On 2/5/2016 9:31 AM, Channel Jumper wrote:
Ralph Mowery;851568 Wrote:
"Bob Wilson" wrote in message
...--
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-

That grease is fine for inside a house where it does not get wet.
Outside
for antennas it would probably wash off after a few rains. Then with
the
wet conductors you get what is called galvanic corrosion.

The more distance in the chart it is, the faster this action is.
https://en.wikipedia.org/wiki/Galvanic_corrosion

You can buy stainless steel tape at most welding shops.
The tape is used to protect threads and valuable machined parts from
weld slag. If you apply it to the copper, the aluminum will not
corrode.
The problem with stainless steel is that it is an alloy and has a
different dielectric constant than either the aluminum or the copper.

I don't want to be pedantic, but the dielectric constant is of virtually
no impact. The important properties of conductors used in a loop
antenna are conductivity (resistivity) and permeability. Even so, an
adequately thin piece of material will have little impact on the
properties of the loop. The real issue is that welding any of these
materials will be difficult.


As one poster said, your efforts would be rewarded if you just used a
larger diameter aluminum loop and forgot about the copper. Especially
if you were going to install this antenna permanently in a place that
was not easily accessible.

1+

Aluminum is your friend. Light and corrosion resistant, it weathers
very well if you keep it from contact with certain metals like copper.
Unlike many metals, on contact with air aluminum creates a thin very
tough barrier of aluminum oxide that prevents further corrosion in most
situations.

--

Rick