AIS Class B Transponder Installed

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Feb 3, 2009
292
Knysna 550 SE Knysna, South Africa
Recently I replaced my Smart Radio SR161 AIS receiver with a Comar CSB200 class B transponder. Since we do so many off-shore passages, I wanted to be able to see vessels using AIS and to be seen by the other vessels!



The installation was painless. I already had a second VHF antenna which was shared between a spare VHF radio and the AIS receiver via a VHF splitter. I removed the splitter and ran the antenna directly to the transponder. Should the need arise, I can simply move the VHF antenna from the primary VHF to the backup VHF.

The AIS transponder requires its own GPS antenna. This is required so that you can't feed it bogus position data.

The NMEA output of the AIS transponder goes to a RayMarine C-80 chartplotter, where the AIS vessel data is overlaid on the chart. I went to a neighboring vessel who had an AIS receiver and BlueJacket showed up! Yeah!

The following photo shows a target underway with basic information displayed. In this case it shows the vessel moving 17.2Kts on a course of 185T. The closest point of approach will be 5.25nm and will occur in 51 minutes.


If you ask for detailed information on the target, here's what you get:


Here's a photo of radar output with AIS targets overlaid in NY Harbor. Clearly this is an anomaly, but it certainly shows the power:


The SR161 AIS receiver and VHF splitter are on eBay at
http://cgi.ebay.com/ebaymotors/ws/eBayISAPI.dll?ViewItem&item=320388826604.

-- Geoff
 
Feb 3, 2009
292
Knysna 550 SE Knysna, South Africa
Geoff, how come "Cosmos Ace" shows as moored?
This is a common error that you see. It's a crew-set parameter and they often forget to change it. Either that or it's dragging very quickly! :) You also see ships with destinations in the past...

-- Geoff
 
Jan 1, 2009
371
Atlantic 42 Honolulu
Geoff, how come "Cosmos Ace" shows as moored?
'cause they forgot to change their status. It was pretty common to see underway vessels clearly anchored and moored vessels zipping along in SF bay when I was there.

Geoff, how much power does it draw? Can you turn the xmit off and have just a receiver and if so does that draw less power?

--Tom.
 
Feb 3, 2009
292
Knysna 550 SE Knysna, South Africa
Geoff, how much power does it draw? Can you turn the xmit off and have just a receiver and if so does that draw less power?
You can install a switch on the tranceiver to keep it from transmitting. It transmits every 30 seconds if under 14 kts and then I think it transmits every 10 seconds above 14 kts. If you're not moving, it transmits every 3 minutes.

-- Geoff
 
May 6, 2004
916
Hunter 37C Seattle
Geoff, so can you set your "status" to say anything, such as "under sail" or "under sail w/broke engine"
 
Feb 3, 2009
292
Knysna 550 SE Knysna, South Africa
Geoff, so can you set your "status" to say anything, such as "under sail" or "under sail w/broke engine"
AIS class B is much more limited in the amount of information that it supplies. It doesn't include things like destination, status, rate of turn, etc. There are some supplemental statuses that can be sent, but I know nothing about them and I believe that it would require connecting a PC to the transceiver to change it.

-- Geoff
 
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