Didn’t find an elegant compact solutions out there. I’m using only the GPIO pins, no need to route the audio jack output back to the PCB like existing solutions. Also using an on board amplifier which supplied from RPi 5V. Built a few prototypes yet and working nice 🙂 Enjoy! https://github.com/rfsparkling/RPi_Speaker https://www.reddit.com/r/RASPBERRY_PI_PROJECTS/comments/55hk5k/rpi_speaker_an_open_source_fully_integrated/
Remote Spectrum Monitoring Drone from RTL-SDR, RPi, 4G internet using OpenWebRX Can be used as an improvised “virtual antenna tower” for example in emergency situations, ham radio activities or experimenting. Possibly words cheapest aerial spectrum monitoring tool as of today. You can see APRS and ham radio FM repeaters in the spectrum plot of the Read more about Remote Spectrum Monitoring Drone from RTL-SDR, RPi, 4G internet using OpenWebRX[…]
“An ocean going marine buoy containing a GPS and QRP-Labs Ultimate3S based transmitter. This project is intended to drift in the Pacific Ocean at the mercy of the tides, currents and wind directions while sending its position, battery voltage and temperature information via HF radio telemetry in WSPR and JT9 modes.” Source: http://www.qsl.net/zl1rs/oceanfloater1.html
http://hackaday.com/2016/03/16/tiny-raspberry-pi-shield-for-high-quality-rf-signals/
Check my friend, András Retzler’s new blog about cutting edge SDR technology at: blog.sdr.hu
It uses a LTC 14-bit 65 MHz ADC and Xilinx Artix-7 A35 FPGA, and also has an integrated SDR based GPS receiver which is used to automatically compensate for any frequency drift from the main 66.6 MHz oscillator. The features of the KiwiSDR include: 100% Open Source / Open Hardware. Includes VLF-HF active antenna and associated power injector PCBs. Read more about KIWISDR: 30 MHZ BANDWIDTH SDR FOR VLF/LF/MF/HF with OpenWebRX[…]
Here is an excellent article about that: http://www.g8jnj.net/softwaredefinedradio.htm Here is where I’ve found it: http://www.rtl-sdr.com/measuring-the-input-impedance-of-the-rtl2832u-direct-sampling-input-pins/
http://www.rtl-sdr.com/building-a-ham-tranceiver-with-an-rtl-sdr-raspberry-pi-and-rpitx/
https://www.youtube.com/watch?v=8Wzb1mgZ0EE #coherent #phase #sdr