[eagle] Re: Latest 70 cm Receiver Test Results

John B. Stephensen kd6ozh at comcast.net
Sun Jun 10 18:14:20 PDT 2007

The bump is the combined phase noise of the two VCOs. The maximums at either side show the approximate loop bandwidth. The measured phase noise is a few dB lower than the original requirements.

I think that we can ignore the ripple problem for now as the adjacent circuitry has to change to meet thermal requirements.

The microphonics problem needs to be resolved.


  ----- Original Message ----- 
  From: Juan Rivera 
  To: 'John B. Stephensen' 
  Cc: 'AMSAT Eagle' 
  Sent: Sunday, June 10, 2007 22:17 UTC
  Subject: RE: [eagle] Latest 70 cm Receiver Test Results

  John and group,




  1)       What about the phase noise?  I'm assuming that that big hump is phase noise.  Do you consider that to be excessive?

  2)      What about the passband ripple?  That needs to get fixed.

  3)      If the next generation of the radio is going to be autonomous, fixed tuned, and have continuous power, what exactly is the CAN-Do module doing except returning a few parameters to the IHU?  It makes sense to me to get it away from the radio completely.  You can feed it whatever it needs such as loop lock status and temperature.  That also fixes our lack of front panel space problem.


  Until question 3 is resolved it doesn't make any sense to me to spend the time necessary to desolder the CAN-Do module and relocate it.  For now we can initialize the receiver and then kill the CAN-DO module (RFC10 id removed and the receiver is powered separately.)  That will create the same conditions as perfect CAN-Do module isolation would without the work.


  I'd like to get back to the ATP testing but until we have items 1 and 2 resolved and correct the microphonics, there isn't too much sense in starting the ATP now.  I'll focus on the microphonics while you folks digest this latest information.


  By the say, are there new specs for the receiver yet?  Is it still expected to cold soak to -70C?  That's close to the temperature of liquid CO2 and well below the storage temperature of most components and way below the operating temperature limits.








  From: John B. Stephensen [mailto:kd6ozh at comcast.net] 
  Sent: Sunday, June 10, 2007 12:51 PM
  To: juan-rivera at sbcglobal.net
  Cc: 'AMSAT Eagle'
  Subject: Re: [eagle] Latest 70 cm Receiver Test Results


  The time that I spent optimizing the layout of the U17 switching regulator appears to be worth it if it isn't polluting the VCOs. What would be ideal is a module case where the CAN bus can exit from one side and the RF and IF from the other.  


  For now, the RF and IF can be run back to the connector bracket with SMA jumper cables. What is needed is a CAN-Do widget without the header connector so that wire leads can carry power and signals to the receiver PCB. 18-22 guage wire should work for power and 22-26 guage for signals. The wires need to be wound around a torroidal ferrite core to kill any common-mode noise. It may also be necessary to run the coax through ferrite beads. Do you have any beads or torroids made of material 75 or 77?






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

    From: Juan Rivera 

    To: eagle at amsat.org 

    Sent: Sunday, June 10, 2007 17:59 UTC

    Subject: [eagle] Latest 70 cm Receiver Test Results




    As I troubleshoot the 70 cm receiver I stop and add to my logs every few minutes.  I won't bother to announce every step I take (I just made an addition) because it takes too long.  If you are interested please check the latest log at the top of the list or go to my web site.  If you have a comment or suggestion just drop me an email via this Eagle/AMSAT mailer and everyone can participate.  I'll check email often when I'm working on this project.


    Here's the link to the AMSAT/Eagle receiver page --> http://www.amsat.org/amsat-new/eagle/EaglePedia/index.php/U-Band_Receiver

    From there find the latest log at the top of the list under Project Status.  At the moment it's 'Spur Troubleshooting'




    Go to my web at http://www.juanr.com/

    Select Amateur Radio, select AMSAT/Eagle, and select the log you want to see from the menu.










    Via the Eagle mailing list courtesy of AMSAT-NA
    Eagle at amsat.org
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