Mallo, I haven't checked but suspect the galvanizing will be nearly "invisible" at radio frequencies. Conducting high frequency electricity works differently from conducting plain CD, the signal will jump straight though things that you might think are insulators. Like think layers of galvanizing, or even paint.
If you don't have copper strap, do you have a roofing supply on the island? Sometimes copper foil is sold in rolls for roof flashing, if they don't have it in stock a hardware supply can order it in.
Mallo, I haven't checked but suspect the galvanizing will be nearly "invisible" at radio frequencies. Conducting high frequency electricity works differently from conducting plain CD, the signal will jump straight though things that you might think are insulators. Like think layers of galvanizing, or even paint. OR AIR
If you don't have copper strap, do you have a roofing supply on the island? Sometimes copper foil is sold in rolls for roof flashing, if they don't have it in stock a hardware supply can order it in.
Very correct. Technical term is 'capacitive coupling' Applying the same principles for a bonding system or a lightning protection system is not necessary for your counterpoise system. In fact for us fiberglass, wood and aluminum boat owners it isn't even desired. You don't want to create current paths through your counterpoise system. With the steel boat example this is not as much of an issue. Just be sure keep your DC and AC systems floating.
Ah jeez. Now you're going to get everyone confused with today's announcement from California about Gay Coupling Rights.
"Very correct. Technical term is 'capacitive coupling' "
I was hoping to keep the technical stuff, and all five genders, out of this. Although if each of the natural genders can be re-assigned in four more ways...does that mean we need 59,049 sepsarate but equal restrooms too?
Ah jeez. Now you're going to get everyone confused with today's announcement from California about Gay Coupling Rights.
"Very correct. Technical term is 'capacitive coupling' "
I was hoping to keep the technical stuff, and all five genders, out of this. Although if each of the natural genders can be re-assigned in four more ways...does that mean we need 59,049 sepsarate but equal restrooms too?
You Americans are very strange..
Now I know why they call this the "lucky country" - we are nowhere near you lot!!
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Hi all,
Thanks for all your replies over the last few days, I have been away from a “proper” computer.
So hallosailor and sailboy21 are you saying that I don’t even need to clean the paint off? Or am I still better cleaning it off?
hellosailer I have some copper sheet 1.5mm thick I was going to cut some of this into to 75mm strips.
On another question can the copper ground have sharp corners or should they not like lightening conductors?
Sailboy21 I am not sure how floating our DC is as I sure there is a common between the negative side of the batteries and the hull, the only common with the AC is the earths which indirectly must be connected to the neutral line??.
btrayfors thanks for a bit of an insight into the antenna question, as you say I am lucky to have a steel hull, however I have a few more questions, I was planning to mount the tuner (alongside the steel hull) under the deck (wooden with steel frames, quite wide in places), and take the antenna out through the steel hull or out up through the deck, however this would be through the steel frames too, will this affect the aerial (the fact its passing through the steel) or should I try and opt for the wooden route?
I take it that the standing rigging will affect the radiating pattern so putting the aerial next to the rigging (I was thinking half way between the mast and the standard rigging won’t give particularly good results), if I was to somehow insulate the stays nearest to the standard rigging would this help much?
The triatic is also connected to the ground through the stays and the cap, that could be insulated an use this stay but is probably only 30ft in length? I can’t run anything up through the masts, they are nearly 70 years old and they didn’t plan for electronics then!!
As you have suggested I had wondered about taking it from the top of the main mast to the afterdeck but I am not sure that would work that well, I then thought of using the inner fore stay and fitting insulators in the stay, but the top end would be fairly close to the ground, would this matter?
I could try and insulate it with some bushes on the fixings as well as the proper wire insulators would this be a possibility?
I am sorry for all the questions, life would be much simpler if it was just an ordinary fibre glass boat, but it wouldn’t be so interesting…..
Best Wishes
Michael
Of those you mentioned, I think the best antenna would likely be an insulated triatic stay, fed through the mizzen mast, with the tuner located as close as possible to the base of the mizzen mast, and with the antenna led through the deck.
If the steel beams under deck are affixed to the steel hull...as I assume they are...you can just tie the tuner ground to the nearest steel beam. That should make a dynamite antenna system.
You don't have to guess. Buy the roll of insulated wire I suggested earlier. AWG #16 or #14 would be fine. Run it up the mast -- outside is fine for the test -- and under the existing triatic to the truck of the mainmast. Just use nylon line for insulators (at the truck of the main mast and the mizzen mast). Actually, since this is a temp setup, you can just use dacron halyards to hoist the insulated wire.
