HF Back stay antenna connection corrosion

[pendragon]

How do i prevent corrosion between the HF coax connections to SS back stay (center core)and the SS push pit (shield)?
Taping the connections up with self amalgamating tape fails, as water gets in eventually, as does spraying them with some plastic sealer. -->already tried a couple of times. Inspecting these taped connections is a problem in itself.


My current setup is:
All connections from coax to stainless(back stay & push-pit) have double SS hose clips.
The connection to the 500W 1:1 Balun(It forms a dipole) is done with soldered eyes on the coax and SS bolts/nuts/washers.
ALL the stainless bits are 316 and the RG8 coax is tinned copper inner & shield.


Is there a type of waterproof conductive grease/paste (or ?? ) that will actually seal the touching surfaces of these connections.?

[S/V Illusion]

Don’t use coax but rather GTO or equivalent wire between tuner and antenna. What I have found is that leaving the connection open to the environment by simply using SS wire clamps worked best.

Coax is designed to feed a balanced line - a backstay is not.

[Frankly]

While I have a typical HF tuner set up, I soldered my GTO15 center conductor to a small length of copper foil which is wrapped and taped to the SS backstay. The foil/ wire is secured with a short length of solid #18 wire twisted and overtaped. I no longer use a lower insulator so of recent times the coper foil/ wire is wrapped around the SS swage fitting. Just check it every few years and retape. If I understand your balun arrangement might consider just potting the coax/ balun side of things (small PVC pipe form) and bring the antenna and ground leads out with simple single strand copper. IME keeping water out of exposed coax cable connections takes a little extra effort.


Frankly

[Albro359]

"I no longer use a lower insulator"

You want to be sure no one is hanging on to that backstay when you're transmitting ! They' ll get the message for sure if they are !

[Frankly]

Length of pex covering wire up to bimini and over that 3/4" PVC. One little benefits is that PVC is easier on the hand than grabbing the bare wire moving around the cockpit. Matching PVC on the other side for the solar panel wiring.

Normally I don't allow anybody in the cockpit when using the HF radio. A lookout standing in the companion way and AP steering.


Frankly

[Brian.D]

Originally Posted by S/V Illusion

Don’t use coax but rather GTO or equivalent wire between tuner and antenna. What I have found is that leaving the connection open to the environment by simply using SS wire clamps worked best.

Coax is designed to feed a balanced line - a backstay is not.

Sorry to go OT here, but coax is NOT used to feed a balanced antenna. Coax is an unbalanced feed source. 300Ω or 600Ω twin lead is used to feed a balanced antenna as they are balanced feed lines.

Again, sorry to go off topic.

[Poeme]

I second the motion that a GTO cable "sandwich" of copper foil be clamped to the swaging of the lower insulator. Any connection to the wire backstay itself will sooner than later corrode from water intrusion coming down the strands. Also, I loop the last number of inches of cable so that the wire is "pointing down" to the connection...anything to keep water out. Looks funny but RF energy doesn't know the difference.

[Frankly]

Sounds like he needs an unun as he is unbalanced on both ends but that is getting into the weeds a little. If what he has works, so be it. I used to talk East Coast to West Coast on a coat hanger out the window (good old 10 meters days) but don't use a coat hanger on my sailboat (coat hangers were metal back then).


Frankly

[aqfishing]

Originally Posted by Frankly

Length of pex covering wire up to bimini and over that 3/4" PVC. One little benefits is that PVC is easier on the hand than grabbing the bare wire moving around the cockpit. Matching PVC on the other side for the solar panel wiring.

Normally I don't allow anybody in the cockpit when using the HF radio. A lookout standing in the companion way and AP steering.


Frankly

Easy way to check all your connections and tx power!

[caffel]

The conductor in solid strand automotive ignition wire is a good match for ss rigging wire. Usually tiined or nichrome.
Plated split bolts from the electrical suppliers make compatible clamps.
'never sieze' grease with aluminum, nickel or bronze powder in it will inhibit corrosion in all merine electrical connections while conducting some of the current. Also tends to wick up the wire strands to inhibit salt water traveling under the insulation.

CA

[waterman46]

There's little need for corrosion inhibitors in the copper to SS interface other than a good cover of amalgamating tape. As others posted, if you use some copper foil wrapped around the stay, then with oxidation of copper you'll be forming a capacitor. When applying the foil you should press it tightly against the stay so that you can see the shape of the strands of SS beneath. You want to maximize the contact area.

Since the dielectric, the oxide, is so thin, it doesn't take much area of foil (less than 10 cm of tight wrap, and strongly bound with amalgamating tape) to form a capacitance great enough such the electrical impedance is much less than an ohm at all marine SSB frequencies.
If you want DC conductance (not necessary), there are silver-bearing pastes and epoxies. Don't be misled by the "conductive" epoxies in general since they are usually referring to thermal conductivity and often use oxides, not actual silver.

I have not used foil myself, just wrapped about 10 turns of the wire from the tuner, around the backstay, hose clamped it top and bottom and taped it. Even this simple configuration has always worked fine for me.


And then there's gold epoxy . . .

[Privateer01]

No-ox and other electrical connection protective greases are very good for this. You can also use coax seal over the connection.

[pendragon]

Thank you to all contributors so far...
But, I did not ask for comments regarding my installation. The install is fine and has been so for over 20 years, but every time I do an ocean voyage, I need to sand (240grit)the connections to clean up the oxidation..
Using amalgamating tape: It is impossible to exclude moisture from the balun connectors and water seeps in between the back stay wires.

In the past, I have done resistance measurements with Copper-cote, Never sieze, ResQ-steel, some conductive silicones. All showed pretty high electrical resistance.

So....

My question was "Is there a compound/grease or whatever, that seals out water and conducts AC with near zero resistance?

[MicHughV]

do what I did.....

I made a U-loop in the coax connection to the wire.....a small loop....maybe 1" or so....ie, the downward leg of the coax was about 1".....then I trimmed the insulator back about 1/2" or so, which left enough of the coax cable so this was connected to the wire with a wire clip.....but being upside down....water....rain or salt could never wick down the coax connector as the connector was pointed in the wrong direction....

I then squirted some 5200 sealant around this connection..wrapped the the connection with regular electric tape, which in turn I wrapped with some coated twine..

never ever had a problem with this....worked like a charm for all the time I had that boat. My next boat, I repeated the same thing....also never a problem...

hope this helps....

[Brian.D]

Anything you use, even bare wire to bare wire, will add resistance. That is just the nature of making any kind of connection. However, the resistance is really so small that it should be negligible.

As far as trying to keep corrosion from happening, I don't think that is really possible. Even with SO239/PL259 connectors or N-Type and even BNC Type connectors are not impervious to corrosion, regardless of how well they are protected.

With the nature of the construction of the backstay, moisture is going to wick in. Unless you can find a way to prevent that then you might consider the antenna as part of your routine maintenance cycle. If this was a alternative backstay antenna (one that is not a backstay but a wire running to the top of the mast and is non-load bearing) then maybe a good dual wall shrink wrap. At least some of the adhesive might wick into the space of the wire rope.

Just some thoughts.