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AIS Transponder & Vesper WatchMate

John MacDougall, Annie Laurie, #26

Hello to all,

A little background info first.

1) Back in 2005, I started researching AIS, etc. for my boat…but never got around to doing anything more than "research"…

Then in the fall of 2006, while doing a total electronics upgrade, I looked into getting an AIS receiver, primarily for use offshore, on long ocean passages, etc. but as I didn't wish to use my chartplotter(s) as a primary AIS display (as I don't normally run the E-80 or E-120 when offshore), my choices were very limited…

2) So, in the fall of 2006, I ended up installing a "standalone" AIS receiver with its own 5" B&W LCD display…this was a "Sitex AIS Radar" (made by Nasa Marine in the UK)…

I mounted it at the Nav Station (using a RAM mount), and used my 144mhz/220mhz/440mhz mast-top mounted ham antenna as my AIS receive antenna…this arrangement worked very well, with no AIS receiver damage, from my 25 watt VHF transmissions from their antennas barely 12" away…allowing me to see AIS targets out to the unit's 32 mile range limit…

When offshore, my typical AIS target aquisition (from Class A AIS transponders on large vessels) was in the 25-30 mile range…okay when well offshore, but I found that to be too long of a range when approaching heavily trafficked areas, as I was then only using the unit on it's 8-mile range setting, to allow for easier target viewing, etc…

And, this set-up has served me well for > 5 years, ~12,000 miles offshore, and two Atlantic crossings, etc…and it still works! But, it is technologically outdated, and cannot display Class B AIS targets (designed before the Class B standard was set), nor can it be used as a "outboard receiver"/connected to another display, etc. nor be used effectively with an AIS transponder…

So, if I wished to add an AIS transponder (which I did), and still have the advantage of using a simple low-power AIS display, I needed to change my AIS display as well…(I'm keeping my current AIS receiver/display as an on-board spare…)

3) So, here I am this spring (2012) deciding on an AIS transponder and display…

a) Actually the "display" part was a No-Brainer!!!

The Vesper Marine guys make just about a perfect line of AIS devices, including a wonderful, simple, easy-to-use, yet VERY feature-packed and powerful, AIS display…the Vesper WatchMate 670 (and last year's model, the WatchMate 650)…www.vespermarine.com

This fantastic display unit is only an inch wider than my old AIS display, and has many great features (multiple ranges, CPA alarms…multiple use profiles, multiple filters, etc…) and is a VERY low-power unit, which means it can be left running 24/7 when sailing on long passages…

I chose the Vesper Marine WatchMate 650 (last year's model), on close-out at West Marine / Port Supply for $190!!!! It is mounted at my Nav Station, right where my previous AIS display was…easily visible and not in the way!!! It is mounted and secured/adjusted at a good viewing angle…

The WatchMate display typically uses 1.2 watts or less…that's 1/10 of an amp at 12vdc…meaning that in a 24 hour day, it uses only about 2 A/H…compared with a Raymarine E-120 display only, spec'd at 32 watts (~ 2.6 amps) using about 60 A/H's per day (just for the display!) And, of course use of the WatchMate display does not interfere with sending AIS NEMA data to the chartplotters…

b) There are many choices of AIS transponders…whether Class A (for SOLAS / large commercial vessels), or Class B (mostly for pleasure craft or other non-SOLAS vessels)… Although a Furuno FA-150 Class A AIS transponder is a fine piece of gear, with its own easy-to-use B&W display, it is still about $3500+…and even if it was a bit cheaper, it's certainly "more" than most offshore cruising boats will ever need… And, while there are other some other Class A units in the $2300 - $2400 range that is still more than I desire to spend!!!

Further with Class B AIS transponders now selling for $450 to $1100, it seemed like Class B was also a no-brainer…

Which one???
Hmmm???

