Fast cheap AIS using $20 rtl-sdr DVB-T SDR Dongles !

[deandavis1]

Thanks, that makes sense... but given given most people have a VHF transceiver on board why does it take a $500 second AIS transceiver to transmit AIS. Isn't it technically possible for a manufacturer to build a low cost, approved, black box that uses our existing VHF to give full transmit and receive AIS? (it would seem there is a big market for this).

Some manufacturers (eg Standar Horizon GX2150) build a VHF transceiver but still only allow AIS receive. Why?

Anyone know what VHF channel AIS is transmitted on?

Thanks again.

[Ambler]

Has anyone got the DVB-T dongle up and running as a receiver yet?
I have just got mine in the post today. It tuned onto digital tv ok, next step is to tune it to receive wx satellites via a qfh antenna?
I already have a proper AIS system and wouldn't compromise the safety value of it with an inferior receiver.
Wayne

[RhythmDoctor]

Originally Posted by deandavis1

Thanks, that makes sense... but given given most people have a VHF transceiver on board why does it take a $500 second AIS transceiver to transmit AIS. Isn't it technically possible for a manufacturer to build a low cost, approved, black box that uses our existing VHF to give full transmit and receive AIS? (it would seem there is a big market for this).

Some manufacturers (eg Standar Horizon GX2150) build a VHF transceiver but still only allow AIS receive. Why?

Anyone know what VHF channel AIS is transmitted on?

Thanks again.

Transmitting AIS is far more complicated than receiving it. Any two boats within 20 miles or so that transmit at the same time will hopelessly corrupt each other's transmissions. As a result, there are extremely complicated timing algorithms built in to AIS transponders to find an unused "time slot" to send out transmissions. This is beyond the feasibility of any DIY project.

I'm sure prices will come down as the technology matures.

[JesperWe]

Being Swedish, I can't resist throwing in a link to GP&C Systems International AB (The inventors of the STDMA algorithm which is the backbone of AIS). Plenty of info there for all interested parties

Implementing STDMA transmission is, as noted above, getting close to rocket science...

[sailorchic34]

Originally Posted by Ambler

Has anyone got the DVB-T dongle up and running as a receiver yet?
I have just got mine in the post today. It tuned onto digital tv ok, next step is to tune it to receive wx satellites via a qfh antenna?
I already have a proper AIS system and wouldn't compromise the safety value of it with an inferior receiver.
Wayne

I've had mine up and running as a general receiver using SDRsharp (windoz software) and zadig, to set the ports on the SDR so SDRsharp can use it. Works pretty well.

Still have to muck about to get the AIS signal over to opencpn.

[klaus53123]

Originally Posted by sailorchic34

Still have to muck about to get the AIS signal over to opencpn.

This is exactly also my problem... But fiut first of all: HI COMMUNITY, I am new here, this is my first post.....

I have set up sdrsharp with zadic and I can receive radio signals from the usb dvt-b stick.

As I live about 600 miles away from the next cost I can however not check the AIS frequencies (in fact I can, but do not receive anything)

The problem is now to get the signal into AISmon and from there into openCPN. I have installed a com5 port with VSPE which AISmon can see.

But here is the problem:
what do I use as output confiq in sdrsharp and what as an input source in AISmon?

How can I test the system? Is there somewhere an AiS audio file (.wav) available which I could run and check whether openCPN can find it via AISmon?

Also I experienced that (at least with my current settings) AISmon can only "hear" signals from sdrsharp as long as I don't tune the volume of the speakers down. I guess I am doing something wrong here, can't believe that I have to listen to this awful AIS noise all the time I try to gather data....

You see plenty of problems. Hope there is somebody out there who can be of help.

All the best
Klaud

[GrowleyMonster]

Originally Posted by kiwiradical

It's a while since I used this, but it's not hard to set up. Just connect an audio shielded cable - centre to the discriminator output (If I remember correctly it's maked 'E' on the PC board) and shield to the battery negative, then connect to an 1/8" jack plug centre connector to tip, shield to ring- easiest to use a jack plug to jack plug cable with one plug cut off. Some relatively easy soldering is required. Then plug into PC sound input. Use AISMon
and configure to input from sound card, and output to a virtual serial port (use VSPE from here Eterlogic - create a device 'virtual' )

Then configure OpenCPN to receive the AIS stream from the serial port.

Obviously the receiver has to be set to one of the AIS channel frequencies.

