Amateur radio satellite

An amateur radio satellite is an artificial satellite built and used by amateur radio operators. It forms part of the Amateur-satellite service.[1] These satellites use amateur radio frequency allocations to facilitate communication between amateur radio stations.

Many amateur satellites receive an OSCAR designation, which is an acronym for Orbiting Satellite Carrying Amateur Radio. The designation is assigned by AMSAT, an organization which promotes the development and launch of amateur radio satellites. Because of the prevalence of this designation, amateur radio satellites are often referred to as OSCARs.

These satellites can be used free of charge by licensed amateur radio operators for voice (FM, SSB) and data (AX.25, packet radio, APRS) communications. Currently, over 18 fully operational amateur radio satellites are in orbit.[2] They act as repeaters, as linear transponders, and as store and forward digital relays.

Amateur radio satellites have helped advance the science of satellite communications. Contributions include the launch of the first satellite voice transponder (OSCAR 3) and the development of highly advanced digital "store-and-forward" messaging transponder techniques.

The Amateur Radio Satellite community is very active in building satellites and in finding launch opportunities. Lists of functioning satellites need updating regularly, as new satellites are launched and older ones fail. Current information is published by AMSAT (for North America, and AMSAT-UK (for Europe



The first amateur satellite, simply named OSCAR 1, was launched on December 12, 1961, barely four years after the launch of the world's first satellite, Sputnik I. The beginning of this project was very humble. The satellite had to be built in a very specific shape and weight, so it could be used in place of one of the weights necessary for balancing the payload in the rocket stage. OSCAR 1 was the first satellite to be ejected as a secondary payload (the primary payload was Discoverer 36) and to subsequently enter a separate orbit. It carried no on-board propulsion and its orbit decayed quickly. Despite orbiting for only 22 days, OSCAR 1 was an immediate success. Over 570 amateur radio operators in 28 countries forwarded observations to Project OSCAR.


Most of the components for OSCAR 10 were "off the shelf". Jan King led the project. Solar cells were bought in batches of 10 or 20 from Radio Shack, and tested for efficiency by group members. The most efficient cells were kept for the project; the rest were returned to RadioShack. Once ready, OSCAR 10 was mounted aboard a private plane, and flown a couple of times to evaluate its performance and reliability. Special QSL cards were issued to those who participated in the airplane-based tests. Once it was found to be operative and reliable, the satellite was shipped to Kennedy Space Center, where it was mounted in the launch vehicle's third stage. OSCAR 10's dimensions were: Height: 1.35 m (53 in) Width: 2.0 m (78.75 in) Weight: 140 kg at launch; 90 kg after engine firings.[3]

Other satellites

Other programs besides OSCAR have included Iskra (Soviet Union) circa 1982, JAS-1 (Fuji-OSCAR 12) (Japan) in 1986, RS (Soviet Union and Russia), and CubeSats. (There is a list of major amateur satellites in Japanese Wikipedia).

Es’hail 2 / QO-100 [4] Launched November 15, 2018.In geostationary orbit covering Brazil to Thailand.

Narrowband Linear transponder

2400.050 - 2400.300 MHz Uplink

10489.550 - 10489.800 MHz Downlink

Wideband digital transponder

2401.500 - 2409.500 MHz Uplink

10491.000 - 10499.000 MHz Downlink


The first amateur satellites contained telemetry beacons. Since 1965, most OSCARs carry a linear transponder for two-way communications in real time. Some satellites have a bulletin board for store-and-forward digital communications, or a digipeater for direct packet radio connections.


Amateur satellites have been launched into low Earth orbits and into highly elliptical orbits.


Satellite communications

Currently, amateur satellites support many different types of operation, including FM voice and SSB voice, as well as digital communications of AX.25 FSK (Packet radio) and PSK-31.

Mode designators

Uplink and downlink designations use sets of paired letters following the structure X/Y where X is the uplink band and Y is the downlink band. Occasionally, the downlink letter is rendered in lower case (i.e., X/y). With a few exceptions, the letters correspond to IEEE's standard for radar frequency letter bands...[5]

Band 15 m 10 m 2 m 70 cm 23 cm 13 cm 9 cm 5 cm 3 cm 1.2 cm 6 mm
21 MHz 29 MHz 145 MHz 435 MHz 1.2 GHz 2.4 GHz 3.4 GHz 5 GHz 10 GHz 24 GHz 47 GHz

Prior to the launch of OSCAR 40, operating modes were designated using single letters to indicate both uplink and downlink bands. While deprecated, these older mode designations are still widely used in casual conversation.

