Catalina 350 International Association

Hi. My Standard Horizon VHF radio has an AIS receiver, but no transmit feature. Has anyone out there installed one?
Thanks
Dave B
NYBOR

I installed an AIS transponder (send and receive) on Trevi #460.
I have an ICOM VHF.
I chose the Digital Yacht Nucleus AIT3000 Class B AIS Transponder which has an built in Antenna splitter so you don't need a second VHF antenna. Purchased from Defender for about $800.
It comes complete with its own GPS antenna which I mounted on the stern rail. It feeds the AIS received information to my Raymarine C80 via the NMEA 0183 input.

Overall I am very well satisfied and have verified that my position transmissions are being picked up by nearby boats!

I think it a worthwhile upgrade.

Trevor Rabie

Trevor,

May I ask where you mounted your AIS transponder?
I am installing an Em-Trak B923 which also acts as a VHF splitter then connects to the NEMA 2000 (Im changing the backbone for other nav gear)
Thank-you

I mounted a Vesper XB8000 with external splitter inside the cabinet at the nav station. Convenient to the vhf coax as well as power. Also makes it easy to check the status led. Mounted the gps antenna on the dinghy davits.

Hi again Tim and Trevor

I recently purchased an Em-Trak B954, also built-in splitter etc. and I'm looking for a good mounting location. Being an older boat I have the big Nav cabinet like you do Tim. However I found info that the AIS unit should be located 3 ft. from a VHF or other transmitting device. Tim yours will be less than 3 ft from your VHF, so wondering if you have had any interference on the AIS like maybe when you are using the VHF?

I do want to put my AIS in the nav cabinet but also thought about putting in on top of the hanging locker in the aft cabin to move it a little further away from the VHF.

It may be that Em-Trak are covering their collective asses by recommending a 3 ft distance.

My backbone runs through the raceway under the side deck in the aft cabin so connections are still all close at hand for Co-ax, power etc.

Thanks

Hi Kirk,
Interesting. I understand the requirement to space antennas, but haven’t heard the devices have to be that far apart. Clearly there will be some rf energy, but I haven’t noticed any issues with having radio and ais less than 3 feet apart. I took a look at the vesper manual and there was no mention either. I used the ais and vhf simultaneously pretty extensively during our icw trip from Galveston to Pensacola without any noticeable issues. I do occasionally check the health stats of the ais on it’s app and haven’t seen any abnormal RSSI on a channel. Could be “cya” as you mentioned. For me, the convenience of installing in the nav station and easily checking the status led’s was very nice! The top of the closet in the aft cabin would work also, but my generator control panel is mounted there as well.

Tim

It may be something specific to the Em-Trak as they state it in their manual, but I can't imagine an AIS that can't be mounted close to a VHF radio. I expect there isn't much energy that emanates from the radio or even the co-ax cable. So yea, cya.

I have my solar controller mounted in that cabinet and it is very convenient to see the status LEDs etc. There is still room in there for more electronic stuff. I'll be on the boat this weekend to finalize the location for the AIS. Even the shelf in the aft cabin isn't 3 feet away maybe 1-1/2 feet max.

Your experience is great feedback.

Thanks

Hi All,

The distance between antenna is suggested to be greater than 3 ft because both VHF and AIS share very similar frequencies, 156 & 162 Mghz, respectively. Less than three feet is the magic distance to set up destructive waves between the two frequencies. If you antenna are closer than that you may not necessarily notice it because it will be directionally affected. E.g. any signal coming in from the AIS direction to the VHF will be interfered with and you may not pick that up, and visa versa for the AIS. Not all that much different from being blind with your radar as the sweep passes the mast.
Insuring greater than 3' helps get full 360 reception.
Also you don't want to share antenna between VHF and AIS as the transmitting frequency on the single antenna, while close to optimal, will compromise your reception and transmission distances.

Take care,
Scott

Hi Scott

Thanks for the great input, I keep learning. I have seen the 3' recommendations regarding distances between 2 antennas and it makes sense.

In my case the Em-Trak AIS has a built in splitter so it doesn't require a second antenna fortunately. That saves me from trying find a good location for another antenna.

The installation manual for this particular AIS says "for optimum performance the transceiver should be mounted at least 1 meter away from other high power transmitting equipment, like VHF radios". However I'm going to test-mount it about 1-1/2' from the VHF and see how it works. I know that others have put their AIS units much closer to the VHF with no issues at all. So I hope to get the same results with this one.... fingers crossed. I won't screw it down into place until I see how it works. If I need to I can move it further away, but it would be a less convenient location.

For the Em-Trak AIS units that require a second antenna, they recommend 3 meters (10') or greater between antennas! So that would make it very hard to mount it at the masthead which is probably the best spot for range etc.

Leaves me a little baffled.

Cheers

Greetings:

I just had a used AIS installed in my boat. GPS receiver is mounted on port dinghy davit with a clamp type base. Line runs through a “clam shell cover” into the interior of the boat. The two black boxes are attached to the ceiling in the aft cabin just forward of the aft bulkhead. After removing the fiberglass cover over the steering cables. You will find plenty of room for the VHF splitter and the AIS box. I thank Bill Cullen for pointing out this great place to hide the boxes out of sight. ( Looking to starboard, Bow is to the left, stern is to the right )

I mounted the AIS unit behind the upper panel of the electrical panel very close to the VHF. Everything seems to be functioning fine, The only downside is that it sure was awkward getting it in and mounted and one can barely see it thru the the lower (breaker) section when it is folded down.

Trevor