Role of Micro Satellites in Amateur Radio Communication


The beep signals from Sputnik-1 on October 4, 1957 heralded the beginning of the "SPACE AGE". Ever since that historic moment many design and launching agencies have launched hundreds of spacecrafts. These also include the World Radio Amateur fraternity. Micro Satellites characterized as “OSCAR” (Orbiting Satellite Carrying Amateur Radio), were designed and launched under the auspice of AMSAT (USA) and used by the Hams world over. The RS (Radio Sputnik) series of Micro satellites are built and launched by the HAMS of USSR. Hams from other nations like UK, Japan, Malaysia and Germany also have launched effective orbiting satellites. Indian Hams under the banner AMSAT (India) are working on a design for an Indian Micro Satellite to be launched by ISRO in one of the PSLV polar launching systems. The technical details are being finalized with ISAC at Bangalore.

Indian Hams led by the pioneering efforts of VU2UV, QQ RM and KX established communication through the OSCARs and RS and covered the global hemisphere bounded by Japan, Australia, South Africa, Italy, Germany and Finland from the year 1970. As on date, more Indian Hams are communicating through amateur satellites and have built all the ground communication support required for tracking and communication. New generation of communication satellites is necessary to continue the opportunities and improve current technology



Successful placing of the spacecraft Sputnik-I in space orbit by USSR on October 4, 1957 launched the `SPACE ERA’ for human civilization. The feeble radio signals from this spacecraft triggered a scientific storm that resulted in a competition between the technically advanced nations; specially USA and USSR. This resulted in accelerated activities in the rocket and satellite technology with rapid advancement and improved results. The erstwhile long distance HF radio communication with the support of natural ionospheric layers was pushed to a second place, giving the first place to VHF/UHF/SHF line of sight communication. The humanity at large, got the benefits in the major areas of extended international telecommunication, global weather and picture coverage, information and data collection for defense etc. etc. Global coverage of polar orbiting satellites, information and data collection for stationary satellites are the order of the day. The limited life imposed by the storage batteries on the early satellites have been overcome by adding the solar energy panels, which keep the battery energy replenished and regulated.

In any field, amateurs are adventurous and will dare to step into the unknown. Radio Amateurs are no exception. The Tiros series of weather satellites operating on 135-137 MHz band, provided ample opportunities by way of a steady source of VHF signal for the interested Hams to enable them to fabricate and test their VHF receivers, tracking and antenna systems. They learnt the art of tracking the satellite at all passes and were able to compute the AOS and LOS accurately. A small success of receiving the weather satellite came to Indian Ham, VU2UV who was working on his VHF front-end in the early morning (0120 hour), during August 1966. After the successful receiving of weather pictures with full ground tracking facility, the obvious next step for the Hams was to try their hands on the satellite itself.


OSCAR – (Orbiting Satellite Carrying Amateur Radio) series. The first amateur satellite, OSCAR-1 was launched on December 12, 1961 by a Thor-Agena B launcher from Vandenberg Air Force Base, California. It was a piggyback load with Discover 36, with an orbit of 372 X 211 km, inclination 81.2 degrees and period 91.8 minutes. OSCAR 1 was the first of the phase-I satellites. A group of enthusiasts in California formed project OSCAR and persuaded the USAF to replace the ballast on the Agena upper stage with the 4.5 kg OSCAR-I package. The satellite was box shaped with a single monopole antenna and battery powered. The on-board batteries supported the 140mW telemetry beacon transmitter for 3 weeks. The beacon transmitted on VHF (144.983 MHz) giving the temperature of the satellite as Telemetry information as HI-HI Morse code format. The number of this code per minute indicated the satellite temperature. All that the ground station required was a stop watch to decode the data in addition to the ground VHF receiving system. More than 570 amateurs in 28 countries forwarded their reception reports to OSCAR data reduction center. The observations provided important information on radio propagation through ionosphere, the spacecraft’s orbit and satellite thermal design. The OSCAR-I mission clearly demonstrated that the amateurs are capable of (a) designing and constructing reliable spacecraft, (b) tracking satellites, (c) collecting and processing related scientific and engineering information. OSCAR-1 led to the creation of the Amateur Satellite Corporation (AMSAT) in 1969.

OSCAR-II was very similar to OSCAR-I and was launched under similar conditions with orbit 384 X 206 km, inclination 74.2 degrees and period 89.8 minutes on June 2, 1962. The batteries supported the telemetry beacon for 18 days.

OSCAR-III was launched piggyback with seven USAF satellites with orbit 924 X 891 km, inclination 70.1 degrees, period 102.7 minutes on March 9, 1965. It weighted 16.3 kg. This was the first satellite to operate with solar power and VHF relay transponder. The 1W 2 meter linear transponders operated at 146MHz uplink and 144 MHz down link with 15KHz band-width. The transponder lasted for 18 days but more than 1000 Hams in 22 countries communicated through the linear transponder. The beacon lasted for a longer period.


