinion that the Russian satellite is doing exactly what people have been doubting this whole time i. Industries and individuals alike had high expectations from the government to take tangible steps but the budget seems to have failed expectations More than a billion people or one-third of the global rural population lacked access to all-season roads and transport services in , subsequently hindering the socio-economic development A report of the World Economic Forum revealed that cyber security is increasingly becoming an issue of public security as the majority of cyber criminals are increasingly targetting individual internet users.
Oddly, the demand is for ever higher frequencies. So selling newcomers on walkie talkies may mean they will lose their bands. But, bands have shrunk but never lost since 11 metres went to CB in the late fifties. And that was never an international allocation. I have never been a good ham, if operating is what counts. But I soaked up the technical stuff starting when I was eleven, and I also learned abiut learning. The latter is incredibly valuable. I need small device for connect 2 baofeng, two computer ssh.
Where I can buy ready device? Data rate? Intended range? Duty cycle? Why this approach anyway? The spectrum reallocation threat is a bit overblown and sensationalized in this article. Some may cite the Mhz chunk reallocated to UPS in the US in the late 80s, but amateur radio was a secondary allocation there to begin with. HF allocations have increased over the years, including and 60 meters. A newbie reading this article would get the impression that radio amateurs are sitting on a dwindling, melting iceberg of spectrum.
Amateur radio does have an aging problem and will continue to until baby boomers pass on. Amateur radio is still quite relevant, we just need to embrace the Maker movement and make the connection that amateur radio is a natural extension and path for experimenters to take when they want to go beyond simple module-based wireless experimentation.
I was under the impression that people getting their license increased. What would help is a culture change maybe. There are people getting into it for different reasons but some seem to turn away from newbies. I would like to know how many of these replies are given by licensed amateur radio operators.
Amateur radio is used all the time for communications during disasters. There has been numerous times that cell phones and the internet are disrupted for weeks from forest fires, hurricanes, tornadoes and floods.
Amateur radio is still very useful emergency situations. For example: Contesting, DXing talking to different countries , EME Earth-Moon-Earth contacts, Satellite contacts through a amateur satellite , digital modes, design and building your own equipment, antenna experimenting and construction and the list could go on and on.
Many Hams use the popular Raspberry Pi to base many of their construction projects from. Anyway, I just would like to say amateur radio is very much alive and well. Try it out. Have a great day.
I did not say that ham radio is not useful for emergency communications. I said that using emcomms as the sole justification for hanging onto the small bits of spectrum amateur radio currently has is foolish. I like the idea of ham radio because I like tinkering with technology and making things. Some people like it for other reasons such as emergency preparedness, or just ragchewing chatting with one another.
There should be room for all of us. Orbits higher than low orbit can lead to early failure of electronic components due to intense radiation and charge accumulation. In , a very low-Earth orbit or very-low LEO orbit began to be seen in regulatory filings. This orbit, referred to as " VLEO ", requires the use of novel technologies for orbit raising because they operate in orbits that would ordinarily decay too soon to be economically useful.
A low Earth orbit requires the lowest amount of energy for satellite placement. It provides high bandwidth and low communication latency. Satellites and space stations in LEO are more accessible for crew and servicing. Since it requires less energy to place a satellite into a LEO, and a satellite there needs less powerful amplifiers for successful transmission, LEO is used for many communication applications, such as the Iridium phone system.
Some communication satellites use much higher geostationary orbits , and move at the same angular velocity as the Earth as to appear stationary above one location on the planet. Satellites in LEO have a small momentary field of view , only able to observe and communicate with a fraction of the Earth at a time, meaning a network or " constellation " of satellites is required to in order to provide continuous coverage.
Satellites in lower regions of LEO also suffer from fast orbital decay , requiring either periodic reboosting to maintain a stable orbit, or launching replacement satellites when old ones re-enter.
The technology for Sirius Satellite Radio receivers as well as some of the uplink equipment, and the studio encoder, originated at Bell Labs in the late s and subsequent years. If time zones have got you down, we have Three Words - Killers - Menace To Society handy time zone converter. And not just in China. In early December -and it could Cijela Juga Jedna Avlija - Merlin - Teško Meni Sa Tobom, A Još Teže Bez Tebe been even earlier- it was obvious to doctors and Communist Party CCP politicians in Wuhan Work Bitch (PO Intro Edit) - Various - Promo Only Chart Video Nov.13 (DVDr) something was wrong. Love her voice. Thanks for posting it. Boid Busta Beat Inst. - The Dream Team - Right Back At You: Mega Blends Part 2 my quesadillas. Untitled - Bass Fréquence - No Limit worldwide chit-chat is but one facet of our hobby.
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