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Old 06-03-2004, 20:12   #1
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Insulated Shrouds

Many boats have installed insulated backstays with tuners so that SSBs and Ham radios can make use of multiple frequencies. My question is whether anyone would dare use a side-stay on a 3-shroud system in such a manner.

Would you install insulators on one of the only three wires that hold up your spar?
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Old 07-03-2004, 00:12   #2
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I'm not sure I would chance it. To have a shroud seperate could be catastrophic under load. When a mast brakes it's almost always to the side. Where the backstay is usually backed up by the mainsail/ mainsheet and boom. And the forestay tension is usually controlled by the backstay.
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Old 07-03-2004, 04:11   #3
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Shrouds as Antenna

MOSTLY RETRACTED SEE LATER COMMENTS:

Without compelling reason, I would not even consider utilizing the shrouds as an HF antenna - so please tell us why you would (presuming you are faced with unusual circumstances - and not mere idle curiosity).

It would be problematical to engineer around the inherent difficulties of such an installation:
1 ~ Possible strength issues, per Delís reply.
2 ~ Reduced Antenna Length, due to initially shorter stay, and maintaining 7' clearance from deck to lower insulator - you donít want anyone to touch an antenna during transmission, and insulating the spreader(s).
3 ~ Possible interference from the (more or less) parallel mast - though a Radio Guru might say Iím out to lunch on this one.

In short, the insulated Back-Stay makes a nearly ideal Antenna - so why screw with success?

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Old 07-03-2004, 06:46   #4
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"so please tell us why you would"
Well, I certainly wouldn't without checking with you, Gord.

"the insulated Back-Stay makes a nearly ideal Antenna - so why screw with success?"
I do not have a chance of a backstay. I have a full battened, outrageous roached, long boomed main; and no more boat back there.

I thought the insulated sidestay a risky concept, but a ham who has sailed big boats longer than I have suggested it. So I thought I would get more opinions on it the best way I knew.

I am investigating all options. Presently, I am considering tossing the tuner idea and sticking with properly matched, specifically tuned inverted vees for the few frequencies I am interested in; and hoisting them from the spreaders only when I want to transmit. Makes them less available for emergencies though.

I also understand that short antennas on the stern rail, with interchangeable coils are an option, with inferior radiation patterns, but I hope to investigate them further as well.

I think your points are all valid. Anybody with a different opinion?
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Old 07-03-2004, 07:51   #5
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I knew there must be a good reason to contemplate such a thing. You are right to examine all thealternatives you can imagine. Maybe the folks at your HAM course can offer some suggestions.
Good luck in solving an interesting dilemma!
Gord
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Old 07-03-2004, 10:46   #6
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I think using a shroud is a comprimisefor all of the reasons stated abouve. One options is the use of a 23' whip antenna. Shakespeare makes one that has a folding base. You could use this at sea, then use a long wire or inverted V antenna when anchored. I would use one of hte auto tuners either way. I think trying to use tuned antennas would be too limiting on a boat. You might tune it for your most used frequency range, then use the tuner for other times. Check this link for more information on the whip...

http://www.onlinemarine.com/cgi-loca....htm?E+scstore
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Old 08-03-2004, 04:58   #7
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Shrouds as Antenna

Iíve given your dilemma some further thought, and retract my previous comments against utilizing the Shrouds as an HF Antenna. My objections were probably overstated.

Assuming that you can get an adequate antenna length (35 Ft works well /w most Auto Tuners) from your particular insulated shroud & spreader arrangement; your inventive proposal could be the best answer. Consult your Tuner manual for specific length recommendations.

Ronstan (for one) provides some technical specifications on their website at: http://www.ronstan.com/marine/
which suggest that backstay (or in your possible application Ďshroudí) insulators may be as strong as the wire itself.

Ie:
From their typical Wire Rope Breaking Loads chart (7 x 19 Type 316 S/S)
3/16" Wire BL = 2882 Lbs
1/4" Wire BL = 5027 Lbs
and
From their Insulator Specs:
3/16" Insulator BL = 3050 Lbs (Stronger than wire)
1/4" Insulator BL = 5430 Lbs (Stronger than wire)

My concern /w unintentional personal contact with a transmitting antenna (5000Volts!!!) could be satisfied by effectively insulating the lower 7 Ft of Antenna/Shroud & Chainplates (Teflon Tubing), allowing for a near-deck lower insulator. I suspect Iíd prefer the upper insulator to be beneath the lower spreader, but an adequate (?) means of insulation at this point could also void my concerns here.

A 23' Whip Antenna is another possibility, though ungainly. What about rigging a dedicated Long-Wire Antenna from the Mast-Head, down to the aft-outer edge of one of your transoms (Iíd forgotten we were dealing with a Catí)? If this arrangement still doesnít clear your large-roached mainsail,; Iíd consider installing an external masthead sheave, for use with an ďat-anchorĒ (or emergency) hoistable antenna (per 'Exposure' above).

Some possible advantages to utilizing the Shrouds are reduced lead wire length (Radio - Tuner - Antenna) and a Ďfriendlierí environment for the Tuner (than the conventional cockpit locker/lazzarette).

I think youíre on to something - keep up the innovative thinking!!!

