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[email protected] · February 4th 16, 06:55 PM posted to rec.radio.amateur.antenna

Bob Wilson wrote:
On 2/3/2016 3:33 PM, wrote:
Irv Finkleman wrote:
Here's a situation I haven't encountered before
and which I know little about.

I am building a magnetic loop antenna and have
an assembly which includes a capacitor and drive motor ideally suited
for the antenna. My problem is that the assembly is welded to an
aluminum mount. I want to attach a copper tubing loop to the mount
which will connect the loop to the motor driven capacitor.

My concern is the matter of dissimilar metals i.e. copper and aluminum
being joined. I would prefer to be able to bolt the assembly to the
copper tubing using star washers to reduce the joint resistance.

Here are my concerns:
1. What about rectification at the dissimilar metals joint? Is it going
to cause problems? Is it of any real concern?

3. Can the copper be welded to the aluminum mount for better joint
conduction? This is a last resort for me as it would mean taking the
assembly to a place where the welding, if possible, could be done.

Thanks in advance for any comments or suggestions which would be greatly
welcomed.

Irv, VE6BP
RADIATE OR DIE TRYING!!

Yes, there is a problem with aluminum to copper connections.

There are various "greases" to solve the problem.

That grease is widely used where aluminum power wiring comes in from a
pole and connects to a lug in a meter. And for that matter when I have
bought wiring panels (I mean the box where your power fuses or circuit
breakers live) they have come with a sticker saying the grease must be
used wherever wire other than copper connects to the panel.
Bob, WA9D

Yep, because aluminum to copper connections without the grease develop
resistive layers which get hot.

Also there is a problem with the differing coefficients of expansion
which loosens the connection and makes the problem worse over time.

The net result is aluminum/copper interfaces not done right tend to
burn down houses.

--
Jim Pennino