"David" wrote in
:


"Owen Duffy" wrote in message
...
"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


....
The only thing I can think of that is different is that I used some
special grease from Vine Antennas on all the joints that was
advertised for antenna joints.

These compounds are often a waterproof grease of some kind with granular
metal particles, often zinc. The concept is that the grease excludes
oxygen and water from the joint and so reduces corrosion, and the
irregular zinc particles improve conductivity by 'punching through' the
oxide layer on the aluminium.

It is conceivable that the stuff you have used may create some kind of
galvanic action which could produce some noise. The goop that I have used
has always worked without apparent problems, but it will depend on the
recipe, and different recipes exist for compatibility with different
metals.

BTW, it is my experience that marine grease does just as good a job on
clean aluminium without being nearly as messy. I use a small stainless
wire brush in a dremel tool to clean the inside of mating tubes, a
regular stainless scratch brush to do the outside, and a little marine
grease on the mating surfaces. Don't be overzealous with the wire
brushing as you embed steel in the aluminium. People often propose non-
metallic scourers, but they also embend non conductive material in the
aluminium surface.

Have you looked for other current loops that could generate noise, AC and
DC. DC loops can be 'powered' by galvanic action from things such as
mixed earth electrodes (eg copper or copper clad electrodes bonded to
galvanised iron water pipes or masts).

Owen