[eagle] Re: New 70 cm Receiver Test Results

Juan Rivera juan-rivera at sbcglobal.net
Sat Jun 9 20:25:39 PDT 2007



I'll tackle that tomorrow.  For this prototype we can actually do exactly
what you suggest and just move the PCB back one set of standoffs and leave
the Can-Do module where it is.  Of course the SMA connectors will be
inaccessible with the cover on but I don't run it that way when testing
anyway, so it won't matter.


Getting the Can-do module desoldered won't be much fun but it should be
possible.  That's a job for next week.  I think I'll find tomorrow that U17
is also a contributor to the noise.  Perhaps I should cut into the VCO
control loop and control the VCO with an external supply if it starts to
look like a culprit.  Right now I'm out of variable supplies since all three
are tied up.   I don't have an oscilloscope that I trust but I may be able
to use the SDR-IQ with a scope probe to look at the VCO control loop since
it goes down to 500 Hz.  That will be an interesting test.  This little
radio is very useful.









From: John B. Stephensen [mailto:kd6ozh at comcast.net] 
Sent: Saturday, June 09, 2007 8:08 PM
To: juan-rivera at sbcglobal.net; 'Robert McGwier'
Cc: eagle at amsat.org; 'David Smith'; 'Dave Black (Work)'; 'Dave Black
(Home)'; 'Samsonoff at Mac. Com'; 'Juan.Rivera (Work)'
Subject: Re: [eagle] Re: New 70 cm Receiver Test Results


Reconnect the switcher on the receiver PCB and see what shows up.


To eliminate the noise, we may have to connect the PCB to the CAN-Do widget
with a ribbon cable and place it at the other end of the module case. If the
internal switcher also pollutes the VCO control voltage, it could be moved
to a separate PCB.






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

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

To: juan-rivera at sbcglobal.net ; 'John B. <mailto:kd6ozh at comcast.net>
Stephensen' ; 'Robert McGwier' <mailto:rwmcgwier at gmail.com>  

Cc: eagle at amsat.org ; 'David Smith' <mailto:w6te at msn.com>  ; 'Dave
<mailto:dblack at mail.arc.nasa.gov>  Black (Work)' ; 'Dave Black (Home)'
<mailto:dblack1054 at yahoo.com>  ; 'Samsonoff at Mac.
<mailto:'Samsonoff at Mac.%20Com'>  Com' ; 'Juan.Rivera (Work)'
<mailto:Juan.Rivera at gd-ais.com>  

Sent: Sunday, June 10, 2007 02:47 UTC

Subject: RE: [eagle] Re: New 70 cm Receiver Test Results





I am quitting for the evening.  I just posted more data on my web (at 1945
Pacific time).  You can jump there by clicking
m>  here, or go to the AMSAT 70 cm receiver page and click on Spur
Troubleshooting under Project Status.


I was able to remove power from the Can-do module and power the receiver
from external power supplies.  All of the spurs disappeared when the 13
volts was removed from the module.  Tomorrow I'll start reconnecting the
receiver internal power supply sections and see how far I can get before
spurs reappear.  I do not believe all the noise is coming from the Can-do
module.  Tomorrow I'll find out for sure.






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