A web-based SDR package for multiple users. Tune an SDR with your web browser, listen to what it picks up. Includes demodulators. 2d and 3d waterfall displays. Supports multiple SDRs, including the RTL-SDR. You can also join the sdr.hu radio network if your server is publically available.
pyrtlsdr is a simple Python interface to devices supported by the RTL-SDR project, which turns certain USB DVB-T dongles employing the Realtek RTL2832U chipset into low-cost, general purpose software-defined radio receivers. It wraps many of the functions in the librtlsdr library including asynchronous read support and also provides a more Pythonic API.
A global network of satellite ground stations, designed as an open source participatory project. A machine readable crowdsourced satellite information database. Built from readily available and affordable tools and resources. Concentrates on satellites in LEO. A significant amount of work is involved so you won't be able to just throw up an RTL-SDR and get going. Designed to be built using readily available materials and access to basic tools and machinery using 3D printers and CNC as provided by average hackerspaces.
A general purpose radio frequency transmitter for Raspberry Pi which doesn't require any other hardware unless filter to avoid intererence. It can handle frequencies from 5 KHz up to 1500 MHz. Plug a wire into GPIO pin 4 (hardware pin 7) and it'll broadcast just about whatever you tell it to. Has an installation script. It's recommended that you use a bandpass filter to minimize noise on the air. Works with just about every RasPi (except the B). Has a text based menu to control it. Defaults to 434 MHz (international free ISM band). You can even broadcast spectrogram pictures! Can even do POCSAG to activate pagers!
Software for investigating unknown wireless protocols. Plug in an SDR and go. Helps you figure out how to demodulate signals, record and transmit signals, generate an overview, write or customize decoding routines to get a clearer picture, annotate and label the signals, fuzz devices (with a transmit-capable SDR), and run simulations of the protocols' state machines.
A page that talks about passive and active sonar sensors. Security uses, especially the seismics. Links to other books and DoD video footage. I think this would be useful for training as well as surveillance applications.
A brief synopsis on the construction of a weapon which can fry RFID chips, including those of passports and ID cards. There are no schematics, just a list of the principles used in the design. You'll need knowledge of electronics to make sense of it and apply them in a practical manner.