OpenMarine

I didn’t want to pollute the other thread about SDR AIS in case this is just my system issue or my understanding

I am using OP2 and the SDR AIS module 2.0.1 beta.

In the last couple of days I have tried to calibrate the dVB stock to work with AIS but do not find a channel:

So I ran the calibration tool see the start in the pic below:


and it stabilizes in the low numbers then every so often there is a large variation:

After this it stabilizes out at a number near zero. After that though, if I use this number I still can not find a channel on the GSM-850 band

Does anyone see anything wrong with what I am doing?

Update to 2.1.0

Do initial calibration again and get the ppm after 1 hour. the ppm will never completely stabilize, this is because we call this "initial".

also insert the maximum gain value in gain field.

be sure you are in GSM850 zone: https://www.worldtimezone.com/gsm.html

I had a similar issue. I skipped the initial configuration and just used kal in terminal. My problem was the local cell towers were not detected so i had to use the gain argument to get a signal.

Assuming you are in N. America the -s GSM850
-g is the gain 
-e is the initial ppm (could set this to 0, but i had a ppm for an old calibration)

Open terminal
kal -s GSM850 -g 27 -e -6

Once you find your channel
-c (mine was 236)
kal -g 27 -c 236 -e -6

Edit for version 2.1.0
I just saw the updated 2.1.0 has a gain field. It will run the same commands as above.
Supported gain values (29): 0.0 0.9 1.4 2.7 3.7 7.7 8.7 12.5 14.4 15.7 16.6 19.7 20.7 22.9 25.4 28.0 29.7 32.8 33.8 36.4 37.2 38.6 40.2 42.1 43.4 43.9 44.5 48.0 49.6
put the lowest gain you can get away with there (I used 29.7)
click find channel
This will give you a list of channels in range. Use the one with the best signal strength.
put this value in the channel input
click get ppm

Some other thoughts. I had to move my antenna to a few positions before I could find a channel. If you are unable to find a channel, try bumping up your gain.

Thanks for the feedback, I will try these options out next time I am at the boat and report back

I upgraded to 2.1.0 and tried again and still failed. Just fails to find a channel, I tried two different Antennas, one at the top of my mast and one small portable one. I tried with multiple different gains and found nothing. I am in N America so think GSM-850 is correct and waited 1hr for the initial PPM. I may have more time tomorrow.

Use the maximum gain value

Tried for a long time today, PI was on for a few hrs. Left the calibration happening while I went provisioning:

When I got back it looked like the ppm was pretty stable:

So I put in 1 and the maximum gain of 49.6

Still did not find a channel. I am starting to question if the antenna is an issue but I did try a different one.

Do you get AIS data if you use ppm 1?

No, I cannot find a channel on the GSM-850 band or are you saying skip that and use the 1ppm for the final PPM?

I have moved location about 25miles:


so will try again and if I don’t get a GSM-850 channel, I will just try with 1ppm and see if I get AIS data. It is very rainy today and looks like rain through Tuesday but I will try to get out there in the few couple of days

Hi
I’ve also had issues with the calibration pop up. From rpi3+raspian, I know my correction is 20 ppm. I have been using kal in the terminal, see screenshots, this works and returns a ppm of 20. As I’m in the UK it’s GSM900 not GSM850. Terminal screenshot is from the app PiHelper which I use on my iPad.

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