SSB Installation Questions

[mallo]

Hi, I would like to pick the brains of some of the members here if possible.
I am currently fitting an Icom M801E to my boat, she is a 48ft steel ketch, I have a few questions if possible for the SSB experts.

Firstly what length is the optimum length for the antenna, I am planning to mount the AT-141 just below the deck under the mast and run a cable up through the deck and make up a cable antenna running up to the top spreader running through the middle spreader.
At this point I must say the mast and spreaders are all wood.
I would fit some insulating material through the spreader where the cable would run and I was thinking of using some plastic coated wire, (although could any type/size of cable be sufficient?) and having an insulator at the top.
I can’t use a backstay insulator aerial easily as the backstay has the rest of the cables running down it for the mast head light, windex and VHF etc.(joys of wooden masts and without any ducting, mind you they are nearly 70 years old, and I don’t suppose they had mast head light/VHF/windex then…. )

Secondly grounding the unit, I am quite keen that the unit works well, I know that the steel hull will provide me with a good ground, however I want to find the best way to connect it to it, I was planning to at both the transceiver and the tuner (two different positions about 20ft apart) to weld some stainless steel lugs/tabs to the steel frames that are riveted to the hull (they are also welded at the tuner end, (tank top))the hull plating is all welded (although the frames at the transceiver end are only riveted) should I weld the frame at this point to the hull?
Once I have the lugs/tabs coming out of the frames I was then going to bolt/clamp a copper strap from the lug to the respective units.
Would this work well, I have full workshop facilities, also what dimensions should the copper be I think I have some 1.6mm thick sheet and was thinking of cutting some strips 2” or 3” wide would that be sufficient, and the tabs I was thinking of something similar width as the copper maybe slightly thicker.
Would to be suitable or can someone suggest something better??
I live on an island without specialist shops for supplying copper strap etc. so a little improvisation is needed from time to time.
I look forward to ant suggestions from the experts on these matters or any thing else that I should avoid.
Thanks for any suggestions
Michael Allo

[sailingdog]

Btrayfors can answer about the antenna question...

As for grounding the unit, I'd recommend brazing/welding a tinned copper lug or tab to the steel frames, not stainless steel, since stainless steel is a poor conductor and has about 30 times the resistance of copper. Then bolt the copper strap to the lug, and you'll have a pretty good ground plane.

Just remember for the radio signal, the wider the copper strap, the better the signal conduction is to a point. I'd think a 1.6 mm x 3" strap would work quite well.

Do not put the copper lug or strap down in the bilge if you have a wet bilge, since they'll effectively turn your boat into a battery. But if you have a wet bilge on steel boat, you got other problems anyways. Epoxy coating the copper to help protect it is probably not a bad idea.

[mallo]

Hi sailingdog
Thanks for that, I think its possible to weld the copper to the steel, (I have welded copper pipe to stainless before with quite good results, however I haven’t to steel, I can feel an experiment coming on!!) but I was going for stainless steel as it would stay clean easier, if I weld tinned copper to the frame the tinning will just burn up.
If the stainless is a poor conductor how does the steel rate??
Would I be better just welding a piece of steel or trying to clean up an area on the frame and greasing it to keep it clean and corrosion free?
As the rest of the steel hull is the ground I was thinking a small area of a stainless steel lug wouldn’t have made that much difference.
Thanks for the suggestion of epoxying the copper that’s probably a good idea knowing what copper goes like on a boat….
We have very dry bilges (the joys of a steel boat) as I find it a good way of cutting back on corrosion.
Thanks again for your help
Michael

[Plumper]

I sailed a steel ketch with wooden masts and the SSB antenna ran between the two mastheads.. The tuner was halfway up the mizzen.

[Hartley18]

Originally Posted by mallo

Hi sailingdog
Thanks for that, I think its possible to weld the copper to the steel, (I have welded copper pipe to stainless before with quite good results, however I haven’t to steel, I can feel an experiment coming on!!) but I was going for stainless steel as it would stay clean easier, if I weld tinned copper to the frame the tinning will just burn up.
If the stainless is a poor conductor how does the steel rate??
Would I be better just welding a piece of steel or trying to clean up an area on the frame and greasing it to keep it clean and corrosion free?
As the rest of the steel hull is the ground I was thinking a small area of a stainless steel lug wouldn’t have made that much difference.
Thanks for the suggestion of epoxying the copper that’s probably a good idea knowing what copper goes like on a boat….
We have very dry bilges (the joys of a steel boat) as I find it a good way of cutting back on corrosion.
Thanks again for your help
Michael

Michael, ordinary black steel is a good conductor, as is copper.

My suggestion (least messy) would be:
1. Clean a small square patch of stringer or rib back to shiny bare metal
2. Through-bolt a copper 'tag' (piece of 1.6mm copper bar or strap and pre-tinned if you can get it) over the patch using an ordinary steel (not galvanised!) bolt + washers either side + spring washer to hold it all tight.
3. Prime & paint the entire thing using metal primer and your usual top coat.

If you can't get tinned copper in your neck of the woods, bare copper is fine - just prime & paint it. Epoxy is nice but messy and won't flex like primer will without cracking off.

As SD pointed out, don't use ever stainless for electrical connections - basically they won't work.

The above procedure is used by the major oil companies to fix earth straps to fuel storage tanks nearly every second day all over the world, so it should work for you as well, I'd have thought..

[thekeip]

I use 'outside-star' washers when trying to make the best physical connections between difficult metals. Epoxy doesn't adhere to copper either. Best cover the joint with a semi removable material like paint or non silicone sealer.
Howard Keiper
Sea Quest
Berkeley

[mallo]

Thanks for all your suggestions, it looks as if the best grounding solution is to just clean the frame and bolt to that, unfortunately the frames were originally galvanised would this cause a problem as I was just going to power wire brush the frame areas that I wanted to make the connections to, should I remove all the galvanizing i.e grind the area instead.
I was thinking of tinning the copper strap once it was bent to the correct shape? Is this the best thing to do? Would it be worth were I will be connecting the copper to the steel put some grease or high conductive paste to stop the steel corroding under the strap?

Plumper: I don’t think it would look particularly nice putting the tuner up the mizzen mast, wouldn’t the aerial work better in the vertical plane than the horizontal plane?
Thekeip: what’s the thinking behind the non-silicon sealer?

Thanks everyone for your input, does anyone have any ideas with regard to the aerial?
Best wishes
Michael

[sailingdog]

The galvanized steel should be fine...it's a pretty good conductor IIRC. Grease is probably a good idea too.

[sailboy21]

A steel lug would be great. No matter what material you use for ground plane you can't 'set it and forget it'. You should be inspecting it frequently, keep a good coating of corrosion block or similar and it will work well. A steel boat is the ultimate ground plane, consider yourself lucky! As for antenna length, this is far less important than it used to be. Modern tuners will literally tune anything. A short wire antenna is by far the easiest to set up on a boat. Good practice is to use 1/2 wavelength of the frequency you most use. i.e. for 14.3MHz use 34.4 feet, but longer is better.

Keep in mind there is no ideal or perfect antenna install for a sailboat. Anyone that tells you otherwise is full of themselves. No matter what you do, esp on a metal boat every bit of rigging, and all the wires going up the mast will work as parasitic elements. Your antenna will be directional to more or less of an extent. There is no way to calculate this, but use trial and error to get to know it, even use it to your advantage.

[btrayfors]

Mallo,

Sorry not to have responded earlier re: your antenna question. Have been busy.

I agree with the advice re: grounds, and think you have that covered. You're lucky with a steel hull...great RF ground system!

RE: antenna material, virtually anything will work, but I tend to favor insulated s/s lifeline because it is robust and will stand up to the marine environment, whereas bare copper wire won't last very long, and other materials are sort of "in-between".

RE: length, it depends a bit on your boat's configuration and, especially, on which bands you wish to favor. Longer lengths favor the lower bands (e.g., the 4, 6, and 8 mHz marine bands), while shorter lengths favor the 12, 16 and 22 mHz marine bands). The antenna should be at least 23' in length, counting the distance from the tuner to the top of the antenna. Forty feet or so is often a good compromise.

RE: placement, this is a bit of a quandry in your case. While the mast and spreaders are wood -- and, therefore, won't radiate or have much affect on the radiation pattern -- all the other standing rigging will. In general, it's good to get the antenna as far away from other rigging as possible. On some ketches, the triatic stay works well. On some, it's possible to run the antenna from the truck of the mainmast to one rail just forward of the mizzen, in such way as to ensure clearance of the main boom.

Assuming your mizzen mast is also wood, and remembering that the radiating part of the antenna begins at the tuner, it might be possible to mount the tuner under the mizzen mast and run the antenna up the mizzen -- either inside or outside -- to a triatic stay. With wooden masts, you wouldn't need insulators on that stay....just connect to the stay itself in a secure manner.

Lots of possibilities. Don't be afraid to experiment, including with temporary lashups before you make them permanent. For example, once you've connected a good ground to the hull, get yourself a roll of insulated wire and use that as the antenna. Experiment with it in different locations. When you find something which works well, go ahead and make the investment in a more substantial antenna material, such as s/s lifeline.

Be sure to do the experimentation when at anchor or at sea, since marinas can be very noisy and will confuse your results.

Good luck. Let us know how it works out.

Bill