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Go Back   SailNet Community > On Board > Gear & Maintenance
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  #1  
Old 04-12-2007
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SSB antenna

Hi guys

I am soon going to be collecting a boat from California and sailing it to New Zealand. The boat doesn't have an SSB (has a Global Star phone) and consequently doesn't have an antenna incorporated into the backstay or any form of ground plane (Dynaplate). I also won't have the time between arriving in the US and leaving for NZ to have the required mods done to the backstay oir absence of ground plane(too much other stuff to do).

Has anybody had any experience with whip antennea for SSB and their effectiveness for long range communication?

I've sort of established that there is a combination of radio, antenna tuner and 16 foot whip antenna that produces results. The question obviously is: How good are those results. . . . really. . . . not dealer opinion.

Any ideas (or even better, actual experience) out there? And given that I know squat from radios, let's try and keep this down to single syllables please.

Cheers
Andre
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Old 04-12-2007
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While you don't say what the boat is, there are other ways to setup an antenna and ground plane for SSB. If the boat has a metal hull or large metal tanks down below, for fuel and water, you can often use those to create a large ground plane fairly quickly.

There are also antenna designs that do not require a ground plane.
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Old 04-12-2007
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Antenna's

Try this for an antenna. Gam Antennas If you are just doing a delivery you can take it with you when your done.

Fair Winds,

Bill
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Old 04-12-2007
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Omatako,

It would be easier to answer your query if you had mentioned the type/size of boat and whether you're talking about ham SSB or marine SSB or both.

The easiest way to put a HF/SSB rig on the air with RELIABLE long-distance communication is to construct one or more vertical dipole antennas. See my posts on constructing a marine dipole: Gallery :: Constructing a Marine Dipole Antenna

and on tuning a marine dipole antenna:

SSCA Discussion Board :: View topic - How to Tune a Marine Dipole Antenna

A vertical dipole antenna will outperform any other seagoing antenna you can put on a sailboat. Period. They are, however, limited to single-band operation for transmitting; they receive well on all bands.

For many years when chartering, I carried a small HF transceiver with big alligator clips on the power cord, and a dipole antenna. It took only a few minutes after stepping aboard to be QRV (ready) to transmit on the ham bands, and to talk with friends around the world.

Good luck on your delivery.

Bill
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Last edited by btrayfors; 04-12-2007 at 04:25 PM.
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Old 04-12-2007
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Inverted V

I was thinking of using an inverted V antenna using a wire cored halyard. Over the top of the mast either abeam or length wise.

I want to install some of my ham gear on my boat as well. There a several installation options and what makes me think the most is the termination of the coaxial connection section of the antenna to a point where it will be easy to hook to the back of the radio. The most obvious that comes to mind is to create a termination block on the cabin top above the nav station, with strain relief for the antenna halyard, and cover it when the antenna is disconnected.

I know for your case you might just want to just run the cable through the companionway to the radio and not modify the cabin top.

Just my 1/2 cents worth...
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Old 04-13-2007
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Hi guys

The boat is a Morgan 44 GRP, sloop, what more can I add? The radio I was thinking of is an Icom IC-M700 or something like that. It'll not be HAM, just marine SSB. Unfortunatley I have no idea what tanks etc. are fitted. Believe it or not I haven't seen the boat in the flesh yet. On my previous boat I had a Kenwood, can't remember the model, with an antenna tuner and it worked a treat on the backstay with no real ground plane to speak of. I spoke to South Africa and Australia from Maldives with pretty clear voice.

Bill Mc
The GAM thing looks pretty good to install in a hurry and then make it more permanent when I get the boat home. Oh, and it's not a delivery, I am buying the boat for myself. I'll get a hold of those guys and have a yarn with them. Thanks for the link.

Btrayfors (Bill)
Can an antenna like this be used with a tuner? If the dipole is cut for a certain frequency then (to me) that's no different to a backstay which is fixed length. If a tuner is used with this, is it fair to believe that more than one frequency can be transmitted? And how would one install one of these on a boat? I guess the two legs of the dipole need to be running in opposite directions so it seems this setup would take up some space.

I also have seen catamarans with long whips (16 feet) on the back of the boat and this is why I figured this may be the easiest way. I'm just not sure about range for transmitting. There'll be times when I'm going to be a heck of a long way from anybody else but HF really doesn't care about that does it?

You guys can probably tell by now that I don't know a whole lot about these things.

Thanks for info so far.
Andre
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Old 04-13-2007
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Andre.

