Backstay antenna connection

MM5AHO

MM5AHO

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About to an antenna into the backstay along with the new standing rigging (10 year replacement).
Whats the best way to connect to the "live" part of the stay? ATU is about 1.5m away below deck. Copper wire perhaps for conductor, but don't really want Cu in contact with SS stay (corrosion). Suggestions?
 
For an SSB tranciever to ATU ? use tinned copper wire clamped to the backstay just above the lower insulator with two stainless bulldog clamps, lead the wire from below, then wrap with self amalgamating tape. Works for me.
 
I have been connecting a backstay aerial to a co-ax cable by seizing the cables inner wire to the rigging with a common whipping of tinned copper wire for about twenty years. The rigging has not failed yet, so I think that this is a safe method.
I will leave the theory to others to explain.
 
I use HT lead for old fashioned cars, which is copper (modern-car ht lead is no good - it is carbon or something which reduces interference) . Wrap it round lots and clamp and tape. Works fine from radio standpoint. Can get it from specialist old car part suppliers.

The problem is that water gets in. I surmise that water runs down the backstay, and because it is "laid" wire the tape can never get completely close all the way round. Eventually the water gets all the way down the down lead and into the turner. In the end I stopped taking the downlead through a gland into the tuner box and used a bolt as a lead through. Fastened the downlead on the outside where it can drip all it likes! Take another wire on the inside to the tuner input screwpost.
 
Time was when all SS rigging wire was swaged around a thimble using a copper sleeve that was crushed into the SS wire. There didn't seem to be any problem with copper on SS. If this is the case then you can solder onto the outside of the copper swage. Otherwise just clamp as suggested.
I think the best wire to use for connection is the inner conductor and insulation of the large RG8u coaxial cable. Remove the outer cover and screen wire. This insulation has a very high voltage rating to minimise burns and would be sufficient insulation to go through a sealed hole in the deck. good luck olewill
 
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Copper wire perhaps for conductor, but don't really want Cu in contact with SS stay (corrosion). Suggestions?


[/ QUOTE ] Copper is perfectly OK in contact with stainless steel, above the water. As others have indicated copper ferules are used on stainless steel rigging. It is OK because stainless steel is fairly close to copper in the galvanic series. According to figures published by Nigel Warren (PBO 254, February 1988) there is only about 0.3 volt between them and the stainless is in fact the more noble of the two!
 
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I use HT lead for old fashioned cars, which is copper (modern-car ht lead is no good - it is carbon or something which reduces interference) . Wrap it round lots and clamp and tape. Works fine from radio standpoint. Can get it from specialist old car part suppliers.

The problem is that water gets in. I surmise that water runs down the backstay, and because it is "laid" wire the tape can never get completely close all the way round. Eventually the water gets all the way down the down lead and into the turner. In the end I stopped taking the downlead through a gland into the tuner box and used a bolt as a lead through. Fastened the downlead on the outside where it can drip all it likes! Take another wire on the inside to the tuner input screwpost.

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I also used spark plug wire - the old fashioned type. Take it up to the backstay and clamp it there - but with the wire that is clamped having the bare end downwards. In other words, the feed wire initially runs up the backstay for maybe 6 inches before doing a 180, being tied onto the backstay with cable ties and then going down to the ATU. Clamp the bare end of the feeder to the backstay, cover the join with marine sealant, and then wrap the whole lot in self amalagamating tape.

Personally, I wouldnt worry about contact between the copper and the stainless, but as a metallurgist you would know better than me.

Make sure that the active part of the backstay is out of reach - you dont want to get RF burns.

73s mw0jhe
 
On our lastboat the backstay ended at deck level (rear coaming) so I chose not to bother with a lower insulator and so could make connection inside where the chainplate passed thro the coaming. Thus the connection was below deck where it was clean and dry. RF burns? Only if you were stupid enough to touch it. And as we sail as husband and wife, Janet knows it the HF radio is on.

As a foot note. Common sense and general awareness of ones surroundings is the best form of health and safety at work.

And as Darwin implied, only the stupid die young. Which is perhaps as it should be.
 
Thanks for the hints. It was the connection to the stay I was thinking about, but the cable ideas are useful too. Was planning to use the inner from RG213 for that.
 
I ran coax (the kind with solid copper corrugated sheath). at the end I soldered a piece of old guardrail with a swaged fork fitting. The slot in the fork was a jam-fit to the backstay, and a small s.s.bolt & nut secured it.Then amalgamating tape. The solder joint had been potted with VC tar on the bench. so no dissimilar metals in the elements. the coax was on stand-offs about 2-1/2" long down the earthy side of the backstay, but they may have been superfluous. The atu had a coax output, if you have a ceramic terminal for longwire, just ground the coax outer to the copper strap going to the dynaplate (or keel..)
As for ignition lead, if it's got copper (better tinned) wire in, it should be OK. The main thing is good insulation and damp-proof, which is what ign cable is all about. I haven't seen carbon-impregnated string for years...
P.S. the good thing about coax over ign cable is that you put the insulators 10metres apart on the backstay, and that is all that radiates, not the great long length going through the back half of the boat, wrapped round pipes, outboards, anchors, tanks, bicycles etc. before it gets to the first insulator! 73s mm5ajt
 
I have the inner from very thick distribution coax. It is about 10 mm on dia. I plan to use this. From the ATU to the backstay.

I think what you are going to use is correct.

In answer to another posters sugestion to use a full coax cable from the ATU to the backstay.

Any wire coming from the output of an ATU will become part of the radiating system. That is unless it is a coaxial output which which is properly terminated at the far end.

Either a centrally fed dipole or a resonant whip aerial could terminate the coax correctly over a limited frequency range.

It a piece of coax complete with an earthed outer sheath is used for this purpose to a backstay then there will more than likely be standing waves all along this coax.

Because of those standing standing waves along the feed coax it would be quite possible to get an RF burn through the insulation of the coax within the boat between the ATU and the backstay.
 
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Can anyone be more specific as to why modern HT lead is unsuitable?


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Next paragraph may be folk-lore: beware.

The conductor is not copper. It is some non-copper substance that I think is carbon. In any event it has high resistance for reasons of radio-interference suppression.

However, I know old fashioned HT lead is real copper so plumped for that.
 
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