20 Meter Antenna

20 Meter Antenna

General

  • Operated by AMSAT-DL in cooperation with Sternwarte Bochum
  • Diameter: 20m, Weight: 140t
    • a 40m high air dome serves as weather protection
    • built in 1965
  • ground support for the Apollo missions
  • drive systems and RF equipment renovated in 2003 (AMSAT-DL)
  • phase-locked receivers fo:
    • 2.3 GHz (DSN/ham-radio)
    • 5.8 GHz (ham-radio)
    • 8.4 GHz (DSN X-Band)
    • 10.4 GHz (ham-radio X-Band)
  • reference oscillator: 10 MHz Rb-Normal, HP Z3801 (GPS-locked)
  • Allen-Variance ca. 1E-11(tau=100 sec)
  • complete RX chain down to baseband phase locked
  • Reception of VOYAGER 1 (2006-03-31) at ~14.7 Billion km (~99AU)
  • Regular (daily) operations of STEREO-A/B space weather beacon since 2009 (upgraded Turbo Coding by AMSAT-DL in 2013) for NASA/NOAA including demodulation and decoding the data before forwarding TLM frames to a central server in US.
  • Coherent transmitter on 2.4 GHz (Magnetron, Pout = 6kW PEP, Rb locked phase)
  • S-Band transmitter (hamradio): 250W PEP
  • Planetary radar echoes on 2.45 GHz at Venus conjunction in 2009 at 42 Million Km distance
  • First detection of ISEE-3 carrier on March 2014, primary downlink for ISEE-3 recovery operations
  • Reception of deep space probes (residual carrier):
    • 2001 Mars Odyssey
    • Mars Surveyor 98
    • New Horizons
    • Rosetta
    • Mars Express
    • Ulysses
    • Akatsuki (Venus Express, Cassini) and IKAROS
    • Spitzer space telescope
    • Venus Climate Orbiter
    • MRO
    • Voyager 1&2

Performance

  • RX: 2.2-2.45 GHz, 8.4 GHz, 10 GHz
  • TX: 2.45 GHz (license limited)
  • complete RF chain phase locked to Rb reference or GPSDO:
  • Allan variance <1E-11@100 sec

Frequency [GHz]

G/T [1/K]

3dB beamwidth [deg]

2.4

32.6 dB

0.43

8.4

41.0 dB

0.124

10.4

42.0 dB

0.10 deg (estimated)

 

  • motor control system accuracy: 10″
  • precise location of Bochum antenna: N51.426990, E7.192566, 159.65m ASL
  • above is elevation axis centre
  • knowledge of phase center: 50mm (estimated)

Digitizers at IF:

  • USRP (max. 50 MS/s)
  • HPSDR (max. 384 kS/s)
  • Soundcard (48 kS/s)
  • 8.4 GHz frequency control ADC 166 kS/s
  • CCSDS standard decoder: work in progress
  • Internet connectivity: 10Mbit/s upstream, 100 Mbit/s downstream

Control Room

 

 

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