Navtex transmissions - can they be received inland?

[Poignard]

I have been given an old NASA Clipper Navtex receiver. I don't know if it's in working order and I want to test it in London before taking it to my boat (or sending it to NASA to be repaired, if necessary).

Can I expect to receive a strong enough Navtex signal inland?

 

[Fr J Hackett]

I received them in Stoke once so any things possible I suspect that Niton will be your best bet, does it need an active antenna or will a length of wire do?

 

[mickywillis]

Yes, I received NAVTEX data on a NASA unit in my spare room, Epsom in Surrey from Niton station. Leave the unit on for at least 24hrs though and put the aerial into the window area or hang outside (the aerial not you!!)

 

[Poignard]

I received them in Stoke once so any things possible I suspect that Niton will be your best bet, does it need an active antenna or will a length of wire do?

It has an active aerial, powered through the coax cable.

(Stoke to Grenoble. A move in the right direction, I should think! )

 

[MM5AHO]

Navtex transmission frequencies are similar to broadcast longwave stations, and their signal propagation is also similar.
The distance covered depends on the antenna at each end, and the transmitter power, and while these are not as good in Navtex as most LW stations, it is indicative of the distance that might be expected. That it is over sea or land isn't so important (though sea is better), the signals can be received at great distances. 25 years ago I used to receive UK Navtex (Niton, Cullercoats etc) in Iceland.

 

[franksingleton]

Leave it on overnight. Select all stations and all message types. If it is working you should get something by sky wave - probably a long way off. Day time reception is by ground wave and signal strength greatly affected by the signal path over land, effects of buildings etc. Sky wave signals are likely to be much stronger than any local transmission.

 

[Poignard]

My Clipper Navtex came back from NASA this morning and it seems to be working well.

According to the engineer's report it is14 years old so, as it was given to me, it has only cost me the £44 repair bill to have a useful source of weather information.

Thanks for the advice. Frank Singleton's excellent website provides a mass of useful information aboit the Navtex system.

 

[Gunfleet]

Sorry to drag up an old thread but it’s relevant to me. I have one of these with a broken Ariel. I’m not mad keen on replacing the Ariel as they get clouted every few years and need replacing - I don’t have anywhere really safe for one. Can it be made to work without the powered Ariel does anyone know? If it’s just ground effect I would have thought a wire running round the boat headlining would do ��

Ps I know ‘try it and see’ but I’m really asking has anyone made one work without the powered antenna (fed up with iPhone capitalising ariel)

 

[Poignard]

All I can tell you is that mine definitely did not work until I had the antenna repaired.

 

[Gunfleet]

Thanks for that response.

 

[awol]

My NASA Navtex is connected to a stanchion bolt under the deck and hence to the guard wires, pulpit, rigging and mast. It works well until the wire corrodes which seems to take ~2 years.

 

[Bilgediver]

What better than connecting to a chain plate bolt. We used to use a long wire on the rigs when these active antennas failed. It should be fine so long as connected correctly . This does not work with some older ICS products as I believe the antenna base also has some radio components.

 

[prv]

This does not work with some older ICS products as I believe the antenna base also has some radio components.

The original ICS "antenna" was the entire radio receiver, it sent the decoded messages to the display over a serial connection. Unfortunately had a tendency to leak and then fail. They replaced it with a receiver box plus a dumb aerial; the display is still just a display. You could connect that newer style receiver to whatever aerial you choose, and keep the receiver itself below decks.

I know they're older posts, but the talk of "leave it on overnight" and "leave it on for 24 hours" is irrelevant for testing. Transmission times for each station are published, so just check the schedule and turn it on for a couple of minutes at the appropriate time. They come round every four hours.

Pete

 

[MM5AHO]

I know they're older posts, but the talk of "leave it on overnight" and "leave it on for 24 hours" is irrelevant for testing. Transmission times for each station are published, so just check the schedule and turn it on for a couple of minutes at the appropriate time. They come round every four hours.
Pete

It's true that they transmit 24 hours to a schedule, but reception at night will be far better that during daylight, so if a weak installation (poor antenna etc), then nigh time reception will be more likely.

 

[macd]

(fed up with iPhone capitalising ariel)

Your iPhone probably thinks you're writing about an elderly motorcycle. Or perhaps a Hebrew name. Now 'aerial' it would have been happy with. It's a diphthong thing

 

[Gunfleet]

Or the BBC house magazine. Nearly fifty years after leaving school I still make that literal and one or two others (artic/arctic is another and probably Navtex and Navtext). Bearing in mind my former career it's an odd one.

