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Satellite reception equipment

Let's see first what constitutes a typical installation before considering other solutions, more compact or integrated.

To be functional, generally speaking a basic station of satellite reception requires basic material : a simple VHF antenna and a receiver tuned on the same frequency.

Low gain antennas

The antenna must be cut on 137 MHz to receive polar orbiting satellites (also named Polar Orbiting Environmental Satellites or POES). The simplest but effective antenna is the turnstile or crossed dipole (70-80 € to Thiecom or Timestep), the same as the one used on other frequencies by AM broadcasters but at a smaller scale. A better solution is to use the Quadrifilar Helix Antenna (QHA). It has the advantage to be fixed, it does not require a rotator, and changes automatically the elevation and azimuth to the satellite direction without interruption. It is circularly polarized and displays a relatively narrow bandwidth. If you are an handyman you can easily build these antennas yourself at very low cost. Unfortunately, blueprints are not easy to find and I don't have any.

At first, two antennas suited to polar orbiting satellites working between 136-138 MHz. At left a crossed dipole right circularly polarized offering a 6.0 dBi gain. At center a Quadrifilar helix antenna made of 316 stainless steel and derelin plastic. Its performances are a little better than the crossed dipole but its price is much higher. At right a discone antenna AOR DS3000A. It is a wide band antenna able to receive between 75 MHz and 3 GHz and to transmit on ham bands of 144, 430, 904 and 1200 MHz. It sustains 50 W maximum. It is more suited to terrestrial telecommunications but one can use it to receive other signals, including satellites if they cross the sky quite low over the horizon. This antenna is provided with a RG-58A/U cable and N connectors. Documents Timestep and AOR USA.

Like any antenna working on VHF bands, these aerial work without preamplifier but require a good coaxial cable to prevent losses that are more important on VHF than on HF. In this configuration the coax length should not exceed 15 meters long. If your coaxial is 15 meters or longer, you should use a 137 MHz preamplifier directly mounted under the antenna. Such antennas also work fine to receive the ISS signal on 145.800 MHz and for the 2-meter amateur band. 

In addition we can use the next accessories : - An antenna preamplifier to increase receiving signals which power is limited to 5 W (37 dBm) - One or more SSB and FM receivers covering the frequencies of 30 MHz, 135-146 MHz (the most used), 430-440 MHz 1.691-1.694 kHz (for METEOSAT), with frequency converters in option. For polar orbiting weather satellites on 137 MHz you also need of an IF filter 30 to 50 kHz wide, neither narrowest or wider. - A DSP modem (V.92 digital) to receive fax signals used by these satellites and other transmissions by shortwaves (e.g. telemetry at 400 bps PSK from OSCAR satellites). Usually, receive signals from polar satellites is never a problem. Orbiting between 200 km (ISS) and more than 1000 km of altitude, even with 5 W of power, you will pick up quite easily their signals. However, orbiting much farther, geostationary satellites require a high gain antenna.

A Timestep preamplifier to place just below the antenna. It has a low noise figure of 0.5 dB and a bandpass filtering giving over 50 dB rejection to pagers on 153 MHz.

High gain antennas

Now, knowing that weather satellites work on various frequencies, we need several types of antennas. To receive weather satellites on VHF you can use your turnstile or your Quadrifilar Helix antenna. It is sufficient but displays a low gain. To receive METEOSAT you also need something larger with narrower bandwidth and tuned on microwave (L-band). This lead us to use high gain antennas, like next models :

- The cross-polarized VHF Yagi (in X-shape) or the helical antenna (in corkscrew shape) with a right circular polarization tuned on 137 MHz, and offering a gain over 14 dBic to receive signals from weather satellites in polar orbit (NOAA, METEOR, etc)

- A dish antenna between 1 and 2m of diameter (90 cm or 3 ft is the minimum) tuned on 1.69 GHz, offering a gain of at least 22 dBic and equipped with a low noise preamplifier to receive signals from geostationary satellites (METEOSAT, etc).

