[eagle] Re: 70 cm Receiver Spur Source Found

John B. Stephensen kd6ozh at comcast.net
Sun Jun 10 17:47:10 PDT 2007


It meets the requirements from more than a year ago that are posted on the U-band receiver page. Matt and Phil can comment on the text-mode uplink requirements.

73,

John
KD6OZH
  ----- Original Message ----- 
  From: Jim Sanford 
  To: juan-rivera at sbcglobal.net 
  Cc: eagle at amsat.org ; Bdale Garbee ; Bill Ress ; Dave Black (Home) ; Dave Black (Work) ; Dave hartzell ; David Smith ; Dick Jannson ; Don Ferguson ; John B. Stephensen ; Juan.Rivera (Work) ; Lyle Johnson ; Phil Karn ; Robert Davis KF4KSS ; Robert McGwier ; Samsonoff at Mac. Com ; Stephen Moraco ; 'Steven Bible' ; 'William A Schmitt' 
  Sent: Monday, June 11, 2007 00:53 UTC
  Subject: Re: 70 cm Receiver Spur Source Found


  All:
  Slightly off topic . . . .

  Somewhere in this discussion, Juan has asked basically, "what is acceptable phase noise at what offset?"  This is similar to a question I asked Bob McGwier some months ago, as I contemplate various options for my 6m to 10 GHz terrestrial station.  The question arises because so many texts have different opinions and the manufacturers each choose a different offset for their specs, carefully avoiding evaluation of the phase noise of their device on whatever communications mode.

  I think I remember Bob's answer as -110dbc at 10 KHz offset.

  If I remember Bob's answer correctly (Which I may NOT, Bob, please correct me) then the picture Juan shows, which is the composite of his signal generator, his SDRIQ, and the U-band downconverter doesn't look too bad -- close, but maybe not close enough, but maybe so.  John, Matt, & Phil:  What is your evaluation of this phase noise on our intended uses of the receiver?

  Thanks & 73,
  Jim
  wb4gcs at amsat.org


  Juan Rivera wrote:

    All,



    The source of the spurs in the 70 cm prototype receiver is the CAN-Do module.





    This is the receiver IF output as designed

    (powered from pins 39 and 40 of the CAN-Do Module)



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