Your not on your own there with HF/SSB/HAM, my question is does the GAM antenna need to go on the back stay could it go on one of the side stays. I have seen these automatic antenna tuners for @$450us, I take it, they will adjust the length or the antenna internaly ! the radio is $999us.
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Old 04-13-2007
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If you want to do it fast and cheap, just put a linear electric cable with two plastic isolators that reaches the tuner, if you have one, Not the best performance, but fast and simple! You rig it with an halyard when you need it or you mount it permanently on the mast. Mine is mounted on the spi halyard and comes down close to the shrouds. Works ok allround.
good luck
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Andre,

OK. With the additional info you provided (boat size, it's YOUR boat, the M700 and tuner, your interest is in the marine bands, not ham, etc.), here are some options:

(1) Most versatile. Install either a Gam antenna (I can't believe I'm saying this) or, better, an "alternate backstay" antenna consisting of a length of insulated s/s lifeline at least 23' long. This can be hoisted with a spare halyard, and the lower end tied off to one side of the pushpit. With either option, locate the tuner under the deck as close to the base of the antenna as possible. With both options you need a good RF ground. Easiest of all, but not very efficient: run a wide copper strap from the tuner to the nearest bronze thru-hull. To increase efficiency, add radials under the deck (insulated wire, any size, the more the better). A couple of 1/4 wave radials (length in feet = 234/Freq in mHz) for each desired band would be sufficient.

(2) Most efficient for long-distance communications -- one or two vertical dipole antennas, constructed according to data referenced in the links I provided above. This is an extremely effective long-distance antenna. A vertical dipole is best rigged forward of the mast, about halfway between the mast and the forestay, tied off to a toerail. This placement works well when at anchor, in a marina, or when under power. When sailing, it's only necessary to undo the lower end of the dipole and pull it back into the shrouds. It will work fine there, but with a bit less efficiency. The coax feedline should be run off at a right angle, or as close to that as can be easily done. Usually, this means running it back to the mast high above the deck, then down the mast to the rig. On my boat, I've fitted a little custom-built "black box" attached just below the gooseneck, which contains connections for the coax and which is permanent. You may find it easier to feed the coax thru a deck ventilator, or a hatch or a s/s coax deck fitting or anything handy.

The dipole is a single-band only antenna. When tuned, it does not require a separate tuner...attaches direct to the radio. While it is possible with a tuner to transmit on additional bands, this is not a good idea and is very inefficient.

If I were making the trip you contemplate, I'd choose both: a versatile backstay antenna with tuner and good RF ground system which could be used on any frequency, and vertical dipoles for 14mHz (MM net) and 21mHz (Pacific Maritime Net) ham bands for really efficient long-distance communication. If you are not a ham or there's no ham aboard you can listen to these nets which have a wealth of information and, in an emergency, you could use them to seek help. For the trip you're about to take, ham radio is much more useful than marine SSB, IMHO.

Re: verticals, they can be very effective. However, for a very long ocean voyage I wouldn't want a 23' vertical (or even a 16' vertical) whipping around back there in a seaway. Not a good idea, IMO. They do make good emergency antennas, though, in case you lose your mast. I have a Hustler mobile antenna mounted on my pushpit and wired to an antenna switch near the rig. I carry the mast and resonators for several bands below, ready to deploy in an emergency.

Bill
WA6CCA

Last edited by btrayfors; 04-13-2007 at 10:13 AM.
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Old 04-13-2007
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Btrayfors

The dipole seems to be (with great respect to the design and your recommendation) a bit messy with wires all over the place. It is also my belief FWIW that you're going to need this radio thingy most when there's 80 knots across the deck and all hell is breaking loose. So the prospect of loose wires in the rig and on the mast and running through hatches that as a result don't really close (remember this is a temporary fitting for one trip only) runs deeply counter to my fetish for neat and tidy.

I'll be more comfortable with the GAM pasted onto the backstay for this trip which by the sounds of your comment will probably give me reasonably good performance across all the bands. I did understand that correctly, didn't I? I am not a ham and SWMBO knows only about ham that goes between slices of bread so those other freqencies you mention are probably of no value to me.

And in your opinion, is the Icom M700 with a suitable tuner satisfactory for this type of setup?

SimonV, what radio are you recommending at $900? A new IC M700 costs about $1900. Your estimate on the tuner is about what the dealer I spoke to came up with. And while I'm on the cost of the radio, who knows of a good used-radio dealer in the San Diego area that may have a good and reliable used unit for sale?

Please keep in mind that when I get to the US, I have two weeks to prepare a boat that I am seeing for the very first time when I arrive, for the voyage. This is very definitely not just about radios!! I need something that finds the best balance between speed of installation, reliability and performance. Gam starts to sound better each time I say it :-).

Thanks so far
Andre

Last edited by Omatako; 04-13-2007 at 10:59 PM.
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