Connect the lower end of the wire to the tuner antenna lug, the tuner ground to the nearest steel beam, and give it a try. Should work just fine.
Now, assuming all is fine, go ahead with a more permanent arrangement, using insulators in the triatic and insulated, tinned wire inside the mast. Remember that the wire going up the mast is a radiating part of the antenna, so the total antenna length will be substantial (30' or so for the triatic plus the mizzen mast height).
What you'll have, in essence, is an end-fed "inverted-L antenna". These can work very well. I actually have one at my home station, using an SGC marine tuner, which is a great performer.
Let us know how it works for you.
Bill
Last edited by btrayfors : 05-19-2008 at 10:58 AM.
Michael-
I don't think sharp corners will matter much at these frequencies. At really high frequencies (not a proper technical term[g]) corners become electrical elements, i.e. on computer motherboards they are a problem. But I'd still think you are better off using foil or ribbon and not having to keep joining lengths of copper up. And, if you can, bond metal to metal without the paint.
Hi all,
So hallosailor and sailboy21 are you saying that I don’t even need to clean the paint off? Or am I still better cleaning it off?
Clean it off! Capacitance is determined by surface area, distance and permeability. Either a really small surface area (i.e. lug connector) or a really large distance will decrease the capacitance to zero. Capacitive coupling, at least as it relates to marine SSB installations, becomes important for fiberglass and wood boat owners trying to create a counterpoise with copper strips in the bilge. There is a coupling effect between the sea water and the copper strip through the fiberglass hull. So, a direct electrical connection is highly desirable. Also remember 'edge effect' as it relates to HF. Use large circumference materials, copper water pipe, 4 ga battery cable, and the shield of RG-8U as well as copper foil work well for this. My personal fav is the flexible 1/2" copper waterpipe. You can solder batter lugs inside the end of the tube. Makes a very sturdy HF friendly connection.
As for a corner on in the middle of a end fed short wire: avoid it if possible. You want your driven element(s) to be straight. What you get with a bend will be a strange unpredictable radiative pattern that won't be stable with changes in frequency or across bands, nulls, and probably a very high SWR that your tuner won't be able to handle. End-fed short wires are not good antennas to begin with, so you don't want to make matters worse. Perhaps you would be better going with a 17' whip like Shakespeare makes, or investigating the possible use of a shroud, or even some other antenna designs. There are many designs that are already balanced, easier to tune, portable, and that can be hoisted up when needed. I just built a nice little magnetic loop antenna that is a square with sides less than 3'. Gets better reception than any short wire and has a near perfect SWR w/o the use of a tuner.
Hi all
Thanks for all your replies, sorry I haven’t replied before now, I have been very busy with boring things, work etc….
I am going to try the simplest way and have mounted the ATU below the deck and have connected it up with a shroud type aerial run up the mast insulated from everything else.
As the masts are now stepped for the season I will see how I get on and make something more longer lasting for next season.
I might go down the route of the triatic but I thought the idea of an aerial was that it was vertical not horizontal, Bill you say you use an inverted “L” and you find it works well, do you find it directional?
One other quick question is there any easy way of testing the set-ups output easily?? Apart from calling another station up?
Thanks again for your help
Best wishes
Michael
Unfortunately, there is no simple way (read, "practical way for most boaters") to test overall transmitting performance, other than to observe performance over time.
This is because propagation conditions vary enormously from one day to the next, from one hour to the next, and even from one minute to the next. Further, the variables of distance, horizontal directionality of radiation pattern, vertical angle of radiation, frequency, efficiency of the radiator, skill of the two radio operators, etc. -- all combine to make a definitive judgment very difficult.
By the way, this is why a lot of sailors with substandard setups believe they are doing just fine (because, sometimes, they can make good contacts).
Re: radiation pattern of an "L" antenna, it is somewhat directional, but not severely so. The advantage of using the triatic stay as part of the antenna is that it is "outside" the other stays, masts, etc. and less susceptible to radiation pattern distortion.
No, hf antennas don't need to be vertical.
However, if your vertical antenna running up the (wooden) mast and "insulated from everything" is at least 23' long, and if your tuner is well grounded to the steel hull, I'd say you will have a passable radio setup.
Bill
Last edited by btrayfors : 05-30-2008 at 12:05 PM.
