This can be done, also! However, you are going to need an AIS Antenna Splitter. Both your marine VHF radio and your AIS receiver make use of certain VHF radio-frequencies. Thus, in case of synchronous AIS and VHF radio transmissions you would be at risk of causing damage to any of your devices - especially to your AIS receiving unit!
Marine VHF radio transmissions make use of the VHF radio-frequency range between 156 Mhz and 162.025 Mhz (this range is known as the VHF maritime mobile band). The upper range of this band, though, is also used for AIS-data transmissions (channels 161.975 Mhz and 162.025 Mhz). So, whenever you are transmitting on your VHF radio you would need to block any possible AIS reception at the same time.
An AIS Antenna Splitter can handle such issues and enables you to seamlessly operate your marine VHF radio and your AIS-receiving station using your existing VHF antenna!
All you have to do is to run the basic components of your station (antenna, VHF radio, AIS receiver) through the Splitter by simply connecting their respective cables to their appropriate ports. Then, the Splitter would automatically block any incoming AIS reception for as long as you are transmitting on your VHF radio.
A fine example of an AIS Antenna Splitter is the ASR-100 by Comar which you can purchase from the MarineTraffic E-shop. In case you are interested in contributing to the collection of AIS-data and start sharing yours with MarineTraffic using an existing VHF antenna, you may contact us as we could be able to provide you with an AIS Antenna Splitter for free!