AIS - Using RX discriminator output

[VK6ADF]

after almost an hour

[VK2GOM]

There you go Leigh - it's our radios!

I live fairly near the sea, at least RF line of sight from here, and decode a max of say 3 ships in 48hrs. Looking on the maps, there are HUNDREDS of ships off the Sydney coast.

Bring on the Uniden scanner!

73 - Rob VK2GOM / G0MOH

[VK2FAK]

Hi all....

Rob, Rob , Rob......Not so quick on the radio thing...hihi

I notice in the Pic provided, there is a strange and different audio card unit used....

I wonder what is that.......Realtek Hi Def Mic input......used...


John

[VK2GOM]

Hi John, I have tried three sound cards now (2 different laptops and a small dongle-type USB soundcard), with both mic and line in, and none are any better than eachother.

The only change I noticed was I got my 3 syncs in 24hrs with the volume turned up a bit, rather than 3 syncs over the course of about 48hrs.

I got an email to say the Uniden scanner is on its way.

73 - Rob VK2GOM / G0MOH

[VK6ADF]

no Rob I am not registered on marinetraffic.com but the ships already show up there, probably from Alec VK6APK in Binningup or some other source. I am probably sharing on the Ship Plotter network though.

John, I have the software loaded on my laptop so plugged the 9600baud cable from the PCR1500 to the mic input socket on the laptop and wound the levels down as low as I could. The mic input is the only input the laptop has. So thats what it is. The onboard sound for the laptop. I think the audio is still higher than I would like normally but seems to be working.

[VK2FAK]

Hi all....

Good to see your scanner is on the way....Rob...

I read here that one turns the sound level up and the other turns it right down....

I guess Rob you have tried turning it down low with that good sound card you have and then checked to see what happens..

John

[VK2GOM]

Hi John, not yet. But, if it works with Phil's on-board laptop sound... I'm sure Phil would understand I'm not putting his laptop down when I say laptop sound systems are pretty ordinary. I wouldn't have thought it'd need a high-end 192kHz sound production quality unit in order to work. Although when I get a chance to make the leads up, I'll try it to at least check!

The modulation method for AIS is strange. It's known as GMSK, Gaussian filtered Minimum Shift Keying. I have read that excessive filtering can destroy the packets.

http://en.wikipedia.org/wiki/Minimum-shift_keying

It makes me wonder is the 9600 tap from the Icom 910H really a true discriminator tap, or does it still have some sort of filtering going on before it leaves the radio, which is causing the packets to become unusable?

The scanner will reveal all!

I will be offline for a bit, but will report back with results when I can.

73 - Rob

[VK2KRR]

Hi John & all,

Would u believe i got the ic910 working via the DIN socket last night, but forgot to press the monitor button
So had no syncs. Will have to give it another run tonight.
Evenings, mornings & night will give highest decode chance here while tropo is at its best.
You will notice if watching 2m logger, I can get repeaters around Melb & geelong when condx are up a bit using the single yagi im using with AIS. But the freq difference may be to much to be sensitive enough.
Anyway will run some more testing tonight.
Thanks for your help & advice everyone.

[VK2KRR]

On since about 6pm here via mini DIN IC910.
No syncs seen yet.
Will leave it running through the night.

[VK5AKK]

On the subject of AIS and using AISMon software, I am dropping offline with the server after my IP upload address line flashes red a few times. This can happen several times a day and is anoying to come home and find that I have not been uploading spots and my status is offline. I have a good ADSL connection and a fast PC so I don't think that my end is the problem. Any ideas or suggestions?
Cheers
Phil

By the way for those interested, in the last week I have succsessfully run AISMon from the 9600 o/p's of my AR5000A scanner, Icom 821H, Yaesu 8900R, and Icom 910H, the 910 giving me the most output level.

[VK2KRR]

Phil AKK,
When you say the IC910 provides the most output, do you mean the IC910 was the best performer with decode numbers and distance? or audio output level ?
I have also seen that flashing red bar came up when I was doing the test file, I thought it must have meant it was working, obviously not. Cant help you with that one at this stage. I have noted with your stats page that it seems to go offline, and I thought it must have been you switching it off, which I thought was unusual, but looks like thats not the case. Maybe email Marine traffic and ask them, or ask the AISmon users group.

On another note, a message was just posted to the WTDN (World Tropo Ducting Network) group from Phil FR5DN on Reunion Island, letting us know that he has had some good conditions over there and his AIS decodes were coming from a long way out.
I have had a look and from what I can he has gotten some decodes from as far out as 2300 Km in the past day or so. Attached is a coverage map for FR5DN :

FR5DN

[VK5AKK]

Leigh,
The 910 gives the highest output and and can easily exceed the top of the level meter whereas the others output is halfway up max. Not yet sure if more is better but seems to work well at around 80%
I have been switching the system off at night but will try to keep to at least 70% on, until the dropping offline issue is resolved.( Emails have been sent).
Yes FR5DN seems to be in a good spot and making the most of it!
Cheers
Phil

[ADMIN]

ADMIN Housekeeping.

