[eagle] CAN-Do noise problem is proving to be a difficult one to fix

Juan Rivera juan-rivera at sbcglobal.net
Fri Jun 15 13:32:02 PDT 2007


All,

 

Please see my write-up here
<http://www.juanr.com/pages/hobbies/ham_radio/Eagle/CAN-Do_Noise_Troubleshoo
ting.htm> .

 

The CAN-Do noise is not lending itself to an easy cure.  I think this whole
subject of RFI/EMI needs to be looked at closely.  Every payload will be
affected by noise on its inputs and can affect other payloads by creating
noise that is propagated back out from within its module chassis.

 

With the current scheme, of having a CAN-Do module located in the same case
as the main payload, there are several issues that need immediate attention:

 

1)    The CAN-Do module provides dirty power - both the +13 VDC output and
the ground are noisy

2)    The CAN-Do's switching power supply inductor, L3, radiates noise that
can affect sensitive circuits several inches away.

 

Both of these factors are adversely impacting the 70 cm breadboard receiver
in the form of 5 kHz spurs on the IF output.  As I mentions earlier, Rather
than work to clean up the CAN-Do module immediately, we should focus on
making the receiver function In the presence of this noise.  This approach
will result in a more robust design.  The CAN-Do module needs to be cleaned
up, but for now it acts as a great real-world noise generator.

 

I'm currently out of ideas.  I'd like to hear what you all have to say.

 

73,

 

Juan

WA6HTP

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