bigal.nz 59 Posted August 20, 2022 Share Posted August 20, 2022 What sort of typical range should I expect from the VHF/AIS. I get there are some variables in this, but today for example I was only intermittently picking up the ferry on AIS when they were 2.8NM away with some terrain in the way.... see picture. AIS and VHF share an antenna with the appropriate splitter. (XB8000 and a Standard Horizon VHF - Furuno antenna (looks old)) Quote Link to post Share on other sites
eruptn 95 Posted August 21, 2022 Share Posted August 21, 2022 It's basically antenna to antenna, so depends on the antenna heights, line of sight plus a bit... 1 Quote Link to post Share on other sites
Jon 360 Posted August 21, 2022 Share Posted August 21, 2022 I’ve frequently seen ships at 30 to 40nm however class B to class B will be only 7 to 10nm depending on the mast heights and sea conditions Transmission intervals vary according to your speed and theirs also so if when they transmitted if you had a house or land in the way you wouldn’t receive their transmission VHF will bend around corners but not reliably so that’s why sometimes you would pick them up. Hope that helps Quote Link to post Share on other sites
Island Time 1,230 Posted August 21, 2022 Share Posted August 21, 2022 If the antenna (and coax) is 10yrs + is will have degraded. It's often the Class B AIS that shows this 1st. Change the cable and co-ax - they are not expensive. Class B should Always give you 7-10 miles across water. Ships with class A should be 20 miles if your antenna and theirs are line of sight. I have seen over 100 Miles once, but that's weird atmospherics. I one had a ship call me from 46miles and ask my intentions - I didn't even know he was there! Quote Link to post Share on other sites
bigal.nz 59 Posted August 21, 2022 Author Share Posted August 21, 2022 Thanks IT. Replacing the coax is easy. Hope thats all it is. LOL @ 46mi intentions. Quote Link to post Share on other sites
Island Time 1,230 Posted August 21, 2022 Share Posted August 21, 2022 Do the antenna as well. Even the stainless ones with the base load (white plastic cylinder) degrade slowly in the weather. Quote Link to post Share on other sites
bigal.nz 59 Posted August 22, 2022 Author Share Posted August 22, 2022 Is there much variance in the brand of antenna? I have South Pacific just down the road. Quote Link to post Share on other sites
Muzza 18 Posted October 4, 2022 Share Posted October 4, 2022 Because AIS channels are at the very top end of the Marine VHF band, dedicated AIS antennas are usually cut for the the top two or three frequencies in the band resulting in a considerably shorter antenna with a centre frequency of around 162 mhz where a normal VHF antenna will be centered around 159 mhz. On our commercial boats the AIS antennas are about 30cm shorter than the normal VHF communication antenna's. Two separate dedicated antenna's at similar height will always work better than one single antenna but on small boats compromises have to be made. Step 1 would be to disconnect the antenna couplings any sign of corrosion can be cleaned up with a small wire brush and sandpaper. If this does not fix the problemhave a look at the solder or crimp joints for signs of moisture. Next would be slice the outer insulation off the coax and have a look at the braid, any sign of green ditch the antenna and coax and buy new. Quote Link to post Share on other sites
Island Time 1,230 Posted October 6, 2022 Share Posted October 6, 2022 On 22/08/2022 at 4:08 PM, bigal.nz said: Is there much variance in the brand of antenna? I have South Pacific just down the road. South Pacific are fine... Quote Link to post Share on other sites
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