<Dick wrote: .... The AIS would pick up any ship within 50 miles.> Georgs, if you are in touch with Ice Dancer can you confirm the AIS system and antenna set-up that they are using to get the 50 mile range? We are still struggling with to get a paltry 20 miles using a 9 db 23' antenna with new cable/connectors, etc. This same set-up works fine with a normal VHF and will reach out 15 miles with a 1 watt handheld attached to it. What ever they have, it must be a super set-up. Cheers Dave & Nancy Swan Song Roughwater 58 Puerto La Cruz Venezuela

The range of AIS is not set in stone. 50 miles is a bit of a stretch under most conditions. However, I think I recall seeing a contact once at 100 miles. Since the frequencies are near 170 mhz. the predictable range is line of sight, antenna to antenna plus a little for some bending around the earth's curvature. Any time a contact shows up beyond that "predictable" distance it has to be due to atmospherics, generally known as a tropospheric duct. At 170 mhz such ducts can be on the order of several hundred to a thousand miles or so, especially in the tropics or semi tropics. In a dry atmosphere, the range will almost always be limited to line of sight. Regards, Mike _____________________________________ Capt. Mike Maurice Beaverton Oregon(Near Portland)

Mike, We have used AIS since May 2004 and the range is variable as you say. We have seen targets at over 100 miles and other times targets have been only 10 miles away. Mostly we will see them 20-30 miles out but the detailed data on them (name of ship, destination, MMSI number etc.) may not be received outside a 20 mile range and sometimes half that distance. Hope all is well with you. Chris On 1/13/07, Mike Maurice <mikem@yachtsdelivered.com> wrote: > The range of AIS is not set in stone. 50 miles is a bit of a stretch > under most conditions. However, I think I recall seeing a contact once > at 100 miles. Since the frequencies are near 170 mhz. the predictable > range is line of sight, antenna to antenna plus a little for some > bending around the earth's curvature. > > Any time a contact shows up beyond that "predictable" distance it has to > be due to atmospherics, generally known as a tropospheric duct. At 170 > mhz such ducts can be on the order of several hundred to a thousand > miles or so, especially in the tropics or semi tropics. > > In a dry atmosphere, the range will almost always be limited to line of > sight. > > > Regards, > Mike > > _____________________________________ > Capt. Mike Maurice > Beaverton Oregon(Near Portland) > _______________________________________________ > > Passagemaking Under Power and PUP are trademarks of Water World Productions, formerly known as Trawler World Productions. > > To be removed from the PUP list send an email with the > subject "unsubscribe" (no quotes) to the link below: > > mailto:passagemaking-under-power@lists.samurai.com > > Passagemaking-Under-Power Mailing List

> We have used AIS since May 2004 and the range is variable as you say. > We have seen targets at over 100 miles and other times targets have > been only 10 miles away. Mostly we will see them 20-30 miles out but > the detailed data on them (name of ship, destination, MMSI number > etc.) may not be received outside a 20 mile range and sometimes half > that distance. > The reception reports from you and from Dave all seem about what I have noticed. I would not expect consistent results better than what you have reported. Regards, Mike