AIS

Show off any of your RTL-SDR or cheap SDR related projects.
xynium
Posts: 12
Joined: Thu May 29, 2014 12:18 pm

Re: AIS

Post by xynium » Fri Jul 11, 2014 2:07 pm

Normally small shift won't have significant effect. I use a sveon adapter the oscillator is precise enough for not being a problem.
Demodulation is made by difference between sample and compared to a mobile mean. So it is robust to frequency shifting.

Can u tell me about your key and the shift you can measure.

73 JP

xynium
Posts: 12
Joined: Thu May 29, 2014 12:18 pm

Re: AIS

Post by xynium » Sat Jul 12, 2014 5:50 pm

It seem R820T tuner doesn't output I/Q signal but only I phase.
If so PNAIS will not run.

73 FM4PN

Dmitry Zhadan
Posts: 3
Joined: Fri Jul 11, 2014 1:00 pm

Re: AIS

Post by Dmitry Zhadan » Tue Jul 15, 2014 11:03 am

xynium wrote: Can u tell me about your key and the shift you can measure.
73 JP
Excuse me for long silence. I'm using RTL-SDR dongle from unknown manufacturer, with R820T. Frequency correction value for it is 35-38ppm, which leading to frequency shift 5-6 KHz.
Also, I'm surprised by your remark that "R820T tuner doesn't output I/Q signal but only I phase. If so PNAIS will not run.". From where this information coming? I can't find any confirmations on the web.

xynium
Posts: 12
Joined: Thu May 29, 2014 12:18 pm

Re: AIS

Post by xynium » Tue Jul 15, 2014 12:11 pm

I only have very sparse info on RTL2832. Pin 1/2 are for I input and 3/4 for Q.
The E4K has I / Q output connected via 4 condensator to the RTL. R820 has only one output connected to 1/2 of the RTL.
These info came from a schematic that explain how to modifie the adapter for a direct antenna connection to receive HF.
As i dont have RTL2832 data sheet i can't tell much more.
May be inside the RTL2832 there is a way to obtain I/Q ...

Concerning your adapter the error is effectively quite important.
I am about to order a R820 adapter and see.

73 JP

Dmitry Zhadan
Posts: 3
Joined: Fri Jul 11, 2014 1:00 pm

Re: AIS

Post by Dmitry Zhadan » Tue Jul 15, 2014 1:05 pm

xynium wrote:I only have very sparse info on RTL2832. Pin 1/2 are for I input and 3/4 for Q.
May be inside the RTL2832 there is a way to obtain I/Q ...
May be this topic on Reddit helps you?
http://www.reddit.com/r/RTLSDR/comments ... deep_info/
User metropolis_pt2 wrote:
"First of all, it depends if you use a zero-IF tuner like the E4000 or a low-IF tuner like the R820T. In the first case, both I and Q ADCs are used, in the second case only one of them is used. The ADCs sample the signal with a fixed rate of 28.8 MHz, which is then passed through a DDC (digital downconverter), a lowpass-filter and into a resampler (which then downsamples to our desired samplerate, 3.2 MHz at max.). The DDC only comes to play for low-IF tuners or the direct sampling mod, and it shifts and filters out the desired part of the spectrum, generating I/Q samples from real samples"

xynium
Posts: 12
Joined: Thu May 29, 2014 12:18 pm

Re: AIS

Post by xynium » Tue Jul 15, 2014 8:41 pm

tks for that info, so it should run on the R820 adapter.

This week end i will add a way to enter a frequency correction.

If one has a need for a frequency correction, this mean that the quartz is shifted. This mean the sampling rate is also shifted.

73 FM4PN

xynium
Posts: 12
Joined: Thu May 29, 2014 12:18 pm

Re: AIS

Post by xynium » Thu Aug 21, 2014 3:37 pm

Hi,
I have received a R820 adapter and saw the problem.
So i build a new PnAis ver 4.1 that should work.
For this adapter the frequencies correction is 55ppm.

73 FM4PN

https://sites.google.com/site/f4eyuradio/ais-decoder

rtlsdrblog
Site Admin
Posts: 2410
Joined: Mon Nov 19, 2012 11:54 pm

Re: AIS

Post by rtlsdrblog » Mon Sep 29, 2014 9:33 am

Seems to work okay for me. It would be good if we could set the gain. When I use max gain I get strong interference from other stations, but at slightly lower gain the interference dissapears.

bobdavis
Posts: 1
Joined: Wed Jan 28, 2015 5:34 pm

Re: AIS

Post by bobdavis » Wed Jan 28, 2015 5:46 pm

Using PNAis 4.3 with NooElec R820TNESDR Mini.

Great job on the software. This works well and it is way more efficient than SRD# > AISMon > Chart plotter.

However, I agree with the request for 'more gain' - or at least being able to control the gain in some config file somewhere. I get a lot more (and distant) stations when I use SRD# > AISMon > Chart plotter than I get with PNAis > Chart plotter. When I use SDR# I need to push the "Volume" slider up to about 3/4. If I could do that with PNAis it would be perfect!

xynium
Posts: 12
Joined: Thu May 29, 2014 12:18 pm

Re: AIS

Post by xynium » Mon Mar 02, 2015 10:55 am

This week end, on "https://sites.google.com/site/f4eyuradio/ais-decoder" I have added a 4.4 version which include 2 checkbox, one choose AGC or manual gain, the other select or deselect AGC for R820.

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