Nasa Navtex Aerials

[philmarks]

General disappointment with Nasa Navtex Pro ( I saw earlier post about aerial siting/earthing). Performance never wonderful, but it has got worse over the last year (and as I've moved down boat down to warmer climes I'm not sure whether it's just poorer service from Spanish and Portuguese transmitters). I dismantled the aerial last week and found water in it and one corroded pcb track which I repaired. No improvement. It's frustrating because other people some to find them OK. I'm wondering whether to be buy a new aerial. Have any readers had cause to replace their aerials?

All advice appreciated
Phil

<hr width=100% size=1>Rgds
Phil

 

[kgi]

the performance of my navtex was never very good until i sent it back to nasa and had them put on alonger cable so i could mount it at the top of my mizzen mast after that ,no probs......keith

<hr width=100% size=1>

 

[Birdseye]

depends where you are in spain. i found that both spanish and portugese navtex stations were cr*p in n spain. could get the scandinavian stations better.

also, deep fjords cause problems as does the spanish relaxed attitude to electrically noisy machinery (ie machinery which emits radio waves in use, drowning out other signals)

can you get other stations than the spanish and portugese. if so, prob no navtex problem. if not, then navtex problem.

<hr width=100% size=1>

 

[Gunfleet]

Been there with the deteriorating Nasa Navtex. Take the screw out and open the ariel. You may be in for a surprise. THey somehow get humidity in them, despite the gasket and gasket grease with which they are originally assembled. A good old dry out on top of the dehumidifyer on in the linen closet may work. Otherwise its a new antenna.

<hr width=100% size=1>

 

[charles_reed]

My Navtex Pro has given good service over the last 6 years - the active aerial is mounted about 4m above sea-level.
I was warned that the one weakness (by NASA from memory), was water ingress into the active antenna box, corroding the PCB - I therefore sealed the box thoroughly, when mounting it, by using lots of silicone sealant.

I did find the Iberian transmitters, on my way down the Atlantic coast, to be unsatisfactory and relied on Corsen le Stiff (callsign A) and Toulon (callsign W). Toulon, though NAVAREA III covers right down to the Straits.
I've found the Italian transmitters to be equally dodgy, but their vhf continuous weather forecast to be very good.

Reception in nearly all the ports was non-existent, but that's down to the mountainous hinterland and blanketing effect of the coast.

It is almost impossible to "mend" a water-damaged PCB - the only satisfactory solution will be to replace the active antenna unit.

I've found that only about 1/3 of the weather bulletins are now issued on 518kHz, but all the rest of the messages are still there - so I'll either be changing to a 2-band Navtex or buying one of NASA's Weatherman units.

From my experience of NASA equipment (doppler log and now the Navtex Pro) I'd have no hesitation in recommending them as cheap/cheerful practical equipment. I'd probably hesitate about buying a transceiver or radar (if ever produced) from them, because of the relative unsophistication of their products and the quality (or lack) of their lcds.

<hr width=100% size=1>

 

[GAJ]

I have had mixed results with the Navtex Pro but this season it has been perfect, I have received UK stations in Sardinia! Not that it was of any use to us!

I had originally had the aerial (old type whip) mounted in a hanging locker and the reception was fine. I then moved the aerial to the top of the mast and it was really very sensitive.
A small incident with a thunderstorm zapped the transistor in the amplifier in the aerial. Nasa repaired it and I mounted it back in the hanging locker, it was fine for a year then it refused to work all last season.
I put it back at the masthead and all was fine.
In between I had tried a new aerial in various positions around the boat all without success. The conclusion I came to was that in fitting additional a radar and SSB something at deck level was masking the Navtex signal because as soon as I hauled the aerial up on a halyard reception was fine.

The Navtex signal is very quiet and I imagine that it wouldn't take a lot to mask it out, a noisy fridge comp. etc.

The essence is that on my boat the siting of the aerial is all important , earthing to a ground plate didn't make any difference to performance perhaps yours is the same.
The tech. chap at Nasa told me that if the set was receiving any message then it was fine, they either work or don't there is no inbetween and that the problem was likely to be the installation. He was right in my case.

GAJ

<hr width=100% size=1>

 

[GAJ]

And another thought a thing that completely fazed the Navtex was having the GPS 12volt supply and the Navtex coming from the same braker/ fuse box, although each with its own fuse.
The Garmin GPS seems to send a signal down the 12v lead that the Navtex does not like at all.

<hr width=100% size=1>

 

[Ric]

I had exactly the same problem - water in the aerial. I sent it off to NASA and full marks to them they replaced it free of charge. With my new one, I took it apart and sealed it with sikkaflex and since then no problems.

<hr width=100% size=1>

 

[philmarks]

THANKS TO ONE AND ALL

Off with the aerial then, replace it and mount it higher up.

Phil

<hr width=100% size=1>Rgds
Phil

 

[philmarks]

I have the dual frequency one. Since the pcb repair, I now get the occasional characters coming through, but the signal to noise ratio is obviously too low - so I think the antenna may be OK, and it may be just a case of siting - it was never very good anyway - it's mounted on the pushpit. I have had it 2 years and never received the Corsen signal (and I've sailed past the station about 6 times!). Boat's steel - maybe I need to get it high up.

I think before removal and all the hassle (boat's in Spain) I will just try hauling it the mainmast. Worth a try.

Thanks for advice.

Phil

<hr width=100% size=1>Rgds
Phil