Tagged: rtl2832u

Listening in on Burger Pagers with the RTL-SDR

Oona has written on her blog www.windytan.com about how she used an RTL-SDR to listen in on those wireless devices that are given out at some restaurants and cafes to notify you when your food is ready.

While at a local burger chain she found a label on the back of the device given to her which specified the radio frequency used by the device. By tuning to that frequency with her RTL-SDR, she discovered that the device uses the POCSAG protocol, which is the same protocol that is used by pagers. She then decoded the data packet and found that it contains the device address, which is used to notify the correct device.

burgerPagerpocsagBurger

Receiving 24 GHz with the RTL-SDR

Over on YouTube Adam Alicajic has uploaded two videos which show an experiment where he successfully receives a test 24 GHz carrier signal with an RTL-SDR dongle.

In the first video he uses mixer setup to convert the 24 GHz signal down to 432 MHz, which is within the tunable range of the RTL-SDR. In the second video he uses a salvaged downconverter unit from some sort of communications device to do the same.


24GHz downconverter mod

Review of the SDR UP-100 Upconverter

Akos from the SDR for mariners blog has written a review on the SDR UP-100 upconverter. The SDR UP-100 is a 50 USD upconverter for the RTL-SDR and similar software defined radios which is made by the same person behind the LNA4ALL low noise amplifier. Upconverters allow the RTL-SDR to receive between 0 and 30 MHz, where ham radio, military, marine and many other interesting signals exist.

In the review Akos tests the SDR UP-100 with a 6 meter random wire antenna and an RTL-SDR. His results show that the upconverter works well as expected. In the future he hopes to compare the SDR UP-100 with the Ham-It-Up Upconverter from Nooelec.

SDR UP-100

2-Channel AIS Receiver with RTL-SDR and GNUAIS

Blogger OZ9AEC has written a post on his blog showing how he made a 2-channel AIS receiver using the RTL-SDR, GNU Radio and GNUAis. AIS is a radio protocol used by boats to broadcast their position and speed which is then used to create a type of radar system to help avoid collisions. AIS signals are transmitted periodically on one of two channels. Two channels are used to improve capacity and help avoid interference if two signals from different boats are broadcast at the same time.

Before this, most AIS receiver implementations we’d seen that used the RTL-SDR received only on a single channel. OZ9AEC’s GNU Radio program receives on both channels simultaneously like a commercial AIS receiver does and is thus a better receiver. He eventually plans to get this receiver to run on a Beaglebone.

See his post for instructions and to download the GRC files.

Update: Another AIS decoder known as gr-ais is also capable of 2 channel AIS, and bristromat from Reddit has written a tutorial on setting it up and running it with OpenCPN.

Two channel AIS Block Diagram

RTL-SDR on the Nokia N900

Over on the maemo.org forums, user xes has written a post explaining how to get the RTL-SDR working on the Nokia N900 mobile phone. The Nokia N900 runs a modified version of Linux known as maemo, and so is able to use the RTL-SDR drivers with some modifications. Attached to the post by xes are the N900 compatible RTL-SDR drivers, GNU Radio 3.6.2, GQRX and also MultimonNG.

Nokia N900 running RTL-SDR

In Car ADS-B with a Raspberry Pi and RTL-SDR

Over on YouTube user adsbrus shows us his project which is an in car ADS-B aircraft tracker using a Raspberry Pi mini computer and an RTL-SDR. The system uses an LCD screen mounted where the car radio usually is to show aircraft identifier, altitude, and speed information in text.

ADS-B in CAR (Raspberry PI & USB TV RTL2832U+R820T)

Exploring Unintended Radio Emissions with the RTL-SDR – Talk now available on YouTube

A few weeks back we posted about some slides from the Defcon conference by information security researcher Melissa Elliot which detailed how she used an RTL-SDR to explore the world of unintended radio emissions.

The talk to go with the slides is now available on YouTube

DEF CON 21 - Melissa Elliott - Noise Floor Exploring Unintentional Radio Emissions

Tip to Reduce Radio Interference on the RTL-SDR

A few months back we posted about a tip to reduce RFI (Radio Frequency Interference) on the RTL-SDR. Now Akos from the SDR for mariners blog has tried this tip for himself and written about his experience with it, after getting inspired to by a post in the rtl-sdr.com/forum.

To reduce RFI, the tip recommends disconnecting the shield connection of the USB cable from the ground connection of the RTL-SDR dongle. This overcomes a design flaw in the RTL-SDR which allows the shield of the USB extension cable to act as an antenna, causing unwanted RFI.

What Akos did was to remove the metal part of the USB extension cables connector to prevent any ground connection. This already reduced an interfering signal by 10dB. He also found that wrapping the connection point in foil further reduced the noise. Connecting coax to the ground then coiling it up and putting the RTL-SDR in the center of the coil also appears to significantly reduce RFI.

Update: Akos has also tried using ferrite chokes on the USB cable, and also found they significantly reduce interference.

Check out the full post by Akos for more information here

RFI noise reduction in the RTL-SDR