OSCAR-IV was launched on December 21, 1965 by a Titan C rocket piggyback along with three USAF satellites. The launch vehicle had a partial failure due to which the satellite was placed on a highly ellipitical orbit with apogee of 29,120 and a perigee of 168 km. The period was 587.5 minutes, inclination 26.8 degrees and the satellite weighted 18.1 kg. The TRW radio club of Redondo Beach, California built the satellite. The output power of the transponder was 3W; with 144 MHz uplink and 432 MHz down link. Due to the faulty launch, the satellite operated only 85 days; but provided the first two-way communication between Hams of USA and USSR.

OSCAR-5 was launched on January 23, 1970 with an orbit 1476 X 1431 km. inclination 101.8 degrees, period 115 minutes. The weight of the satellite was 17.7 kg and the box shaped craft was of 304 X 431 X 152 mm. This was the first satellite of non-American origin being built by students at the University of Melbourne, Australia. Australis-OSCAR 5 transmitted telemetry on both 2 meter (144.5 MHz at 50mW) and 10 meter (29.45 MHz, at 250mW). This was the first satellite to have the passive magnetic attitude control, and functional control from remote. The university of Melbourne compiled tracking reports from hundreds of stations in 27 countries including India. The 2 – meter telemetry signal reception report was by VU2UV on February 8, 1970, which confirmed the sensitivity and tracking capability of the home built system. The life of the satellite was 46 days


OSCAR-6, launched on October 15, 1972, was the first of phase –2 satellite with a weight 16 kg, orbit 1450 X 1459 km; inclination 1017 degrees and box shaped dimension 530 X 300 X 150mm. It had monopole antennae for 144 and 435 MHz and half wave dipole for 29 MHz. This was the first satellite to have (a) complex control system using discrete logic, (b) satellite to satellite relay communication via OSCAR-7 (c) Doppler-location of ground station for search and rescue, (d) store-and forward, Morse and teletype messages (code store) and (e) low-cast medical data relay from remote locations. OSCAR-6 was active for over 4.5 years and served the Ham community as a wonderful investment and achievement. Body mounted solar panels powered the 24NiCd batteries. Subsystems were built in USA and Australia.

Indian Hams built their space capability operating with this satellite. VU2UV established the first satellite contact with the Russian station UJG6AD on December 29, 1972 on mode A. Till January 17, 1974, VU2UV was the most wanted station on this part of the hemisphere being the only station heard through AO-6 from India. During this period, regular two-way communication was established on daily basis with all active Hams located within the countries bounded by Australia, Japan, Finalnd, Rhodesia and South Africa. On January 17, 1974 VU2QQ (IIT), Kharagpur) joined the band and it was a merry going.

OSCAR-7 was launched on November 15, 1974 piggyback with ITOS-G(NOAA) and the Spanish INTASAT. The spacecraft weighed 28.6 kg; orbit of 1444 X 1459, km, inclination 101.7 degrees. The satellite was octahedral shaped 360 mm high and 424 mm in diameter with circularly polarized turnstile VHF/UHF antenna system and HF dipole. This was the first satellite to provide (a) satellite-to-satellite relay communication via Oscar-6, (b) Early demonstrations of low-budget medical data relay and (c) Doppler location of ground transmitters for search-and rescue operations. Similar to Oscar-6, this was built by multi national Hams (German, Canadin, USA and Australian etc). It carried Mode A (14.5.850-950 MHz uplink and 29.40-50 MHz down link) and Mode B (432.180-120 MHz uplink and 145.920-980 MHz down link) linear transponders and two beacons on 29.5 and 145.7 MHz. Code Store-and forward for Morse and tele-type messages was also a part of the facility. AO-7 was operational for 6.5 years and ceased operation in mid 1981. With OSCARs-6 and OSCAR-7 being present on Mode A and Mode B respectively at the same time enabled more Indian Hams VU2QQ, VU2RM and VU2KX to successfully communicate through the satellites.

OSCAR-8, another international co-operative effort (USA, Canada, Germany and Japan) was launched on March 5, 1978, piggyback with Landsat 3. It weighted 27.2 kg., with orbit 903 X 917 km and inclination 99 degrees. It was a box shaped satellite with 33 cm height X 38 X 38 cm other dimensions. AO-8 had a similar store-and forward service as AO-7 and carried mode A (145.850-900 MHz uplink and 29.400-500 MHz down link), and mode J (145.900-146,00 MHz uplink and 435.00 MHz down link) linear transponders and telemetry beacons on 435.095 MHz and 29.402 MHz. AO-8's primary mission was for educational applications and amateur communication. The life of the satellite was 6 years till June 24, 1983.

RS-1 and RS-2 (Radio Sputnik) the first Russian satellites were launched on October 26, 1978 from Plesetsk C1 with Cosmos 104.5. Weight of the satellites was 40 Kg each, orbit 689 X 1709 Km; inclination 82.55 degrees and the cylindrical dimension was 39- X 420mm. Both satellites contained sensitive Mode A (145 MHz uplink and 29 MHz downlink) linear transponders, telemetry beacons and codestore unit similar to Oscar-6. The transponders could be kept operational only for a few months due to battery problems.


