With ShipXplorer dongle, I had to reduce gain to 8.2 to get best results.
-gr TUNER 8.2 RTLAGC off
For details, please see this post:
Gain vs Number of Ships Tracked
Hello @abcd567 @Jonseyt23 @geckoVN
I just made a new maps plotting over 18K ships, visit here to see your sources.
Thanks for feeding.
https://aismap.hpradar.com/
So I am retesting starting at 8.2 gain and RTLAGC off. I will increase the gain by 1 step every 30mins and make a note of msgs and vessels seen in that time and report back,
On an RTL dongle and on an Orange FlightAware dongle, but not a Shipxplorer one I used this method:
- Adjust gain on the AIS-catcher Signal Level (Min/Max db per minute) graph until it is mostly below 0db
then
- I found it easier to “fine tune” the ppm setting by using the AIS-catcher Frequency Shift (avg PPM per minute) and changing ppm (AGC is off) until the ppm was at the zero line (or thereabouts) on the graph. It is easy to see the change and you only have to wait a few seconds to see if you need to move it some more, and in which direction.
Leave it there for a few hours / days and then check the avg PPM per hour graph.
So I did my little test today, reading every 30 mins whilse upping the gain, the results are below.
| Uptronics 33.2 Gain setting | ShipXplorer AIS | ||||||||
|---|---|---|---|---|---|---|---|---|---|
| Time | Total Messages | Last Minute | Vessels Seen | Time | Total Messages | Last Minute | Vessels Seen | Gain Setting | |
| 09:30 | 382 | 15 | 13 | 09:30 | 48 | 1 | 1 | 8.2 | |
| 10:00 | 471 | 14 | 13 | 10:00 | 57 | 2 | 4 | 8.7 | |
| 10:30 | 385 | 18 | 11 | 10:30 | 107 | 4 | 3 | 12.5 | |
| 11:00 | 485 | 31 | 15 | 11:00 | 145 | 9 | 4 | 14.4 | |
| 11:30 | 542 | 16 | 19 | 11:30 | 138 | 4 | 5 | 15.7 | |
| 12:00 | 569 | 18 | 20 | 12:00 | 153 | 5 | 4 | 16.6 | |
| 12:30 | 512 | 20 | 18 | 12:30 | 207 | 5 | 6 | 19.7 | |
| 13:00 | 446 | 14 | 19 | 13:00 | 159 | 3 | 11 | 21.4 | |
| 13:30 | 542 | 18 | 23 | 13:30 | 240 | 5 | 17 | 22.9 | |
| 14:00 | 645 | 27 | 19 | 14:00 | 340 | 13 | 15 | 25.4 | |
| 14:30 | 769 | 20 | 17 | 14:30 | 560 | 13 | 12 | 28 | |
| 15:00 | 741 | 12 | 18 | 15:00 | 307 | 10 | 14 | 29.7 | |
| 15:30 | 220 | 7 | 15 | 15:30 | 143 | 9 | 11 | 32.8 | |
| 16:00 | 227 | 10 | 15 | 16:00 | 156 | 8 | 9 | 36.4 | |
| 16:30 | 259 | 19 | 15 | 16:30 | 194 | 17 | 11 | 37.2 | |
| 17:00 | 532 | 17 | 21 | 17:00 | 241 | 3 | 11 | 38.6 | |
| 17:30 | 623 | 18 | 15 | 17:30 | 253 | 11 | 9 | 40.2 | |
| 18:00 | 222 | 11 | 10 | 18:00 | 163 | 6 | 6 | 42.1 | |
| 18:30 | 332 | 15 | 9 | 18:30 | 174 | 7 | 7 | 43.4 |
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The VHF DX seems quite hot at the moment. Anyone else seeing (real) ships at very long distances?
(I’ve confirmed these ship are where they seem to be - just over 5500 Nm)
This looks like someone is rebroadcasting the location of specific ships.
Certainly these transmissions are not being received directly from the ships themselves.
Are the far away ships members of a specific fleet or have something else in common?
Can’t see anything in common other than geographic location.
I’ve just had another 13 ship (visible about 2min) around Hamburg
The Hepburn predictions say propagation is very strong in my area, so I’m thinking they might be real.
I found this post helpful to me understanding VHF propagation in the 2m band which is right around where AIS lives. The aptly named phenomenon “The Magic Gradient” could explain very brief and very long distance contacts. The strong overall ducting in your area likely helps, too.
