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Old 20-04-2009, 11:07   #1
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SSB antenna and steel boat

Hi folks:
This is the first in a blizzard of information-seeking posts that will be flying your way in the next few weeks.
I bought a Passport 41 March 10 and I plan to ship out on May 10 and my feet are to the fire.
First post has to do with SSB and GAM antenna. My boat is steel, love it or hate it. I had insulators on the back stay when I bought it and an Icom M700PRO SSB. The previous owner said reception was great. I decided to replace the backstay due to its age and the rigger suggested the GAM antenna so as to avoid the insulators.
When I was at the sail show in San Francisco yesterday one knowledgeable chap told me that the GAM will not work with a steel boat/backstay combination. The backstay would have to be insulated for the GAM to work. Something about two wires surrounding a third (the backstay) and energizing the whole boat.
Another knowledgeable guy – an electronics retailer and installer—said the combination would be fine. This is the worst possible situation where experts disagree and me, the schmoe, knows nothing.
Anyone out there with experience with GAM and or steel boats?
Help me, boys.
Pete.
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Old 20-04-2009, 11:17   #2
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30 year professional electronics guy here. I'd stick with an insulated backstay.

Steel hull will provide a great counterpoise (RF ground).

Don't fix it if it ain't broke.

Steve B.
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Old 20-04-2009, 12:47   #3
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Steel boat owner here, and I agree with my neighbor on the next island over. Insulated backstay WFLLT (Works Fine, Lasts Long Time).

73,
Steve
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Old 20-04-2009, 14:07   #4
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I agree that an insulated backstay -- or an insulated "alternate backstay" -- is the way to go. On a steel hull, you've got an excellent built-in RF ground...the hull itself.

If you don't want to break up the standing backstay with insulators, just rig an "alternate backstay" made of insulated s/s lifeline. Hoist one end with a spare halyard, tie the lower end off on the pushpit on either side. Locate the tuner just underdeck, and tie it to the hull.

See pic on my 42' Perry-designed sloop:
http://wdsg.com/gallery/main.php?g2_...geViewsIndex=1

Alternate backstay antenna shown with lower end tied to pushpit on starboard side has been up for almost 20 years and 20K sea miles. Still works like a charm.

Bill
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Old 21-04-2009, 21:05   #5
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Thanks guys for advice. I am going back to the original system of insulated backstay and sending the GAM back. Why mess with something tried and true?
Pete
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Old 22-04-2009, 16:27   #6
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Well, I have to add to the noise level by noting I'm on the next island up (Fidalgo) with a steel boat, but I have no clue which method is better but I am paying attention and taking notes.

Currently have insulated backstay but have never turned on the SSB. Radio is next winter's project.
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Old 22-04-2009, 16:40   #7
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(Hey, neighbor!)

My install is happening in the next few weeks; happy to share any lessons that fall out of it. Steel hull makes for a superb ground plane... key is good solid connections and very low-resistances to the tuner. I'm going to experiment with a big industrial mica capacitor to establish RF ground whilst avoiding a DC loop...

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Old 22-04-2009, 16:55   #8
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Prior owner and builder did the SSB and reputedly it works great. I rewired from tuner to backstay, as the sun did a number on the wire insulation. I never got around to attaching the wire to the tuner because that will require me to empty the bottomless pit called 'cockpit locker.' Someday. Don't really need SSB right now. Shoot, I hardly even use the VHF. Or radar. Or chart plotter.

Card carrying Luddite here.

But I use the depthfinder. I'm not crazy. Goofy maybe, but not crazy.
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Old 24-11-2015, 07:56   #9
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Re: SSB antenna and steel boat

Here's another steel boat SSB question. Situation: Icom 725, 23' whip, tuner just under antenna inside steel hull. Grounds by copper plates to hull. Recieves well enough for me to listen to Bahamas net from Floria panhandle. Does not tune on any frequency, can get only 10% transmit power around 14 MHz, other bands it shuts off when I press the PPT. Idea: Is it possible that the antenna wire leaving the tuner and going through a small hole in the steel deck to reach the whip is leaking RF to ground (the boat)? Other possible problems? The radio itself has been plugged into a ham setup and works fine. Thanks. --Tim
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Old 24-11-2015, 08:59   #10
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Re: SSB antenna and steel boat

You didn't say which antenna tuner you have. Assuming it's an automatic antenna tuner designed for end-fed antennas (random wire, backstay, marine whip, etc.), then....

1. feedline from tuner thru the waterproof deck fitting to the whip should be GTO-15 wire;

2. the copper plate attached to the steel hull is totally unnecessary; direct connection to the steel hull from the antenna tuner ground lug would be sufficient; and

3. this setup should tune all marine and ham frequencies easily.

Unless....

1. the tuner is busted or not receiving DC power and the proper control signals from the transceiver;

2. connectors are poorly fitted and/or corroded;

3. there's a short or open somewhere in the coax and/or the feedline.

Bill
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Old 24-11-2015, 09:23   #11
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Re: SSB antenna and steel boat

Thank you. The copper straps are 6" long and just go from the ground lugs to the nearest steel. The feed is GTO-15. The tuner is running when I press "tune" on the radio, but I'll try tuning from it directly. I'll also look for an antenna ground. It's a maze for a newby.
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Old 24-11-2015, 09:41   #12
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Re: SSB antenna and steel boat

OK. Sorry, I misunderstood your use of the term, "copper plates". These are apparently just copper straps to the steel hull. That's OK, but you need to be sure they're perfectly clean where they attach to the hull.

You said "lugs". Which lugs? The ground straps should attach ONLY to the tuner ground lug. Not lugs.

"look for an antenna ground"?? No....the steel hull IS the antenna ground/counterpoise.

Bill
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Old 25-11-2015, 00:38   #13
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Re: SSB antenna and steel boat

Be careful of how you ground to the steel hull or electrolytic corrosion could be a problem. What you need is a signal ground and not a DC chassis ground. Icom makes a ground strap which includes a capacitor which whilst allowing AC signal ground prevents DC current flow.
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Old 25-11-2015, 01:32   #14
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Re: SSB antenna and steel boat

I know the OP is likely well under way by now but since this thread has popped up again....

We have a steel boat, ICOM M802, KISS grounding wire and AT-140 and are quite happily using the GAM split antenna. Easy to use, can roll it on / off when needed and excellent reception (currently picking up Brussels from mid-Portugal).

For anyone looking for a GAM, I'd say it's money well spent.

n
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Old 25-11-2015, 06:31   #15
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Re: SSB antenna and steel boat

By lugs I meant the grounding studs on the back of the radio and the tuner, confirmed as zero ohms stud to hull. By antenna ground I meant the possibility that the high voltage wire lead to the antenna was grounding to the hull where it passed through the hull. Antenna to hull cold was 5+ Kohms, but I'm replacing the small hole with a ceramic insulator anyway. Let me look into the Icom grounding strap mentioned. I'm not sure that I understand this when it gets beyond having really good gounding for the two units. Thanks. --Tim.
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