AMSAT Pass Prediction Calculator

(Online predictions valid for all radio amateur satellites)

Reception of ISS

I suspect well that this hardware might frighten you if you read this for the first time. That changes from the telescopic antenna of your portable radio ! 

If you want only to listen to astronauts onboard the International Space Station (ISS) on VHF bands - some astronauts are indeed radio amateurs and use the call sign NA1SS - you can bypass this hardware. You can simply use a ground plane vertical antenna or a discone. This kind of antenna being vertically polarized, you can only pick up ISS transmissions when it is low over the horizon and not as long as using a steerable Yagi. Periods of interruption of amateur telecommunications are usually scheduled, and related to EVA and crew changes.

To receive signals from ISS, in Region 1 (Europe, Russia, Africa) you must listen to the frequency of 145.800 MHz in FM (downlink), radio amateurs operating from the ground transmitting on 145.200 MHz (uplink). 

Real-Time position of Amateur satellites above Europe

Latest TLE of the space station ISS

Latest TLE of the american space shuttle

3-line TLE of all satellites on 22 may 2005

3-line TLE of amateur satellites on 22 may 2005

ISS Fan Club

Reception of HF-FAX

To receive fax and other weather messages in HF bands (80-10m), you can tight oudoor some 20m of electrical wire or erect a vertical antenna of about 6m high or longer (cut at 1/4l). A more expensive but more compact solution is to use an active receive magnetic loop like Wellbrook ALA-1530 that works indoors too.

Satellite Tracking (NASA) - Heavens-Above - Celestrak

Amateur radio activities At left we recognize a amateur radio to the large decametric Yagi erected close to his home, and on which directional elements were added for the V/UHF traffics. This picture was recorded on January 27, 1998 at the time of the conjunction of the Moon with Venus and Mercury. At right the astronaut Nancy J.Currie, KC50ZX, onboard the US space shuttle in QSO with hams at Goddard Amateur Radio Club on 145.200/145.800 MHz. ISS crew works also in packet radio on 2m. Documents Astroarts and NASA.

In the same way, if you are amateur radio and want to work by satellite (with AMSAT or ISS) on adequate frequencies, your antenna should be quite performing and idealy you should use a beam, these famous array antennas using in VHF between 5-30 elements. In this application they are used in crossed-polarization, equipped with an antenna preamp (20 dB) and usually two coaxials, one of excellent quality for transmission, the second that can be of lower quality for receive, cables being as short as possible. There are till other differences whether you work in SSB or FM. At my knowledge the only one short beam covering continuoulsy bands from 1.5 to 200 MHz at 1 kW PEP is D2T. But this is another debate.

Reception of Inmarsat

For all fans of maritime activities and adventure, recall that today no expedition, that it is maritime, at ground or evolving in the air does communicate by shortwaves, excepted local contacts in VHF. A the time of satellites, all telecommunications between the crew and the base or the HQ are established using the global network of Inmarsat satellites and other Orbcomm (excepted in polar regions). 

Established in 1979, Inmarsat uses today 13 satellites. They ensure all mobiles communications world-wide. Inmarsat satellites are located on four orbital spots named IOR, AORE, AORW and POR. An Inmarsat link can be done using very modest but expensive means, including a portable PC, an Inmarsat Mini-M telephone (similar to a GSM) and a portable antenna. For information, a portable Inmarsat installation for transmission (Inmarsat M4 terminal, Nera console with a folding antenna and ISDN connection) cost $4000, but this is something else than a GSM !

To check : World at Phone

Inmarsat satellites are divided in 4 categories depending on their functions or supported modes : A (analog), B (digital), C (telex function) and D (telecopy and telephony).

The first satellite of this category is Inmarsat-A that is operational since 1982. It transmits non-encrypted communications, including fax, data and email. Its successor Inmarsat-B is operational since 1993 and reduced the price of communications. Inmarsat-E transmits positions of beacons for safety purposes and relies the information to coastal Inmarsat stations, etc.