  • Mode A: 2 m uplink / 10 m downlink
  • Mode B: 70 cm uplink / 2 m downlink
  • Mode J: 2 m uplink / 70 cm downlink

Doppler shift

Due to the high orbital speed of the amateur satellites, the uplink and downlink frequencies will vary during the course of a satellite pass. This phenomenon is known as the Doppler effect. While the satellite is moving towards the ground station, the downlink frequency will appear to be higher than normal. Hence, the receiver frequency at the ground station must be adjusted higher to continue receiving the satellite. The satellite in turn, will be receiving the uplink signal at a higher frequency than normal so the ground station's transmitted uplink frequency must be lower to be received by the satellite. After the satellite passes overhead and begins to move away, this process is reversed. The downlink frequency will appear lower and the uplink frequency will need to be adjusted higher. The following mathematical formulas relate the Doppler shift to the velocity of the satellite.

=doppler corrected downlink frequency
=doppler corrected uplink frequency
=original frequency
=velocity of the satellite relative to ground station in m/s.
Positive when moving towards, negative when moving away.
=the speed of light in a vacuum (  m/s).
Change in frequencyDownlink CorrectionUplink Correction

Due to the complexity of finding the relative velocity of the satellite and the speed with which these corrections must be made, these calculations are normally accomplished using satellite tracking software. Many modern transceivers include a computer interface that allows for automatic doppler effect correction. Manual frequency-shift correction is possible, but it is difficult to remain precisely near the frequency. Frequency modulation is more tolerant of doppler shifts than single-sideband, and therefore FM is much easier to tune manually.


A number of low earth orbit (LEO) OSCAR satellites use frequency modulation (FM).[6] These are also commonly referred to as "FM LEOs" or the "FM Birds". Such satellites act as FM amateur radio repeaters that can be communicated through using omni-directional antennas and commonly available amateur radio equipment. Due to the relative ease of tuning FM as compared to SSB and the decreased distance of LEO satellites from earth stations communication can be achieved even with handheld transceivers and using manual doppler correction. The orbit of these satellites however causes the available time in which to communicate to be limited to only a few minutes per pass.

List of FM LEO satellites[6]
Satellite name(s) OSCAR
Uplink (MHz) Downlink (MHz) CTCSS (Hz) Status
Hope Oscar 68 HO-68 145.825 FM 435.675 FM 67.0 Beacon only
Sumbandila Oscar 671 SO-67 145.875 FM 435.345 FM N/A Lost
AMSAT-OSCAR 512 AO-51 145.880 FM 435.150 FM N/A Lost
145.920 FM 435.300 FM 67.0
145.880 FM 2401.200 FM N/A
1268.700 FM 435.300 FM 67.0
1268.700 FM 2401.200 FM 67.0
Saudi-OSCAR 50 SO-50 145.850 FM 436.795 FM 67.0
(74.4 to activate)
Saudi-OSCAR 41 SO-41 145.850 FM 436.775 FM N/A Lost
SUNSAT-OSCAR 35 SO-35 145.825 FM 436.250 FM N/A Lost
436.291 FM 145.825 FM
1265.000 FM 436.2500 FM
TechSat 1b-OSCAR 32 SO-32 145.850/145.890/145.930 FM
1269.700/1269.800/1269.900 FM
435.225 FM N/A Lost
ISS3 ARISS 437.800 FM 145.800 FM N/A Active
AMRAD-OSCAR 274 AO-27 145.850 FM 436.795 FM N/A Interference over USA
AMSAT-OSCAR 16 AO-16 145.920 FM 437.026 DSB-SC5 N/A Lost
UoSAT-OSCAR 14 UO-14 145.975 FM 435.070 FM N/A Lost
LituanicaSAT-OSCAR 78 [7] LO-78 145.950 FM 435.1755 FM 67.0 Lost
European-OSCAR 806 EO-80 435.080 FM 145.840 FM 210.7 Beacon only
Fox-1A7 AO-85 435.170 FM 145.980 FM 67 Poor battery condition
LAPAN-A2/ORARI IO-86 145.880 FM 435.880 FM 88.5 Active
Fox-1B AO-91 435.250 FM 145.960 FM 67.0 Active
Fox-1D AO-92 435.350/1267.359 FM 145.880 FM 67.0 Active
Diwata-2 PO-101 437.500 FM 145.900 FM 141.3 Active by schedule
LilacSat-2 (CAS-3H) 144.350 FM 437.200 FM None Operational, but rarely active
FUNcube on ESEO 1263.500 FM 145.895 FM 67.0[8] In commissioning
Note 1: SO-67 suffered a power board failure. The team hoped (2012) recovery to amateur radio operations was possible.[9]

