Minutes of the talk on the:
      ALFA IF/LO System

Lisa Wray (NAIC)

This talk will cover everything inside the dewar and everything downstairs to the backend.

• Receiver:
  • Standard 300 MHz centered at 1.275 GHz.
  • Single stage frequency conversion will bring the signal down to 150-450 MHz (1375 to 300 MHz).
  • Fiber optic converter
  • OMT (orthomode transducer)
  • 14 couplers provide calibration
  • Downstairs, it comes off fiber optic and back to coaxial cable.
  • A splitter divides the signal to accomodate backends.
  • We will try to provide high isolation.
• Downconverter:
  • 34 db gain (relative to 300 MHz bandwidth)
  • 58 db dynamic range, maybe 48 dB usable. This is upstairs after dewar and bandpass filter module.
  • There will be a RFI out-of-band bandpass filter.
  • For RFI in-band, there is the possibility of radar blanking as is currently done.
• Buffer and Distribution: (Still under design.)
  • Will receive from fiber optics and put on coaxial cable.
  • Will provide enough buffering to isolate backends and to provide distribution network for the backends.
  • Also will provide monitoring.
  • Have to divide signal to accomodate N backends.
  • The WAPP is the dedicated backend. Approximate for backends: -10 to -5 dBm over 300 MH, 150-450 MHz.

Questions/Discussion: