Cruising yachts are often fitted with an Insulated Back Stay to facilitate SSB radio on board a cruising yacht. This page describes some practical solutions that require much less installation trouble resulting in a substantial cost saving.
The Bermudan rig offers a Back Stay that is usually cut towards the top and bottom, the removed section is then adapted to fit back between insulators fitted top and bottom of the Stay.
There are costs associated with this of course, more over the Insulators need to perform two roles, that of insulating the wire and being as strong as the wire so as not to affect the mechanical strength of the Stay.
That being said, from an electrical point of view, generally, the longer the wire, the better the antenna. Smallish boats therefore have an inherent disadvantage in that they are obviously small to begin with resulting in even smaller antenna’s when let into the Back Stay.
What though for people who don’t have a Bermudan Rig? Junk Rigged, one of the advantages of the Junk Rig is there are no Stays at all. Gulp!
I came up with the following idea.
I propose an antenna for the masses that can be used on the Junk Rig or Bermudan Rig and that keeps your hard earned money in your cruising fund and not in the hands of the rigger at the dock side.
For people with a wooden mast one can run up a length of wire inside it solving the problem of ‘where to put it’ but now its only as long as your mast. For me with a metal mast this isn’t going to work so I came up with the idea of a piece of string.
Not just any piece of string, rather an 8mm multiplait rope with a wire inside it. You won’t as far as I know buy it off the shelf, besides which its something you can make yourself. Here’ how.
Couple of caveats – my boat is out of the water, the sail is removed and my windows are due for replacement. There is little point in absolute detailed instructions since everyones situation is different. What you need and what you’ll get is the germ of an idea to make your own.
Usually we melt the end of the Multiplait rope to keep the inner and outer ropes bound together. To start with we chop off this securing end so the outer sheath can slide up from one end of the rope.
The other end was fixed, as in tied on to a boat cradle so I could keep tension on the inner rope while I pushed up and bunched up the outer sheath to this fixed end. The rope I used was a new 15 meter length of rope.
The idea is then to open the weave of the outer sheathing to a hole and feed in an equal length of wire.
The wire I used was a ‘special wire’. Oh here we go you say, he’s got magic wire. It was special because its what I had to hand, it was laying around doing nothing, and I had bought it years ago before copper prices soared. I was damned if I was to buy more. Truth be told I had used this wire on a previous antenna and it snapped in high winds. Why was I going to use it again for another antenna?
Well, in this case the wire is supported by the rope so it doesn’t have to be uber thick and strong by itself. The actual wire is Automotive rated at 8 amps and its multi strand. Nothing magical about that.
The multi strand wire I feel is important not for its electrical characteristics but its mechanical properties. Multi strand wire is much better in environments where vibration and flexing is going to happen. Thats why you don’t wire your boat with domestic house wire that is solid strand.
So use what ever wire you have to hand. The thicker the better as long as you can work with it, but eventually you’ll going to pull that bunched up outer sheath back down over the length of wire and secure the end. As mechanical loads are placed on the rope that outer sheath is going to work to grip the wire against the inner core and this will take the strain off the wire. Multiplait rope is not stretchy but the wire being copper is softer and will give in length if it has to.
Now be realistic. This is your antenna, its not a mooring rope any more. It might double as an emergency halyard. The finished halyard isn’t as flexible as it was, it feels stiffer and little knobbly compared to ordinary rope.
So that was the plan, poke the wire into the hole and pull it through.
What was the reality?
Horrible horrible horrible to make but perhaps you can do better from my experience.
I can hardly believe just how fine the strands of Nylon that make up the Multiplait rope. It was so easy to snag one or more with the end of the wire. It took alot of jiggery pokery to get it started and for the first four feet I only managed to progress a couple of inches at a time before making an exit hole and pulling the entire wire length through. Then I inserted it back through the hole it had come out of and further along under the sheath.
If you don’t put the wire back through the hole it came out of you’ll end up stitching it in and out of the outer sheath and the rope won’t support the wire, it will pull it along when under load. But with each inner and outer poke it was so easy to pick up a strand of nylon. This made it very slow painful work.
Eventually I found that dangling the rope vertically helped instead of laying along a table top and after much perseverance I was making progress by a couple of feet at a time. In other words experiment with positioning the rope to ease your progress.
What I longed for was something stiff, small and flexible. What that looked like in my minds eye was the stainless steel whip from a mobile antenna, or an old whip from a VHF antenna but I could not find one. I didn’t own one.
I reckon it took about four hours to poke it all along 15 metres of rope. Half of that would be spent in first couple of feet.
After I got all the wire through I began pulling down the outer sheath. It stuck before getting to the end leaving a pregnant bulge of outer sheath about 5 foot from the end.
The problem seemed to be that I got the wire through the strands of the inner cable. It only happened in one place about five foot from the end. There was no amount of massaging that did any good resulting in having to unpick it, pull back and re-thread from there forward.
I left a pig tail of wire to poke out at the end, the last six inches of wire. This was so I could ‘know’ where it was and also if I ever wanted to check its continuity I could. That is if I ever suspect the wire has broken theres some chance of checking it. I still longed for an old VHF whip for threading. I simply sealed this loose pig tail with some hot wax to prevent the ingress of moisture.