Note 2: As of November 29, 2011 AO-51 has ceased all transmissions.[10]

Note 3: The ISS FM repeater is rarely activated.[11]

Note 4: New bootloader and OS for AO-27 was successfully written and installed by the team. Satellite experiences interference during uplink while above US.[12]

Note 5: The AO-16 downlink transmits in DSB-SC instead of FM, but the satellite otherwise operates like the other FM Birds.[13][14]

Note 6: EO-80 is currently completing a science mission and the FM transponder will be activated upon completion of that mission.

Note 7: As of 2019-02-12, AO-85 is turned off due to poor battery condition and low voltage during eclipse periods.[15]


Past launches

The names of the satellites below are sorted in chronological order by launch date, ascending. The status column denotes the current operational status of the satellite. Green signifies that the satellite is currently operational, orange indicates that the satellite is partially operational or failing. Red indicates that the satellite is non operational and black indicates that the satellite has re-entered the Earth's atmosphere. The country listing denotes the country that constructed the satellite and not the launching country.

In development

  • KiwiSAT - A microsatellite built by AMSAT-ZL. Flight-ready, but no launch provider found yet.[17]
  • Fox-1 - Five 1U cubesats from AMSAT-NA. Three in orbit and functioning, known as AO-85 (Fox-1A),[18] AO-91 (Fox-1B),[19] and AO-92 (Fox-1D).[20] Fox-1Cliff (formerly Fox-1C) suffered a failure[21] and Fox-1E is in development.


Multinational effort

Currently, 24 countries have launched an OSCAR satellite. These countries, in chronological order by date of launch, include:

  1. United States of America
  2. Australia
  3. Spain
  4. United Kingdom
  5. Japan
  6. Brazil
  7. Argentina
  8. Pakistan
  9. Russia
  10. France
  11. Portugal
  12. Korea
  13. Italy
  14. Mexico
  15. Israel
  16. Thailand
  17. South Africa
  18. Malaysia
  19. Saudi Arabia
  20. Germany
  21. India
  22. Colombia
  23. the Netherlands
  24. Indonesia

SuitSat, an obsolete Russian space suit with a transmitter aboard, was officially known as "AMSAT-OSCAR 54". Coincidentally, "Oscar" was the name given to an obsolete space suit by its young owner in the book Have Space Suit—Will Travel, by Robert A. Heinlein. This book was first published a year after the launch of Sputnik 1, the world's first artificial satellite.

International regulation

Amateur-satellite service (also: amateur-satellite radiocommunication service) is – according to Article 1.57 of the International Telecommunication Union's (ITU) Radio Regulations (RR)[22] – defined as «A radiocommunication service using space stations on earth satellites for the same purposes as those of the amateur service


This radiocommunication service is classified in accordance with ITU Radio Regulations (article 1) as follows:
Radiocommunication service (article 1.19)

Frequency allocation

The allocation of radio frequencies is provided according to Article 5 of the ITU Radio Regulations (edition 2012).[23]

In order to improve harmonisation in spectrum utilisation, the majority of service-allocations stipulated in this document were incorporated in national Tables of Frequency Allocations and Utilisations which is within the responsibility of the appropriate national administration. The allocation might be primary, secondary, exclusive, and shared.

  • primary allocation: is indicated by writing in capital letters (see example below)
  • secondary allocation: is indicated by small letters (see example below)
  • exclusive or shared utilization: is within the responsibility of national administrations
Example of frequency allocation
Allocation to services
     Region 1             Region 2             Region 3       
135.7–137.8 kHz
7 000–7 100   AMATEUR
14 000–14 250    AMATEUR
18 068–18 168    AMATEUR
21 000–21 450    AMATEUR
24 890–24 990    AMATEUR
28–29.7 MHz       AMATEUR
144–146              AMATEUR
5 830–5 850
5 830–5 850
10.5–10.6 GHz    AMATEUR
24–24.05             AMATEUR
47–47.2              AMATEUR
76–77.5               RADIO ASTRONOMY
Space research (space-to-Earth)
77.5–78               AMATEUR
Radio astronomy
Space research (space-to-Earth)
78–79                  RADIOLOCATION
Radio astronomy
Space research (space-to-Earth)
79–81                 RADIOLOCATION
Space research (space-to-Earth)
134–136              AMATEUR
Radio astronomy
136–141              RADIO ASTRONOMY
241–248              RADIO ASTRONOMY
248–250              AMATEUR
Radio astronomy

