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AIS What Antenna

Old 10-09-2019, 04:53 AM
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Default AIS What Antenna

I have AIS on my boat and need to buy a new vhf antenna. Does AIS work with a standard antenna or do I need a special one?
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Old 10-09-2019, 05:33 AM
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Is your AIS receive only or transmitting as well? If it's receive only any VHF antenna will do. If you are transmitting AIS, it is recommended to have an AIS tuned antenna.
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Old 10-09-2019, 05:50 AM
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Originally Posted by Mstar5202 View Post
Is your AIS receive only or transmitting as well? If it's receive only any VHF antenna will do. If you are transmitting AIS, it is recommended to have an AIS tuned antenna.
^^^^this
if receive only, any VHF antenna will work.
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Old 10-09-2019, 06:05 AM
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AIS works on Ch 70, so any VHF antenna will work, whether receiving or transmitting.

There are special "AIS" antennas tuned for channel 70 though, that would be optimized for best AIS performance. Whether or not you would actually notice any difference though, depends on a lot of other factors.
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Old 10-09-2019, 06:12 AM
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Originally Posted by km1125 View Post
AIS works on Ch 70, so any VHF antenna will work, whether receiving or transmitting.

There are special "AIS" antennas tuned for channel 70 though, that would be optimized for best AIS performance. Whether or not you would actually notice any difference though, depends on a lot of other factors.
Wrong...just got a new Raymarine AIS 700 , we are getting VSWR fault trying to transmit with standard antenna.


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Old 10-09-2019, 06:35 AM
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Originally Posted by OffshoreApparel.com View Post
Wrong...just got a new Raymarine AIS 700 , we are getting VSWR fault trying to transmit with standard antenna.
Sure you didn't have an antenna problem?? The AIS 700 even supports a "Built-in antenna splitter simplifies installation with existing VHF radio antenna"
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Old 10-09-2019, 06:40 AM
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Most antennas sold as a normal VHF Marine Band antenna for a ship station are tuned for 156-MHz, the low end of the band. That end of the band is where all ship stations transmit.

AIS transmitters operate at the high end of the band at 162-MHz, and a normal antenna tuned for 156-MHz will usually exhibit a poor impedance match at the AIS frequency, often causing the transmitter to shut down due to high VSWR.

For those reasons, antenna manufacturers now offer antennas tuned for 162-MHz as their AIS models.

Because an AIS transmitter needs its own antenna, you should buy an antenna tuned for AIS to use with an AIS transmitter. To buy an antenna that was tuned for a ship station VHF radio for use with an AIS transmitter would be a mistake.

If you want to share one antenna between two transmitters, a VHF radio and an AIS transmitter, by using some sort of fast-switching antenna changeover device, you should buy a special broadband antenna that will be tuned for the center of the VHF Marine Band band and provide a reasonable VSWR at both the 156 and 162-MHz frequencies.
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Last edited by jhebert; 10-09-2019 at 07:35 AM.
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Old 10-09-2019, 08:31 AM
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Originally Posted by km1125 View Post
AIS works on Ch 70, so any VHF antenna will work, whether receiving or transmitting.

There are special "AIS" antennas tuned for channel 70 though, that would be optimized for best AIS performance. Whether or not you would actually notice any difference though, depends on a lot of other factors.

wrong. The 8’ Shakespeare antennas do not work with ais. The higher gain must have a smaller bandwidth. The 4’ work ok.
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Old 10-09-2019, 03:04 PM
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I've a standard base model 8ft shakespeare antenna on the work boat and AIS works fine with it.
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Old 10-09-2019, 05:46 PM
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Call Morad, they are super nice and advised what I needed and even gave me a discount over the phone. Shipping is fast and very reasonable.

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Old 10-09-2019, 09:04 PM
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Originally Posted by smac999 View Post
wrong. The 8’ Shakespeare antennas do not work with ais. The higher gain must have a smaller bandwidth. The 4’ work ok.
The Wrong” you wrote only applies to you, my friend. The 8’ Shakespeare Galaxy 5225-XT-AIS antenna DOES work with AIS. I previously had a regular 8’ Shakespeare Galaxy VHF antenna and it also worked but not nearly as well as the new antenna. I am using a Garmin AIS-600.


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Old 10-10-2019, 07:17 AM
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Unless your boat is small and there is insufficient room to install a second antenna for AIS, I would not use a fast-switching antenna change-over relay device to share one antenna between your VHF Marine Band radio and an AIS Transmitter.

The fast-switching antenna change-over devices typically cost more than a second antenna and mount will cost. The fast-switching antenna change-over device will need to be powered, adding complexity. Also, the antenna change-over device adds a new single-point of failure that could disable both transmitters.

Considering that a VHF Marine Band radio is a primary safety device, it should have its own, unshared antenna.

The antenna for AIS does not need to be mounted extremely high. As a recreational boat with a CLASS-B AIS transmitter, you really do not need to be transmitting your position to other ships 20-miles away.
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Old 10-10-2019, 04:19 PM
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Jhebert, do you recommend a pis transmitter? I just bought a Icom M605 that only receives . Thanks for any information.
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Old 10-11-2019, 09:58 AM
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I have an 8' digital 900 series
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