Advansea AIS

[BrianH]

Just to confirm that the Advansea RX-100 definately does contain a true dual channel receiver - I have had one apart.....
For those who are interested in such things, dual channel operation is achieved witha single (crystal multiplier) first LO and then two custom first IF filters, seperated in frequency by 50KHz. Custom second conversion crystals then bring both channels to a standard second IF frequency where they are demodulated by seperate FM demodulators and decoded using Microchip dsPIC. A well though out design geared up for low cost high volume manufacture, with every chance of performing well. As an RF engineer by trade, I was quite impressed.
The PCB inside the Advansea unit is supplied by SRT (www.srt-marine.com) and is I beleive common to AIS receive solutions badged by a number of suppliers.

Thanks Rob, good to know.

I was on the verge of ordering one but hesitated. I have been using a really cheap Taiwan product for six years now that is single channel, by that I mean both VHF channels but switching from one to the other (like the NASA engine), and it has worked well. But it was programmed before the Class B standard was established and cannot resolve the static data of those although they do display just as Class A does in OCPN. It also can be up to 15 minutes to resolve Class A static data because of the single channel operation when out of sync with the transmissions.

But it has something the Advansea RX-100 does not ... an integrated GPS chip whose sentences are also output in the same data stream and thus requires only a single USB input to the PC. This seems such an advantage to me that I cannot imagine why, for the sake of a $10 chip and a few lines of code, it isn't included on all AIS receivers.

So I think I'll wait a while.

 

[Arida]

Banac1e,

Yes, agree on integrated GPS - I guess it is generally assumed that the AIS Receiver will be connected to a plotter and will therefore not need GPS.

Actually though, the Advansea unit does include an NMEA multiplexer, with an external 4800bd NMEA input which is suitable for GPS data. And the multiplexer output is presented both as a serial line (38,400) and via the USB port. So, if you have an old style serial GPS available, it can be connected via the AIS RX in order to provide both AIS and position data to a PC via a single USB connection as per your Taiwan unit.

I have done this using a small Telit OEM GPS module in a hand fettled box. (Actually, my box goes further by also including a Wi-Fi module for connection to Tablet/phone, though this last functionalty is currently a little flakey for "mission critical" use. In the end, I came to the conclusion that my time was better spent learning how to sail properly than coming up with electronic gizmos which are really not required for my day sailing in and around Chichester harbour!!)

Regards, Rob

 

[BrianH]

Yes, agree on integrated GPS - I guess it is generally assumed that the AIS Receiver will be connected to a plotter and will therfore not need GPS.

Ah, yes, of course. Didn't think of that. Just shows how we can sometimes only see a situation from our own limited perspective.

Actually though, the Advansea unit does include an NMEA multiplexer, with an external 4800bd NMEA input which is suitable for GPS data. And the multiplexer output is presented both as a serial line (38,400) and via the USB port. So, if you have an old style serial GPS available, it can be connected via the AIS RX in order to provide both AIS and position data to a PC via a single USB connection as per your Taiwan unit.

Point taken ... but I don't have such an animal other than the existing AIS receiver. Now if I could suppress the AIS sentences . . .

Thanks for your input.

Brian.