AIS Setup on 0.15.1

[felizcortez]

I did a complete re-install on my pi 3 yesterday.
Installed  RPI v0.10.0 NOOBS
Updated Raspian
Updated openplotter to 15.1

When I now ran calibration of SDR I got -37 ppm. Tried again after the SDR had warmed up and got -38 ppm.
With this ppm setting I did not get a single ship on the AIS. I remembered that the calibration had been around +48 ppm before, so I used this and voila!

(OpenCPN is running on my phone and I send the AIS and GPS data over bluetooth :-)

I conclude that there is something wrong with the calibration software...

If there are boats with AIS-transmitters in your harbour, then I guess you will be able to pick them up with the supplied antenna, but it is designed for a completely different frequency.

I have tested the following antennas:
http://www.metzcommunication.com/manta6.htm
https://www.aliexpress.com/item/2016-NEW...87854.html
https://www.aliexpress.com/item/2016-New...38821.html

The big expensive works best, but the small cheap ones from aliexpress works OK if you use a ground plane for the antenna (fasten the antenna to a metal plate).

Thanks for the reply.  I'm wondering if it's calibration related as well.  The negative number confused me.  If I just leave the gain value alone since it's maxed out at 49.6 then step through the ppm values starting at say 5 then working my way up one by one.  Does the channel or anything else need to be set to anything, and can I just enable AIS and expect to see something show up in OpenCPN?

Also I believe the connector on the DVB-T dongle is an MCX connector, does that sound correct? So I'd need a converter to BNC or whatever is on the actual antenna.  I'm thinking I might be able to unplug my onboard VHF radio from the antenna it uses to test this out, but I'll need a converter for the connector.  

i like what you did with transmitting GPS and AIS targets via BLE so you can run openCPN natively on your phone.  I'm planning on doing this headless and am not quite happy with interacting via VNC on the phone - it works well on the laptop, but the phone experience isn't as good.  Were there some instructions you followed on how to set this up?

[Sailoog]

I think calibration software is working right.

Cheap dongles have bigger variation with temperature. Connect your dongle for 1 or 2 hours and then calibrate.

The ppm tolerance is +/-7 ppm.

OP calibration method is based on GSM stations and is quite accurate. You need a visual confirmation of your calibration with gqrx or "take a look button".

There is another method, disable AIS reception, open a terminal and type "rtl_test -p" you will get something like this every 10 seconds:

real sample rate: 2048184 current PPM: 90 cumulative PPM: 90

run this for hours until the PPM value stabilizes.

[felizcortez]

I think calibration software is working right.

Cheap dongles have bigger variation with temperature. Connect your dongle for 1 or 2 hours and then calibrate.

The ppm tolerance is +/-7 ppm.

OP calibration method is based on GSM stations and is quite accurate. You need a visual confirmation of your calibration with gqrx or "take a look button".

There is another method, disable AIS reception, open a terminal and type "rtl_test -p" you will get something like this every 10 seconds:

real sample rate: 2048184 current PPM: 90 cumulative PPM: 90

run this for hours until the PPM value stabilizes.

Do I wait for Current PPM and Cumulative PPM to match?  Or do I use the Cumulative PPM for the value after running for a few hours.  I've started running this and am piping the output to a log file so I can share after a while.

The dongle has been plugged in all day, so temperature shouldn't be a huge issue at this point.

[Sailoog]

Just wait for Cumulative ppm value to estabilize after few hours and that is your ppm

[felizcortez]

Just wait for Cumulative ppm value to estabilize after few hours and that is your ppm

Here is the Log.  It looks like it stabilized at 39ppm.

Should I use the Maximum Gain value of 49.6?  I'll need to go to the Marina tomorrow to see whether any targets show up with the current antenna.  

I also included a screenshot of what the output of "Take a look" Looks like.

[felizcortez]

I went sailing today and was able to get AIS signals on the boat!!! The range wasn't great because I was using the antenna that came with the DVB-T stick, but I can make an antenna to fix this. Thank you so much for the help.

[shipahoy]

Great that you got things working!

I unplugged all other sensors and did a new calibration today. Now the calibration worked again! I probably had a power or noise issue last time...

You are right that you need an adapter cable to fit your antenna. And even if you want to build your own antenna, it is proabably best to buy a cable with the small MCX connector mounted.
I used this for the big VHF antenna: https://www.aliexpress.com/item/New-UHF-...0.0.EEJzsG
, and this for the small antennas: https://www.aliexpress.com/item/Sale-100...0.0.uI8gUk


To use Bluetooth you first need to enable Bluetooth on your phone and also enable sharing of internet over Bluetooth on your phone.

Then I opened a terminal and typed:

Code:

 sudo apt-get install blueman
 sudo usermod -G bluetooth -a <username>

, where <username> is pi if you have not changed it.

Then you select "Perferences" -> "Bluetooth Mananger" in the start menu.
Press the Search button.
Select your phone when it is discovered and press Setup.
Pair the device.
Connect to: Network Access Point.

When the device is already paired, you only have right click on the device in the list and choose "Network Access Point".

Type ifconfig in the terminal to find the ip-address of the Bluetooth connection bnep0.

On the Connection tab of the settings of OpenCPN on your phone, add a new connection:
Connection: Network
Protocol: TCP
Address: <bnep0 ip-addresss on pi>
Dataport: 10109
   


Unfortunately there is no reconnect if the connection is lost, so you have to manually reconnect.
I think it would be better if the pi was the Bluetooth access point instead of the phone, but I have not been able to do that yet.