LBS Noise Update and Ground Loop Revelations

I’ve been convinced.  I have ground loops.  In fact I have so many it’s hard to count how many.  So this called for some further reading. (ohoh) Reading a few different points of view on the subject was enlightening and I came across some interesting things.
 

In summary and for consideration, here are couple of points:

1, when mounting rf connectors on a pcb, create a separate ground plane running around the perimeter of the board.  Make one connection to this plane at one end of the board near where the main ground has been established.

2, when using coaxial cable on a board, ground one end and leave the other end open.  This will allow any noise picked up by the shield to run in one direction to the ground and not create a loop.  The loop being the shield and the chassis.

Thoughts:

I can see where there are considerations to account for depending on the style of construction used.  Multiple boards will be built one way and if using just one main board, then point 2 will come into play.

Early on I was not comfortable with the thought of the shield carrying the return for the 12v system. This is why I ran the twisted pair to each board for the power.  I did not realize that its loop itself that can cause the noise. Not just some wire picking up noise from somewhere else.  I thought this to be most interesting.

Making good bonds to the ground plane does not eliminate the possibility of creating a loop.  The difference between the characteristics of a cable, copper trace, or chassis is enough to create the loop.

I’ve now come to the understanding that when building a radio, no matter what the subject is, it can become complicated at times.  Doesn’t really take away from the fun, but can cause some frustrations none the less.

So over the next couple of days I shall start removing the various 12v return lines and allow the rf shields to supply the return.  This should eliminate all the loops in my setup.  Once that is cleaned up then back to the carrier issue. I've designed another mixer board if I end up not being able to control the carrier.