AirNav Systems Forum
AirNav ShipTrax => AirNav ShipTrax Discussion => Topic started by: dorsetderek on February 05, 2012, 09:19:08 PM
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Will there be any advantage using a larger aerial with the ShipTrax?, I live quite close to the sea, dorsetderek
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It's not so much about the size of the aerial as the height and making sure it's the correct type.
AIS uses Marine VHF frequencies and VHF is "line of sight", which basically means if you can see the target then you can hear it.
To get more range then the higher the aerial the better.
I don't know about ShipTrax but any normal AIS unit will work fine with a standard marine antenna.
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I find that you don't need clear line-of-sight, just "nearly" line-of-sight. I can't see Invergordon, there are hills (and houses) in-between, but I get a good signal from ships there.
And to be honest, I tried a couple of marine antennae, and actually found that my standard £30 discone antenna gave much better reception of AIS. I never really understood why, but I get great reception with a cheap discone mounted in the loft, with concrete roof tiles blocking the signal.
That's using the ShipTrax receiver. Using a Comar AIS-2-USB isn't anywhere near as successful though!!
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Get here the best results with a combi-antenna for 144/430 mHz, it's abt. 2.25 in length, mechanical very strong; it is now abt. 15 years in use on rooftop and still standing strong.
Tried also a yagi antenna, also a combi for 144-430 mHz, nice if you have the shiptraffic in one direction.
The difference between a (cheap) general scanner antenna and a professional marine antenna will be mainly its mechanical stability of the last one.
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The atmospherics also play a part in the range that can be obtained.
During summer high pressures I've managed to pick up AIS base stations in the Faeroes, that's something like 250 miles.
I currently use something similar to this Metz Manta (http://www.saltyjohn.co.uk/metzmantavhfantennaaerial.htm) which is mounted on my anemometer mast on the chimney of the house at about 45m ASL.
You can see the range map of what I get with this and my Comar AIS-2-USB on MarineTraffic (http://www.marinetraffic.com/ais/default.aspx?zoom=7¢erx=-6.176¢ery=58.249&oldmmsi=459).
Note: The reception to the far south, Kyle of Lochlash, is most likely the local Coastguard helicopter rather than shipping. ;-)
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Note: The reception to the far south, Kyle of Lochlash, is most likely the local Coastguard helicopter rather than shipping. ;-)
Yes, helicopters can play havoc with reception range measurements. I asked Airnav to exclude Type 9 (SAR) messages from the polar chart in ShipTrax. I also get the occasional long-range signal from the west coast:
(http://farm8.staticflickr.com/7029/6816228833_f7b104247c_m_d.jpg) (http://www.flickr.com/photos/tarbat/6816228833/sizes/o/in/photostream/)
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The atmospherics also play a part in the range that can be obtained.
During summer high pressures I've managed to pick up AIS base stations in the Faeroes, that's something like 250 miles.
I currently use something similar to this Metz Manta (http://www.saltyjohn.co.uk/metzmantavhfantennaaerial.htm) which is mounted on my anemometer mast on the chimney of the house at about 45m ASL.
You can see the range map of what I get with this and my Comar AIS-2-USB on MarineTraffic (http://www.marinetraffic.com/ais/default.aspx?zoom=7¢erx=-6.176¢ery=58.249&oldmmsi=459).
Note: The reception to the far south, Kyle of Lochlash, is most likely the local Coastguard helicopter rather than shipping. ;-)
Your right I have got ships off Africa-- Italy and India many many times over the years with my ShipPlotter program, i use the Watson 6m/2m/70cm Tribander from Waters & Stanton
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I had a marine aerial and like Tarbat, found that my Discone mounted outside on the chimney, at half the specialist aerial cost, is far better on AIS. I'm 12 miles inland, but can see to the 40 mile radius, i.e. 25 - 30 miles out to sea under flat conditions, and sometimes as far as Rotterdam under a lift! I don't use an aerial amplifier, that picks up every thermostatic blip and corrupts the data. I do use top quality coax though, UR67 when I bought a 100m. That has been superceeded with lighter, and no doubt a more user friendly replacement!
