AIS Questions

[KR8MR]

I live 3 blocks from the Grand Haven MI channel less than a mile to the pier and the lake. I hear what sounds like loud modem noises on either channel 16 or 13. Probably 16. I don't know since I monitor both. Last night the UNDAUNTED arrived around 10:30. So there was more traffic (modem noise) brrrrraaap!! And close by too. So i assumed its associated with the arrival of this boat.

One thing I don't understand is; during the interval that I hear these modem sounds I almost always hear people talking in the background. Could be an image? but It doesn't sound like that. What protocol are these ships using on CH16 or CHAN13. Is it some kinda SMTP or something? Is it clear or encrypted? What do ya know about this? Is there someway they are sharing that bandwidth to have voice as well as data and the data is strong enough to open squelch and allow me to hear both?

Anyone here using an SDR to receive these things? How far does AIS terrestrial data go?

 

[jtwalker]

AIS should be on these channels.


Maybe DTMF tones to request something?

 

[KR8MR]

No I know what DTMF and Autovon sounds like. This is a loud modem sound with voice 10dB or so down.

 

[KR8MR]

AIS should be on these channels.
View attachment 171643

Maybe DTMF tones to request something?

Thank you I wasnt aware of the other 2 freqs. But as I said I am monitoring Marine Ch13, and Ch16 simultaneously on either a Pro668 or a baofeng in which I put one on Channel A and the other on Channel B. I walk the beach with the inexpensive baofeng in my pocket and only know it's affecting one or the other channel. I don't know what the IF bandwidth is set at. I think there are a couple of choices in Chirp. It's all I have available now. We bought a home and I'll have better receivers once we get moved in.

 

[mmckenna]

Thank you I wasnt aware of the other 2 freqs. But as I said I am monitoring Marine Ch13, and Ch16 simultaneously on either a Pro668 or a baofeng in which I put one on Channel A and the other on Channel B. I walk the beach with the inexpensive baofeng in my pocket and only know it's affecting one or the other channel. I don't know what the IF bandwidth is set at. I think there are a couple of choices in Chirp. It's all I have available now. We bought a home and I'll have better receivers once we get moved in.

AIS doesn't run on Channel 13 or 16. If someone was, the USCG would bust them pretty quick. The marine radios/AIS transceivers won't even let you program them to run AIS on those channels.

Based on your description of hearing voice in the background, and this being a Baofeng/CCR, it's more than likely intermod that the radio is picking up, or some mixing going on inside the radio between the voice on channel 13 or 16 and a paging or telemetry system near, but outside, the marine VHF band. AIS is a pretty narrow signal, and really short. Nothing like what you are describing. When you hear it, it's very quick and low modulation.

 

[KR8MR]

Yes, agreed I saw a youtube of what AIS sounds like and looks like on the waterfall. I believe you are right and I am hearing intermod from some paging tower. I once had a PAR filter made to notch a nearby one but that was another time and place.

 

[hill]

Baofengs like all CCR are terrible when it comes to other signals that can interfere. A real marine radio HT or commercial radio wouldn't have these issues.

Back in the in my we had an Aerosat used for coastal defense monitoring and when it was used all CCR received tones all over the 2 meter band.