I like EmTrak (EmTrak/ACR) units, as they seem to be well made and actually designed for "marine use"!! (sealed, splash-proof or even submersible housings, etc.) and when I saw that they had a few "different" Class B units designed for niche markets, I looked hard at them… www.em-trak.com

They make Class B units with the option to use 12.5 watts (vs. the standard 2 watts), still not FCC approved yet…as well as units specifically designed for Turkish vessels / waters, as well as a couple different "normal" Class B designs…

I chose an EmTrak B200 version, a B212 model (and operate it at the standard 2 watt Class B power…my passion for low power consumption!!) It is mounted behind one of my hinged Nav Station panels, near my Icom M-802 SSB transceiver…(and its GPS antenna is mounted behind a saloon locker)…and it sends all the AIS NMEA data (at 38400 baud) to both my WatchMate display and to my Raymarine chartplotters (E-120 and E-80)…

Its spec'd average power consumption is 4 watts, or about 1/3 amp at 12vdc…meaning that it will use about 8 A/H's per day, combined with the 2 A/H per day of the WatchMate display, makes for a very low power system, even if the units use more power than spec'd, it's still going to be small!!!

c) As for an AIS antenna… I desired to attain a decent range from my AIS unit (both my transmitted signal and other vessels received signals), of at least 12 - 15 miles, and hopefully more…

If I wanted to use a mast-top antenna, I needed to move the antennas further apart horz and/or vertically, in order to keep any damaging radio energy from the main VHF transmitter and AIS transmitter out of the adjacent units' receivers…(this is something I've had a GREAT deal of experience with in VHF repeater design/installation over the past 30 years…and I determined that 6' - 10' of sep was required…but others have made do with 3' of separation…) This antenna isolation (separation) would entail building and installing a couple of stand-offs at the masthead, and adding extra cabling to the antennas and/or mounting one antenna on the top spreader and running all new cabling…(neither was a project that I looked forward to!!!) BUT… But, as I thought more about it I realized that many cruising boats have used a rail-mounted or bimini-mounted AIS antenna (about 10' off the water) to good success…so, I thought I'd give it a go, and see what results I got!!!

I added a stout mounting bracket and a Shakespear VHF 3' SS whip antenna (I actually bought the "AIS" version…same price as the "regular" one!), on the stern…it is mounted about 10' off the water and is fed with 35' of low-loss coax (LMR-400UF)… I chose this antenna as opposed to a 4' fiberglass "dipole" type antenna, so that it would not present a harmful shadow on my solar panels…as well as being the same type I have at the masthead (and stowed below as a spare)…

4) Results… The results I've gotten so far have passed my expectations…good weather and small seas (2' - 3')… (please note that there were NO enhanced vhf radio propagation conditions in my area during this past week, when I was doing some coastal sailing and evaluating my new AIS system…so, my results are "nominal"…)

a) Receiving AIS data from Class A units has been great… Typically I've seen 20 - 25 mile range, from Class A AIS targets… (saw a vessel entering Lake Worth Inlet from 22 miles up the coast, and later another few vessels moored / entering Port Everglades from 26 miles away…) The only Class A target that I called on the VHF was an ocean tug, 8 miles away, and he reported seeing my AIS data…

b) Receiving AIS data from Class B units has been acceptable, but varied…I suspect the variations are due to the wide variations in Class B installations and antenna placement???? Typically I've seen 10 mile range from Class B AIS targets…… (a couple didn't show up until about 5 miles away…but most were displayed by 8 - 10 miles…) The only Class B target that responded to my voice VHF call (I didn't want to bother others with my evaluations/testing, so didn't signal via DSC) was 6 miles away, and he reported seeing my AIS data "just fine"…

5) Any problems??? a) Even though they are only 3' long, I don't like the small power wires (22 ga??) of the EmTrak transponder (nor the small wires on the WatchMate…), and spliced larger (14 ga?) wiring to the unit, to run the few feet to the breaker panel… b) Placing the transponder (and its wiring) near/next to my M-802 SSB, I found some VERY slight broadband RFI being radiated (from the transponder's wiring), which a couple of ferrites cleared up completely!!!

6) Anything to change??? Actually NO… I'm quite happy with how everything works!!!

I will use my 144mhz/220mhz/440mhz mast-top antenna for my occasional vhf/uhf ham radio operation, but mostly it's a "spare"…(and I do have another "spare" VHF antenna, stowed below in a locker, in addition to the "AIS antenna" now mounted on the stern…)

That's all for now…
Fair winds…

John
"Annie Laurie", #26

(Click on picture for full size)

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