Regards,
Gord
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Old 08-03-2004, 05:19   #8
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Thanks for the comments. I'll continue working on it.

One other point against the sidestay and tuner option, however, is that it brings radiation into the living area. Apparently the wire from the tuner to the antenna radiates significant energy. On Cat Tales, this would be in one of the bedrooms. A 2002 article in Ocean Navigator suggested that the tuner shouldn't be in a living space for this reason, and indeed should be 5 feet from a living area. I just happened to look through it on Sunday, after posting.
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Old 08-03-2004, 06:55   #9
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One downside to using the shrouds is that there are other pieces of metal in proximity and nearly parallel to the radiating element. Namely, the other shrouds and the mast. They will have a strond negative effect on the performance of the antenna, especially if they are "grounded".

Could you run a wire from one of the bows to the masthead? It may only interfere when using a spinaker.
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Old 08-03-2004, 10:10   #10
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EXPOSURE:
I too, had some concern about antenna proximity (& parallelism) to the mast (& other shrouds); but Sonosailor's webpics seem to indicate an outer shroud (Masthead - Outer Hull) that is fairly well separated and divergent with these other metals. This outer sgroud may not pass thru' the spreaders - I couldn't tell.

SONOSAILOR:
If my above is wronge - then I wouls share Exposure's concerns.

Regards,
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Old 16-06-2004, 13:12   #11
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Well, I finished my Ham course - got 95% - highest in the class

I have purchased three "loaded" antennae: one for 15 metre, one for 20 metre, and one for 40 metre. Each are "Hustler" style, if you are into antennae. They each have a primary body 4 feet in length, incorporating coils to simulate a 1/4 wavelength, and a narrow "stinger" that is bolted to the top and moves in and out for fine tuning. These will be used, one at a time, on the far side of an economical marine automatic tuner, then wired to a Kenwood TS-50. The antenna that is in use will be connected to the stern rail using a trucker-style connection. The stern rail, bow rail and interconnected safety lines will serve as the grounding plane initially. If a better ground is required, I may have to glass in some copper mesh to the inside bottom of the hull(s).

I intend to get a modem capable of managing Pactor II.

I will also keep on board a home-made inverted vee antenna for 20 metres, that I can hoist to the spreaders. This will be an alternative if the other antennae don't work. It does not need a special "ground" as part of the antenna works as the ground.

Launch is still a week or so away, and I am still working out many problems. However, I will attempt to keep you folks informed as to how (whether?) this all works.
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Old 16-06-2004, 21:04   #12
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For sometime, I hoisted an antenna on a spare halyard when I was using the radio and stowed it when not in use. If I intended to use the radio more frequently, I would hoist it out of the way of the sails.
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Old 17-06-2004, 10:33   #13
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Temporary Antenna

I was considering the temporary antenna as an option as well, and was thinking of how it could be used in different circumstances. My idea was to have it come from a stern corner, but have it such that I could temporarily stow it by pulling it forward and connecting it alongside a sidestay.

However, combining your idea with Exposure's idea of using a bow to masthead configuration is something I might try. The tuner could then be placed in the bow, and the only real time I could not use it would be when the gennaker was in use. That also allows the gennaker halyard to be used for hoisting the antenna. The tuner and the output radiation would also be much further from living areas, and from normal deck habitation while at sea. Onboard a Tobago, the coax wiring wouldn't travel through high profile areas either, so easy to install "Bristol-fashion.

I'll keep that idea in my back pocket while I play with the toys I already have. All good stuff.
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Old 18-06-2004, 21:41   #14
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Hey,

Well I read a post the other day where you asked about using insulators on standing rigging other than the back stays for the SSB antenna. Well Iím walking down the dock to run off to work for a few hours and what do I see Ė It is a Fisher 37 ketch rigged. It is new to the dock so I walk over to take a look. There it is the fore mast, starboard side stay has insulators. Then I notice on the aft mast, from the spreader there is another insulator on one of the two lower stays. Neither are back stays. The boatsí name isĒFinesseĒ. It has Destin FL on her stern as home port. Iím a few miles away in Shalimar FL. Havenít met the owners yet. I am looking for them. Iíll try to get a couple pics if youíd like.

http://www.yachtworld.com/core/listi...59&slim=quick&

Found a site with a boat like the one here in FL.

Gary
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Old 14-07-2004, 19:09   #15
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I am happy to report that I got my SSB hooked up this weekend and managed to complete the modification for Ham band use today. The rig is an Icom IC-M600. It is and older unit.

It came with my boat along, with an AT-120 antenna tuner. Both were installed, but never wired. I ran 3" copper foil from the rig to the tuner in the aft port hull. From there I installed an insulated wire to the port backstay that has insulators top and bottom. The foil is also grounded to a large dyna plate mounted outside the hull, just under the tuner.

I checked into the maritime net on 14.300 today. The net control in Arizona could not copy me well, but a relay in the Turks and Caicos copied just fine. I plan on installing more copper in the port hull going forward, and also to install some in the starboard hull, at least in the mid and forward sections. I'll tie all of these to the through hulls as well.

There is also a mod to make this radio suitable for email, I'll do that down the road when I get a Pactor modem.

Hey Sonosailor, Perhaps we could have a chat after you get your ticket in the mail.

Woody (AA7HN)
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