navtex reception

MarkJohnson12345

MarkJohnson12345

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Joined
23 Dec 2004
Messages
1,177
Location
Swansea Wales UK
www.markjohnsonafloat.org.uk
Been away for a fortnight to and around the Scillies and was very disappointed with Navtex reception. The set did pick up some data when set to the all inclusive programming, but then was decidely piccy in what it received.

In Swansea I cannot pick up Niton which covers my area. My previous boat did not seem to have any reception problems in the same area.

I have read an article in Frank Singletons weather page were he covers the reception problem. He says that the ariel is not earthed properly.

His suggestion is to take the negative lead from the Navtex and connect it directly to the boats anode.

Anyone tried this, or have any other solutions?
 
What set do you have?

My NASA Navtex Pro with switchable aerial picks up Niton E,K and I, Corsen A, and sometimes, Oostende, from Falmouth with no problem. The aerial is on the pushpit.

As I is selected for 490/Local/Niton, Las Palmas also comes in "loud and clear" when switched back to "International"

Could you have an aerial problem?
 
Tend to agree with philip_stevens.

I can get international stations on a NASA Clipper Navtex in the marina on the west coast of Scotland and the national ones once out of the marina with the aerial mounted below.
 
Mark,
I am in phase 2 in Swansea and do not normally get a problem with either Niton or Portpatrick. We are just slightly closer to the Isle of Wight than Portpatrick.
However, there is an awful lot of QRM (man made noise) in the marina, which comes off all the flats around, it may be this which is causing the problem.
What antenna are you using?
Earthing should not normally be a problem and usually can only improve the system...unless you have a completely isloated engine installation, which is rare these days.

Steve.
 
My Navtex is old bog standard one, single frequency.

Had one in the old boat, in phase two, Swansea, and it worked well. I bought this one from Ebay, as new, so am begining to wonder whether its a duff one.

All in all, I am disappointed with Navtex, the broadcast times never seem to be on time, but maybe thats because I have not had a good working set.

Might look around for alternatives now.

Regards
 
Mark,
Thats not a problem...I think my Navtex antenna will probably work on yours...plus I have a wideband HF antenna as well.
Failing that we'll try a long wire.
I could bring a RF Frequency generator with me and test the sensitivity of it for you.
I'm on N Pontoon. There most weekends.

Steve.
 
I installed a NASA Clipper navtex this season and am just going through the process of getting the reception right.

I saved a bit of work and started with the 'active' antenna mounted below to see how well it works. Answer, not very well but slightly better at sea than in harbour (Gosport marina).

I read Frank Singleton's excellent advice on his site. While in Alderney this week I experimented by grounding the antenna - attaching a wire from the screen of the co-ax antenna lead through to the bolt of a sacrificial anode. Bingo - excellent reception in Alderney of Corsen, Niton, Ijmuiden and Ostende. This was with the antenna position unchanged and on the same mooring buoy as before adding the ground. Before reception poor, after excellent.

So I've discoverd on my installation that adding an antenna ground does the trick.

Being a bit of an experimenter, I'm wondering if all I'm doing is compensating for poor antenna location with a good ground. So next I'll try without a ground, moving the antenna to see if that works too. I rather think it will, because (a) some people get good reception with no ground and (b) the manufacturers say (to paraphrase) 'Pick a good location for the antenna' not 'Stick the antenna wherever you want but make sure you ground it'.
 
I also had problems with Navtex reception using a NASA Target Navtex Pro-Plus with the supplied stub aerial mounted by the previous owner inside the saloon; obviously not an ideal arrangement. As a very simple experiment, I plugged into the aerial socket a bit of 75 ohm tv coax, and attached the signal wire with a pipe clip to a metal stay connected to one of the long mast shrounds. No fancy earthing. (Must remember to unplug it in thunder storms!) The bodged aerial was a dramatic improvement. With my boat currently in Stockholm I now get excellent reception, not just the local Baltic stations in 2-300 mile radius but also Ostende, Niton, the Med and Turkey! A lot of cable laying going on in the Sea of Marmara! Having said that, I find the Hamburg weather service on Weather Fax, picked up on a NASA Weatherman on short wave, complementary to Navtex. It has various f.o.c ., software programmable services covering the Baltic, N Sea, Channel, Med and Atlantic. It is updated much more frequently than Navtex and, most importantly, includes 5 day outlooks.
 
An update to my posting above.

During the season, I moved my antenna to alongside the GPS antenna on a pole rising above the pushpit. Initially the results were disappointing, and reception was no better than with the same antenna mounted in the saloon.

Then I checked with an electric meter the two places where I had soldered co-ax connectors (that is four solder joints in all). These joints were necessary to extend the cable and also to allow it to be threaded without connectors through small gaps. I found I had made the joints badly. I resoldered them and at once started getting excellent reception- getting the usual messages from all over Europe and, at night, North Africa too.

So the results of my experiments are that the NASA antenna works well if mounted in the open with a good view of the sky. It doesn't need a separate ground. If mounted badly, a ground sometimes makes up for the poor siting.
 
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