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My lat/lon plug in has gone to pot, redid the plug in from the text on the github site, but still not working properly. All the rest look fine and work
If they are real then I am surprised that there don’t seem to be reports of any similar distance contacts in the 2m amateur band. As far as I am aware the current distance record on 2m is around 4500km whereas your’s are over double that. Interesting.
To fix your problem, there are two options:
Option 1:
Delete lat-lon plugin from folder my-plugin. Without plugin, the lat-lon will start displaying in decimal degrees
sudo rm /usr/share/aiscatcher/my-plugins/latlon_in_dms.pjs
sudo systemctl restart aiscatcher
Option-2:
The plugins downloaded from github are saved here:
/usr/share/aiscatcher/AIS-catcher/plugins
A copy of these plugins is made during installation here, and is used by the AIS-catcher
/usr/share/aiscatcher/my-plugins
Copy downloaded plugin to the in-use plugin folder by following command
sudo cp /usr/share/aiscatcher/AIS-catcher/plugins/latlon_in_dms.pjs /usr/share/aiscatcher/my-plugins/
sudo systemctl restart aiscatcher
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Thanks @abcd567 I thought copying the text into the existing file would of done it, but sudo cp sorted it.
I have the ShipXplorer dongle running concurrently with an ADSB one. I used the script to install sxfeeder and aiscatcher. The script installed Ais-Catcher v0.31. v0.44 is curent. Does anyone know how I can update it?
Thanks!
~ $ rtl_test -t
Found 2 device(s):
- 0: Realtek, ADSB, SN: 00001090*
- 1: Realtek, AIS, SN: 00000060*
Using device 0: Generic RTL2832U OEM
usb_claim_interface error -6
Failed to open rtlsdr device #0.
~ $ AIS-catcher
AIS-catcher (build Jan 28 2022) v0.31
(C) Copyright 2021 jvde-github and other contributors
This is free software; see the source for copying conditions.There is NO
warranty; not even for MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.
Device selected: Realtek, AIS, SN: 00000060
usb_claim_interface error -6
RTLSDR: cannot open device.
~ $ sudo nano /lib/systemd/system/aiscatcher.service
- GNU nano 5.4 /lib/systemd/system/aiscatcher.service*
[Unit]
Description=AISCatcher Service
After=network-online.target
[Service]
Type=simple
User=aiscatcher
Group=aiscatcher
PermissionsStartOnly=true
ExecStart=/usr/bin/AIS-catcher -q -u 127.0.0.1 10110 -u 127.0.0.1 10111 -u 127.>
ExecStop=/bin/kill -TERM $MAINPID
Restart=always
[Install]
WantedBy=multi-user.target
Which script you used to install AIS-catcher?
As you have not informed which script you used to install AIS-catcher, I reviewed your aiscatcher.service file, and came to conclusion it was NOT installed by my script at Github.
However you can update AIS-catcher to latest version by following method:
The above line from service file shows that the current location of existing executable “AIS-catcher” is /usr/bin/AIS-catcher.
Please run following commands to build the latest version of executable “AIS-catcher” and copy it over the old version /usr/bin/AIS-catcher.
git clone https://github.com/jvde-github/AIS-catcher.git
cd AIS-catcher
sudo git fetch --all
sudo git reset --hard origin/main
sudo rm -rf build
sudo mkdir build
cd build
sudo cmake ..
sudo make
sudo systemctl stop aiscatcher
sudo killall AIS-catcher
sudo cp build/AIS-catcher /usr/bin/AIS-catcher
sudo systemctl restart aiscatcher
Sorry. I used the one provided by ShipXplorer:
sudo bash -c “$(wget -O - https://www.shipxplorer.com/install_sxfeeder.sh)”
The ShipXplorer script installs pre-built aiscatcher.deb package from their repository.
In this case use following commands to upgrade:
First check if they have latest version
sudo apt-get update
apt-cache policy aiscatcher
The 2nd command above will show versions of installed and available (candidate) as follows
aiscatcher:
Installed: [version]
Candidate: [version]
If a Candidate [version] is newer than Installed [version], then go ahead with following commands to upgrade:
sudo apt-get update
sudoapt-get install aiscatcher
Looks like ShipXplorer did not update the package:
~ $ apt-cache policy aiscatcher
aiscatcher:
Installed: 1:0.31.0+deb11
Candidate: 1:0.31.0+deb11
Version table:
*** 1:0.31.0+deb11 500
500 https://apt.rb24.com bullseye/main armhf Packages
100 /var/lib/dpkg/status