On topic, I have a NASA set, not one of those dinky ICS things with a bus ticket spilling out of the front. I'm encouraged and am going to experiment!

 

[Playtime]

Sorry to drag up an old thread but it’s relevant to me. I have one of these with a broken Ariel. I’m not mad keen on replacing the Ariel as they get clouted every few years and need replacing - I don’t have anywhere really safe for one. Can it be made to work without the powered Ariel does anyone know? If it’s just ground effect I would have thought a wire running round the boat headlining would do ��

Ps I know ‘try it and see’ but I’m really asking has anyone made one work without the powered antenna (fed up with iPhone capitalising ariel)

You could try mounting the active antenna under the deck. I have done this with the antenna on my NASA Navtex engine, which (I think) uses the same active antenna as the units with display screens, and it works well, picking up foreign stations as well as Niton.

 

[GHA]

Transmission times for each station are published, so just check the schedule and turn it on for a couple of minutes at the appropriate time. They come round every four hours.

Pete

Always wondered how accurate the transmission times were after having problems years ago with a ssb receiver & laptop, so with the wonders of node red and a raspberry pi connected to a nasa navtex engine...

Tarifa - bang on, full marks

12/11-13:00 - Navtex received- >GA8212 0712 UTC NOV 17
COASTAL WARNING
NR/1837/2017


SPAIN S COAST
UNMANNED WOODEN BOAT OF 5 METERS LENGTH ADRIFT IN POSITION 36- 03.4N 003-01.2W. CANCEL NR-1835/2017.

12/11-17:00 - Navtex received- >GA8212 0712 UTC NOV 17
COASTAL WARNING
NR/1837/2017

-----------
Niton - 11 minutes late - must try harder...

12/11-17:41 - Navtex received- >KA80KA 80
DOVER - LARGE CAP GRIS NEZ
CANCEL AND SUPERSEDES AVURNAV 162/17 (TA78)
A GREEN - 10 METERS FISHING NET ADRIFT
PSN (WGS84): 50-59,7N 001-41,6E
CANCEL THIS MESSAGE 141000 UT
12/11-17:41 - Navtex received- C NOV 17*

--------------
Malta - 5 minutes late - room for improvement..

12/11-18:25 - Navtex received- >OA75MALTA*ADIO UNMWRNG
T*E OUTER MUNXAT EWST CARDINAL BUOY FLASHING 3 T*MES EVERY 10SECON*S IN*POSITI*N- 35-50.94N 014-35.9*** *S IRR**U

---------------
Netherlands - 2 minutes late , not bad

12/11-18:32 - Navtex received- >PA48

NETHERLA*DS COASTGUARD


NAVIGATI*NAL WARNING NR. *I QOWPPT UTC SEP


OBSTACLE ON SEABED*IN 51-3*MI**N 003-06.53E WITH A LENGTH OF**MTR

-----------------
Corsen - Bang on, well done

12/11-20:00 - Navtex received- >AA2410**PP *U** NOV 17*
*VU*NAV BREST 525/1*
PAZ*N*
UNDERW*TER TARGET LA*N*HING WITHIN 40 MIL*S RADIUS OF 47-40N,*PPUAPPW
- 14 NOV 2017 : FROM *IPP TO 2000 UTC
CANC*L THIS MSG 142000

http://f1agw.free.fr/Navtex/Schedule_Navtex.pdf

 

[prv]

Niton - 11 minutes late - must try harder...

Eh? Niton K is at 1740 by every schedule I found in a quick google. So that transmission is one minute out according to the timestamp in your post - but it looks like said timestamp is put in by the NASA receiver and we don’t know whether that clock is actually correct anyway.

Pete

 

[GHA]

Eh? Niton K is at 1740 by every schedule I found in a quick google. So that transmission is one minute out according to the timestamp in your post - but it looks like said timestamp is put in by the NASA receiver and we don’t know whether that clock is actually correct anyway.

Pete

Indeed it is, my eye had glanced up to varna, niton is off the hook.

The timestamp is actually inserted into the file when a message comes in by a tiny bit of javascript in node red from the rapsberry pi clock which is in turn set from gps so should be pretty good, though you're right, the navtex clock might be out a bit which could cause the slight delay.