FeatherHAB: 2-gram High Altitude Balloon Tracker using Si4464 EZRadioPRO
An excellent and clever solution using a SoC ISM radio as 2m APRS transceiver: FeatherHAB: 2-gram High Altitude Balloon Tracker
Tag: ham
TINY RASPBERRY PI SHIELD FOR HIGH-QUALITY RF SIGNALS
http://hackaday.com/2016/03/16/tiny-raspberry-pi-shield-for-high-quality-rf-signals/
Optimal impedance matching of RTL SDR in direct sampling with 16:1 BALUN
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/