Navtex Antenna

[Tim Good]

Never used the Navtex which came on board my boat but when I turn it on then it just displays scrambled messages. I checked the antenna and it doesn't seem to have one. The box is there but no wire sticking out of the top.

On photos online I see the antenna just looks like a piece of thin wire like a car radio antenna. Is this right or is it special? I.e if I find an old coat hanger and stick it in, would that work at all?

 

[SlimRick]

Scrambled message usually means poor reception. My antenna looks like this one:

 

[sailorman]

Never used the Navtex which came on board my boat but when I turn it on then it just displays scrambled messages. I checked the antenna and it doesn't seem to have one. The box is there but no wire sticking out of the top.

On photos online I see the antenna just looks like a piece of thin wire like a car radio antenna. Is this right or is it special? I.e if I find an old coat hanger and stick it in, would that work at all?

My Nasa Navtex Pro is just as you say, just a ss whip. a ss welding rod of the correct dia & length should work

 

[PaulRainbow]

When i bought my current boat it had a very old NASA Navtex, which had an active antenna, looking like this one :

http://www.ebay.de/itm/NASA-NAVTEX-...D&orig_cvip=true&rt=nc&_trksid=p2047675.l2557

If this is the correct aerial for your Navtex, it's redundant here, so yours for the cost of postage.

 

[Heckler]

Never used the Navtex which came on board my boat but when I turn it on then it just displays scrambled messages. I checked the antenna and it doesn't seem to have one. The box is there but no wire sticking out of the top.

On photos online I see the antenna just looks like a piece of thin wire like a car radio antenna. Is this right or is it special? I.e if I find an old coat hanger and stick it in, would that work at all?

If it is a box with a stub on top, then there should be a screw on the side of the stub which holds a piece of SS wire in. Mine was knacked at the end of the wire, I phoned them up. They said the length of the wire is not that critical. So yes you could, mine is now about 30cms long. Iirc he said it works on about the same frequency as the medium wave radio, a coathanger works on that!
Stu

 

[vyv_cox]

The old NASA navtex antenna was a black box with a metre(ish) wire sticking out of the top. This was replaced with the type shown by SlimRick. The original one accumulated salts internally, shorting out the PCB inside. I have had some success in washing these deposits off. The version with the white plastic top was presumably an attempt to overcome this problem, although my early one had a breather hole that allowed moisture in, so the same thing happened. I blocked it off and sealed the base, since when it has operated perfectly for many years.

 

[Tim Good]

Interesting thanks guys!

Mine is the old type so will try with a coat hanger first. I also have one of the new types as SlimRick shows which came in the boat spares box. If the coat hanger doesn't work I'll try the white tube type!

 

[Ric]

The old NASA navtex antenna was a black box with a metre(ish) wire sticking out of the top. This was replaced with the type shown by SlimRick. The original one accumulated salts internally, shorting out the PCB inside. I have had some success in washing these deposits off. The version with the white plastic top was presumably an attempt to overcome this problem, although my early one had a breather hole that allowed moisture in, so the same thing happened. I blocked it off and sealed the base, since when it has operated perfectly for many years.

I had same problem, and like you sealed it up with sealant. However it continued to degrade due to UV (my boat in Med). I have now discovered that the NASA Navtex antenna works perfectly well under the deck, so it is now in a completely dry, shaded location.

 

[DanTribe]

What the others have said is correct and NASA antennas do seem to have a finite life but are cheap to replace.
BTW, you are aware that the messages don't appear instantly, but need a while [hours] to accumulate?

 

[vyv_cox]

I had same problem, and like you sealed it up with sealant. However it continued to degrade due to UV (my boat in Med). I have now discovered that the NASA Navtex antenna works perfectly well under the deck, so it is now in a completely dry, shaded location.

I think we were in Atlantic France or Holland when I first sealed it but the boat has now been in the Med since 2005. Quite surprisingly neither it nor the Weatherman that seems to have the same antenna case have deteriorated in the Greek sun. They are on the stern arch and too much trouble to move but, as you say, on another boat in Wales I just left the antenna in the wheelhouse, where it worked fine.

 

[Poignard]

I'm pleased to learn that the aerial works inside.In that case I will fit mine inside the coachroof when it comes back from being repaired at NASA.

I suppose the coachroof being wooden won't matter?

 

[vyv_cox]

My wheelhouse is all wood and perspex.

 

[Paddy Layback]

It doesn't need to be outside, this works fine, it doesn't get UV'd, damaged, shyted upon, etc.

 

[Poignard]

It doesn't need to be outside, this works fine, it doesn't get UV'd, damaged, shyted upon, etc.

So it even works inside a steel boat. I am surprised.

 

[prv]

BTW, you are aware that the messages don't appear instantly, but need a while [hours] to accumulate?

It's not so much that they need time to "accumulate", but that they are only broadcast at certain times. Bit like turning on the telly and complaining that "it isn't the News" - it will only be the News when that's what's being broadcast, in between it might be crap cookery programmes, soap operas, or costume drama.

The Navtex schedule is published in various places online (beware some might be out of date) and in almanacs. Turn it on at the right time and see if anything comes through. It's a much surer way than just wondering whether you've left it turned on "long enough".

Pete

 

[Ric]

Incidentally NASA are shortly bringing out a new Navtex model - no crappy screen - just a box which stores navtex messages that can then be downloaded via bluetooth to iPad.

 

[Paddy Layback]

So it even works inside a steel boat. I am surprised.

I would be surprised, but she's wooden, and the metal you can see is aluminium!

 

[franksingleton]

So it even works inside a steel boat. I am surprised.

No need to be surprised. It is a LW (about 600 metres). You can receive radio 4 LW inside your boat.

NAVTEX reception is or can be problematic and I have heard much misinformation over the years. I am far from being a radio expert but have a page http://weather.mailasail.com/Franks-Weather/Navtex-Reception-Problems-And-Cures. That is a plain man's guide - written by a plain man. You may (or may not) find it useful. I also give schedules around Europe.

 

[lw395]

Navtex is around 500kHz.
That makes it easily blocked by radiation from such things as mobile phone chargers.
It's also much lower power than the 198kHz R4 transmission, so giving it a fair chance with an outdoor aerial may be worthwhile.
If nothing else, it's further from interference sources on your boat.
With an outside aerial and reasonable weather, you should receive several stations, not just the nearest one. So you know you have a bit of margin for rain etc.
But reception can be poor in a marina up a river.

 

[coveman]

I have my aerial fixed inside the boat and it works fine. It is well worth leaving the set on for 24hrs and you may well find it will be OK - tends to be scrambled until it has been on for some time