Peter
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Yes, helicopters can play havoc with reception range measurements. I asked Airnav to exclude Type 9 (SAR) messages from the polar chart in ShipTrax.
The only problem with excluding Type 9 is that you're also excluding all the rig stand-by vessels and maybe the RNLI Lifeboats as well as the SAR aircraft. Considering that there are only 4 Coastguard Helos in Scotland, and only two of those will normally be flying (one from Stornoway and one from Sumburgh) then it's denying you quite a lot to save very little. ;-)
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Hi All I`ve been using Shiptrax since saturday,first impressions not bad i`m finding the software a bit clunky like the first iterations of the RadarBox software. I`m used to shipplotter so was surprised not to be able to see the Thames RNLI boats, I could hear them on the marine radio, so now I know why a bit of a bummer really as I live in London my range is quite limited is there a workaround to re-instate. Regards Lou.
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Lou.
Keep them reports coming.
What range are you getting, and report the likes and dislikes and a few photos would be niece.
Thanks.
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The only problem with excluding Type 9 is that you're also excluding all the rig stand-by vessels and maybe the RNLI Lifeboats as well as the SAR aircraft.
As I understand it, type 9 messages are for SAR aircraft only, not ships. See http://gpsd.berlios.de/AIVDM.html#_type_9_standard_sar_aircraft_position_report
I would not expect rig stand-by vessels to be transmitting aircraft messages. In fact I think I've seen several rig stand-by vessels in Shiptrax on there way in and out of Invergordon. But even if there are ships transmitting type 9 messages, surely they are most likely to be in areas covered by other ships anyway. The problem with including SAR helicopters in the polar chart was that it quickly got distorted by returns from helicopters >60 miles away.
Hi All I`ve been using Shiptrax since saturday,first impressions not bad i`m finding the software a bit clunky like the first iterations of the RadarBox software.
I didn't realise Airnav had started shipping ShipTrax to customers, so great to see some real users. Do you have anything specific about it being a bit clunky? Maybe there are suggestions to help make it less clunky for you.
I`m used to shipplotter so was surprised not to be able to see the Thames RNLI boats, I could hear them on the marine radio, so now I know why a bit of a bummer really as I live in London my range is quite limited is there a workaround to re-instate.
Type 9 messages are all displayed in ShipTrax, they are only excluded from the polar chart. here's an example:
(http://farm8.staticflickr.com/7167/6525025693_fd0e83043d_t_d.jpg) (http://www.flickr.com/photos/tarbat/6525025693/sizes/o/in/photostream/)
Maybe the Thames RNLI boats aren't AIS equipped?
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As I understand it, type 9 messages are for SAR aircraft only, not ships.
Looks like you're correct, we only see "SAR" in the type box on both ships and aircraft so I wasn't aware they transmit different raw data packets.
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Looks like you're correct, we only see "SAR" in the type box on both ships and aircraft so I wasn't aware they transmit different raw data packets.
In ShipTrax you'll also see the type as SAR. Here's an example from today:
(http://farm8.staticflickr.com/7025/6846008787_b1f24114f5_o_d.png)
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Hi Tarbat is it ppossible you could PM me,I have a problem I would respect your advicee on.Regards Lou ( no nothing is dropping off)
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Hi Tarbat is it ppossible you could PM me,I have a problem I would respect your advicee on.Regards Lou ( no nothing is dropping off)
I've sent you a PM, although it's just as easy for you to PM me!
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Am I right in thinking there was going to be A software only option aswell?
Thanks
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At the moment there are no plans for a software only option.
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Thanks for your relpy's so Shiptrax how is the product selling?
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Hello Everyone,
I ordered my ShipTrax unit eight days ago from Waters & Stanton in the UK and they told me it would be shipped via Royal Mail and I should have it in 4 days.
Should I be concerned that it hasn't arrived here in Maryland USA?
I am planning to share my data from the Port of Baltimore and the surrounding waterways.
I will be using a DPD AIS half wave antenna at 33 feet with low loss LM400 Coax.
I am currently using Shipplotter with a ACR 2 channel USB receiver with a discone antenna at 25 feet and can receive ships out to 25 to 30 miles from me. I have also tried marine antennas and found the discone out performs them.
