Satellite Reception- Frequently Asked Questions Last update: (30/09/2012 22:47:25 +0100)
If you have a question you'd like answering here, please send it to faq at uhf - satcom . com after you have read through the Q's and A's below. Some of the questions we've received so far are listed below - check back regularly for updates etc. Thanks are due to the folks at #HearSat IRC channel for the answers below!
Welcome to visitors from Slashdot btw! If you are interested in receiving signals from deep space, go here. If on the other hand you want to listen to typical 'cleartext' comms heard via the UHF satellites, you can visit this page. There is some specific stuff divided up by frequency, you can visit the main page then look at the UHF/L/S/C/X/Ka band pages etc.
Items for all satellite observers:
Q: Where did the idea behind UHF-Satcom.com come from ? - A: This website is a hobby site, run by radio enthusiasts. The information in these pages has been compiled over many years, from a large number of sources, and of course from input provided by the folks in the #hearsat IRC channel. UHF-Satcom.com does not in any way condone illegal satellite activity. Use the information in these pages for legal activities only.
Q: Can I steal content from this website for use in presentations about satellite communications security etc? - A: No, The content of this site and its relevant mirrors is copyright. If you are working for a UK (or any other) company, government department, or spin off department, and are writing for example a presentation on satellite communications security, then you MAY NOT COPY any content from this website unless you have permission in writing - this goes for any classification of presentation (i.e. Classified). Copyright infringement is reported back to the authors of this site on a frequent basis, and is always progressed under EU law regardless of the offender. (Note: If anything about copyright is unclear, contact the authors via the e-mail addresses on the homepage, for clarification)
Q: Who can I talk to about my discoveries ? - A: The first point of call should be the HearSat email list. You can share information on your findings or ask fellow satellite enthusiasts questions about relevant items. i.e. what antenna ... which frequencies... where can I get orbital elements for... etc. If you are looking for real-time chatter on Satcom, you can join the #hearsat IRC channel.
Q: What should I do if I hear some unusual traffic via satellite ? - A: Post a description of it to to Hearsat-L, noting the time, frequency, any modulation characteristics, direction you received the signal from (if you have steer able antennas) and your location. The time (in UTC / GMT) for acquisition and loss of signal may also give an important clue, if it were to come from an orbiting satellite. Where possible, try to leave a VOX recorder hooked up to your radio in order to catch unusual signals.
Q: I want to submit something for inclusion on this excellent website, who do I send it to ? - A: You can submit any relevant satellite information to the email addresses that are at the bottom of the homepage.
Q: Where can I learn about new satellite launches? - A: One of the best places to start is by subscribing to 'Jonathans Space Report'. This report is frequently generated and emailed to list members. It contains details of recent launches as well as a description of the mission etc.
Beginners Start here:
Q: What do I need to get started ? - A: This really depends on what satellite communications you want to listen in to. It can range from a simple hand-held scanner for VHF polar orbiters, to complex microwave components to make down converters for the GHz bands. You should think about starting with VHF and UHF satellites, these are easy to receive with fairly basic equipment. Once you have gained experience, start moving up in frequency.
Q: What's out there ? - A: A lot of satellites! Almost every function you can imagine is probably being carried out in orbit. Interception of communications by crooked governments, image reconnaissance satellites taking photos of ground activities, meteorological or environmental data collection, military communications, TV direct to home broadcasting, ship to shore telephone calls, the list is virtually endless, and its all waiting for you to discover it!
Q: Can I transmit signals up to satellites for others to hear ? - A: Yes. If you hold a valid amateur radio license, you will be able to use a range of different amateur satellites, build and launched by radio amateurs. More information about amateur radio satellites can be found at http://www.amsat.org. Transmitting outside of the amateur radio bands is illegal unless you hold the appropriate radio license. Operating through Amateur satellites is good fun and will quickly teach you the basics you will need for monitoring. UHF-Satcom.com does not promote satellite piracy in any way, shape or form. Some piracy does occur on the UHF satellites, but this is definitely not recommended, as the penalties could be severe.
