The source of the spurs in the 70 cm prototype receiver is the CAN-Do module.
This is the receiver IF output as designed
(powered from pins 39 and 40 of the CAN-Do Module)
This is the receiver running off of a separate power source
(bypassing the CAN-Do Module +13 volt output on pins 39 and 40)
This is the same configuration as above, but with the CAN-Do module shut down
From the above it appears that:
1. The CAN-Do module is the source of all the spurs that I see
2. None of the spurs are being generated by the receiver’s internal power supplies
3. Some, but not all, of the noise is entering the receiver via the switched +13 volt CAN-Do output on pins 39 and 40
4. The remainder of the noise could be entering the receiver on other CAN-Do pins, or being radiated to receiver components or traces in close proximity
See my log for all the intermediate steps I took to reach these conclusions.
Remaining RF issues:
1. Phase noise