"David" wrote in
:

David,

If your tests are not exposed to temporal effects (eg comparing the R4 last
year with the MA5B now), then the reduction in S/N with the MA5B on
boresight is telling. Something is wrong somewhere. (A prophetic statement
I know!)

Some of the earlier suggestions remain relevant. Does the noise in a
battery powered receiver reduce significantly when you turn the power off
to everything in your own premises?

Owen