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!!

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.

This is just one of them:

http://www.dxengineering.com/search/...rder=Ascending

Here are some mo

http://ecat.burndy.com/Comergent/burndy/cat/602945


--
Jim Pennino

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.

This is just one of them:

http://www.dxengineering.com/search/...plies/product-
line/jet-lube-ss-30-pure-copper-anti-seize?autoview=SKU&N=4294952247&sortb
y=Default&sortorder=Ascending

Here are some mo

http://ecat.burndy.com/Comergent/burndy/cat/602945

There is something to be said for using aluminium[1] tubing instead, and
any increased losses might be oounteracted by using larger tubing. The
skill and equipment to weld aluminium to aluminium is widely available.


[1] as spelled here
--

Roger Hayter

"Irv Finkleman" wrote in message
...
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!!

I read somewhere that the aluminum and copper should be seperated by
stainless steel to prevent problems.

Roger Hayter wrote:
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.

This is just one of them:

http://www.dxengineering.com/search/...plies/product-
line/jet-lube-ss-30-pure-copper-anti-seize?autoview=SKU&N=4294952247&sortb
y=Default&sortorder=Ascending

Here are some mo

http://ecat.burndy.com/Comergent/burndy/cat/602945

There is something to be said for using aluminium[1] tubing instead, and
any increased losses might be oounteracted by using larger tubing. The
skill and equipment to weld aluminium to aluminium is widely available.


[1] as spelled here

Not on this side of the Atlantic.

https://en.wikipedia.org/wiki/Alumin...ferent_endings


--
Jim Pennino

wrote:

Roger Hayter wrote:



There is something to be said for using aluminium[1] tubing instead, and
any increased losses might be oounteracted by using larger tubing. The
skill and equipment to weld aluminium to aluminium is widely available.


[1] as spelled here

Not on this side of the Atlantic.

https://en.wikipedia.org/wiki/Alumin...ferent_endings

"Here" is the other side of the Atlantic!

--

Roger Hayter

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

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

"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.

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.