QO-100 Satellite: Getting On the Geostationary Ham Satellite

Most amateur satellites race across the sky in a few minutes, and you have to track them, time your passes and compensate for Doppler shift. The QO-100 satellite is different. It sits in a geostationary orbit, so from your garden it appears to hang at one fixed point in the sky, available twenty-four hours a day. That single fact changes everything about how you operate: you point a dish once, and you can hold a long conversation with a station thousands of kilometres away. This guide explains what QO-100 is, where it can be used, how the transponders and band plan are laid out, what equipment a ground station needs and how to behave on a transponder that is shared by many operators.

It is also a good chance to learn microwave techniques without the complexity of tracking. For a European operator it is one of the most reliable ways to make contacts with Africa, the Middle East and Asia from a modest station.

What QO-100 Is

QO-100 is the amateur radio payload of the Es’hail-2 communications satellite, built by Mitsubishi Electric and launched on a SpaceX Falcon 9 rocket on 15 November 2018. As the American Radio Relay League reported at the time, it was the first amateur radio payload destined for a geostationary orbit. The payload was developed jointly by the Qatar Amateur Radio Society and the satellite operator Es’hailSat, with AMSAT-DL, the German AMSAT organisation, as technical lead. AMSAT designated the satellite Qatar-OSCAR 100, which gives the shortened name QO-100, and the sequence number 100 made it a milestone in the history of amateur satellites.

The satellite is located at about 26 degrees east longitude on the geostationary arc. The commercial part of Es’hail-2 provides television services in the Middle East and North Africa. The amateur payload is a passenger on that platform, which explains the unusual frequencies: it uses the S-band around 2.4 GHz for the uplink and the X-band around 10.45 GHz for the downlink.

Where You Can Use It

A geostationary satellite sees roughly two fifths of the Earth’s surface. The ARRL launch report said the payload could link radio amateurs from Brazil to Thailand, and that it was unlikely to be accessible from North America with typical amateur satellite gear. That covers Africa, Europe, the Middle East, much of Asia and South America.

From Lithuania, the satellite is almost due south and quite high. A simple calculation for a station at about 55 degrees north, at nearly the same longitude as the satellite, gives an elevation of roughly 26 to 28 degrees above the horizon. That is high enough to clear most obstacles, but low enough that a house, a tree or a neighbour’s building to the south can block it, so survey your site carefully before you buy anything.

The Two Transponders

QO-100 carries two linear transponders. The narrowband transponder serves conventional operating modes such as SSB, CW and narrow digital modes. The wideband transponder, which is 8 MHz wide, was designed for digital amateur television and other high-speed data. The table summarises the frequency plan as listed in the public reference entry for the satellite.

The transponders are non-inverting, so a signal sent slightly higher in frequency on the uplink appears slightly higher on the downlink. This is simpler than the inverting transponders on many low-orbit satellites and makes tuning feel like an ordinary HF band. The design assumes about 50 simultaneous two-way carriers, serving around 100 users, on the narrowband transponder.

The Narrowband Band Plan

On a shared transponder everyone has to stay in their lane. The plan summarised on the reference page divides the narrowband passband into segments, with the uplink frequencies shown here. The downlink is the uplink plus a fixed offset of 8089.5 MHz, so a signal at 2400.245 MHz returns at 10489.745 MHz.

• 2400.005 to 2400.040 MHz: CW only.
• 2400.040 to 2400.080 MHz: narrowband digital modes with a maximum bandwidth of 500 Hz.
• 2400.080 to 2400.150 MHz: digital modes up to 2700 Hz.
• 2400.150 to 2400.245 MHz: SSB only, up to 2700 Hz.
• Around 2400.245 MHz: middle beacon, a 400 bit/s BPSK signal. Do not transmit here.
• 2400.255 to 2400.350 MHz: SSB only.
• 2400.350 to 2400.495 MHz: mixed modes up to 2700 Hz and special purposes.

There are also beacons at the lower and upper ends of the transponder. The published guidance says that no transmission should be made beyond the nominal edges of the passband, and in particular nothing below the lower beacon or above the upper one. FM must not be used, because it takes too much power and bandwidth. Band plans can change, so check the current version from AMSAT-DL before you transmit. Our article on the IARU band plans explains how such plans are maintained.

The Golden Rule: Never Be Louder Than the Beacons

The transponder has limited downlink power, shared by all users. If you transmit with too much power, you take power from everyone else. The rule is simple: your downlink signal should never be stronger than the beacons. If a signal is too strong, it is marked by a siren-like tone called LEILA, from the German for power level indicator, and the operator must reduce the uplink power at once.

Because the satellite is so far away, many new operators are tempted to turn up the power when they cannot hear themselves. The better approach is to improve the antenna and the pointing. A good ground station hears its own downlink well with only a few watts, which is polite, effective and saves equipment.

