AIS - Using RX discriminator output

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AIS - Using RX discriminator output

Postby VK2KRR » Thu Sep 29, 2011 10:06 pm

What do you think of the NASA AIS Engine? how would the RX sensitivity compare to something like a IC910 ? Just wondering if its worth using a dedicated unit like this or tune a Ham rig onto the freqs?
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Re: AIS Marine Traffic Tracking (tropo indicator)

Postby VK6ADF » Fri Sep 30, 2011 8:07 am

VK2KRR wrote:What do you think of the NASA AIS Engine? how would the RX sensitivity compare to something like a IC910 ? Just wondering if its worth using a dedicated unit like this or tune a Ham rig onto the freqs?


You have to use an output from the discriminator output. It's not just plain audio from the speaker. If you listen on a "normal" radio you don't hear much on frequency. So a ham rig would require mods.
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Re: AIS Marine Traffic Tracking (tropo indicator)

Postby VK2KRR » Fri Sep 30, 2011 6:11 pm

Hi Phil,

I would have thought taking the audio from the ACC port on the rig, same port as using WSJT etc, would work ? Maybe not.

I saw the spots on land there too, not sure what the story was there, maybe someone towing their boat?
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Re: AIS Marine Traffic Tracking (tropo indicator)

Postby VK6ADF » Fri Sep 30, 2011 10:19 pm

VK2KRR wrote:Hi Phil,

I would have thought taking the audio from the ACC port on the rig, same port as using WSJT etc, would work ? Maybe not.

I saw the spots on land there too, not sure what the story was there, maybe someone towing their boat?


Hi Leigh, taking the audio from the 9600 baud packet output might work but not the same audio as WSPR or digital modes in general. I managed to see ships when I used my PCR1500 and plugged into the 9600 baud socket.
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Re: AIS Marine Traffic Tracking (tropo indicator)

Postby VK6ADF » Sat Oct 01, 2011 12:25 pm

and a cheaper option thats reasonably new http://www.aircrafttrackingavionics.com ... %20AIS.htm

A PCR1000/PCR1500/PCR2500 also work as will any scanner/receiver with a discriminator output. Descriptions on mods to various scanners can be found here (no ham rigs mentioned) http://www.discriminator.nl/ais/index-en.html

Reading the info on that page with AIS equipped ships transmitting at 2 to 10 second intervals it would be very crowded RF space near a large port. Easy to get missed transmission or corrupted data I guess which could account for way out positions.

I wonder why something that travels reasonably slowly would need to update so often. I know it's a safety device of sorts but 2 to 10 seconds seems a bit quick to me.
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Re: AIS Marine Traffic Tracking (tropo indicator)

Postby FR5DN » Mon Oct 10, 2011 8:34 pm

Hello,

As said, on AIS, i use a yeasu 2m FM rig, the FT-2500M. It is capable of 9600bds after easy mod. I use the discriminator output and decoding is made via PC soundcard. Very probably some better results with dedicated ais rx using both channels at same time. I rx only on 1 qrg at time.
Antenna is DK7ZB style, with boom on eletrical platic tubing, simulated for some 10dbd. The LNA is just behind the reflector and the antenna is pointing ZS, at some 5-6m above ground. The LNA is directly having 12v from the coax, as it is only rx setup, not much trouble here.
The vertical end of mast is wood, not a perfect isolator, but...
AIS not 100% correlates with 2m tropo, but so far a good indicator.
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Re: AIS Marine Traffic Tracking (tropo indicator)

Postby VK2KRR » Tue Oct 11, 2011 10:29 am

Hey Phil,

Great, thanks for the info and photos. I will need to get a bit more antenna power happening I think.

As said I look at your AIS info page quite a bit to see whats happening over there.

Not seen any signals here yet.
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Re: AIS Marine Traffic Tracking (tropo indicator)

Postby VK6DZ » Fri Oct 14, 2011 8:43 am

Thanks Leigh and Rob

Just using an old Uniden (UBC-760xlt) scanner with a discriminator output mod to RX either 161.975mhz or 162.025mhz ( don't scan though, just one channel or the other) feeding the discriminator output into the computer sound card.

The decoding software is AISMon 2.2, which is very simple to use, just select your sound card and IP:Port to upload the data to.