UoSAT-OSCAR-9 was built by the University of Surrey, UK, and launched piggyback with Solar Mesosphere Explorer satellite on October 6, 1981, by a Thor Delta Launcher. It was a 52 Kg package; orbit 538 X 541 km sun-synchronous LEO orbit; inclination 97.46 degrees; box shaped 740 X 420 X 420 mm. This spacecraft was the first to have on-board computer Integrated House-keeping Unit (IHU). It was scientific and educational low-earth orbit satellite containing many beacons but no. amateur transponders. It ceased to operate on October 13, 1989 after 9 years of service.

RS-3 to RS-8

Six Russian satellites were launched together on a common launch vehicle on December 17, 1981. RS-3 and RS-4 were experimental satellites and did not contain transponders for general use. The remaining satellites contained Mode A linear transponders. RS-5 and RS-7 contained “Autotranspoinders” called ROBOTS. These robots made it possible to carry on a CW telegraphy contact with the spacecraft. A typical communication with the Robot would be initiated by the radio amateur on the Robot uplink frequency and the satellite would respond with a short message and issue a QSO number. (Acknowdegement sernial number).


As on to day, the OSCAR series has reached OSCAR 41 and the Russian Sputnik series has reached RS-18. The basic bench mark performance for all the new satellites were set by the performance achieved by the phase 2 satellites OSCAR 6,7 and 8. These may be summed up as:




Power Supply



Battery power, fully supported by body mounted solar array with a possible life in excess of 5 years.











Linear Transponders operating on Mode A, Mode B, and Mode J with a minimum band width of atleast 100 KHz








In Band Beacons



Telemetry beacons in all down link frequency bands that would provide the monitored telemetry signals on state of health of the satellite.








Power Output



Down link power output in the region of 5 Watts for the transponders and 0.5W for the beacons.











Circular polar orbit to provide global communication with orbital height of 1000 to 1500 km, inclination 110 degrees.








Shape and size



Rectangular or other shapes taking account of launch limitations and solar array requirements of exposure to maximum sunlight.








Remote Control



Possible stabilized platform with remote control subsystem and loading of code store for general info and transmission.


The dawn of space era in 1957 found the Hams, world over, fully equipped for HF communication using the World War-II surplus receiving equipment with valves. Receivers type AR88, BC779, SX28, BC348 and HRO were the main support. Home built HF transmitters of 100 Watts was the dream of most of the amateurs on CW. A few Hams possessed rigs operating on AM phone. Dipole antenna was in general use though some Hams used three element Yagi for higher bands. Operation on VHF and UHF was still on infancy due to non availability of special components within the Ham budget. The space era also witnessed the revolution of solid state devices. Hams were quick to take this opportunity to make solid state receivers or to design low noise front ends to make the existing setup more sensitive. Many Ham groups moved into VHF on a regular basis.

Launching of weather satellites introduced more Ham activities on VHF receiver design. This proved to be a blessing in disguise when the phase-1 OSCAR series satellites were launched. More amateurs already had the VHF receiving setup and they concentrated on the improvement of the VHF front end of receivers and the antenna gain, and the challenges were well met. The concurrent availability of Oscars 6, 7 and 8 with mode A, Mode B and Mode J made the satellite communication flexible and one could choose as per the ground station’s equipment.

For example, VU2UV started with Mode A operation capability when OSCAR 6 was launched i.e. 100W erp VHF transmitter and sensitive 29.5 MHz receiving setup. By the time OSCAR-7 was launched, the station was equipped with a new home built dual band (29.5 MHz and 145 MHz) solid state receiver, Mode B uplink transmitter on 432 MHz band with 100W erp. The fully Azimuth elevation steerable antenna group of 4 turn Helical antenna for 144 MHz and 11 X 11 element yagi for 432 MHz were also built. 144 MHz 6 element cubical quad antenna was added at a later date. Today’s scenario is much different. The required ground equipment; transmitter, receiver and antenna system in most modern technology package is readily available. It is just a question of acquiring the package that suites to individual Ham’s operational requirement.


AMSAT (India), an organization of Indian Hams had been working with a scheme to design and produce a Micro-satellite that will meet the launching requirements of ISAC. The initial plan is to have Mode-B (432 MHz uplink and 145 MHz down link ) capability linear transponder along with a telemetry beacon. Initial discussion with Indian Space Agency is very encouraging for a PSLV polar orbit launch and is being finalized. The required satellite hardware is being worked out between the partner groups of Hams and the payload is being fabricated. The Micro sat work is slated to be completed by 2003. For detail refer website (


Round the globe and round the clock hundreds of satellite tracking and communicating committed work force of Radio Amateurs backed with experience and ever growing interest is available for any satellite working in amateur band of frequencies. Automatic and total voluntary updating of the ground facilities to meet new challenging requirements is available free of cost. All satellite experiments by Hams are bound to succeed without fail. Radio Amateurs always find new solutions for new problems in communication field. Amateurs are always adventurous in fabricating, launching of micro satellites and communication through them.


Acknowledgement to the World Radio Amateur Community. Because of their efforts we are an improved lot today.