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Satellites reception

Notice to fans of shortwaves (I)

Let's see what material is at our disposal to receive transmissions from radio amateurs satellites and other orbital laboratories (RS, ISS, METEOSAT, NOAA, INMARSAT, etc).

Like for radioastronomy, a satellite receive system requires specific material that often counts among the accessories of a ham shack or the one of a listener.

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Satellite reception equipment

Let's first define 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 erected in an open space (not to close to buildings), a receiver tuned on the same frequency, and some meters of coaxial cable.

Cheapest solution

Here is a cheap solution to receive weather satellites. The result is not guarantee as the configuration is not optimized, and the signal is not poweful but you can receive and decode images of weather satellites.

Several accessories are for example available to Amazon or WiMo :

- VHF receiver : RTL-SDR receiver ($12.99)

- VHF whip antenna : Tram 1185 dual-band antenna ($24.99) or Diamond MR-77 avec connecteur PL (35 € to WiMo)

- Coaxial cable M/F SMA to SO-239 : RF coaxial cable ($5.70)

- SDR software (free) : SDR console for Windows or Cubic SDR for Mac OS X

- Weather image processing software (free) : WXtoImg for Windows and Mac OS X

- Audio piping software (free) : VB-Audio Virtual cable for Windows or Soundflower for Mac OS X

- A computer.

Total cost : for less than $50 plus the computer you can already set up a receive installation !

NB. If you have difficulties to find the antenna and the coaxial cable, consult a shop dedicated to amateur radio equipment.

We will see next page specifications of RTL-SDR doggles and software.

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 more efficient solution is to use the Quadrifilar Helix Antenna (QHA or QFH). 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 last, there is the discone antenna. 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.

To read : Quadrifilar Helix Antennas, Gogan.org

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. 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 aerials 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.

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.

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.

High gain antennas

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 :

A 90 cm Timestep dish to receive geostationary satellites. It offers a 22.5 dBic gain and 20 dB return loss.

 - 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).

The dish surface is either made of a plain metal plate or constituted of a simple wire mesh. Some come with or without a sturdy tripod in option. A high-end or tactical model can reach very high prices but amateurs products are more accessible. Many amateurs also rely on TV dishes.

These two high gain antennas must be equipped with a rotator as their beam is very narrow (10-20°).

At last, if you wish to use a satellite tracking software to steer your antenna and track satellites in real time, David H. Lamont, ZL2AMD, provides an UNI-TRAC card, a tracking and tuning interface for PC that, connected to a rotator, ensures a real time tracking on any satellite. This interface replaces the Kansas City Tracker/Tuner no more available.

All these accessories are available to any good dealer of electronics or ham material such as ICOM, Kenwood, Yaesu, AOR and other UKW-Berichte. Most of them can provide you cross-polarized Yagis and dish antennas as well.

Compact antennas

A compact log periodic AX-31B antenna from WinRADIO able to receive all frequencies between 230 MHz and 1600 MHz.

This rather cumbersome material, which must be installed outdoors, can scare beginners discovering this type of installation. Indeed, it changes from the usual telescopic antenna of a portable radio!

But we can go without this material. If you have few free space to install several antennas or even to erect a vertical, a disk or a discone, there is a "compact" solution that will please to listeners and amateurs living in flats or apartments.

To capture signals above 230 MHz, you can purchase to WinRADIO a compact receive log periodic antenna and multiband AX-31B. It is a beam not larger that a A4 sheet delivered with an included 20 dB antenna amplifier and 2 metres of coaxial cable. It is a good compromise and it also works indoor.

The italien company PKW sells also log periodic antennas for receive or transmission working in different bands, e.g. the LP-22eV model covering from 130 MHz to 1.3 GHz (124 €).

Below 200 MHz, if a 1 to 2 m long whip antenna can captures HF or VHF emissions within a range of 100 to 1000 km depending on the frequency, this type of antenna is limited to a relatively narrow frequency band  and remains very sensitive to parasites (noise) and all forms of local QRM.

Bonito MegaLoop ML200 antenna.

In order to reduce this inherent sensitivity of vertical antennas, Bonito (Ham Radio Shop) sells two active magnetic loops consisting of a single wire forming a circle or a square of 5 m in diameter able to receive all frequencies between 9 kHz and 200 MHz (MegaLoop ML200, 369 €) or between 9 kHz and 180 MHz (MegaLoop FX, 399 €). This type of antenna does not even have to be placed outside; it can be fixed on a balcony or on a window. Due to its small size, it is suitable for a portable installation or a SDR dongle (see next page).

For the LW and HF bands, Wellbrook also sells an active ALA-1530 (240 £) magnetic loop in aluminum measuring 1 m in diameter but covering only the frequencies between 50 kHz and 30 MHz. It is as effective as a dipole to capture amateur radio, coded messages and broadcast stations. It works also perfectly indoors.

However, a magnetic loop is not a magic antenna. If this type of antenna is able of capturing any type of signal (from broadcast stations, amateur, military, civilian services, etc.) within a radius of about 10000 km or even more if the propagation is very good (during the maximum of the solar cycle), this design is not as efficient as an rotatble Yagi antenna cut at the working wavelength. Moreover, like any antenna, it is sensitive to nearby broadcasting transmitters that can drown the weaker signals from far stations. A magnetic loop is equivalent to the performance of a dipole while capturing less noise, sources of interferences. Aluminium models are even steerable. Thus, from Europe, for example, apart from the very powerful international radio transmitters (from Russia, Brazil, Midwest, Central Africa, India, China, etc.) that can be picked up quite easily, it is virtually impossible to capture emissions from local emitters located overseas, in USA, South America, Asia or in the Pacific. To achieve this (and it is not even certain given their low power), it would be necessary to install an external steerable HF or VHF antenna tuned on the working frequency of theses emissions and to equip it with an amplifier to guarantee a good reception.

Reception of ISS

If you want only to listen to astronauts onboard the International Space Station (ISS) on VHF bands you can also 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 Satellite Tracking and Prediction

3-line TLE of satellites (CelesTrak)

ISS Fan Club - ISS Latest TLE

Satellite Tracking - TLE of 5000 satellites (2006)

Reception of videos from ISS

About the direct reception of video images transmitted by ISS or from 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!

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 6 m 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.

Real Time Position of Amateur Satellites over Europe

AMSAT Pass Prediction Calculator

(Online predictions valid for all radio amateur satellites)

Heavens-Above - Spaceweather

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. A 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.

There is also the NASA Television's Public and Media channels carried by QPSK/DVB-S modulation on satellite AMC-3, transponder 15C, located at 87° West. The downlink frequency is 4000 MHz, horizontal polarization, and MPEG-2 digital C-band signals.

Note that a Digital Video Broadcast (DVB) compliant Integrated Receiver Decoder (IRD) is needed for reception.

Knowing that the signal reaches 40 dBW over New York but is 1000 times weaker in the middle of the North Atlantic ocean, its receive from Europe requires a high gain dish (diam. > 4 m) equipped with an antenna preamplifier and a NTSC/PAL or SECAM decoder but the result is not guaranted.

So if your signal contour is 0 dBW in Europe, you are 40 dB down. Knowing that 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 2 m or 128 m) to yield the same signal quality ! Hopefully, if you visit the USA, you can easily receive this channel.

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

Second part

Reception of weather images

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