Category: RTL-SDR

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

Improved SDR Support for Kali Linux

The blog at needsec.com brings us news that Kali Linux is soon to be updated to version 1.0.5 which will come with several software defined radio tools preinstalled. Kali is a Debian Linux based operating system that is popular with the security and penetration testing community as it comes with several relevant tools preinstalled. This new version adds several useful SDR software programs including

  • Kalibrate for RTLSDR
  • gr-air-modes
  • RTLSDR Scanner
  • pyrtlsdr
  • GNU Radio Signal Scanner
  • libosmocore 0.6.3
  • grextras
  • gr-baz
  • gr-osmosdr
  • gr-iqbal
  • rtl-sdr 0.5.0
  • HackRF for SDR
  • gr-fcdproplus for SDR
  • UHD Images

via needsec.com

Update: Official Release now out

kali-site-logo2

LNA4All Low Noise Amplifier Review

Over on the SDR for Mariners blog, author Akos has reviewed the LNA4All low noise amplifier. The LNA4All is a 25 euro amplifier designed to improve the performance of the RTL-SDR.

His results show that the LNA works very well. Akos tested the LNA4ALL on multiple frequencies and applications including commercial radio, airband, NOAA weather satellites, AIS and ADSB. As an example of the improvement, his ADSB reception was improved from 83km to 94km. In his review Akos also shows how to provide power to the LNA, and puts the LNA through some simple stress tests.

LNA4ALL Airband Performance

Potential Major Security Flaw on HP Laptop Discovered with RTL-SDR

Over on Reddit, user cronek discovered by using his RTL-SDR that the microphone on his HP EliteBook 8460p laptop computer was continuously and unintentionally transmitting the audio from the built in microphone at 24 MHz in FM modulation. He found that the only requirement needed for the microphone to transmit was that the laptop needed to be turned on – even muting the microphone did nothing to stop the transmission.

Click here to read the original post.

I accidentally stumbled upon a signal in the 24MHz range, appearing to be 4 carriers. I tuned to it and heard silence, then someone came into my office and started talking and I could hear them speak. The signal appeared to be coming from my other laptop (not the one running the SDR) and was pretty weak (my antenna, the crappy one that comes with the dongle, stuck to a metal stapler was right next to the HP laptop).

This is of potential concern as as the US Military is apparently transitioning to this particular laptop. However, this may be an isolated incident, as in the thread cronek explains that other laptops he tested did not display this behavior.

HP Laptop Microphone Leak at 24 MHz

RTL-SDR and RDS Spy with HDSDR

On YouTube user pe1etr shows us a video where he uses his RTL-SDR combined with HDSDR, Virtual Audio Cable and RDS Spy to decode a distant RDS signal. RDS Spy is a free advanced software program capable of decoding weak RDS signals contained in many broadcast FM radio stations.

RDS stands for Radio Data System and is a digital signal embedded into broadcast FM signals. It is used by radio stations to display the name of the radio station and current song playing on an LCD screen.

HDSDR & RDS Spy side by side

ViewRF – RTL-SDR Spectrum Analyzer Software for the BeagleBone Black Released

Last month we showed a video of a spectrum analyzer project by Stephen Ong. He used a BeagleBone Black (mini embedded Linux capable computer similar to a Raspberry Pi), a touch capable LCD screen, and an RTL-SDR dongle to create a portable spectrum analyzer.

Now Stephen has released ‘ViewRF’, which is the software that powers his spectrum analyzer. It is released under the GPL licence. Also on his post are the download and install instructions.

Spectrum Analyzer using Beaglebone Black and RTL-SDR

Rain Scatter 10 GHz Reception with the RTL-SDR

YouTube user feri67000 who last month showed us that the RTL-SDR can receive 10 GHz signals with a cheap avenger LNB PLL now shows an interesting experiment where he uses a technique known as rain scatter to receive a 10 GHz beacon with his satellite dish pointed in the opposite direction of the beacon transmitter.

Usually communications at 10 GHz are line of sight only, but by using the rain scatter technique, the 10 GHz signal can be bounced off a precipitation cloud and received with line of sight to the cloud, rather than the transmitter.

rain scatter 10ghz LX1DB beacon

NOAA Weather Satellite Antenna and Software Guide

Over on the SDR for mariners blog, author Akos has written two new beginners posts on getting up and running with receiving and decoding NOAA weather satellite APT images.

The first post discusses antennas that are useful for NOAA satellite reception, and shows how to build a homemade turnstile and QFH antenna. His second post shows a beginners guide to the software that can be used to decode the APT signal in order to obtain a live weather satellite image.

sdrformariners_apt_image QFH Antenna