New rtlsdr Plugin

[piluso]

there are large high speed ferries doing 40 kts

Ferries....
Is interesting to share experiences that show differents situations. The "Instructions in Notices to Mariners" are scary, no doubt in such scenario your criteria is very reasonable

[LeoA]

Originally Posted by the_muck

That is interesting... on this weekend i can test a bit more . can you tell something about the stick and start oparators?

The sdr stick that I use is a NooElec R820T2 Amazon.com: NooElec NESDR Mini 2 USB RTL-SDR & ADS-B Receiver Set, RTL2832U & R820T2 Tuner, MCX Input. Low-Cost Software Defined Radio Compatible with Many SDR Software Packages. R820T2 Tuner & ESD-Safe Antenna Input, Guaranteed: Electronics

"C:\SDCard\Program Files\rtl_ais_win_v0.1\rtl_ais.exe" -p74 -g 38 -n are the parameters for rtl_ais program.

[seandepagnier]

Originally Posted by piluso

I think a library could be built using MinGW and used into VC. I'll try this as a next step.
This is like to automate a graphical method, seems to be feasible, would be great if we can code it.

I think I'll try to build it in for linux, then maybe you can make it work on windows?

It would be cool to autocalibrate from AIS in an intelligent way, but also we can code an option to transmit on a known vhf frequency which a lot of people can easily do to quickly calibrate the dongle.

Any more news on softfm vs rtl_fm? I would like to offer different filters. The more feedback I am seeing it is less and less clear what setup is optimal... Probably has more to do with the antenna than anything else.

[rgleason]

Sean,
QUOTE]Can code an option to transmit on a known vhf frequency which a lot of people can easily do to quickly calibrate the dongle.[/QUOTE] Good thought, Yes.

At first I understood this incorrectly which leads to the next question. Is there some way to manually transmit using VHF DSC Vessel name, mmsi, lat long, course, speed? Kind of a manual AIS transponder? --Maybe this is way to convoluted. You are just going to get on the VHF and hail the boat.

I wish I'd gotten the newer noelec dongle, but I tried them again.

This time I followed:
RTL-SDR Tutorial: Cheap AIS Ship Tracking - rtl-sdr.com

To set up an AIS ship radar on a windows system you will need four things.

1. An RTL-SDR dongle working with SDRSharp.
2. An audio piping method.
3. A vertically polarized antenna tuned to 162MHz.
4. Software for decoding the AIS signals.

In particular Item #2 using Windows Stereo Mix
Tutorial: How to Enable Stereo Mix in Windows 7 - rtl-sdr.com

I thought that was the missing link to Opencpn, but stilll no dice. the Rtlsdr dongle sort of works in SDRsharp etc and not in Opencpn.

[rgleason]

Boston tests:
1. Rooftop with DVB-T+DAB+FM USB dongle and rough AIS Colinear Antenna. Nothing
2. Out Window 50' high AIS antenna horizonatal with dAISy AIS reciever. 20 ships
3. Out window with DVB-T+DAB_FM USB and AIS antenna. Nothing.
--Rooftop is not really a viable location, too many buildings in direction of harbor with no signal.

Some pics showing the rough antenna and coil with duct tape on the roof, then later antenna out the window horizontal with dAISy receiver.

[piluso]

I think I'll try to build it in for linux, then maybe you can make it work on windows?

Sure, I can try !
Beside all the parameters actually used, would be nice to be able to change some of them at runtime: ppm_error,gain, turn on/off rtl AGC, turn on/off debug messages (audio level, nmea senteces), for a fine tunning directly from the plugin (may be in advanced mode).

It would be cool to autocalibrate from AIS in an intelligent way, but also we can code an option to transmit on a known vhf frequency which a lot of people can easily do to quickly calibrate the dongle.

It's a good option, I think the only drawback is that an onboard, or neighbor VHF as RF source will deliver a signal too strong for this may be.

[Maelruan]

Tried rtl_ais successfully this afternoon, and found it uses only 25% or less CPU than AISRec. It's very simple to use with a .bat file. Tracked High Speed Ferries leaving port, but lost signal @ 9 nm range (speed then 35kts), which was about half the antenna horizon. I could still see it. Max range for any target was just over 10 nm but for slower surface targets. I suspected a doppler problem until I got a signal from a SAR heli @ 11 nm doing 139 kts. I'm using a "100KHz-1.7GHz full band UV HF RTL-SDR USB Tuner Receiver/ R820T+8232 Ham Radio" which is more stable than the original dongles with a correction of only -5ppm, and also far more versatile.

[bluegoose57]

As an update, I have everything now running under Windows 10 without any issues so far. I did have to delete the dongle from the control panel, install and re-run Zadig 2.1.2 to enable it. SDRConsole, rtl_ais and OpenCPN seems to be running fine.

[piluso]

Thanks your feedback Maelruan.

Could you please start rtl_ais using -s12k (default is 24k) , and tell us if you see any improvement ?

Regards,David

[Maelruan]

Hi Piluso,
I'm ashore now, and tried -s12k and other values with a spare Slim Jim out the window. -s17K seemed to work a little better than 12. Also varied other arguments. Better overall results using SDRSharp & Shiplotter with the same hardware. 6nm was greatest range from home. It will be a day or 2 before I can try it on board.

[rgleason]

Regarding 162 mhz colinear antenna location. Can I secure it to the backstay? Must it be vertical? Must it be away from and not aligned with other metal things like stays backstay radar mount pipes, etc?
Could I find a hollow fiberglass rod mount it in that and attach that vertically next to the backstay pole mount radar 9' high?

[rgleason]

PS the very simple duct tapped antenna taped to our stern pulpit pops up more "contacts" than I can believe. Everyone seems to have AIS transponders, boats I would not expect..

[rgleason]

There are lots of cpa alarms and there seems to be a scale difference between when I normally get attentive and the greater distance of the alerts. This could become a bother acknowledging all the alerts. I will have to study the setting in greater detail.

[piluso]

there seems to be a scale difference

"Objects in AIS are closer than they appear."
Happy sailing !

[Maelruan]

My best results with RTL_ais using Slim Jim 162Mhz antenna, -g43, & -s25k, are ranges for AtoN 18.6nm, & 14nm for a 29m high ship.
Results with AISRec are still better, also using g43: AtoN 47.4nm (this is on an elevated site), ship 22nm, albeit with far higher CPU demand.
Ranges using a 162Mhz colinier were about half in each case.
Encasing antennas in a non conductive tube & keeping them clear of other conducting material should preserve their designed characteristics. I've been using a Slim Jim encased in a PVC tube very successfully as a temp (2 yrs now) replacement for the u/s VHF whip at the top of my mast.