Zoltán OM7AQ was the first to respond to our request for a post on CQ.sk. He offered us the opportunity to publish his older articles. Thank you!
Today we bring you an article about amateur satellites. It is extensive material on satellite communication, technology and operation, and Slovak stations dedicated to this fascinating area of amateur radio.
Amateur radio satellites make it possible to make better use of very short waves - from the lower limit of the shortwave band to the microwave bands. On board the satellite there is usually a converter - a transponder - which, like a terrestrial converter, has an input and output frequency - uplink a downlink. Most satellites have a linear converter on board - for SSB and CW operations, but there are also satellites that have an FM transponder. The satellites can be low-range (LEO) – such as RS-12, RS-15, FO-20, FO-29, etc. and high-speed (HEO) - such as AO-10, AO-13 or AO-40.
The first amateur radio satellite – OSCAR 1 – was launched in 1961. It only had a lighthouse on board. Satellite OSCAR 3, launched in 1965 already had a 145 MHz/145 MHz linear transponder. Satellites were successfully launched in 1972 and 1974 OSCAR 6 a OSCAR7.At the beginning of the 80s, the Russian amateur satellite program RS successfully started.
After a successful start OSCAR 10 real DX operation has become a reality also via satellites. The long-planned supersatellite OSCAR 40 today it is also a reality.
For each satellite mode, we must have a transmitter on the uplink (input frequency) and a receiver with appropriate antennas on the downlink (output frequency). Each satellite mode has a recommended effective radiated power of the earth station (ERP or EIRP) - this value should not be exceeded. By following the recommended ERP (EIRP), we avoid disturbing other stations and ensure safe and stable operation for ourselves.
For LEO satellites (RS-12, FO-20, etc.) we obviously need less power (around 100 W ERP – less transmitter power and a simple antenna) and for HEO satellites (AO-10, AO-40) more power (around 200-300 W ERP on CW and 800-900 W ERP on SSB – more transmitter power and multi-element directional antennas).
Our receiver should be sensitive - we can use low-noise preamplifiers placed directly under the antenna for reception.
We can do experiments with any antennas, but for serious work we will need suitable antennas. For LEO satellites in the area of KV bands - 29 MHz - we can use dipole, crossed dipole, but also GP, LW or directional antennas. For VHF bands - 145 MHz - it is also advisable to use antennas with a wide radiation pattern - there are no problems with antenna routing. For HEO satellites, we can use classic VHF antenna designs, but it is better to use antennas for circular polarization - cross yagi, or Helix. It is necessary to rotate the antennas in both planes – horizontal and vertical AZ/EL.
We can use a computer to track satellites - there are satellite programs for different platforms - DOS, Windows 9x, Linux, etc.
Before the first attempts, we will study the frequency plan of the given satellite. Frequency plans can be obtained from the PR BBS network or on the Internet. Internal bandplan satellites must be observed. We will choose a suitable round trip - for the first attempts, such rounds are more suitable when the transponder is not very busy. If we have directional antennas, let's point them at the satellite. We tune the receiver to the frequency of the beacon transmitter.
Due to the Doppler shift, the received frequency will not be the same as the nominal frequency. When we hear the signals of the beacon transmitter, we can search for stations in the frequency band of the satellite transmitter. Let's find a free place and lock the transmitter, while turning the tuning knob of the transmitter - of course in the uplink frequency range of the satellite - until we hear our own signals on the receiver. If it was successful, then we can call the challenge - SSB or CW. Be careful with SSB operation: some satellites have an inverting transponder. This means that in order to hear a USB signal on the downlink (output), we must transmit on the uplink (input) LSB. So are the AO-10, FO-20, FO-29 satellites. The procedure can also be reversed - on the receiver we find the station that calls out the call. We tune the transmitter to its frequency - we make sure that we can hear our own signals - if so, the opposing station will probably hear us as well. During operation, make sure that your own signals are not stronger than the signals of the satellite's beacon transmitter. Let's remember: working with great achievements is great, but spoiling the joy of others is not good...
In addition to satellites that have linear transponders, there are also satellites that have a single-channel FM converter or digipeater on board, or BBS. Satellites with a crossband FM transmitter, such as AO-27 and UO-14 can also be used by less technically equipped stations: a two-band "handle" with an antenna on 2m/70cm should be sufficient for operation. Digi satellites usually use a protocol like terrestrial packet radio - AX.25, speed 1200 Bd (BPSK/AFSK), and 9600 Bd (FSK/FSK). In addition to satellites, orbital complexes - space stations - are also involved in amateur space communication. The Russian space station MIR and also the international space station ISS have gained great popularity among amateurs - voice FM operation is also possible, as well as digital (packet) communication
Slovak stations on satellites
OM7AQ – op: Zoli,QTH: Lučenec
QRV via all active analog satellites
Equipment: 2m: FT290R, PA100W/preamps, 4, 2×5, 13 ele. 70cm: FT790R, PA100/350W/preamps, 2×15 ele. 13 cm dish
Other: QRV HF/VHF/UHF
e-mail: gye@isternet.sk
website: http://om7aq.host.sk
OM3WBC – op: Joe, QTH: Fiľakovo JN98VG
QRV via all active analog satellites
Devices: ICOM IC910H, PA 100W/preamps., 2m: 2×13 ele F9FT, 70cm: 2×19 ele
Other: QRV on 2m/70cm/23cm (tropo, Es...)
ax.25: OM3WBC@OM0PBB.#SSL.SK.EU
OM0MS – op: Števo, QTH: Humenné KN08
QRV via all active analog satellites
Devices: 2m: home made 50W, 70cm: IC471H, PA 300W/preamps.9ele/19 ele
Other: KV band and 70cm EME
e-mail:om0ms@QSL.net
ax.25: OM0MS@OM0PBB.#SSL.SVK.EU
web: http://www.qsl.net/om0ms
OM3WAN – op: Alojz, QTH: Žilina
QRV via all active analog satellites and AO-40
Equipment: home made 2m TCVR 30W/trnsv. 70cm 30W, ant. 4 ele/9 ele
Other: 2m/70cm 13 cm: DB6NT conv.+1m dish
OM1AVK – op: Vlado, QTH: Bratislava
QRV via all active satellites
Equipment: ICOM IC 821H, PA 100W/preamps, ants. 9/21 ele F9FT
Other: 2m/70cm
e-mail: vrm1@pobox.sk
ax.25: OM1AVK@OM0PBM.#ZSL.SVK.EU
The following Slovak stations work/worked through LEO
OM3TPS,OM8RA,OM8AMY,OM7AC,OM0AB,OM3TPG (nw OM3BH), OM3AU (silent key), OM3KII, OM3MM, OM9FI, OM3KEG, OM1II, OM3IM, OM3TLF, OM3GB, OM3LU, OM3CPY (nw OM7PY), OM3CFL, OM3IS, OM3CAF,OM3WAO
gye@isternet.sk
http://om7aq.host.sk