All,
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
2. Microphonics
73,
Juan
WA6HTP