OpenMarine
RTL-SDR Troubles - Printable Version

+- OpenMarine (https://forum.openmarine.net)
+-- Forum: OpenPlotter (https://forum.openmarine.net/forumdisplay.php?fid=1)
+--- Forum: How do I...? (https://forum.openmarine.net/forumdisplay.php?fid=3)
+--- Thread: RTL-SDR Troubles (/showthread.php?tid=2771)



RTL-SDR Troubles - dj11223344 - 2020-07-21

Hi everyone,

I am setting up openplotter. For the most part, it has been pretty easy. However, I cannot figure out how to properly calibrate the RTL-SDR. The ppm is all over the place. I am beginning to wonder if it is a hardware issue or an interference issue. Honestly, I don't know much about radio calibration.

I think I have consumed about every resource in Google and YouTube and still can't figure it out. The device has also been allowed to warm up.

I will attach a screenshot of the ppm script results. 

Thanks in advance!

This is the hardware I am currently using:
NooElec NESDR Smart v4 Bundle - Premium RTL-SDR w/Aluminum Enclosure, 0.5PPM TCXO, SMA Input & 3 Antennas. RTL2832U & R820T2-Based Software Defined Radio. https://www.amazon.com/dp/B01GDN1T4S/ref=cm_sw_r_em_apa_i_SrWfFb6C3AVV8


RE: RTL-SDR Troubles - abarrow - 2020-07-21

Try calibrating it with a local cell signal.


RE: RTL-SDR Troubles - dj11223344 - 2020-07-21

(2020-07-21, 04:36 PM)abarrow Wrote: Try calibrating it with a local cell signal.

That is pretty vague. Is there a specific way to calibrate using a local cell signal?

Thanks


RE: RTL-SDR Troubles - Sailoog - 2020-07-21

The ppm of your device should be always 0.5 so use 0 or 1 in ppm field and forget the calibration process.

Use the maximum gain allowed by your device, for most cases 49.6:

[Image: calibration51.png]

Here is the incomplete manual, no text yet, just screenshots Big Grin

https://openplotter.readthedocs.io/en/latest/sdr-vhf/sdr-vhf_app.html


RE: RTL-SDR Troubles - dj11223344 - 2020-07-21

(2020-07-21, 06:40 PM)Sailoog Wrote: The ppm of your device should be always 0.5 so use 0 or 1 in ppm field and forget the calibration process.

Use the maximum gain allowed by your device, for most cases 49.6:

[Image: calibration51.png]

Here is the incomplete manual, no text yet, just screenshots Big Grin

https://openplotter.readthedocs.io/en/latest/sdr-vhf/sdr-vhf_app.html

I have already tried this. To no avail. This was the first thing I tried. Usually, I don't even get a channel. Kind of hit or miss.


RE: RTL-SDR Troubles - Sailoog - 2020-07-21

But there are channels in your screenshot: 27 and 29

try ppm 1

anyway your device does not need calibration because you already know the ppm

what about the antenna?


RE: RTL-SDR Troubles - marcel - 2020-07-26

I have similar device, indeed ppm=0
I do have the gain only around 38

Try to use your marine radio antenna for testing.
Then you are sure proper reception.

In my case it was the difference between 18 miles of range or 2 miles of range for the ais.( Hundreds of ships Vs handful)


RE: RTL-SDR Troubles - holgerw - 2020-07-26

These newer NOOELEC Devices use an factory-calibrated ppm module for the frequency.
For the sensitivity there is also an automatic mode included, this is an special init, which is activated from an workaround by using an empty gain setting.


RE: RTL-SDR Troubles - seandepagnier - 2020-08-01

I also used a vhf radio to easily calibrate it. The standard dongles are +- 150 ppm error and it must be within about 5 to work for AIS> The other way is to use a script that tries every error ppm until it receives AIS but this takes a long time.

It would be interesting to implement code to very quickly calibrate, or not care about ppm error for AIS. This is because the rtlais receiver is wide enough it could automatically find the ppm using a little more cpu by searching the signal.


RE: RTL-SDR Troubles - dj11223344 - 2020-08-01

Thanks for all the suggestions. Still trying to figure it out. I got side tracked on other projects. I can't even seem to tune into known FM radio stations. Maybe I received a bad antenna or dongle.