All posts relating to using a receiver's discriminator output, and then feeding that audio to a PC's soundcard have been moved out of the on-going AIS topic (over 17 pages long now!), and into this new, specific, topic.
(As opposed to using a purpose built AIS receiver)

You will see remnants of the old topic title.
It is too time consuming to manually edit each post with the new title, and it appears the forum does not have this global rename function.

This should make it easier for others to find information about using your scanner, IC-910 etc as an AIS receiver.

[VK4GHZ]

I've registered with Marine Traffic and have an ID of 448.

I'm taking the 9600 data output from my Icom IC-R1500 (standard facility on the 1500 as a 3.5mm jack on the rear), and feeding the audio into the PC.
Shipplotter has been configured to enable Audio Input.

I'm only getting garbage though.
I have experimented with the demodulator setting check boxes, but nothing improves it.

Yes, I am hearing the data bursts on 161.975 and 162.025 on the speaker, BTW.
Yes, audio is getting to the soundcard, not clipped, as evidenced by other apps such as Spectrum lab.

I was wanting to experiment like this initially, (it's zero-cost entry), and have less than 10 days left on the ShipPlotter trial.
If I deemed worthwhile, I would look at purchasing a dedicated (network enabled) AIS receiver.

Any suggestions specific to ShipPlotter using demod audio?

[ZL1UJG]

Hi,
I ran ShipPlotter with the internal soundcard of my laptop, and had only 1 decode.
I had seen comments that line input is needed, and bought a NZ$25 external USB soundcard (that had line input) and installed that (actually windows self installed it) the decodes started coming.
Also viewing on the waveform monitor on ShipPlotter showed that the waveform is more peakier using line input. I personally think its a timing issue with the small data burst and the RC time constant of the microphone inputs on most PC's.
I use Shipplotter and run AISmon sometimes in parallel. They are quite close in decode %. Mind you I am about 100km from the port, with a 2 to 3000 ft mountain range in the way.
I use an old secondhand laptop and it works ok.
(I am No 238 on Marinetraffic).

Hope that helps
Kevin
ZL1UJG

[VK4GHZ]

Hi Kevin

I'm using the line input of the integrated sound card on my bold XP box.
To rule out the receiver, I've also hooked up the 9600 packet output of the IC-910 into the sound cards line input.
Got one decode, but that's it.
(Which never appeared on the marine traffic map anyway, despite it reporting me being "online")

If the limitation is the internal soundcard, then I've reached the end of this road.

[ZL1UJG]

Hi,
I wouldnt think its the internal soundcard. What does the noise waveform look like on the Shipplotter monitor screen. I run straight out of a diode discriminator, via a coupling capacitor.
I know what my Radio frequency accuracy is, so have adjusted dial.
I also run an LNA.
How far from shipping are you and what antenna are you using.
Thanks
Kevin

[VK6ADF]

Adam, I assume you have looked at the wave patten in the signal window that pops up to see it is getting into the program and not clipping. Maybe that's how you know it was not clipping. The other mistake lots of people do is to forget to press the green button.

I have a PCR1500 here so I will set mine up to audio decode and see what I get.

Got one decode, but that's it.
(Which never appeared on the marine traffic map anyway, despite it reporting me being "online")

thats one of the limitations of Marine Traffic. If someone else already reports the same ship at that time it only shows on their stats but should have shown up on the 3 hour and 24 hour map view I think, just not the live one.

[VK6ADF]

Ok, I set my PCR1500 to 162.025 FM, plugged a 3.5 to 3.5 stereo cable into the packet output socket on the back of the PCR1500, the other end into my very poor quality laptop mic input socket (According to Rob, read earlier in the thread) and this is how I had it setup on the ship plotter screen

The incoming signal looked like this

The process audio tick box in the top left corner was ticked. You can copy what else I have I guess. It's mainly for my SBS-3 which uses ethernet input for ship plotter and before you ask, yes I disconnected the ethernet cable so the only input was the audio to the microphone.

and luckily there's troppo around at the moment so a few ships displaying.

The laptop is an Acer so certainly not top quality, running windows 7.

[VK4GHZ]

Hi Phil

Appreciate the screen shots.

I was about to give up, but thought I'd try one last option.
Try the notebook computer.

Bingo!

Instantly getting good data, and appearing on marinetraffic.com.

It all comes down to the soundcard.
Previously, I was feeding it into the line input of a circa 2004 Windows XP box with integrated soundcard.
I am now feeding it into the mic input of a 2010 Samsung Notebook, running W7.
Mic input, with levels suitably adjusted.

The data isn't clipping, but is close to the edge of the box, unlike the XP line level input, where it was 1/2 way.
Perhaps this is level dependent.

ShipPlotter warns you against clipping, and the tendency is to back the level off.
Perhaps it is better to drive it a bit harder?
I will try this next, back on the XP desktop box.

Now I'm enthused!