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Putting Together Your System | Table 1. Receiver Types | PreAmp | Antennas | Modems
What Do Amateur Satellites Transmit? | Receiving Pictures From Weather Satellites
Tracking Satellites with Your Bare Eyes | Table 2. Uplink/Downlink Frequencies

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Putting Together Your Receiving System Top ^

An optimum radio amateur satellite receiving system consists of antennas, rotor, preamplifier, receiver, and a modem for the digital modes. The receiver is usually the most expensive piece of equipment, so let's start by analyzing the characteristics an ideal receiver should have. The table lists types of receivers and all of the satellites that can be received with each receiver.

  • It should cover 135-145MHz, 435-437MHz, 1.2GHz.
  • If it's a transceiver, it should be able to receive and transmit simultaneously.
  • Tune increments of 10-20Hz should be available.
  • The microphone should have UP/DOWN button tuning.
  • It should have a 9600 Bps digital I/O connector.
  • Non standard FM offsets should be available.
  • You should be able to change the IF filters to wider ones if necessary.

The receiver doesn't have to have all of the above characteristics, but the more it has, the more modes and more data you'll be able to copy.

Table 1. Receiver Types and the Satellites You Can Work With Each Top ^
10-meter SSB Receiver RS-10/11, RS-12/13 and RS-15 using Voice and CW
2-meter SSB Receiver AO-13, AO-10 using Voice, CW, RTTY and SSTV with 400 BPS PSK modem: AO-13 telemetry with 1200 BPS Bell 202 modem: UO-1 1 data and telemetry
2-meter FM Receiver MIR, DOVE, SAREX using Voice with 1200, BPS AFSK AX.25 modem: DOVE, Mir, SAREX and AO-27 digital data
70cm SSB Receiver FO-20 Voice and CW; with 1200 BPS PSK AX.25 modem: AO-16, WO-18 and LO-19 digital mail and experimental data
70cm FM Receiver (with 430-440 MHz coverage) AO-27 in digital voice mode; with 9600 BPS FSK modem: UO-22, KO-23 and KO-25
2.4 GHz SSB Receiver or Receive Converter AO-13 using Voice and CW

Preamplifier Top ^

Adding a preamplifier at the bottom of your antenna is an easy and cost effective way of improving your satellite reception. As the received frequency increases, so do the losses in signal strength caused by the coax cable connecting the antenna with your receiver. A preamp placed just underneath the antenna will amplify the signal received making up for the losses induced by the coax cable.

Antennas Top ^

There are several types of antennas that may be used to work with amateur satellites, such as turnstiles, eggbeaters, helixes. The most used one for frequencies below 1.2GHz is the cross Yagi, with both horizontal and vertical elements. To work digital satellites a 12-14dB gain antenna is preferred, for FO-20 a 14dB gain is fine, and for the AO-10 and AO-13 satellites the longer the antenna the better…

A rotor capable of azimuth/elevation movements is also a desirable thing. You are then capable of aiming the antennas at the satellite as it passes overhead.

Currently LogSat supports the Kansas City Tracker, an interface card which is mounted inside your computer. This card acts as an interface between the rotor and the computer. Using this card LogSat can automatically control the rotors and move the antennas for you, tracking in real time any satellites you select.

Modems Top ^

As you can see from Table 1, each digital satellite mode usually requires a different kind of modem ($100-$150). If however you buy a DSP modem you'll pay more, but you'll have all the modes in one box.

What do Amateur Satellites Transmit? Top ^

The analog satellites have voice and CW (Morse code) signals, as well as occasional RTTY (Radio TeleType) and SSTV (Slow Scan Television) signals. All satellites also transmit telemetry signals, such as how much power the satellite is using to transmit, the satellite's temperature, solar cell current and many other interesting things. This telemetry is transmitted as AX.25 (packet data). Some data is also sent using ASCII, CW or RTTY.

Receiving Pictures from Weather Satellites Top ^

There are two kinds of weather satellites. They can either be geostationary or spinning in polar orbits around the earth. Geostationary satellites are satellites 36000km above our heads, whose position in space relative to us on earth never changes. Once you point your antenna at them you won't have to move it again. The European Meteosat satellite and the American Goes satellites are geostationary weather satellites. Meteosat transmits continuously on 1.69GHz, and can be received using small satellite dish, a receive converter which converts the 1.67GHz into 137MHz, a receiver capable of receiving 137MHz with a 30KHz bandwidth, a simple interface to convert the receiver's analog data into digital data which is fed into the computer through the serial port. Shareware software like JVFAX 7.0 will then decode these signals and give you a photo on screen just like those in the weather forecasts you see on TV. The dish runs for $50-$100, the receive converter is about $150-$200, the receiver ranges from $100 to $500, and the software is shareware.

There are also polar weather satellites. Among these are the Russian Meteors and the American Noaas. These satellites have very low orbits (~1000Km) compared to those of geostationary satellites (~36000Km). Their photos are thus a lot more detailed, but will cover only a small portion of the earth. They transmit at around 137MHz, and can be received using a couple of simple round dipole antennas. The equipment needed is the same as for the Meteosat, with the difference in antennas and the unnecessary receive converter.

Tracking Satellites With Your Bare Eyes Top ^

It is possible to watch satellites with your bare eyes, given the right conditions. Using LogSat just select a very low orbiting satellite, as could be the Russian space station MIR, or the space shuttle during one of its flights, see when it passes overhead, go outside and with a bit of luck you should be able to spot it. The key is choosing a good time of the day. The best chance of seeing one is a little after sunset, when you're in the dark, but the satellite is still illuminated by the sun, which will reflect onto the satellite body, allowing you to see it.

Table 2. Uplink/Downlink Frequencies for Amateur Satellites Top ^
Satellite Uplink Downlink Beacons Notes
OSCAR 10 435.025-175 145.83-98 145.81/987  
OSCAR 11 (UoSAT 2)     145.826
Experimental beacon on 2401.5 MHz
OSCAR 13 (Mode B)
(Mode S)
OSCAR 16(PACSAT) 145 90-96 437 051 437.026/051 S beacon 2401.143
OSCAR 17(DOVE)     145.825 S beacon 2401.221
OSCAR 18 (WEBERSAT)     >437.102 spare TX on 437.075
OSCAR 19 (LUSAT) 145.84-90 437.126 437. 126/154 CW on 437.l27
>OSCAR 20 (Fuji) 145 9-146 435.8-.9 435.797/91 .797=CW, .910=packet
OSCAR 22 UoSAT 5 145.9/.975 435.120 435.120  
OSCAR 23 KITSAT 1 145.85/90 435.175 435.175  
OSCAR 25 KITSAT 2 145,87/98 436,500   spare TX 435.175
OSCAR 26 145.875/90/925/95 435.822   secondary TX 435.867
OSCAR 27 AMRAD 145.850 436.797    
RS 10 (Mode A)
(Mode K)
(Mode T)
145. 86-90
29 36-40
29 36-40
29 357/403
Robot uplink 14S.820
Robot uplink 21. 120
Modes KA & KT also
RS 11 (Mode A)
(Mode K)
(Mode T)
145 91-95
21.2 1-25
145,9 l -95
Robot uplink 145.830
Robot uplink 21.130
Modes KA & KT also
RS 12 (Mode A)
(Mode K)
(Mode T)
145 91-95
Robot uplink 145.831
Robot uplink 21.129
Modes KA & KT also
RS 13 (Mode A)
(Mode K)
(Mode T)
145 96-146
145 96-146
Robot uplink 145.840
Robot uplink 21.138
Modes KA & KT also
RS 15 (Mode A) 145.85-89 29 36-40 29.353/398  
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