Additional allocations

In addition to the formal allocations in the main table such as above, there is also a key ITU-R footnote RR 5.282 that provides for additional allocations:-

5.282 In the bands 435-438 MHz, 1 260-1 270 MHz, 2 400-2 450 MHz, 3 400-3 410 MHz (in Regions 2 and 3 only)
and 5 650-5 670 MHz, the amateur-satellite service may operate subject to not causing harmful interference to other
services operating in accordance with the Table (see No. 5.43). Administrations authorizing such use shall ensure that
any harmful interference caused by emissions from a station in the amateur-satellite service is immediately eliminated
in accordance with the provisions of No. 25.11. The use of the bands 1 260-1 270 MHz and 5 650-5 670 MHz by the
amateur-satellite service is limited to the Earth-to-space direction.

Of these, the 435-438 MHz band is particularly popular for amateur/educational small satellites such as Cubesats.


  1. ITU Radio Regulations, Section IV. Radio Stations and Systems – Article 1.57, definition: amateur-satellite service / amateur-satellite radiocommunication service
  3. John A. Magliacane, KD2BD. "AMSAT Spotlight". Archived from the original on 1996-10-28.CS1 maint: BOT: original-url status unknown (link)
  4. "Es'hail 2 / QO-100". AMSAT-UK. 2015-06-05. Retrieved 2019-06-22.
  5. Standard Radar Frequency Letter-Band Nomenclature (IEEE Standard 521-1984, IEEE Std 521-2002(R2009))
  6. "FM Satellite Frequency Summary".
  7. "OSCAR Number for LituanicaSAT-1".
  8. "ESEO". AMSAT-UK.
  9. "SA AMSAT". Southern African Amateur Radio Satellite Association. Retrieved 2012-08-09.
  10. "AMSAT AO-51 Control Team News". AO-51 Command Team and Operations Group. Archived from the original on 2007-10-31. Retrieved 2012-01-15.
  11. "ISS Fan Club". ISS Fan Club. Archived from the original on 2012-01-20. Retrieved 2011-07-27.
  12. "Official AO-27 HomePage". AO-27 Control Operators Association. Archived from the original on 2002-06-01. Retrieved 2013-01-06. AO-27 Turned on today. Seems good on the bootloader
  13. "2010 AMSAT Field Day Competition" (PDF). The Radio Amateur Satellite Corporation. 2010. p. 1. Archived from the original (PDF) on 2010-11-30. Retrieved 2011-07-26. ...the FM voice satellites like AMSAT-OSCAR 16, AMRAD-OSCAR-27, SaudiSat-Oscar-50, or AMSAT-OSCAR-51...
  14. "AMSAT OSCAR 16 (PacSAT)". The Radio Amateur Satellite Corporation. Archived from the original on 2011-03-03. Retrieved 2011-07-26. Mode FM Voice Repeater (Downlink is DSB. Operation is Intermittent)
  15. "AO-85 Turned Off due to Return of Eclipse Periods and Poor Battery Condition". American Radio Relay League. Retrieved 2019-02-12.
  16. "VO-52 "Hamsat" end of mission". AMSAT.
  17. "KiwiSAT, Status". Retrieved 2019-12-11.
  18. "AO-85 (Fox-1A) – AMSAT-NA". Retrieved 2018-02-14.
  19. "RadFxSat (Fox-1B) Launched, Designated AMSAT-OSCAR 91 (AO-91)". AMSAT-UK. 2017-11-18. Retrieved 2018-02-14.
  20. "Fox-1D Launched, Designated AMSAT-OSCAR 92 – AMSAT-NA". Retrieved 2018-02-14.
  21. "Fox-1Cliff/AO-95 Receiver Suffers Apparent Failure". ARRL.
  22. ITU Radio Regulations, Section IV. Radio Stations and Systems – Article 1.57, definition: amateur-satellite service / amateur-satellite radiocommunication service
  23. ITU Radio Regulations, CHAPTER II – Frequencies, ARTICLE 5 Frequency allocations, Section IV – Table of Frequency Allocations
  • Martin Davidoff: The Radio Amateur's Satellite Handbook. The American Radio Relay League, Newington, ISBN 978-0-87259-658-0.


  • AMSAT Corporation - a nonprofit corporation that coordinates construction and launch of amateur radio satellites
  • Project OSCAR - club commemorating the original Project OSCAR group
  • Work-Sat - Private site with instructions for using amateur radio satellites
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