QO-100 Ground Station

The station supports both Narrowband (NB) and Wideband (WB / DATV) operation on the Es'hail-2 / QO-100 amateur radio satellite.

šŸ›°ļø Receive Setup

RX dish (right) and TX dish (left)

The receive chain is based on a dedicated 130 cm satellite dish equipped with a modified multi-output LNB.

  • One LNB output is re-used for a GPS-disciplined reference (GPSDO) providing a stable frequency reference
  • Additional outputs feed the SDR and DATV receivers

Narrowband (NB)

  • SDR: ADALM-Pluto
  • Software: mainly SDR-Console
  • Modes: SSB, CW, and digital modes

Wideband (DATV)

  • Receiver: MiniTiouner
  • Software: MiniTiouner software / OpenTuner
  • Used for DVB-S/S2 television signals

šŸ“” Transmit Setup

Helix feed system

Narrowband (NB)

  • SDR: ADALM-Pluto
  • RF chain: Pluto ā†’ CN0417 ā†’ HP8762 Coaxial Switch ā†’ PA from PE1RKI
  • Antenna: 130 cm uplink dish with helix feed
  • Software: mainly SDR-Console

Used for SSB, CW, and digital uplink on QO-100.

Wideband (DATV)

  • Controller: Portsdown (Raspberry Pi based with display)
  • SDR/Modulator: LimeSDR Mini 2.0
  • RF chain: LimeSDR ā†’ driver amplifier ā†’ HP8762 coaxial switch ā†’ PA from PE1RKI (LDMOS-based: PTF21030E + PTFA21180E)
  • Antenna: 130 cm uplink dish with helix feed
  • Software: mainly OBS Studio

Used for DATV transmission (DVB-S/S2).

šŸ§­ Frequency Stability

The ADALM-Pluto is frequency stabilized using an external GPSDO (Leo Bodnar GPSDO).

Additionally, the LNB is stabilized with a DXPatrol GPSDO.

This ensures:

  • Minimal frequency drift
  • Reliable digital mode operation
  • Precise alignment with the satellite transponder

šŸ”€ TX Path Switching

HP 8762 coaxial switch

Both Narrowband and Wideband transmissions use different SDR sources (Pluto vs. LimeSDR Mini 2).

  • Switching is performed using an HP 8762 coaxial switch
  • Control is handled via a GPIO pin of the Portsdown Raspberry Pi
  • This setup also suppresses the typical initial transmit spike of the LimeSDR, protecting the power amplifier

šŸ’§ Power Amplifier Cooling

The power amplifier is water-cooled.

  • Closed-loop liquid cooling system
  • Water-air heat exchanger with active fan
  • Designed for continuous high-power operation

šŸ“Š Monitoring & Telemetry

The PA is installed close to the uplink dish and monitored locally.

  • Sensors:
    • PA temperature
    • Coolant inlet temperature
    • Coolant outlet temperature
    • Coolant flow rate
  • Data acquisition:
    • Microcontroller-based (Arduino)
    • Transmission via Modbus to a Linux system (antiX)
  • Visualization:
    • Custom Python-based monitoring interface

šŸ”§ Notes

The station is continuously evolving.

  • The current PA will likely be replaced by a custom-built amplifier
  • Further optimization of the DATV transmit chain is ongoing