[TG] [TG11] AIS 650 stops displaying targets

[Tom - Raymarine - Moderator]

Hello Tim,

That's interesting.
Since you're in the business: what I would be advising one of our technical dealers here in Australia to do, if they came to us with this problem, is suggesting that they put their portable oscilloscope on the power supply (this isn't a joke, we now push all technical service dealers in Australia to carry a low-cost oscilloscope in their toolkit: I use a Bitscope BS05 with x10 or x100 probes), but more importantly - since the feeling seems to be that the problem is airbourne RF interference - to use a low-cost RTL-SDR spectrum analyser to check for radio interference at 162MHz.

RTL-SDR is our standard tool for looking at all sorts of RF problems. It's a combination of very low-cost USB hardware (~$25), a VHF/AIS antenna and free or very cheap computer software (Win/Mac/Linux/Android but not iOS) to 'listen in' to the same band that your AIS is listening to (~162MHz.) You should be able to run the SDR with the solar system off, then power it on and see whether there's a big change in background noise level. You should be able to see received AIS messages as well as the noise. SDR is an amazing tool for this sort of thing, if you put in a little effort to getting to grips with what it's showing you.

There's a good bit of background info on https://www.rtl-sdr.com/about-rtl-sdr/, you can get suitable low-cost dongles from Ebay and the like.

Attached is a screenshot from my Android phone using the low-cost RF Analyzer app, showing a sequence of AIS signals on the two channels either side of 162MHz in the middle, an FM radio broadcast on the far left and a VHF radio call (a taxi company) on the right. In between all this is just background noise. In your situation i'd expect you to see AIS signals like these when the solar wasn't running and then the AIS transmissions being lost in a higher background noise level when they were. If you get the chance to do this, I'd be interested to see some images.

Good luck with it,
Tom