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Old 24 July 2005, 15:53   #1
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Country: UK - England
Town: West Wickham
Boat name: Aries IV
Make: Scorpion
Length: 8m +
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ICS Nav6 plus - Interference?

About 17 years ago, I had my nice new sports cruiser fitted with Decca.

It was absolutely fantastic (for its era) PROVIDED I didn't run the engine (a V8 petrol inboard).

No matter how much I tried to suppress the engine's HT circuit and alternator, I couldn't get it to a level where the navigator was any use at all. The problem? Interference on the operating frequency range, caused by the engine.

Fortunately, GPS came along some time later, which - working at far higher frequencies (mHz rather than kHz) - meant that it still worked when the engine was running!

My concern is that Naxtex works on both 490 kHz and 518 kHz, both of which look pretty low frequencies, not dissimilar to Decca.

I expect to be running with a single large E-tec (or possibly 2 smaller ones say 175s, when they come out). Does anyone know if I am likely to experience a repeat of the problems that accompanied my (albeit relatively early) Decca set?

Thanks!

Chris.
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Old 24 July 2005, 17:11   #2
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Country: UK - Scotland
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Obviously, it's not possible to say how your new setup would be, but I ran a Nasa navtex, without a problem, on my previous rib and it used a V6 outboard.
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Old 25 July 2005, 07:15   #3
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Country: Australia
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Engine: Mercury 90 ELPTO
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Chris,

I've just fitted navtex to three vessels which were built here in Australia, but exported to a commercial fleet in the US. Two of the boats are 12m RIBs fitted with twin Evinrude E-Tec engines, the third is a 7m plate alloy boat with a 225HP Mercury Optimax, and all three setups work without a problem.
The units have been in service now for about 6 months, and no problems with the electronics have been reported. I was a bit concerned about RF emmisions from the high tension side of the ignition circuit and the coil packs, but some testing with a gaus meter indicated that the level of emitted RF was so small as to be unimportant. We don't use navtex here in Australia, but I've done a bit of work with it overseas, and haven't had a problem with any outboard yet.

Hope this helps. Cheers - Chris.
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Old 25 July 2005, 16:06   #4
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Country: UK - England
Town: West Wickham
Boat name: Aries IV
Make: Scorpion
Length: 8m +
Engine: Etec 250
MMSI: 235036477
Join Date: Dec 2002
Posts: 273
Thanks JW and Chris!

This is really helpful to know. In that case, I shall order the Naxtex, subject to it fitting on the console.

Much appreciated.

Chris.
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