NASA DSC

[SP2]

Has anyone had a problem with the NASA DSC VHF? We fitted one in March and have been very disappointed with the range achieved. Aerial and 12 volt supply have both been changed and still no joy.

Have bitten the bullet and fitted a second VHF - Simrad which was much more expensive but even with a shorter aerial works so much better. NASA says there is nothing wrong and chandlery supplier bottled out too (now spending my overdraft elsewhere!)

Any views?

Mike

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[Robin]

We have a NASA DSC and it works fine, range on transmit and receive with a masthead aerial is excellent.

Is the key to your problem in your comment <<but even with a shorter aerial works so much better>> that you really had an aerial problem? In the past on a previous boat we fitted a new aerial when the mast was down for re-rigging. It seemed fine on a radiocheck but later was found to have limited range (shows the meaningless result of a CG radiocheck where their aerial may be only a few miles away). After remaking every connection many times over it turned out to be a faulty aerial, replaced FOC by V-tronix and range restored.

<hr width=100% size=1><font size=1>Sermons from my pulpit are with tongue firmly in cheek and come with no warranty!</font size=1>

 

[SP2]

Glad to hear your set is fine. We tried three different aerials on the NASA (even bought a new one) all to no avail. As I said, the new Simrad works perfectly on one of them. Also 12 volt supply was replaced, rerouted, rewired. Tried everything.

Just a shame that NASA dismissed my concerns as if I did not know what I was talking about. Been boating since the 70's and we had one of the original Seavoice 100's installed in 1973 and have been through a whole variety of sets.

Think we will put it down to experience and steer clear of NASA in the future. Mike

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[whisper]

We had one on our previous boat and it was fine. Think you must have had freak one. All the more annoying that NASA/Dealer didn't believe you.

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[woody001]

People rate nasa customer support, but i think it's crap

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[wooslehunter]

Assuming the antenna insallation is OK and when you get a positive radio check report you're not told the audio is down, then limitted range can meen two things - limitted transmit or limitted receive. i.e transmit power is down or the receiver is deaf.

If you want to take things further, find a local radio techician or radio ham that could help you out.

For the transmitter, measure the transmit power. This is easy since any radio ham, ham shop or radio tech will have a pretty good power meter & dummy load. If it's significantly down on the 25W it's supposed to be then the set's likely to be faulty. Make sure you do have 13.8v though as the power will drop with supply volts.

For the receiver it's more complex since you'll have to find someone with access to an FM signal generator. Even with this, you won't be able to make a calibrated measuremnent since this requires an audio analyser. You can however make a comparitive measurement with your other set and compare what signal level is required to give the same audio tone quality.

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[Plum]

My NASA DSC radio works fine and have been satisfied with the range to other yachts.

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[Andrew_Fanner]

Had serious rfi issues with mine as soon as the plotter was switched on. I stuck ferrite beads all over the power lead, NMEA lead and aerial wire. Not much improvement. I then moved the twig from next to the cockpit to mounted on a davit.

Looks a bit odd but reception is fine, I certainly pick up signals from 20 odd miles away.

<hr width=100% size=1>Two beers please, my friend is paying.

 

[Robin]

All of which goes to confirm how useless a radiocheck with the local CG is! The few times I have ever asked for a radiocheck have been for either a new aerial or a new VHF set installation. When we fitted a new aerial on our previous boat the radiocheck with Portland CG from Poole was'loud and clear', however Portland have an aerial only 10 mls away and in practice we found our range was just 20mls on receive, less on transmit but changing to a deck level emergency aerial we were able to receive much father away. After remaking all the connections with no improvement I finally called V-Tronix who told me how to test the aerial with a meter, I did and it was faulty. After replacement, the range on transmit and receive went back to normal, but the point I guess was that checking with the CG was really a waste of time - unless done from considerable range from ANY of their aerials.

On our current NASA DSC set with a V-Tronix Windex type S/S whip 50ft up the mast we can receive routinely at ranges over 60mls from coast stations, often much more. We have transmitted at 60mls range too as a 'test' by reporting safe arrival in France from the UK, but at night when the local traffic would have been quiet.

Maybe there is a case for fitting one of those signal strength meters in the aerial feed, they don't seem too expensive.

<hr width=100% size=1><font size=1>Sermons from my pulpit are with tongue firmly in cheek and come with no warranty!</font size=1>

 

[milltech]

To be fair to Nasa this is not home production but a pretty established radio made I think in Japan and sold under several brands.


<hr width=100% size=1>John
http://www.on-line-marine.com

 

[SP2]

Thanks for all your input, guys. I think we have decided it has caused so much grief that we will leave it in situ (don't want holes in the new headlinings) and hope that one day it will see what fun it is missing out on and join in with the Simrad.

Having said that... well, the winter is coming and there are never enough jobs to keep one entertained so maybe...

Mike

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[LORDNELSON]

I use a Simrad dsc vhf and, when in the Solent or close to the South Coast, we routinely receive Cherbourg radio (chasing up merchant ships entering the channel) and French Coastguard(?) mayday calls (french swimmers missing off beaches etc) this would seem to indicate good reception but of course we do not know how well we are transmitting since we are usually close to a CG station or a repeater.

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[Robin]

Yes the French stations are well in range especially in high pressure for some reason. Cherbourg transmissions BTW are what I referred to as coming from Jobourg Traffic Control, this is the actual transmitting station which is at Jobourg on the NW tip of the Cherbourg peninsulsr, near cap De La Hague. You sometimes hear Barfleur Signal Station chip in too and contact ships.

<hr width=100% size=1><font size=1>Sermons from my pulpit are with tongue firmly in cheek and come with no warranty!</font size=1>

 

[davidfox]

VHF transmits and receives essentially by 'line of sight' at night funny things happen to radio signals, its to do with the ionisphere changing when the sun is not shining on it. to transmit 6o miles is unusual and is because on this occasion the relatively weak signal bounced off the ionisphere increasing the range over the horizon

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[Robin]

We transmit over that range fairly regularly, provided there isn't too much local traffic at the other end to overide our transmission. We have a tall mast at 50ft and that doesn't include the aerial, with the height of the aerials for Portland and Solent (high on Hengisbury Head for Portland and IOW for Solent) 60mls isn't unreasonable. We have MF/HF SSB too if needed. I agree sometimes you can get extreme ranges, I once put a Link Telephone Call through Lands End Radio from a buoy in L'Aberwac'h and then called Falmouth CG for the UK forecast, range probably 110-120 mlies, that was on our previous boat with a lower mast height too!

<hr width=100% size=1><font size=1>Sermons from my pulpit are with tongue firmly in cheek and come with no warranty!</font size=1>