[eagle] Preliminary CAN-Do EMI Findings and Suggestions to Mitigate in the 70 cm Receiver

Juan Rivera juan-rivera at sbcglobal.net
Thu Jun 14 22:21:09 PDT 2007


All,

 

I've completed a preliminary evaluation of the CAN-Do RFI problem.  Please
see my log for details by clicking here
<http://www.juanr.com/pages/hobbies/ham_radio/Eagle/CAN-Do_Noise_Troubleshoo
ting.htm> .

 

 

Preliminary Findings...

1.    The spurs seen in the receiver IF enter the receiver in two ways

o        As radiation from the CAN-Do inductor

o        Via CAN-Do module switched +14 VDC power on pins 39 and 40

2.    I/O line filtering appears to be unnecessary

3.    The switched power from the CAN-Do module pins 39 and 40 must be
filtered

4.    The CAN-Do module will either have to be kept physically separated
from any sensitive components, redesigned, shielded or a combination of the
three.

5.    Moving the Can-Do module 2-1/4" forward of its normal location on the
receiver PCB lowers the EMI level below the noise floor.

Suggestions...

*         Create a full size PCB for the next generation receiver and shift
the RF components to the back of the board (away from the CAN-Do module.)

*         Add DC input filtering to the receiver

73,

 

Juan

WA6HTP

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