The outer sheath is now shorter than the inner rope. It would be. Its had a larger diameter to cover – inner rope plus the thickness of the wire so something has to be shorter to compensate and that’ll be the length. A thicker wire will result in bigger difference between the inner and outer lengths. Bear that in mind. I tried melting the inner and outer together without much success since I wanted to leave the inner core longer than the wire so there is a normal bit of rope for tying on to things. You could if you want to be professional perform a splice on the ends complete with thimbles.
The inner and outer were secured together using a cable tie pulled as hard as I could a couple of inches after the pig tail end had emerged.
Fixing the SSB antenna to the Junk Rig
There was currently no other option for me than to use the flag halyard to haul it up. A dog bone insulator is cable tied to the halyard using one hole from the dog bone. The other hole was drilled out to a generous 8mm, the largest drill bit I had to hand. Having used 8mm multi plait rope plus a wire there was no surprise when it didn’t fit. Another cable tie was pressed into service but it wasn’t pulled fully tight so there is some ‘give’ at this apex.
As the pictures show I used the anchor roller to secure the forward end. On an ‘in service boat’ anywhere on the pulpit would have done. Thats be beauty of a bit of string for an antenna. The after end is secured at the pushpit being just lashed on.
There we have it. A ‘long wire’ antenna that is almost twice the length of a small boat, about 12 meters in length, twice the length of the boat. Its a start.
I almost forgot. While putting the antenna up I found laying on the side deck the remains of my mobile antenna that gave up the ghost some years ago. It was just what I had needed. An old Whip antenna with a rounded baubly end.
The reality due to the sail plan is that securing the after end to the Pushpit isn’t really practical. The sail is bound to foul the antenna on certain points of sail.
While I have hinted at the Lazy Jacks their ropes aren’t likely to be contiguous sections. But once you have the germ of an idea something on your set up may suggest itself. The only thing to guard against is that you don’t double the antenna back on itself, generally they don’t like that. This antenna describes an inverted V.
One place that does suggest itself is the cockpit end of the boom, perhaps using the Lazy Jack ropes to secure the antenna in its descent to this point. The antenna will therefore follow the boom around without being a problem.
There is a further niggle applicable to the Junk Rig. Unlike the Bermudan Rig the exit point from the hull for the antenna lead is usually on the aft deck straight onto the Back Stay. This wire rope antenna can affix there. On the Junk Rig this won’t work as the sail will foul any wire rope you attempt to lead from here to the mast head.
As I mentioned in the beginning, my windows are down for replacement. For this experiment I simply drilled a hole and affixed an SO239 socket. The perspex is an excellent mount. Actually this is beginning to get a little complicated electrically here so I will post what I was going on to say in an alternative page. For the moment if we consider that you have an Antenna Tuner which you will need regardless, if its feeding on to a Long Wire Antenna, which this is, then the wire from the ‘wire rope’ can be ‘let in’ to the boat though a hole drilled and filled with some Sikaflex compound.
This lead in hole just can’t be in the arc described by the sail, which means as likely its going to be at the foot of the mast, or on the foredeck. What ever way you do it, this lead in wire forms part of the antenna and therefore must be ‘factored in’ that it will radiate RF energy when transmitting so don’t have people laying on it or likely to touch it in some capacity and keep it away from sensitive electronics and free and secured from boat rigging and equipment.
Incidentally any wire that you’ve not bought on the basis of it not requiring a second mortgage is likely to be PVC covered. There is such stuff as ‘out door wire’ that probably means its at least UV stabilised PVC covered wire or ‘harder’. As this antenna is hidden away in the rope its going to last a little longer than just a bit of wire hung out in the sun.
I’m beginning to get to the point where I am writing more and more about less and less.
So on the other side of the antenna is the ground. this isn’t a ‘ground’ as in ‘it goes to the black wire and that goes to the battery’, its an RF ground.
Just to help clarify this. If you’ve ever been listening to a radio, or a Tv or your mobile phone and you’ve moved and noticed the reception has either improved or deteriorated and you know this because you can move back improving or degrading the signal at will, this is RF or Radio Frequency. Have you ever moved closer or further away from your car, boat, or household lights and seen the same thing? Your lights got dimmer or brighter depending on where you stood? No, thats because that’s an AC or DC circuit.
So your RF ground is not the same as your DC ground. Although they may share apparently common connections they are electrically different. It maybe an extreme example but so be it to make it clear.
It is for this reason that you need to have some copper or conductive surfaces under your boat and in the water to balance your antenna up top. If you can manage half a square meter or more that would be great. Your going to need to connect to it too. Its really getting beyond a simple story.
If its all too much you can get by with throwing a length of wire off the back of the boat into the water and trailing it along. Clearly this is temporary and your bound to prop wrap it at some point unless you’ve the memory of the devil.
If sea water is so wonderfully conductive, can’t we use it as an antenna?
Well yes we can and yes its been done and no its not all that practical.