Over on YouTube user SilverXiaify has uploaded a video of a project he completed for a class in his electrical engineering school. His project involves controlling a remote controlled car using a ham radio. The remote control car carries on board an RTL-SDR for signal reception and an Raspberry Pi for data processing and control. The communications protocol they used is a naive version of AFSK700.
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.
Over on our Facebook page Micheal Kent has posted about his raspberry pi based RTL-SDR receiver which runs rtl_udp. There’s not much more information on this project, but the video he posted shows what appears to be a Raspberry Pi and RTL-SDR dongle mounted inside an icecream box. There are two knobs mounted on the outside that control the brightness of an LCD screen which shows the tuned frequency, and another knob which controls the frequency itself.
Hackaday brings to attention a simple hack where hacker Marc uses an antenna connected to a general purpose I/O (GPIO) pin on his Raspberry Pi to wirelessly transmit a wav file via AFSK modulation to his RTL-SDR. He uses a program called minimodem to encode the wav on the Raspberry Pi and then on the PC to decode the data received by the RTL-SDR.
Using this method, it is claimed that a signal can be transmitted up to 50m away, even through walls.
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.
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.
Blogger and ham radio enthusiast F4GKR has written a brief tutorial post on his blog showing how he got an RTL-SDR working with an Aria G25, and in another post some benchmarking results. The Aria G25 is a very small low cost, Linux capable embedded computer, similar to the Raspberry Pi.
He was able to get rtl_tcp running with a 2 MSps sampling rate and found it used about 60% of the CPU.
On YouTube, Stephen Ong has posted a video (and written a short post on his blog) of a portable home made spectrum analyzer he made using the RTL-SDR, a Beaglebone Black and an LCD touchscreen. The Beaglebone Black is a small Linux capable PC that fits in a hand, similar to the Raspberry Pi but with slightly more processing power.
Earlier in the year we posted about another Beaglebone based spectrum analyzer, but this new one by Stephen seems to be much improved with touchscreen capabilities and an improved user interface.
