Comet 712EFC -- no ground plane radials

[WSHH887]

Depending on the alloy stainless steel can be highly magnetic or not. After being burnt, literally, by Chinese stainless steel that wasn't what it said it was my first quick check was a magnet. The alloy we used in chemical piping should not have been magnetic.  
 

After that incident, the piping came from an ISO manufacturer, I specified US or European manufacturer only. All Chinese metal is mystery metal as far as I'm concerned. 

[WRTC928]

My radials are on the way from Comet. I hung it from a tree and ran a few tests using my improvised "mystery metal" radials. I think I'm going to like this antenna. I had a lot of work to do to get my deck ready to support the mast, but I think I have it ready now. I can raise the antenna as soon as the radials get here. Well, when I also have someone to help me. I can raise it with a rope using a tree branch as a pully, but I need someone to guide it and secure the clamps while I hold it up.

[WRUE951]

On 5/19/2025 at 12:47 PM, WRTC928 said:

TBH, I'm not sure. It has that dull sheen like aluminum, but that could just be the finish. I don't have a magnet handy, but a lot of stainless steel isn't very magnetic anyway. I think the whole "dissimilar metals" things is a bit overblown anyway. Cars and motorcycles bolt aluminum to steel all the time. If it were a part that carries a current, it might be different, but I've seen lots of aluminum wire secured to an outlet with steel screws for decades without any issue, so maybe not even then. 

Cars and motorcycles do use dissimilar metals for fasteners and they also advise use of anti-seize.  Also, dissimilar metals for fastening use does not promote the corrasion effect as much as it does when electrical current flows through the dissimilar metal.  

[WRTC928]

4 minutes ago, WRUE951 said:

Cars and motorcycles do use dissimilar metals for fasteners and they also advise use of anti-seize.  Also, dissimilar metals for fastening use does not promote the corrasion effect as much as it does when electrical current flows through the dissimilar metal.  

As I said, I've seen houses wired with aluminum wire and secured with steel screws without any significant corrosion. Granted, they aren't exposed to the weather, but they carry a lot of current. I'm not saying it doesn't happen and I'm not going to start randomly screwing dissimilar bits of metal together, but if Comet uses stainless steel radials screwed into an aluminum base, they must not be too concerned. 

[SteveShannon]

2 hours ago, WRTC928 said:

As I said, I've seen houses wired with aluminum wire and secured with steel screws without any significant corrosion. Granted, they aren't exposed to the weather, but they carry a lot of current. I'm not saying it doesn't happen and I'm not going to start randomly screwing dissimilar bits of metal together, but if Comet uses stainless steel radials screwed into an aluminum base, they must not be too concerned. 

Once upon a time aluminum was used for house wiring but there were fires in some places. It’s a little trickier to work with aluminum because aluminum oxidizes very quickly and aluminum oxide is a pretty good insulator. We still use aluminum for utility conductors but with quite a bit of extra training to do it right when joining copper and aluminum. Gil @WRUU653 would be much more likely to understand the process than me.

But that’s at DC and and 60 hz.  RF travels through molecular thin oxide layers pretty well and I agree with you that stainless steel and aluminum don’t appear to bother Comet. 
 

[WRUE951]

3 hours ago, WRTC928 said:

As I said, I've seen houses wired with aluminum wire and secured with steel screws without any significant corrosion. Granted, they aren't exposed to the weather, but they carry a lot of current. I'm not saying it doesn't happen and I'm not going to start randomly screwing dissimilar bits of metal together, but if Comet uses stainless steel radials screwed into an aluminum base, they must not be too concerned. 

Yea, i have as well..  Water and moisture surelty contribute to the corrosion factor.  About 10 years ago i restored a 1970 Yamaha 250 Enduro Motorcycle.  It sat in my dads back yard for over 30 years. Many of the steel bolt used for the aluminum casing were seized with some destroying the threaded casing. The bolts that were steel to steel cam out with ease.   

[WRUE951]

33 minutes ago, SteveShannon said:

Once upon a time aluminum was used for house wiring but there were fires in some places. It’s a little trickier to work with aluminum because aluminum oxidizes very quickly and aluminum oxide is a pretty good insulator. We still use aluminum for utility conductors but with quite a bit of extra training to do it right when joining copper and aluminum. Gil @WRUU653 would be much more likely to understand the process than me.

But that’s at DC and and 60 hz.  RF travels through molecular thin oxide layers pretty well and I agree with you that stainless steel and aluminum don’t appear to bother Comet. 
 

I just got currious about anti-seize and pulled mine out of the cabinet to read.  It's a copper base antisize recommend for electrical connections. I wonder if Comet recommends a copper base anti-seize to enhance the electrical connection with their antennas?  

[WRUU653]

45 minutes ago, SteveShannon said:

Once upon a time aluminum was used for house wiring but there were fires in some places. It’s a little trickier to work with aluminum because aluminum oxidizes very quickly and aluminum oxide is a pretty good insulator. We still use aluminum for utility conductors but with quite a bit of extra training to do it right when joining copper and aluminum. Gil @WRUU653 would be much more likely to understand the process than me.

But that’s at DC and and 60 hz.  RF travels through molecular thin oxide layers pretty well and I agree with you that stainless steel and aluminum don’t appear to bother Comet. 
 

Part of the problem with aluminum wiring in homes was an issue with dissimilar metals and how they expand and contract at different temperatures. Special outlets were used with aluminum screws but if the wrong outlet was used which typicaly had brass srews or copper wires joined with the aluminum and a joint compound (antioxidant, aka Noalox) wasn't used then arcing and oxidation would occur and it's all down hill once the arcing starts. Later people started using stab style connections on new outlets and these are a recipe for disaster. Larger feeders isn't an issue when wire is prepared properly and isn't as prone to outside movement like an outlet in a home that gets plugged into and out of constantly or your DIY people installing things incorrectly.  Back in the day electricians would put noalox into wire nuts and use this for splicing. Then some manufacture saw this and made wire nuts with the compound pre installed and got UL listing and a patent. Damn why didn't I do that moment .

More info than anyone wanted I'm sure. Anyway it does not hurt to put a thin layer of Noalox when connecting aluminum to another metal. You don't need a lot.