Here is the SR162 receiver. It is a dual channel receiver. AIS is sent on two channels for redundancy.
Here is the SR161 receiver. It is a single channel receiver. In respect of the package contents, you get identical accessories, the power cable with fuse, the serial cable and the manual.
Here is a comparison of the blinky lights of the SR161 single channel receiver (on the top) and the SR162 dual channel receiver (on the bottom). It is not completely fair as the SR162 is connected to an antenna on the roof and the SR161 is connected to an antenna inside the room for testing purposes. Still the reception was quite good indeed in the room. The SR162 is obviously more busy as it is processing messages from both channels and therefore doing relatively twice the work as the SR161.
The cost of the receivers is a consideration. The single channel SR161 is 199 euro and the dual channel SR162 is 379 euro.
Since I do not have benchmarking software for these AIS receivers I can only comment as to my personal opinion in testing. In respect of whether you would be rather dissapointed in choosing the cheaper SR161 rather than the expensive SR162, I believe that you certainly would not be dissapointed. The SR161 offers good performance for a satisfactory installation, especially if your main intention is to upload the data to a website periodically rather than analyse ship movements up to the minute.
As said before the AIS system uses two channels for redundancy.
If we look at the raw data output of the SR162, we can see the A and B which signifies the AIS A channel and the AIS B channel. The unit is definitely receiving data from both channels.
The SR161 on the other hand will remain on one channel until it encounters interference. The unit I tested was only staying on the B channel which I assume to indicate that there was not any interference encountered. This is different to other single channel receivers which claim to be dual channel but in fact switch channels automatically after a certain few minutes.
What is the real world difference then? Well I can see the SR162 picks up the ships much faster from the beginning but the SR161 is not terribly far behind. In the end it is likely that you may have to wait longer than 12 minutes to pick up all the ship names (These are transmitted not as frequently as the regular positional reports). This was definitely an issue but many ships names were found quickly. There is a possibility that some ship's AIS receivers may also be defective and not transmitting on both channels so with a single channel receiver you might miss them completely.
In the end, if you are on a budget then get the SR161 and a good antenna and be happy. The SR162 is likely to pick up more far away ships but generally coverage within the 30nm or so guaranteed range will be reasonably identical for both receivers, just the SR161 will take some minutes longer to pick up all the ships names.
However if you are looking at making an installation for navigational purposes you probably should get the SR162.