A Basic Ground Station

A QO-100 ground station has two chains: a receive chain for 10 GHz and a transmit chain for 2.4 GHz. The reference material gives some guidance on antenna size. For the downlink, a dish between 60 and 90 cm covers most locations, depending on how close you are to the centre of the coverage area. For the uplink, a typical figure is a transmitter of 5 to 10 W PEP with a 75 cm dish of about 22.5 dBi gain. Common choices are:

1. The dish. An offset satellite television dish, 60 to 90 cm, mounted rigidly, because a small pointing error costs a lot at these frequencies.
2. The receive converter. A low-noise block converter (LNB) converts the 10 GHz signal to a lower frequency for an SDR or receiver. Frequency stability is the key issue for narrowband modes, so many operators use an LNB with a better reference oscillator or a GPS-disciplined source.
3. The receiver. A software defined radio is the usual choice. Our comparison of SDR receivers explains the options.
4. The transmitter. A 2.4 GHz transmit chain, either a dedicated transverter or an SDR transmitter with an amplifier, feeding a circularly polarised feed at the dish.
5. Cables and connectors. Use short runs of good coax or low-loss cable at microwave frequencies, and quality connectors. Our guides to RF connectors and coaxial cable explain why loss and connector quality matter so much.

Keep the transmit and receive systems separated, and be aware that the 2.4 GHz band is also used by wireless networks, so a poor installation can cause or receive interference. Pointing is done by listening to the beacon, and once the downlink beacon is peaked, you can work out the uplink.

Licences and Rules

Your licence must cover both the uplink and the downlink bands, and your national rules define the permitted power and modes. Operators in Europe generally have access to the 13 cm band at 2.4 GHz, but power limits and other conditions differ between countries. Check the conditions with your regulator or national society before building a transmit chain.

Operating Tips

• Listen first. Spend an evening listening on the beacon and the SSB segments to learn the culture and the call procedures.
• Call briefly. Use your call sign and a short CQ, then listen. Long calls waste a shared resource.
• Check your downlink level. If you hear yourself louder than the beacon, reduce power.
• Use the right segment. Respect the narrowband plan, with CW, digital and SSB in their own parts.
• Be patient with weak signals. Weather, especially heavy rain, can reduce the strength of the 10 GHz downlink.

If you are new to satellites in general, read our introduction to amateur radio satellites first. The ideas of uplink, downlink and polarisation apply here, with the helpful difference that you do not need to track anything.

Try Before You Buy: Listening and Pointing Tools

You can hear the transponder before you spend a cent on hardware. The British Amateur Television Club and AMSAT-UK run a web receiver project with a WebSDR for the narrowband segment, hosted at Goonhilly Earth Station in Cornwall, and a spectrum viewer for the wideband segment. Listening through a browser teaches you what the band plan sounds like, how SSB and CW stations space themselves and how busy the transponder is at different times of day. The same site offers a dish pointing calculator with a map, which is helpful for finding the exact azimuth and elevation for your location and for checking whether a tree or a roof blocks the path.

What a Typical Contact Looks Like

A QO-100 contact feels different from an HF contact because the path is the same for everyone and the delay is noticeable. The signal travels more than 36,000 km up and the same distance down, so you hear your own downlink about half a second after you speak. Operators get used to the pause quickly, and good practice is to speak in short phrases and wait for the other station to finish.

A typical SSB contact starts with a short CQ in the SSB segment or an answer to a station you hear calling. After the call signs, stations exchange names, locations and signal reports, and many conversations turn into relaxed ragchews because the band is not subject to the fading, noise and contests of HF. Many stations also use the narrowband digital segments for weak-signal modes, where a narrow bandwidth gives an excellent signal-to-noise ratio. Because the link is stable, it is also a good place to test new equipment, such as a new feed, a new amplifier or a new software defined radio setup.

Common Mistakes

• Transmitting with too much power. Stay below the level of the beacons.
• Operating outside the plan. Do not transmit below the lower beacon or above the upper one.
• Using a poor mount. Wobble at these frequencies ruins the link.
• Ignoring local obstacles. Check the line of sight at about 27 degrees elevation.
• Neglecting frequency stability. A drifting converter makes narrowband modes unusable.

The Bottom Line

QO-100 is the easiest satellite to use and one of the most technically interesting. Because it is geostationary, you can learn microwave techniques at your own pace, and the contacts are reliable. Check your line of sight to the south, study the band plan and the rule about the beacons, and start with a receive-only setup to listen to the transponder. When you hear it clearly, add the transmit chain with modest power and enjoy a satellite that is always there.

Frequently Asked Questions

What is QO-100?

QO-100 is the amateur radio payload on the Es’hail-2 geostationary satellite, launched in November 2018. It was designated Qatar-OSCAR 100 by AMSAT and carries a narrowband and a wideband transponder.

What frequencies does QO-100 use?

The uplink is in the 2.4 GHz band, around 2400 to 2410 MHz, and the downlink is in the 10 GHz band, around 10489 to 10499 MHz. The narrowband transponder uses the lower part of each range.

Where can I use QO-100?

It can be used across Africa, Europe, the Middle East, much of Asia and South America. It is generally not accessible from North America with typical amateur satellite equipment.

Do I need to track the satellite?

No. A geostationary satellite stays at one point in the sky, so you point your dish once and fix it in place.

Why must I never be louder than the beacons?

The transponder shares limited power among all users. A signal stronger than the beacons takes power from others and may trigger the LEILA warning, after which you must reduce your power.

What equipment do I need to receive QO-100?

A satellite dish of about 60 to 90 cm, a low-noise block converter with a stable oscillator and a software defined radio are the usual components for a receive-only station.