Q: What time of day is best to receive signals ? - A: Satellites are generally operating continuously. Any time of day or night is good for monitoring. Satellite pass prediction software can really help to determine when a satellite is over your location, increasing your chances of hearing signals from it.
Q: Is it legal in my country ? - A: The short answer is 'probably not'. If the frequencies in use are outside of Amateur Radio, Broadcast or Time Signal bands, then you probably need a license to receive the signals. The exception may be with Weather Satellites but you should check your countries laws. If you are interested only in detecting signals and not demodulating them to extract useful data, then basically anything goes.
Q: Is it illegal to decrypt TV channels ? - A: If you have a valid subscription then its not illegal. If you are using software like 'ProgDVB' with the Yanksee plugin and 'softcam.key' from Internet, then it is probably not legal.
Q: Where can I find preamp circuits and antenna designs ? - A: The best bet is to Google for specifics, i.e. a search for 'uhf gasfet preamplifier' should return some schematics for easy to build preamplifiers. One of the aims of this site is to provide a taster as to what is achievable by those with an average knowledge of electronics and radio. Spelling out the information letter by letter such that it can be directly copied doesn't result in any learning taking place.
Q: Are preamplifiers really necessary or can I hear signals without them ? - A: As frequency increases, then so does cable loss. You may be able to get away with using 10 meters of good quality coax (RG213 etc) at 250MHZ. But if you were to try using the same cable at 1500MHz, then the cable would be so lossy, that very little of the signal picked up by the antenna, would reach the receiver. To counter this, we would use a preamp. This should be placed at the antenna, so that the signals are strong enough to overcome the cable loss. If it were to be placed at the receiver, then nothing amplified up, would still be nothing! As said, you could 'get away' with this coax at 250MHz, a preamp for this band would give a very noticeable improvement.
Q: Where can I get a preamplifier, either as a kit or ready built? - A: UHF-Satcom.com can recommend preamplifiers from Kuhne Electronics and Minikits of Australia. Kuhne Electronics can supply preamplifiers from VHF up to 50GHz, and are generally regarded as the best 'off the shelf' amplifiers for the amateur radio community. Minikits of Australia sells some nice preamp kits, originally designed for the 1.3GHz and 2.3GHz amateur radio bands, however these preamps are excellent from 900MHz to 2.5GHz, and can be built by anyone with a moderate level of electronics knowledge. A nice S-Band preamplifier kit has been produced recently (2008) by G4DDK.
Q: What is the best receiver for satellite work ? - A: It depends on what you are listening for. A continuous coverage receiver is ideal, but failing that, one with coverage of the VHF satellite band (136-138MHz) and the UHF satellite band (225-400MHz) would be quite useable. Also reception of L-band signals including the 1.5GHz Inmarsat band bcan be interesting. SSB reception capability is a must, and can help to characterise some modes and of course it helps to detect weak signals. An Icom R7000 can be picked up quite cheaply these days and is still a very capable receiver. Several of the receivers from AOR can also be recommended for satellite work. These include the AR-5000+3, the AR-8600, the AOR-3000A and the AR8200 hand held scanner. AOR receivers are used by many of the folks on the Hearsat-L mailing list, and have proved to be extremely capable.