Range depends on antenna height and size, but should be much the same as any AIS unit. Using the handheld antenna I saw signals from as much as 20miles away when inland at home in a noisy electrical environment.

Wow... thanks for that! What a simple but clever hack! And actually it looks kinda practical!

[larsed]

I've been following this thread a couple of months to see if someone really managed to get ais working the way wetduck scetched in his initial thread. As it seemed no one did or, me and my Slackwarefriend thought we should give it at try.
-After a couple of weeks we finally got it working in OpenSUSE12.3 displayed in OpenCPN with two different DVB-T-sticks for some 150.- SKr.

Greetings

Lars

[Viking Sailor]

Kewl!!!

Good Job !!

Details please!

[larsed]

It is yet to come!

The days att the yard are long this time of the year, we have launching coming weekend then it's the mast and rigging. -After that there will probably be some time for editing and translating. Today the description fills 9 pages 12 p text in swedish that I doubt anyone should be interested in.

Regards

Lars

[seandepagnier]

9 pages? Sounds very complicated. Could a computer translator make it intelligible in english?

If you could get this soon, maybe I could work on some specialized support in opencpn to make things easier.

[larsed]

Dear boat_alexandra!

It's not that I'm reluctant or in anyway want to tease, the process to get it work was complicated and the description is a representation of that. -I do want to stress though that the installation/configuration in no way is too complicated! To that comes that I haven't "cleaned" the description up. Repeatedly we used zypper to make completary installations, repeatedly had to search for dependancy-software that was not in the SUSE repo's and to that comes the ordinary cmake builds, installations.
Our intension is to
Initially:
-describe kernel and module requirements and perhaps an additional description of possible builds of required modules.
-collect all zypper installations to one containing all repo requirements
-collect all rpm and sourcecode collectings/installations to one containing all
Then:
-describe the successive builds of the rtl-sdr software that is required to get AIS working.
-Finally some guidelines about frequency-correction and tuning.

Could a computer translator make it intelligible in english?

I've up to now never found a translation engine capable of making intelligible translations of anything swedish <-> english. Besides, the cleaning up of the description still remains.

If you could get this soon, maybe I could work on some specialized support in opencpn to make things easier.

Here I do not quite follow your intensions or what you mean?

I think I explained what I have to do around my yacht in the weeks to come.
[[I very rarely use to express any disappointment in any forum like this because I know how busy most of the forum members, sometimes developers, normally are. I once was encouraged to make a usable description of how to build OpenCPN in current Slackware because there were some members who described the interest in that or even that I published it on the OpenCPN-Linux-build site. -I can say I worked my ass off for a week to get it ready. Only to find that the interest immmediately dropped to zero.
I have no real objection or complain to make about this! I think the members who expressed their interest really were serious about their interest! But I guess they were all too occupied with other important tasks to have any time discussing this peripheral matter any further. -I respect them in their prioritations! I can only hope that you can respect my priorities of my yacht in the weeks to come?]]

There will be a description, in due time!

Regards

Lars

[seandepagnier]

I was thinking along the lines of a plugin for opencpn that would be statically linked to all the required libraries to make it work.

This plugin would communicate with rtl-sdr and set the parameters correctly. Do you use gr-ais?

Also.. did you get both channels? The two ais channels (161.975 and 162.025) should be close enough so as one of these modules can pick up both channels at the same time.

Also it could automatically play signals on other vhf channels at the same time on the speakers.

[rgleason]

larsed,
I hope I am not the one who made you work so hard...but I think that work is not lost in any event and I learned a lot from it. It was clear you had determination and success and I wanted to understand so it would not be lost.

Indeed, right now I am just looking for a good simple linux installation (dual boot or wipe a Windows install) , which gets me going with opencpn without too much hastle. I am doing some work for Sean and need a Linux install. What do you think?

I have to tell you that many people wok hard on projects in this forum, but I do respect your time. I am also very interested in your success with the rtl-sdr DVB-T SDR Dongle and AIS and hope you can share your methods with us some time soon after your boat. Sean is leaving on a trip, but is a very good programmer working on some great plugins for all of us. He has made a weatherfax plugin that could possibly use this dongle to receive weatherfaxes at sea, also he would very much like to get AIS working with it before he leaves. I would like too do the same.

Just out of curiosity, which manufacturer and model did you get? Chipset?

Thanks.

[sailias]

Thanks larsd for all your work, Cant wait to read your write up. I followed these notes with limited success on Ubuntu.

rtl-sdr

Really looking forward to your notes, no matter how long it takes....

Thanks in advance.

/ch