NAVTEX reception

[Kantara]

I recently installed NAVTEX on my boat. While I get superb reception of Malin Head transmissions, those from Portpatrick get extremely garbled and usually result in a Lost Signal. This happens on both National and International. Is this me, or do others have the same problem?


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[Twister_Ken]

Can't comment on Portpatrick, but I know mine (Nasa Target Pro) often takes offence at being asked to work in marinas - maybe something to do with all the other electronics around, or several hundred masts degrading the signal. Much better on a mooring or at sea. It can be so bad that I don't get Niton (Isle of Wight) when in a Solent marina.

Could this be your problem?

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[Guest]

We have an ICS Navtex, one of the older ones with a fax roll, we elect to only receive Niton which gives us all the info we need for across Channel and down West, never had a problem, even in a marina. Naxtex was our principle source of weather data during summer criuse, arial is mounted on pushpit.

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[davehu]

I am thinking of getting a Nasa Navtex. I can understand reception being poor in marinas, how about the West Country rivers, such as the Dart and the Yealm where the VHF coastgard reports are also dodgy. Do you find it best to have the 490 or 518 switched on for coastal work. We are based in the solent. Would you go for the Nasa Pro again or the Clipper unit

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[Kantara]

I don't think it's electronics - unless it's my own boat's. To begin with I thought it was because I was deep in a sea-loch (although Malin Head came in loud and clear), but the same thing happened off Ardnamurchan Point.
It may be that there are too many hills in the way, but in that case that would affect any transmitter on the same coast.

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[Kantara]

Maybe they use different signal strengths for different stations. When I was testing it, I did get signals through from Niton.
I was around 100 miles away from Portpatrick at the time, but I thought these stations were meant to cover large areas

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[claymore]

The skipper of VIC 32 which is a Clyde Puffer converted to some charter work was saying that his reception could be spasmodic - It didn't seem to like being in Craighouse - but then neither did my vhf - I wonder if its a line of sight thing and as you suggest- the signal just doesn't happen in some places. Other Scottish sailors have commented some time ago on this when I was thinking of buying a PC programme - I seem to remember a fairly mixed opinion on whether or not it worked OK

<hr width=100% size=1>regards
Claymore
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[AlanPound]

We fitted an ICS 6, and had horrible problems getting any kind of reception, anywhere. Fitted extra grounds, power supply filters etc all to no avail. The unit and aerial went back to ICS, again with no effect. Had several "full and frank exchanges" with ICS ("That receiver is good - perhaps too good" !!!!!!!!), then finally gave up in disgust.

A few months later, our Heart charger/inverter had a 'heart attack' and died in a puff of smoke. We removed it (previously, turning it off had caused no improvement to the Navtex).

Result - instant, perfect Navtex reception...

It seemed that the way it was fitted, the Heart unit never was entirely "off". The charger part was always hooked up to the battery, and somehow, some circuitry or other was always running, and was making loadsa noise...

... humble pie in respect of ICS...

Alan

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[Oldhand]

Navtex frequencies are very prone to interference from many sources, some of which may be onboard your own boat. To avoid problems from "local" sources a masthead mounted active antenna is preferable in my experience. Using a passive long wire (backstay) with another receiver has proved slightly less successful, probably due to onboard interference.

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[Twister_Ken]

Ah but

Given that Malin and Portpatrick are broadcast on the same frequency, maybe it's not interference as much as no clear signal path?

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[Chris_Stannard]

i have an ICS 6 with the antenna on the pushpit. I sail in the Solent area and cross channel. I keep the boat in East Cowes and get reception from the French Meteo and Dutch coastguard as wll as Niton. With the frequency of Navtex the position of the antenna should not make much difference to reception so if your antenna is masthead try the set on a rail mounted antenna to see itf it makes a difference, |it could well be interfernce in the antenna run.

<hr width=100% size=1>Chris Stannard

 

[Kantara]

Re: Ah but

I think you've hit the nail on the head Twister_Ken. The fact that Malin is coming in with error counts of zero while even Niton comes with perhaps 40 errors and Portpatrick has hundreds of errors implies that the installation on my boat isn't causing problems and it is a question of signal quality.
Perhaps it would be better if the Scottish area information was transmitted from Malin Head and the Irish info from Portpatrick. Similarly, I'm sure you would get better reception along most of the South Coast from the French transmitters than the one nearer you, but shielded by hills.
That is certainly how the ITV transmitters seem to work.

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[Oldhand]

Re: Ah but

What do you call a clear signal path? Navtex frequencies can be received both by ground wave and skywave propagation, the latter especially at night. Niether require line of sight but gorundwave reception could be reduced by mountains in the propagation path. Skywave reception will depend on the distance between the transmitter and reciever and the altitude of the reflecting layer at the time of interest. Navtex frequencies are simialr to low MW broadcast transmissions but the transmitter power is low by comparison.

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[Spacewaist]

My experience is that reception deteriorates whenever I go inshore. The further up a creek I go, the worse the reception.

HAd a signal free night last Friday at Malpas (limit of 2 m navigation on the Fal) and poor reception in the Bag at Salcome the previous weekend. Last summer in Scotland was worse, particulalry when in a Loch surrounded by hills (ie most of them).

My presumption is that it is a radio signal that is impeded by large land masses.

<hr width=100% size=1>A pontification from the Panjandrum of orotund bloviation AD2003

 

[salamicollie]

Re: Ah but

I have actually failed to rcv Port Patrick in Port Patrick Harbour! Admiditedly this was at the bottom of a big tide when the signal probably skipped over the top of us. I also have probs in Holyhead (IOM and Snaefell in the way) but nearly always get Malin Head.

It is definitely a propogation issue and 518kHz is always better than 490kHz, and while line of site is not entirely relevant the more in the way does seem to cause problems. Unfortunately I think you have just got to accept it isn't perfect until you get offshore

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