Q: What do the terms LNA, LNB and LNC mean ? - A: LNA: First there were LNA's, which stands for Low Noise Amplifier. These were typically 3.7 to 4.2 GHz in and out, and they required a heavy duty (low loss) coaxial cable, in the order of several dollars per foot. LNB: This problem of expensive coax was later solved with the LNB, which stands for Low Noise (amplifier) Block down converter. It takes the whole 3.7 to 4.2 GHz range and converts it down to 950 MHz to 1450 MHz. Advantage was that it could use the standard (low cost) RG-6 cable and that multiple receivers could be hooked up since the whole frequency band was brought into the building. This became very useful when the Ku band became popular since it allowed for the use of cheap cable. To bring the actual Ku band (11 GHz) signal into the building would have been very expensive. In the early days, a hundred foot length of cable (30 meters) for Ku band would have cost between $600 and $1000, including connectors. LNBF: This is basically a LNB with an integrated feed horn, which is where the letter F came from. These are typically found on Ku band systems, although some LNBF C-band feed horns exist, mostly made by Chaparral. LNC: A company named Dexcel invented the LNC. This stood for Low Noise (amplifier) converter. These were LNA's with 3.7 to 4.2 GHz in and 70 MHz out. They required a separate cable cable to control the build-in down converter. The down converters were VOLTAGE controlled ! Inside the LNA was a down converter which took the 3.7 to 4.2 GHz signal and converted a single TV channel to the then standard IF of 70 MHz. This was done at the focal point of the dish. Although some separate down converters existed, most people selected the Dexcel "all in one" LNC for convenience. Advantage was no more expensive cable, the disadvantage was poor stability, a pre-made 125 foot cable and no multiple receiver hook-ups possible since only ONE television channel went down the cable and only one receiver could tune the channel.
Q: Where do I need to point my antenna to hear UHF satellites ? - A: This depends on where you are located. The best method is to find some satellite tracking software, such as the excellent 'WXTrack', install that, then load geostationary satellites around the rough area you need to look at. For example, if you wanted to look for the UHF satellite cluster around 15West of South, you would go to the SatCo-DX website and look down the list for a satellite at 15W, make a note of it's name. Then in the 'WXTrack' software, locate the same satellite, and add it to your list of currently tracked satellites. When you return to the world map screen, you can click on the satellite, and at the bottom, the appropriate azimuth and elevation will be displayed. Once you have the azimuth and elevation set, use your scanner to monitor a beacon frequency from the satellite in question, for a final peak up of the antenna.
Q: How can I get started in L-band and S-band reception ? - A: There are now a number of scanners/receivers on the market that will cover the bands up to 3GHz. In addition, you will need an antenna and preamp for the band. If you already have a receiver which does not cover these, then converters can be constructed from MMDS units (for 2.2GHz) or Meteosat units (1.6GHz).
Q: Is it possible to hear communications from the Space Shuttle ? - A: Yes it is, and its easy to do! Firstly check the NASA website for a launch date, then check that you will be in the ground track of the shuttle during the first few orbits. It you are, then you can listen on the UHF Air to Ground 1 frequency of 259.700MHz AM, and if you are lucky, you'll catch some of the communications between Houston and the Shuttle. Some examples of audio clips sent in to UHF-Satcom.com can be found on the 'Sound Samples' page.
Q: How do I decode NOAA weather satellite pictures ? - A: You'll need a receiver capable of covering 136MHz to 138MHz, with a IF bandwidth of about 30KHz. From a software perspective, Google for Wxsat or Jvcomm32 - both these pieces of software are excellent for decoding weather satellite images.
Q: Where can I get more information about Weather Satellites ? - A: There is a group in the UK called 'GEO' - there website contains a lot if information that is relevant to those interested in weather satellite reception.
Q: What receiver can I use to find weak or short duration signals? - A: Typically you'll want a Software defined radio that can cover the frequencies of interest, or at least cover the IF frequency of your radio. For satellite monitoring, you can connect an SDR to the IF output of your radio, which will give you some front end selectivity. An absolutely fantastic SDR is available from RFSpace - the SDR-14 or the SDR-IQ. Both units cover DC to 30MHz and offers a whole host of interesting demodulator and display features through the SpectraVue software suite.
Those with intermediate knowledge start from here:
Q: What is all this about Keplerian Elements and where do I get them ? - A: Keplerian Elements are basic a set of data used to define an orbiting satellite. Satellite tracking software use these element to calculate where the object are, how high, where its going and how fast. Read more about Keplerian Elements here: http://www.marine.rutgers.edu/mrs/education/class/paul/orbits.html. To obtain Keplerian Elements, register at http://www.space-track.org This site has the latest Keplerian Elements.
