All,

I’ve completed a preliminary evaluation of the CAN-Do RFI problem.  Please see my log for details by clicking here.

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