Connected to Inmarsat global network, you can hear all crews at sea, transatlantic liners, some business men and many scientific expeditions. Inmarsat is also used in remote countries linking students with their teacher. At last, through the ISDN network and an Inmarsat GAN terminal, you can be connected to the Inmarsat though the Internet.

To listen to these transmissions, all you need is a receiver (scanner) and an antenna tuned on L-band on 1525-1559 MHz (transmission on 1626.6-1660.5 MHz). Signals being emitting at low power, here also a 20 dB antenna preamplifier showing a low noise figure (0.5 dB) is recommanded. The antenna can be either a dish offering a gain of at least 20 dBic (or 10 dBic for a Mini-M) or an helical antenna right circulary polarized.

If you want to pick up these satellites when they are low over the horizon (as to some boats) an omnidirectional antenna tuned on L-band can be used.

Note at last that most Inmarsat antennas can be used to receive weather satellites in polar orbit (GOES, etc).

Some solutions among many others to pick up telecommunication satellites. Surrounding a portable Motorola for Ka-band (Iridium) equipped with its microwave antenna, at left an Inmarsat L-band dish (1.5 et 1.6 GHz, folding down) of 1.44m of diameter offering a 23 dBic gain, and at right a Ka-band dish (Iridium, 20-30 GHz) of 1.8m of diameter offering a 49.3 dBic gain. Documents Seavey Antenna and Motorola.

Reception of Iridium

List for memory the Iridium constellation of 66 satellites (Low-Earth Orbit) orbiting at about 780 km of altitude. They work on Ka-band (19.4-19.6 GHz downlink and 29.1-29.3 GHz uplink) and use L-band (1616-1626.5 MHz) for telephony servicesas well as Ka-band (23.18-23.38 GHz) for inter-satellites links. This newtork is basically used to ensure communications in rural and maritime areas where terrestrial links are non-existent. The Iridium networ transmits also data and can be linked to any computer and to the Internet. At last, Iridium offers Pager services permitting to receive and send messages, emails and SMS anywhere in the world.

Excepted L-band, the Iridium network is thus not available on a common scanner. It requires downconverters and high gain dishes, reserving this type of listening to skilled handymen able to build their own receive installation.

Reception of NASA TV

NASA's Johnson Space Center broadcasts 24 hours a day educative documents and reports of current space missions, essentially on the geostationnary AMC-6 satellite located at 72° West. This is a standard TV satellite transmitting two signals : a video signal vertically polarized in NTSC format on C-band at 3880 MHz, and an audio FM monaural audio signal on a subcarrier of 6.8 MHz. Knowing that the signal reaches 40 dBW over New York but is 1000 time weaker in the middle of the North Atlantic ocean, its receive from Europe requires a high gain dish (>4m in diametre) equipped with an antenna preamplifier and a NTSC/PAL or SECAM decoder and the result is not sure.

So if your signal contour is 0 dBW in Europe, you are 40 dB down. If the dish gain increases of only 6 dB each time you double the diameter, you need a dish 64 times the diameter of the 40 dBW contour dish (thus 64x 2m or 128m) to yield the same signal quality...

Recall that these transmissions are also accessible with much less ressources on the Internet and extracts can be donwloaded from various websites (Spacelink, CNN, etc).

Reception of images from ISS

About the direct reception of video images transmitted by ISS or the space shuttle to the control center, it is vain to try. Indeed, signals are transmitted via a satellite relay system named TDRS (Tracking & Data Relay Satellite) which data are encrypted for security reasons. The transmission is established in microwave band close to 15 GHz. At those frequencies you need very exotic hardware and a lot of know-how to setup a receive installation. If you are not a skilled telecom engineer, better to give up... But if you need more information check the website of UHF-Satcom or join the Amateur DSN Group on Yahoo!.

Second part

Reception of weather images

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