Q: What is a squint angle ? - A: The squint angle is the angle between the axis of direction of the satellites antenna, and your ground station. i.e. if the antenna is beaming towards the USA from a HEO, then a moderate squint angle would result for those listeners in Europe. You may find that odd results can be obtained where the squint angle is high, especially where helical antennas are used on the satellite - this can be the result of polarity nulls occurring at various off-bore sight angles.
Q: What is meant when you say something is in the 19.2E constellation ? - A: Geostationary satellites operate from an orbital slot, this could be 19.2E (19.2 degrees east of zero degrees longitude) If more than one satellite operate from the same orbital slot, its a constellation of satellites.
Q: How can I hear the Smart-1 lunar Orbiter ? - A: This is fairly straight forward. You'll need a receiver that covers 2.2GHz (such as an AOR8600, AOR5000, AOR5000+3, AOR-AR-One, AOR-Alpha), and a suitable preamplifier and antenna, and a time machine to go back to August 2006. With a 1 metre dish, 3 turn helical feed and something like a Minikits of Australia 2.3GHz preamp, the signal should be easy to hear. You will have to tune +- a few 10's of KHz from the nominal frequency of 2235.100MHz, to compensate for the Doppler shift - Note Smart-1 impacted on the moons surface at the beginning of September 2006.
Q: I want to be able to look over a wide bandwidth of RF in order to catch signals that I might otherwise miss, any suggestions as to how to do this? A: The simple way is to look at getting a SDR, something like the SDR-14 or the SDR-IQ. Both of these units can display 190KHz of RF and demodulate audio in that bandwidth. The SDR-14 can display a maximum bandwidth of 4MHz which is extremely useful for looking at satellite transponders.
Those with advanced knowledge start here:
Q: I'm really interested in learning more about microwave radio, how can I do that ? - A: You should join an amateur radio group that specialises in microwave radio. In the UK you can join the 'UK Microwave Group', who also have a email reflector at 'Yahoo Groups'. A very well known group in the USA is the 'North Texas Microwave Society'
Q: Is there an easy method of listening to signals coming from Space Probes ? - A: There is no easy method. These spacecraft are millions of Km's away from Earth, meaning only a very small amount of signal arrives on our planet. The equipment needed to hear these spacecraft needs to be very stable in frequency, and extremely sensitive. Kuhne Electronics sells a ready built converter, the KU LNC 8084 A and matching super low noise preamplifier, the KU 8000 A. This equipment along with a reasonable sized dish antenna (1m and bigger) will give you a pretty much state of the art receive system. You can of course follow the design notes on this website, and build your own down converter from scratch.
Q: Can I modify a satellite TV LNB to hear 7GHz signals ? - A: Its possible to do this, but it requires a lot of test equipment. Retuning microwave circuits is not easy, but its possible to do. A standard Ku band LNB would need modifying such that its waveguide is made bigger, as WR75 / C120 waveguide has a cut off frequency that is higher than 7GHz.
Q: Can I use parts from a satellite TV system ? - A: Yes! There are several items intended for use with satellite-TV systems that are also very useful for Satcom reception in the L and S bands. Inline amplifier modules covering 900MHz to 2.5GHz can be used if you have a long cable run to your receiver. Place the inline amplifier a few metres for your antenna / receive LNA. Other parts that can be used are 2 and 4 way satellite IF splitters, these are useful for serving the signal to several receivers, spectrum analysers, signal meters etc. Parts taken from satellite TV LNB's can also be used to make low noise receive preamplifiers.
Q: Where can I find designs of GPS locked 10MHz oscillators? - A: There are a couple of excellent designs for GPSDO's available. In the UK, Andy G4JNT has written up his GPSDO project. James G3RUH also has a good design on his web page of a simple GPS stabilised oscillator. Both designs will provide a highly accurate 10MHz signal which can be used as a frequency reference for higher frequency converters and receivers such as the AOR5000 or the AOR5000+3. If you are searching for other 10MHz reference solutions, you could try eBay for a Rubidium Oscillator.