Tutorial QO 100

Tutorial: QO-100 (Es'hail-2 amateur satellite)

What it is. QO-100 (Es'hail-2) is the first geostationary amateur radio satellite. It covers Africa, Europe, the Middle East and Asia from a fixed point in the sky, with a narrowband transponder (SSB, CW and digital modes) and a wideband transponder (digital amateur TV, DATV) at 10.49 GHz. In OnAir you receive the downlink through a Ku-band LNB and a dish. The mode uses the satellite's two CW beacons to measure and correct the LNB's frequency error and drift, so the frequencies you see and the SSB stations you hear are exact.

What you need

• A dish aimed at the satellite (a 60 to 90 cm offset dish is typical) and a Ku-band LNB. Because the beacons correct the error, a normal inexpensive LNB works; a GPS-locked LNB needs no correction.
• A radio that tunes the LNB's IF: the downlink 10489.5 to 10500 MHz minus the LNB oscillator. With a 9750 MHz oscillator that is 739.5 to 750.5 MHz. Oscillators in the LNB list: 9750 (standard Ku LNBs), 9739, 10000, 10600 MHz, or a custom value. An oscillator above 10489.5 MHz mirrors the spectrum, and the mode turns it back. The mode asks for 10 Msps to see the whole downlink and works down to 2 Msps for the narrowband part alone.
• Power for the LNB (a bias-tee or a power inserter; check what your radio supplies).
• Frequencies, from the frequency database: the narrowband transponder is 10489.500 to 10489.990 MHz (uplink 2400.050 to 2400.300 MHz), its beacon at 10489.750 MHz; the wideband beacon is at 10491.500 MHz and the DATV wideband transponder starts at 10491 MHz (uplink 2401.5 to 2409.5 MHz). The receiver looks for the CW beacons at 10489.500 and 10490.000 MHz.

Before you start

• Aim the dish with a satellite finder or the pointing data for your location.
• You only receive in OnAir; transmitting to the satellite needs a licensed amateur station and a 2.4 GHz uplink (outside what this tutorial covers).
• Keep the radio's gain moderate: a Ku LNB output is strong.

Step by step

1. In the mode list open Satellite & navigation and choose QO-100 (second line Es'hail-2, 10.49 GHz).
2. In the tuner, choose LNB LO (9750, 9739, 10000, 10600 MHz or a custom value). The panel prints the downlink and the IF it corresponds to.
3. Press Whole downlink (tunes to 10494.0 MHz, both beacons and the DATV channels; needs 10 Msps) or Narrowband only (tunes to 10490.1 MHz; 2 Msps is enough).
4. Press Start. The Beacons lamp shows lock. Until then: "searching for the CW beacons (10489.500 and 10490.000 MHz)".
5. Keep Auto frequency correction on (the default): the LNB error is measured on the beacons and every frequency shown is corrected.
6. Open the QO-100 tab. The narrowband transponder is shown as a high-resolution spectrum and waterfall. Click on an SSB signal to listen (upper sideband, 2.7 kHz); -100 and +100 nudge the dial by 100 Hz; volume and mute are there too.
7. The wideband transponder lists the DATV carriers it finds, with symbol rate (ks/s) and SNR. Decode with DVB-S/S2 decodes a carrier at its frequency and symbol rate; the picture and status appear in the panel below while the spectrum and beacons stay live.

What you should see

• The two CW beacons as narrow steady peaks with a PSK beacon between them in the narrowband area. The lamp turns green when the beacons are locked.
• LNB error in kHz and ppm, and drift in Hz/min once measured. An ordinary LNB is off by a few to tens of kHz and drifts as it warms up; the history plot shows how it moves.
• SSB stations in the narrowband transponder, each a few kHz wide.
• DATV carriers in the wideband part, listed with their symbol rates.

Reading the screen

• Beacons lamp: green = locked, amber = held (beacons lost, the last value is kept), grey = searching.
• LNB error (kHz and ppm), whether it is applied, and the number of measurements.
• The signal list ("SIGNALS" on the left) gives the narrowband stations with their frequencies and the wideband carriers.
• The audio level in dBFS and a dial frequency for the SSB listening.
• A detail pane: the radio's tuning and sample rate, the bin widths of the two views, the beacon levels before correction, and the LNB oscillator with its measured offset from nominal.

Options and settings

• Auto frequency correction off: for a GPS-locked LNB; the beacons are still measured and the error shown.
• LNB LO custom value.
• The test signal simulates the beacons, a test carrier at 10489.650 MHz, four SSB stations and two DATV carriers through an LNB 27 kHz off that drifts; sliders set the LNB error and Drift, and Noise only shows the empty case.

Troubleshooting

• Searching for beacons forever. Check aiming, LNB power, the LO setting and that the radio's range covers 739.5 to 750.5 MHz (for a 9750 LO). If the narrowband part is outside the radio's band the panel says so: use Narrowband only or raise the sample rate.
• The spectrum is mirrored. The LO is above the downlink; the mode corrects this.
• SSB sounds off-pitch. Beacons not locked; turn Auto frequency correction on and wait for the lock.
• Wideband part missing. The wideband transponder (10491 to 10499 MHz) is outside the radio's band: choose Whole downlink and 10 Msps.
• DATV decode fails. The carrier is weak or its symbol rate is outside what the DVB-S/S2 receiver handles; see DVB-S/S2.

Tips

• Narrowband traffic: stations tune to each other with the beacon as reference, so you can hear a QSO exactly where it is.
• Checked with generated signals and impairments; recordings of real signals welcome.

Legal and privacy notes

Receiving is legal in most countries. Transmitting needs an amateur licence and follows the satellite's operating rules (AMSAT-DL publishes the band plan).

Under the hood

The CW beacons are measured by a narrow FFT: the offset between the measured and nominal frequency gives the LNB error in kHz and ppm, and the change over time gives the drift. The narrowband transponder is decoded as USB at 2.7 kHz; the wideband carriers are found from the spectrum and handed to the DVB-S/S2 receiver (DVB-S2 per ETSI EN 302 307).

Related

Mode page: QO-100 | DVB-S/S2 | Spectrum explorer | General receiver | Supported radios