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Hi Larry,
Send support an email with your order details and we will check whats happening.
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dorsetderek,
ShipTrax is selling well and we are getting good comments from customers.
larry.putman,
As informed via email but just to keep the forum up to date, you purchased through a dealer and not us so you will need to contact them on delivery queries.
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Larry,
I don't which type of delivery they are using but when I've ordered items from the U.S to be delivered to me in the UK it normally takes about 10 days. That's using USPS & Royal Mail, including clearing Customs. ;-)
You should have got a tracking number, if not then email W&S and ask if they can provide one for you.
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Hi, Can anyone who has Shiptrax tell me what the shiptrax network is like?, Will the network coverage get bigger as units are being sold?
Thank you
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Hi John,
The network uses AISHUB's network as well so its already quite busy, as more Shiptrax units are sold the coverage will get even better.
The link below shows a map of the amount of ships in specfic areas.
http://www.airnavsystems.com/ShipTrax/network.php
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Hello to All,
I have received my ShipTrax software/hardware!
Thanks to AirNav for thier assistance!
I am very impressed with the software and hardware!
I am also impressed to see how big the network of users is!
I am located in Pasadena Maryland and I am now adding shipping from the Port of Baltimore and beyond.
I will take a polar plot of my discone antenna for a couple of days and then switch to my DPD antenna to compare the range and patterns. I will report back to the group with the info.
Larry
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Thanks Larry, will be interesting
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Larry, happy to see you are finally playing with your brand new ShipTrax.
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The receiver sensitivity is definitely better on the ShipTrax receiver then my SR-162!
I find that I can copy ships 5 miles farther away so AirNav has a winner!
Larry
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The receiver sensitivity is definitely better on the ShipTrax receiver then my SR-162!
I find that I can copy ships 5 miles farther away so AirNav has a winner!
I have to agree. During beta testing I was seeing around 40-50% more AIS messages being received, and better range than other receivers. There are some great hardware designers working for Airnav.
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What is the purpose of the "Ground Station" ?
I have one 38.6 miles away that shows up on the map.
Since I can not see the messages I can't tell what if anything the station is transmitting.
Thanks
Larry
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Ground Stations transmit a TYPE 4 message type every 10 seconds. A bit like a digital lighthouse. They also transmit data link messages regularly, and serve many other purposes within the AIS system. See http://en.wikipedia.org/wiki/Automatic_Identification_System for a bit more information.
"Shore based AIS transceiver (transmit and receive) which operates using SOTDMA. Base stations have a complex set of features and functions which in the AIS standard are able to control the AIS system and all devices operating therein. Ability to interrogate individual transponders for status reports and or transmit frequency changes."
My STRAXMON utility lets you see what message types you are receiving. See http://www.airnavsystems.com/forum/index.php?topic=6160
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Hi Tarbat,
Thanks for the info!
The link to the STRAXMON utility says it is off limits to me :(
I am very interested in it though so how do I get it?
Thanks
Larry
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Hi Larry,you can download a small programme free from Aishub.net it is lightweight and runs straight from the desktop, it lists all twenty four types of messages, be aware that you cannot run this programme while your AIS reciever is running.Regards Lou
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Sorry should have said while your AIS software is running.Lou
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The link to the STRAXMON utility says it is off limits to me :(
Sorry, it was posted in the beta testing forum. Attached is the STRAXMON program. It's designed to read the port 40004 output from the ShipTrax software, so it works alongside ShipTrax at the same time.
I've been using this program that I developed to see what AIS message types ShipTrax is processing and count the number of messages. I guess others might find it useful.
(http://farm6.static.flickr.com/5064/5733170644_57e9a7989a_o_d.png)
A. Download and unzip to anywhere.
B. Run ShipTrax
C. Run straxmon.exe.
D. Read the instructions, which are:
1. In ShipTrax ensure "Share received data on port 40004" is ticked.
2. Adjust the poll interval to a level appropriate to the message rate at your location.
3. Press the START button.
4. To reset the counters back to zero, press the RESET COUNTERS button.
5. To exit, simply close the window.
Some warnings:
1. FIXED It doesn't handle multipart messages correctly, although it handles the first part correctly.
2. There is NO error handling.