Only using a Discone antenna which is mounted relatively low at the moment, hope to get a 6el Yagi up pointing East soon.
The system seems to work OK so far, has RX'd 1300 messages in one day, not bad for Albany.

I tried this AIS system about 4 years ago and only RX'd about 4 ships in 2 months, a lot better now :wink:
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Re: AIS Marine Traffic Tracking (tropo indicator)

Postby VK2KRR » Mon Oct 24, 2011 6:04 am

Im currently using my IC910 via the ACC socket which should run 9600bbs.

Im using AISmon software, last night I got 25 Sync's but was 100% errors. Would these have been real signals causing this? maybe I have something set up incorrectly ?

Its hard for me to know whats going on when I dont have reliable signals close by.
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Re: AIS Marine Traffic Tracking (tropo indicator)

Postby VK2GOM » Mon Oct 24, 2011 6:47 am

Hi Leigh, have you set the 9600 'on' in the menu on the 910H? You should have a small '9600' showing on the display underneath and to the right of the main band freq.

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Re: AIS Marine Traffic Tracking (tropo indicator)

Postby VK2KRR » Mon Oct 24, 2011 9:26 am

Hi Rob, yes I do have the 9600 enabled and see the little 9600 indicator on screen.
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Re: AIS Marine Traffic Tracking (tropo indicator)

Postby VK2KRR » Mon Oct 24, 2011 4:51 pm

Has anyone used an Icom IC910 to decode AIS signals with success??
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Re: AIS Marine Traffic Tracking (tropo indicator)

Postby VK2GOM » Mon Oct 24, 2011 6:42 pm

I decoded one ship! Out at about 100nm from me. But that is the only ship so far. A few decodes of it, but only the one vessel.

It looks like my IC910 auto AFC-tuning might have been an issue, so have disabled that.

Are there any specs on the AIS transmission, in terms of deviation etc.?

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Re: AIS Marine Traffic Tracking (tropo indicator)

Postby VK2GOM » Mon Oct 24, 2011 6:46 pm

A little info... mentions of amateur gear with a discriminator output (ie. 9600bd) are made with a view to it being usable.

I might try the evaluation version of ShipPlotter instead.

http://www.discriminator.nl/ais/index-en.html

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Re: AIS Marine Traffic Tracking (tropo indicator)

Postby VK6ADF » Mon Oct 24, 2011 7:46 pm

VK2GOM wrote:A little info... mentions of amateur gear with a discriminator output (ie. 9600bd) are made with a view to it being usable.

I might try the evaluation version of ShipPlotter instead.

http://www.discriminator.nl/ais/index-en.html

73 - Rob VK2GOM / G0MOH


I have received AIS transmissions with my PCR1500 using the packet output socket. This was last year but not tried recently. I must try again. This was using the trial version of Ship Plotter which was then registered.
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Re: AIS Marine Traffic Tracking (tropo indicator)

Postby VK2KRR » Mon Oct 24, 2011 7:58 pm

Rob thanks for that link, looks interesting. Am still unsure if im RXing real signals or not, not sure what else would cause it to think there are syncs, there is no interference etc.
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Re: AIS Marine Traffic Tracking (tropo indicator)

Postby VK2FAK » Mon Oct 24, 2011 8:23 pm

Hi all....

Can we assume that you have run the Sample wav files that should come with AISMon and they all decode ok ....to eliminate that as a problem.

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Re: AIS Marine Traffic Tracking (tropo indicator)

Postby VK2KRR » Mon Oct 24, 2011 8:32 pm

Hi John,

Its funny u mention that, because I have been doing that as ur msg come through.

It claims to have 100 valid and 15 errors when u run the wav file. The best I have managed from the file is about 50 syncs with about 5 valid the rest are errors ! :shock:
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Re: AIS Marine Traffic Tracking (tropo indicator)

Postby VK2FAK » Mon Oct 24, 2011 9:01 pm

Hi all...

Well are you using the Mic input ....I have seen it mentioned to use the "Line Input"..

What difference this makes I have no idea....but try it and try adjusting the level control while running the Sample wav and see if that helps...

John
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Re: AIS Marine Traffic Tracking (tropo indicator)

Postby VK2KRR » Mon Oct 24, 2011 9:14 pm

Am trying to make adjustments, Ive gotten it better, but its still about 50 - 50 errors to valids.
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