AIS Marine Tracking Bight path openings

[VK5AKK]

Brilliant detective work Leigh. And I was ready to give it away if truth and accuracy could not be established. Been going through all my maps with the view of what if there was a repeater at Fremantle and things just did not add up.
That brings my maximum Rx distance back to a more realistic 2948 Km.
Thanks
Phil

[VK4GHZ]

Thanks for the update Leigh.
Nice to know digi-peaters are not involved, in this case at least.

But if repeaters were involved, you would have to assume that they are repeating signals in their own immediate region, much like any any ham FM voice repeater?
And like stumbling across a distant 2m FM repeater, it's highly likely most of the traffic on that repeater is local to the repeater.
So, in theory the AIS system is still giving a useful indication of propagation into an area.
Whether it's a land based repeater 5, 10, 20, 30 miles away from the ship, do we really care?

This falls down of course, if the repeater is picking up enhanced signal well outside of its own region... exactly what we are hoping and looking for!

I wonder if there is any authority in Australia we could contact to ask the question:
Are AIS repeaters in actual use, and if so, where?

[VK2HRX]

........

I wonder if there is any authority in Australia we could contact to ask the question:
Are AIS repeaters in actual use, and if so, where?

Someone at the Maritime College in Launceston would know. We need a VK7 in Launceston (VK7PD?) to hunt this down.

[VK2KRR]

Some of Phil VK5AKK's coverage this morning -

VK5AKK 14.02.13

[VK2KRR]

VK5ZEA Port Lincolns coverage this morning -

VK5ZEA 14.02.13

[VK5PJ]

Hi,
looking at both those plots Leigh, it is evident that there are spots from the N/W of West Aust. so once again we are in the situation are these actual direct path spots or does the possibility of an AIS repeater bob up again? I would love to think there is the possibility of an opening to Indonesia one day but there is just that thread of doubt in there after the possibility of repeaters was raised.

I do not want to be Mr Negative but we have to some how find out one way or the other, I do not have any contacts so I hope other forum readers may be able to shed some light on this.

Peter, vk5pj

[VK2KRR]

The only way to get more knowlegde of whats happening is for VK5AKK (or 5ZEA) to have Shipplotter running. Spotting to marine traffic .com only shows partial amount of spots heard if there is multiple stations hearing the same signal. Running Shipplotter shows everything that is heard, but only the local SHipplotter program on PC connected to AIS rig.

IF in fact there was a repeater, Alek should be hearing it, Phil 6ADF should be hearing and the Freemantle station. Only the person who logs the spots first gets them on the map on marine tracking. So if VK5AKK had Shipplotter and was hearing a repeater in VK6 somewhere, he should log ALL spots that anyone else is hearing onto the Shipplotter logs within his own system, not just the two northerly ones showing up on the map.
If he only got the two ships to the north then I would suggest that its a direct signal.

Also I will send a email to Alek VK6APK at Bunbury as ask him if he has heard of any such repeaters. Although one person who is in the area is Phil VK6ADF just north of Perth who does read the logger posts.

Alek VK6APK is the most southerly station but he always hears more spots than anyone and at greater distance. If there was a repeater it would have to be more northerly past Perth to be able to pick those signals up north. Thus stations like VK6ADF VK6XLR and the Freemantle station should have a better chance at hearing these signals but they rarely compare to what VK6APK hears on the marine tracking maps.

Similar to last time though, there was an inland low pressure trough, well inland down the west coast. BoM MSLP attached -

5am MSLP 14.02.13

[VK2KRR]

VK5ZAI was also in on the NW coast WA spots from yesterday morning -

VK5ZAI 14.02.13

[VK2KRR]

Just for comparison, here Ive attached VK6XLR, VK6APK and the Fremantle stations 24 hr maps-

VK6XLR Geraldton 14.02.13

VK6APK 14.02.13

Fremantle 14.02.13

[VK6ZFG]

Hi

Some years back when I was commissioning the new Dampier Port Authority (Karratha) communications system ships where visible as far a Indonesia. This is a normal occurance for Dampier/Karratha area.

The AIS information is used with the radar information. Repeaters are not use with AIS. Two frequencies are used for the AIS so to overcome co-channel interference to the AIS signal by making use of both frequencies for the AIS so as to give a "second" chance for the AIS signal to get through in heavily congested areas.

Igor

[VK6ADF]

I have not had my PC connected or have been monitoring since Sunday due to being away. I have not seen anything in the past that would make me think a repeater is being used anywhere. Last time this came up was due to human error. The only way to know for sure is as Leigh said, to run software that displays on a map locally.

[VK2KRR]

Some enhancement across the Bight over past 48 hours. Path was terminated before a low pressure trough/cold front between Esperance & ALbany.

VK3ZQB

VK5ZAI

VK5AKK

[VK2KRR]

VK5ZEA

[VK2KRR]

Phils coverage this morning -

VK5AKK morning 09.04.13

[VK2KRR]

Phil VK5AKK this morning got a couple of decodes on the west coast of VK6. Well done Phil.
The most distant one is in the area of 2400 Km.

VK5AKK to west coast

[VK2KRR]

I'll post this one up here for start of the Bight Path. I picked these 72 signals up from 1500 to 1700 utc last night.
There were 11 x Class B 2 watt signals in this also, they came from the vessel RV NGERIN.

VK2KRR AIS morning 05.06.13

[VK2KRR]

Just a quick snap shot of what im hearing at the moment on my marine track set up. Some fantastic signals this evening from the westerly direction near Adelaide (800km) but also some brilliant signals up north of the Spencer Gulf (900km).

VK2KRR Marine tracking 10.39pm 24.07.13

[VK2KRR]

First good one for the season. Well done Phil.

VK5AKK early morning 04.10.13

[VK2KRR]

My system was able to hear 2 ships out in the Bight this morning, I got about 12 signals from the more distant vessel around 1900 utc hour and about 20 from the closer spot. This was about 2100 hour.

VK2KRR AIS morning 04.10.13

[VK6LD]

Hi Leigh,

I am looking after an AIS system here for a while. There was some ducting running up the west coast last night and this is what the AIS system here heard.

Cheers,

Rob...

2M AIS from Perth - 15 October 2013.