[eagle] Re: 10.7 MHz Spur

John B. Stephensen kd6ozh at comcast.net
Sun Jul 1 21:00:38 PDT 2007

The possible sources are the PLLs and the logic inside the onboard TCXO. Can you turn off the internal TCXO by removing the ferrite bead feeding it power and use and external 10 MHz reference?

If this doesn't work, the PLL division ratios can be changed.


  ----- Original Message ----- 
  From: Juan Rivera 
  To: 'John B. Stephensen' 
  Cc: eagle at amsat.org ; 'Bill Ress' ; 'Dave Black (Home)' ; 'Dave Black (Work)' ; 'Dave hartzell' ; 'David Smith' ; 'Don Ferguson' ; 'Juan.Rivera (Work)' ; 'Samsonoff at Mac. Com' 
  Sent: Monday, July 02, 2007 03:19 UTC
  Subject: RE: 10.7 MHz Spur



  The short answer is 'no'.  Click here for details and scroll to the bottom of the log...




  -----Original Message-----
  From: John B. Stephensen [mailto:kd6ozh at comcast.net] 
  Sent: Sunday, July 01, 2007 2:42 PM
  To: juan-rivera at sbcglobal.net
  Cc: eagle at amsat.org; Bill Ress; Dave Black (Home); Dave Black (Work); Dave hartzell; David Smith; Don Ferguson; Juan. Rivera (Home); Juan.Rivera (Work); Samsonoff at Mac. Com
  Subject: Re: 10.7 MHz Spur


  Does the spur go away if the external reference is on (whether or not it is 

  routed to the PLLs)?







  ----- Original Message ----- 

  From: "Juan Rivera" <juan-rivera at sbcglobal.net>

  To: "John B. Stephensen" <kd6ozh at comcast.net>

  Cc: <eagle at amsat.org>; "Bill Ress" <bill at hsmicrowave.com>; "Dave Black 

  (Home)" <dblack1054 at yahoo.com>; "Dave Black (Work)" 

  <dblack at mail.arc.nasa.gov>; "Dave hartzell" <hartzell at gmail.com>; "David 

  Smith" <w6te at msn.com>; "Don Ferguson" <kd6ire at sbcglobal.net>; "Juan. Rivera 

  (Home)" <juan-rivera at sbcglobal.net>; "Juan.Rivera (Work)" 

  <Juan.Rivera at gd-ais.com>; "Samsonoff at Mac. Com" <samsonoff at mac.com>

  Sent: Saturday, June 30, 2007 14:22 UTC

  Subject: 10.7 MHz Spur



  > John,


  > I found the source of the 10.7 MHz spur.  It's being generated inside the

  > receiver itself.  This is the first spur I have found that is not caused 

  > by

  > switching power supplies.


  > The origin appears to be in the 10 MHz reference area.  I turned off and

  > unplugged the SDR-IQ and fed the IF output from the 70 cm Receiver to my

  > TS-2000.  The spur is still there.


  > Next I connected the RF input to my sniffer loop and moved it around the 

  > PCB

  > surface.  I get the strongest signal near the long trace between the two

  > Freq inputs to U4 and U9, the two phased-locked loops.


  > 73,


  > Juan



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