CentaurPipedream
regular
Reged: 20/09/2006
Posts: 1136
Loc: Essex
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I have recently fitted the NASA AIS Radar - lets not get into the radar/ais discussion again tho. My question relates to aerials and what type/location people are using to get the best result. I haave a whip aerial on the pushpit which gave very duissapointing results. An emergency aerial strapped to one of the shrouds seems better but not brilliant. What have you found to work
best ??
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The jester Challenge is starting May 31st and I'm going to give it a go. Have a read of this ......... www.justgiving.com/alancharlton
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alan
regular
Reged: 07/06/2001
Posts: 658
Loc: Nettuno, Italy
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I have a 1m (I think) Glomex antenna on the pushpit. I use an Easy AIS.
Sitting in the marina surrounded by other masts e.t.c., I am able to pick up ships at 18M where I have "line of site". Typically the ships are going from/to Naples from the north Italian area, and passing my marina at about 5 to 7 miles off the coast.
I have yet to do a range test when I am sea with 360 degs unrestricted visibility.
Alan.
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Alan Cloke
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alldownwind
regular
Reged: 10/08/2004
Posts: 1260
Loc: Medway
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Yes, don't forget that VHF basically works within line of sight. A whip on the pushpit is really low down, and if you have anything else immediately around you the reception is going to be even more restricted.
Higher the better.........
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EndeavourQuay
regular
Reged: 29/08/2007
Posts: 218
Loc: Gosport
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I recently fitted my Nasa AIS Radar and used a 1m Glomax on the pushpit rail of my little Contessa, It is picking up boats up to 20 miles away whilst in the Portsmouth Harbour and still does well in the Marina. The Longer range test will be at the weekend. 
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DipperToo
regular
Reged: 07/01/2005
Posts: 50
Loc: Suffolk
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Just fitted an EasyAIS with a small 'stubby' pushpit aerial. Picks up targets 19 miles away when I am in the marina (Shotley) surrounded by many other boats.
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hubertfairweather
regular
Reged: 12/04/2006
Posts: 105
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I have the nasa ais radar. With a 1 metre whip about 3 metres above sea level I get well in excess of 20nM.
It is important you set the thehold correctly. Signals below the threshold will not be recorded. I set mine just one stop above the quiescent level. Setting it higher clears more distant targets from the screen.
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Saltyjohn
regular
Reged: 06/09/2004
Posts: 1850
Loc: UK
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Range is line of sight and determined by a combination of transmitter and receiving antenna heights.
Because AIS is transmitted from large vessels with antennas located high above sea level it is less important to have your antenna high up. If your antenna is 10' above sea level and the transmitter is 100' above sea level the theoretical range is 16 nm.
If you aren't getting anywhere near this range you probably have an antenna system fault - typically a bad connection or broken coax, or possibly a duff antenna.
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John
http://www.saltyjohn.co.uk
Uncommon cruising kit: Metz, Loos, Bandit, Bilge-Mate...
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AliM
regular
Reged: 24/06/2004
Posts: 417
Loc: UK, Herts/Essex
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With a 1 m whip aerial on the pushpit and NASA AIS, I can see ships in the Thames, when I am in the Crouch (say ~10 miles away). I know that there are no hills in Essex, but that is a bit better than line-of-sight!
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Fireball
regular
Reged: 15/11/2004
Posts: 7151
Loc: Chichester
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My engine - now returned to NASA for examination - would only pick up 5 miles (see a recent post of mine) ... I suggest you eliminate the engine being at fault by either testing a known good unit on your setup or your engine on a known good setup ...
Can you keep us informed of your results as we may be able to use this as evidence of a quality issue if necessary (it probably won't come to it, but might as well be prepared).
When did you buy your engine?
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Don't be sad boy, people die all the time, just like that, why you could wake up dead tomorrow. - Homer Simpson
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Captainslarty
regular
Reged: 12/08/2007
Posts: 2012
Loc: Currently La Coruna Spain
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Using the AIT250 Mode B transponder, the supplied antenna is a rubber duck type unit.. mounted on the pushpit.. works perfectly.
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PM me for info re SSB's etc. Bought, sold, repaired, fitted and optimised.
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