Hi Juan,
One of the purposes of the CAN-Do! was to provide a standard interface so that a module couldn't do something nasty and take out the entire satellite. So custom mods to the CAN-Do! are not allowed. Having said that, we have always assumed that a jumper across the CAN-Do! power switch would be installed for those modules that needed to be powered up no-matter-what.
Chuck
Juan Rivera wrote:
Chuck,
I don't want to tear into the CAN-Do module. I feel like it is a loaner and not mine to modify. It would be interesting to disconnect the switch and the current monitor from the CAN-Do power input and move it to those user pins as you suggest. That might just work, but I also know they don't want to have multiple versions of the module floating around and this would be one.
We also can't loose sight of the radiated noise from that inductor. I can see signs of EMI if it gets within 2 inches of the sensitive areas of the receiver.
73,
Juan
73,
Juan
-----Original Message----- From: Chuck Green [mailto:greencl@mindspring.com] Sent: Sunday, June 17, 2007 9:18 AM To: juan-rivera@sbcglobal.net Subject: Re: [eagle] 70 cm Receiver IF Spurs - Problem Solved
Hi Juan,
I am impressed with your testing and analysis.
I find it curious that you were unable to filter the power from the CAN-Do! . But switching noise is notorious for being difficult to filter. So maybe that is something to just forget. But in a total system (satellite) it may not be possible to forget. We may need to find a way to filter the power for sensitive modules even if not using power from the CAN-Do! ; in which case, such a filter may also filter the noise from the CAN-Do! .
If your analysis is correct, and it certainly seems to be, then it would also seem possible to remove the switch from the CAN-Do! (not just bypass it) and rout your clean power source through the CAN-Do! current measurement circuit thus saving having to do this in the module.
Great work! And thanks.
Chuck
Juan Rivera wrote:
Hi Chuck,
Bad news I'm afraid. See my report for details... I've sent out a link
to
the group.
73,
Juan
-----Original Message----- From: Chuck Green [mailto:greencl@mindspring.com] Sent: Saturday, June 16, 2007 8:57 AM To: juan-rivera@sbcglobal.net Cc: eagle@amsat.org; David Smith; Dave Black (Work); Dave Black (Home); Samsonoff@Mac. Com; Juan.Rivera (Work) Subject: Re: [eagle] 70 cm Receiver IF Spurs - Problem Solved
Hi Juan,
This is fantastic!
Please try one more experiment. Pass the module current through the current measuring circuit on the CAN-Do! while bypassing the switch transistor (you could just short across the switch transistor) and see if the problem reappears.
If you end up having to use the user pins, you will need to add current measuring circuitry to your module. While this is no big deal, its one more thing you might not have to do.
Chuck
Juan Rivera wrote:
All,
The 70 cm Receiver spur problem has been solved. Click here
<http://www.juanr.com/pages/hobbies/ham_radio/Eagle/CAN-Do_Noise_Troubleshoo
ting.htm>
for details.
73,
Juan
WA6HTP
Via the Eagle mailing list courtesy of AMSAT-NA Eagle@amsat.org http://amsat.org/mailman/listinfo/eagle