Navtex Question

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emnick

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I bought a Navtex at the boat show and want to fit it during the winter lay up, (1) It says that the unit should be grounded? this is in addition to the neg from the battery. Am I right to say that I should ground the casing to the earth bond system/anode system? (2) Where is best for the aerial? di you get a decent reception if mounted on the stern rail or should it be as high as possible (FurunoNX300)
Thanks for any advice.
 
I have a Furuno NX something or other - quite a few years old. Antenna - which is pretty old fashioned by todays standards is on the pushpit. The ground goes to the underneath of one of the stanchion bolts which is nearby (wooden boat). Works fine.
 
I've got a NX300 as well and it's been just brilliant. Even when out of VHF reception it's been totally reliable. It should be grounded as you describe (mine isn't but will be for 2008 and hopefully will perform even better). The position of the aerial is not too sensitive and the pushpit is fine - that's where mine is located. Take a look at http://www.franksingleton.clara.net/navtex.html for advice.

Cheers, Ron.
 
Navtext is an H/F signal not VHF and uses ground wave propagation to the hight of the arial does not matter but, like SSB does need a radio ground which should be either the sea or a chunk of metal substantialy bigger than the arial. An external keel is good or a thinly encapsulated one, bonding system is fine provided you don't get interference but you can get noise on this as motors, alt etc cut in an feed back through the 12v neg if that is also connected (usually via alt or engine sensors & engine block if not directly connected). They do usually work without ground connected but you should get a better signal at longer range if it is.
 
I am curious.
My boat is fitted with a NASA Navtex PRO, and I have looked in the installation section of the manual. It just says for the unit, connect red wire to + supply and black wire to -, the orange wire for lighting can be connected to an instrument lighting circuit or just to +.

The aerial just says connect the aerial lead to the receiver with the moulded plug.

No mention of any special grounding of either set or aerial?
 
I've got the Furuno also, and it's a great bit of kit ... really user friendly. I did not connect the earth wire and the antenna is mounted below near the chart table inside a locker. Works fine where I am. Previously had a NASA (not user friendly) and used this with antenna mounted on pushpit and also with antenna mounted inside a locker .... no discernible difference! So, before you go through the hassle of running the antenna cable through the boat, give it a try with the antenna mounted below decks and see if works.

Alan.
 
To answer ...

a) There is no need to mount the antena at height, mine in fact is wedged behind the seatback in the saloon and whip goes up into toe-rail.
b) Grounding out of antena .... this would possibly increase antena performance in marginal areas and is usually done by connecting to a metal object in contact with surrounding water. Another way is to ground to a metal object that is bigger than the antena - creating a ground plane. (CB radios indoors often had metal plates for mounting the antena on that were large diamter to provide the plane).

My antena is not grounded and in UK waters worked fine ... in Baltic area I am now - reception is weak and I may find that grounding might improve it.

My suggestion ..... connect + / - ..... connect antena .... swith on - see what happens and then place where best suits you !!
 
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