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Author Topic: Maritime Mobile installation help  (Read 520 times)
KI4TMM
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« on: May 02, 2007, 07:11:22 AM »

I guess this qualifies as a mobile, Maritime Mobile.

Beginning. We live and cruise on our sailing catamaran Makai generally in the southern Caribbean and south America.  Next trip out in a few years we will be heading in to the Pacific for 5-10 years and am looking at upgrading/installing icom 7000 160-10m, 6m, 2m radio onboard.  Current equipment which I will keep as a redundancy for ham is the Icom 802, at 130 tuner, and Shakespeare 390 23 foot whip.  To stay legal in the US only a marine certified radio can be used on maritime HF, and because it also covers 2-30 MHz and is capable of TX on the ham freq. with in the range and I already own it makes sense to leave it onboard.

Rigging, it is common on sailboats to add the antenna in the backstay or side stay by cutting and adding insulators.  Our boat designer and builder and I agree this is a poor structural practice.  So that leaves whips or standalone antenna/s.

Price is not a great concern, I will buy or build the best I can afford that makes sense.  I don’t believe in installing a lesser quality item just to save a few bucks as it generally costs more in the long run to upgrade or be dissatisfied with performance.

Having said all of that I am trying to determine the best approach for installing and using the all band radio and a multiband antenna/s so that it can be permanently mounted if possible without interfering with ship operations

Any thoughts or directions would be greatly appreciated

Bil Thomas
KI4TMM
www.sv-makai.com
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K0BG
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« Reply #1 on: May 02, 2007, 07:33:54 AM »

I disagree with the stay idea.

I don't own it, but I have a friend who owns a 43 foot cat. The starboard stay is insulated at the top. The boat has been through two hurricanes, and the stay has never failed.

The bottom end is mounted in the fiberglass hull. The lightning ground was replaced with a large, well spaced inductor. An AH-4 is used to feed the stay, which is about 6 inches long. The ground side runs to the keel plate using a 3 inch wide strip of monel.

The stay in long enough (about 56 feet if memory serves) to allow the AH-4 to work from the top side of 160 through 6 meters. If an AT-120 or AT-130 (or one of the SGC units) were used, I'm sure you could work all of 160.

The radio was a 706, which was recently replaced with a 7000. Although perhaps not as efficient as some other methods, but for casual operation it works rather well.

Alan, KØBG
www.k0bg.com
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KI4TMM
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« Reply #2 on: May 02, 2007, 07:50:36 AM »

thanks for the quick response.

I have seen a few boats that we were cruising with have the insulators fail. With the modern mast rigging design of a raked and prebent mast without a backstay I will tend to error with the designed/builder recommendation in this case.  

It sounds like the icom 7000 will work with a longer wire antenna whic I can probably rig, but what about a whip and can i use my existing tuner in at130 in place of the AH with an antenna switch.

Thanks

Bil
KI4TMM
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KI4TMM
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« Reply #3 on: May 02, 2007, 07:52:01 AM »

Sorry misread.  I see that the at tuner will work.
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K0BG
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« Reply #4 on: May 03, 2007, 07:10:02 AM »

If your boat builder took the time to look at the various stay insulators, he'd find out they are actually stronger than the stay itself. Those that I have seen fail were improperly installed. I was in Ft. Pierce, FL just recently. I saw first hand how some people maintain their boat, and it isn't pretty. I'll stand behind what I said before.

If you have an AT-130, I just use it instead of purchasing an AH-4. You'll need two things. One an antenna switch which is a no brainer. The other is a 4 pole double throw switch to switch the control lines between the radios. Just about any will work as the load is very low. Four pin Molex connectors are available from Radio Shack, and wiring such a switch would not be a difficult task.

The main difference between the couplers is, the AT-130 has an additional inductor to allow the coupler to tune a short vertical (25 feet of so) down to about 1.6 MHz. The AH-4 will do it too, but the radiator has to be over 60 feet in length. Neither are very efficient at these frequencies, but you'll get by at least for short distances. One good aspect of doing it this way (using switches), is you won't be over loading either front end.

Alan, KØBG
www.k0bg.com
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KI4TMM
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« Reply #5 on: May 03, 2007, 01:46:18 PM »

Thank You very much.  That saves me money, weight, and space
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K9FV
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« Reply #6 on: May 09, 2007, 11:30:58 AM »

Just to agree with Alan on the strenght of stay insulators - I've had my backstay rigged with insulators for the last 20+ years....  Just read the specs on a good Norseman (or other) insulator - more than the stay it insulates.  and they are sooo convenient.

Good luck and have fun,

Ken H.
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