Juan,
I have a couple of suggestions.
Based on previous messages I presume you will not want to use the switched power from the CAN-Do! regardless of the noise issue. I also see that the switch transistor in the CAN-Do! is in the same area of the PCB as the CAN-Do! power supply.
1) Put a jumper between pins 2 and 3 of the switch transistor (TO-220). This will bypass the switch and any noise it is picking up from the power supply. This will keep the 2 amp fuse in your power source and the current measurement circuit.
2) You might also eliminate the 2 amp fuse from your power source by placing a jumper from pins 1,9 of the DA15P to pin 2 of the switch transistor after removing the transistor (or just cutting it's leads). This will preserve the current measurement of the power going to your module.
3) You might also bypass everything by putting a jumper from pins 1,9 of the DA15P to any unused user pins on that same connector (pins 2,3,5,10,11,12) then picking up the power from the corresponding user pins on the 40 pin connector. If you do this, you should provide a current measurement circuit on your module and attach it's output to one of the analog input pins of the 40 pin connector.
The above may eliminate or reduce the noise in your power source while accomplishing other power source objectives.
Chuck
Juan Rivera wrote:
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_Troubleshooting.htm.
Preliminary Findings...
- 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
I/O line filtering appears to be unnecessary
The switched power from the CAN-Do module pins 39 and 40 must be
filtered
- The CAN-Do module will either have to be kept physically separated
from any sensitive components, redesigned, shielded or a combination of the three.
- 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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