VK Logger Ham Radio Forum Archive

I've known about this tool for quite a few years, and I know of a number of Amateur Ops who have used it before. Some are using it as an Tropospheric Ducting range indicator. So I guess its time to raise the subject and see if we can maybe get a few more participants.

Marine Traffic .com live ship map - http://www.marinetraffic.com/ais/

Freq asked questions - http://www.marinetraffic.com/ais/faq.aspx?level1=160

At a simple guess, AIS means Automatic Identication System. Ive only been looking into all this today so am fairly new to it all myself. Basically marine ships transmit there position and other data which can be received by anyone with a received capeable of hearing FM on 161,975 MHz or 162,025 MHz with output to a computer with a specific AIS program installed. This gets uploaded to server.

One DXer who uses it quite a lot is Phil FR5DN on Reunion Island. This is a link to stats gathered from Phils AIS RX station - http://www.marinetraffic.com/ais/statio ... ion_id=329

You can see in some of the graphs Phil has at times been able to hear out to over 1200 miles (2000 Km) at which times he has gone on to make contacts with South Africa.

Since we cant put beacons out on floating bouys half way across the Bight, perhaps this is the next best thing. Particularly suited to those stations living close to the coast.

Im going to look into it further, I think I have my AIS RX running, but I need a vertical antenna to have any real luck with it. Yes, I am a long way from the coast, but quite often I hear to the waters edge, how far beyond it goes, maybe I can find out using this method.

Ive attached a map, sourced from Phil, FR5DN site showing some of his AIS 'spots' during a time of good ducting.

I use it quite a bit for Tropo up and down the West Coast.
Here's my station in Geraldton: http://www.marinetraffic.com/ais/defaul ... ldmmsi=649

73,

Hello Rick,

What other details can you tell us about your AIS RX station ? antenna etc?

I see that in around December last year you heard a signal from a vessel almost 2000 Km away, do you recall anything about this incedence ? where was the boat located ?

Nothing special about the station. It's a NASA AIS Engine 3 coupled to a homebrew SlimJim approx 40m above sea level.

DX is very common when tropo is active. As it happens a great deal, I don't bother with screen saves unless it's impressive.

Actually, I think this one may be from December 2010

That blue square on it's own at the left may be the ship in question.

Here's one from April 2010

This was an interesting link: http://www.marinetraffic.com/ais/freestation.aspx

You probably stand the best chance to qualify for a free receiver if you are along the coast somewhere - I think I'd be pushing it, being this far inland. But worth a try for others in better seaside spots.

Gee, I wish ADS-B receivers had been on offer as a freebie!!!

73,
Barry
VK3BJM

Can anyone explain this to me?

See attached map, yesterday I saw a station in Japan, who appeared to be hearing a boat signal near the northern tip of Australia? Surely this could not be correct ? I cant zoom much more than this without losing everything sorry. But where I have the arrow pointing, you will see a small blue dot, this was a ship supposedly reported from that Japan station.

Leigh,
We use the AIS a lot in Karratha to monitor costal ducting especially usefull for a number of hams working off shore on boats using only a hand held
I have even worked Perth via Exmouth repeater

on the 26th we had a repeater interfering with the Wickham repeater, its output was on the same freq, call sign was YB9ZTP Repeater id was in voice

73 from Michael
VK6BHY
NWWA

VK6ADF wrote:[
and ship/ships on the Northwest Coastal Highway and Great Northern Highway too from the looks of it

I'm thinking that could have been SAR aircraft. Only logical explaination.
Unless someone with a boat on a semi forgot to turn the AIS off, lol.

73,

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?

NASA Engine is fine. Does the job well.
No point wasting a $1500+ radio when $200 will do. Then you need to feed the radio's output to a computer and process the audio, etc, so more $$ tied up there. AIS receivers output the processed data directly via RS232. Also the NASA Engine switches between both AIS frequenices where as a non-AIS radio won't.

73,

VK2KRR wrote:Can anyone explain this to me?
See attached map, yesterday I saw a station in Japan, who appeared to be hearing a boat signal near the northern tip of Australia? Surely this could not be correct ? I cant zoom much more than this without losing everything sorry. But where I have the arrow pointing, you will see a small blue dot, this was a ship supposedly reported from that Japan station.

Hi Leigh, I don't know if this explains it but it is one possible answer. Ships tell lies. I have often seen them reporting their position inland. See the example below from today. A ship north of Mount Isa.



So the ship may have been local to the Japanese station but reporting as elsewhere. Note. Only a possible explanation, I don't know for sure.

Wouldn't it depend on how robust and how good the error-checking / check-summing of the sent data was? It'd only need a couple of decoded glitch errors to place something well off in terms of position.

BTW, I know nothing about the protocol it uses, just suggesting possible causes.

73 - Rob VK2GOM / G0MOH

Unsure about the ins and outs of how the data TX RX operates, there is probably info out there though.
Interesting to see quite a few amateur operators in California using these devices, possibly looking across the water to Hawaii.

Icom actually sells a AIS receiver http://www.icom-australia.com/products/ ... -5000.html

Thanks Phil for info.

I agree.. 30 to 60 seconds would be plenty of updates I would have thought ?

I dont know how they would actually even work properly around ports like that, txing so often ? weird.

Just found some info regarding the timing etc, this is from the ShipPlotter FAQ page, I dont have the URL, but do a search.

AIS uses two frequencies in the Marine VHF band: 161.975 and 162.025 MHz. All ships use both frequencies and successive message transmissions are radiated on alternate channels. Professional AIS equipment monitors both channels simultaneously. This doubles the channel capacity and also combats interference. Monitoring a single channel with ShipPlotter means that you only hear half of the transmissions. Since the transmissions are often made at intervals of only a few seconds, this does not significantly prejudice the topicality of the view obtained. Messages are transmitted at 9600 bits per second using GMSK modulation. Each message is typically only 30ms (1/30 second) long – scarcely more than a click.

Ive got my station registered on Marine Traffic .com. My station number is 283.

You can view the info and sats on my stations reception here -
http://www.marinetraffic.com/ais/statio ... ion_id=283

Im running a Comar SLR200N, LMR400 coax, 2m 13 ele yagi and pre-amp. Antenna about 25ft high.

Im not really expecting to see any signals except when the tropo condx pick up. Will advise if anything comes though.

Ive noticed this evening that there has been some greatly enhanced Tropo signals along the VK4 coast, thanks to VK4FGB's AIS station in Cairns who is hearing 12W FM signals all the way along the coast and out in the ocean, this is one of the maps.

Noticed another unknown station from Mackay hearing this in past hour -

And another station from Gladstone getting good coverage 162 MHz this evening -

I am the unknown Mackay statioon vk4ajl
I some times get good signals though antenna is only a mobile verticle but seems to get good tropo conditions at times
Regards George vk4ajl

I now have AIS up and running, my station ID is NO:874
Currently running on a Discone antenna, will put a 6el Yagi up at a later date( when it stops raining )