AIS reception with a marine VHF radiotelephone
To receive AIS using a marine VHF transceiver, you need:
- A modified VHF radiotelephone with a discriminator output
- An audio cable between your receiver and PC
- A PC with soundcard, runningthe appropriate software:
- Shipplotter, a complete solution. Or
- AISMon with navigation software like SeaClear or
WinGPS. This requires somewhat more computer
knowledge to configure.
New channel allocation
There is one snag however. AIS is transmitted on two frequencies: 161.975 and 162.025 MHz.
In older marine equipment, as well as equipment with a USA channel allocation, this corresponds with duplex channels 87 and 88.
Old channel allocation
| Channel |
Transmit |
Receive |
| 87 |
157.375 |
161.975 |
| 88 |
157.425 |
162.025 |
Recently (from 2000 to 2004), in most parts of the world, channels 87 and 88 have been reverted from duplex to simplex channels.
New channel allocation
| Channel |
Transmit |
Receive |
| 87 |
157.375 |
157.375 |
| 88 |
157.425 |
157.425 |
Unfortunately, a marine VHF radotelephone with this new channel allocation can't be used to receive AIS.
How do I know if I can use my VHF radiotelephone to receive AIS?
There are several ways to find out:
- Look in the manual. It usually contains a table of channels and corresponding frequencies
If the receive frequency of channels 87 and 88 are 161.975 and 162.025 MHz, you can receive AIS. In some cases, the user can switch between two channel allocations.
- Take a second VHF transceiver and tune both sets to channel 87 or 88. Transmit with the second marine VHF set. If you can receive the transmission on the first one, it has
channel 87 or 88 programmed as a simplex channel. The receiving radiotelephone can't be used for AIS.
Programming your equipment
In case your equipment has a new channel set: your dealer may be able to program AIS1 and AIS2 (161.975 and 162.025 MHz) as additional ('private') receive-only channels in your marine VHF.
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