Pranking Colleagues with the USRP B210 Software Defined Radio

The Ettus USRP B210 is an advanced $1,100 software defined radio that is capable of both transmit and receive. Balint, one of the researchers at Ettus, has posted a video showing how he was able to play a light hearted prank on some of his colleagues using the B210.

Earlier in the year we posted about how Oona Raisanen was able to use her RTL-SDR to receive and decode restaurant pagers (the wireless devices given out at some restaurants to notify you when your food is ready).

Balint used his USRP210 controlled by a mobile phone app to transmit a fake signal to his colleague’s pager, causing it to activate before his food was ready.

You Can Page Me Anytime – USRP B210 + GNU Radio (teaser)

Great new Guide to SDR#

Tyler Watt has posted over on his blog a new post showing some tips on the use of SDR#. He makes use of animated gifs to clearly show the action in SDR# that he is performing. If you’ve been wanting to learn more about how to use SDR#, or what the various options do, check out his guide.

env_c

Measuring the Frequency Response of a Bandpass Filter with the RTL-SDR

Lacking both an expensive signal generator and spectrum analyzer, Hans used his RTL-SDR together with a simple diode based wideband noise generator to measure the frequency response of a 137 MHz bandpass filter.

To do this he used the RTL-SDR Scanner software which allows you to create a composite spectrum over a frequency range wider than the maximum 3.2 MHz of bandwidth the RTL-SDR provides. The wideband noise generator was cleverly constructed out of a diode operating in it’s reverse breakdown mode.

Apart from the obvious excessive spurs, this method worked quite well and the shape of the filter is clearly visible.

Bandpass Filter Response
Bandpass Filter Response
Wideband diode noise source
Wideband diode noise source

Receiving Urban Drainage And Flood Control Weather Sensors

In Boulder, Colorado (and possibly other US cities) there is a radio based weather monitoring system known as ‘Urban Drainage and Flood Control’. This is a system that monitors rainfall and other weather information and transmits data using the ALERT protocol.

Over at scalaeveryday.com, blogger cparker has posted how he was able to receive and decode the RF signals sent by these stations using an RTL-SDR. Using radioreference.com cparker was able to determine that these stations transmit at 169.5 MHz using frequency shift keying (FSK).

Using his RTL-SDR and GQRX, he made a recording of some of the weather station packets on that frequency. Next he used a command line utility called minimodem to convert the recorded packets into binary data. After looking up the protocol online, he was then able to understand the binary string and extract the station ID information from it. Cparker then went on to write code that would plot the received stations on a map by cross referencing the station ID with a website containing location information about these sensors. Finally, he managed to get the whole system running live on a Raspberry Pi.

Urban Drainage and Flood Control
Urban Drainage and Flood Control Sensor Station

Raspberry PiRate Radio FM Transmitter

In November last year we posted a story showing how a Raspberry Pi could be used to transmit a digital AFSK signal to an RTL-SDR or other radio simply by connecting a wire to a GPIO pin.

Now an rtl-sdr.com reader has written in to let us know that this concept has also been used before to create a 1 – 250 MHz FM transmitter using the Raspberry Pi and a program called PiFM. It uses the same concept of connecting a wire antenna to one of the GPIO pins but modulates the frequency using hardware on the Rpi meant to generate spread spectrum clock signals. It is claimed that it can transmit up to 50m away.

Below we show an example YouTube video of the Raspberry Pi FM radio transmitting to an RTL-SDR running HDSDR.

PiFm & R820T & HDSDR

Interest Check for an ADS-B Folded Monopole Antenna

Adam, manufacturer of the LNA4ALL and LNA4HF is putting out an interest check for an ADS-B folded monopole antenna. The antenna can efficiently cover the 1030 MHz to 1090 MHz frequencies that are used by ADS-B.

The major advantage to Adams antenna is that it uses a DC grounded design, eliminating static build up problems that can potentially fry your LNA or RTL-SDR dongle.

If there is sufficient interest, Adam will sell the antenna for 20 Euros.

ADS-B Folded Monopole Antenna
ADS-B Folded Monopole Antenna

Nooelec Ham It Up Upconverter Metal Case Now For Sale

Nooelec, manufacturer of the popular Ham-It-Up upconverter has now begun selling metal enclosures for the upconverter. The Ham-It-Up is an upconverter which allows the RTL-SDR to receive HF (0-30 MHz) signals.

  • High-quality custom aluminum enclosure for Ham It Up v1.1 & v1.2.
  • Metal case helps to protect PCB from stray EMI, improving sensitivity.
  • Includes all required hardware to mount your PCB!
  • Ample room inside the case to make modifications and even include a dongle inside the case if you are so inclined.
NooElec Ham-It-Up Upconverter Case
NooElec Ham-It-Up Upconverter Case

 

New RTL-SDR Android App: SDRWeather

A new RTL-SDR Android app called SDRWeather has appeared on the Google Play Market. The new app allows you to listen to weather radio and decode EAS (Emergency Alert System) alerts. The app will only work in the US and Canada. More information about the app and its open source code can be found at http://sdrweather.thecongers.org.

This software along with a supported USB software defined radio turns your Android device to a portable weather radio.

Current Features:
* Listen to weather radio in the US/Canada.
* Decode EAS Alerts US/Canada
* Selectable Pre-defined Frequencies
* Alert Notifications
* Widget to display alerts
* Option to unmute audio when alert recieved
* FIPS and CLC Location Code Databases
* Event Code Database
* No internet connection required

Possible future features
* Switch to using rtl_tcp_andro
* Option to only show alerts if you are currently in the affected region
* Affected region map

Screenshot of the Android RTL-SDR App SDRWeather
Screenshot of the Android RTL-SDR App SDRWeather

Two new SDR# Plugins

Last month two new SDR# plugins where released on rtl-sdr.ru. The first is TimeShift SDR. This plugin creates a buffer which allows you to listen to any signal at any point in time on the waterfall within the buffer time. It is very useful for catching signals that you might have otherwise missed by being too slow to click on them. Update: Turns out Timeshift SDR isn’t exactly new. But it has recently been updated to work on the latest SDR# releases.

Timeshift SDR# Plugin
Timeshift SDR# Plugin

The second plugin is a Digital Audio Processor which adds in a squelch slider bar, an audio inverter, an audio band-pass filter and a de-emphasis filter.

digital_audio_processor_sdrsharp_plugin
Digital Audio Processor Plugin

GPS Tracking with a modified TCXO RTL-SDR

Michele from Michele’s GNSS blog has posted his results with using a modified R820T RTL-SDR with Temperature Controlled Oscillator (TCXO) for GPS reception and decoding. The RTL-SDR is capable of tracking GPS even without TCXO but improved performance can be expected with a more stable oscillator. He notes that the R820T with it’s 3.57 MHz IF is ideally suited for GPS reception when combined with an active GPS antenna. Using this setup he was able to track GPS satellites and the Galileo E1B/C GNSS satellites as well.

Michele modified his R820T RTL-SDR with a 28.8 MHz TCXO he obtained from a friend. It is however possible to purchase modified TCXO R820T dongles directly from the 1090mhz webstore.

Modified TCXO R820T RTL-SDR used for GPS reception.
Modified TCXO R820T RTL-SDR used for GPS reception.