In most varieties, a ghost box or spirit box is a radio that sweeps over a range of frequencies. I'll assume that most people here have some exposure to ghost boxes, their usage, and applications.
There is a type of device for computers known as a software defined radio (SDR.) For our purposes, these are devices that allow a computer to tune and receive signals from a range of the radio spectrum. Cheap ones are available, and it is possible to purchase decent USB SDR devices for as little as $10. The lower end devices usually support tuning between 24 MHz and 1.7 GHz. This excludes AM, though more expensive devices and upconverters can be used to provide that part of the spectrum.
The program that I wrote is called gqrx-ghostbox. It is freely available and open source. It controls another open source program called Gqrx, which is a receiver for SDR devices. You can provide options such as the direction and style of scan, the speed, the demodulator mode, and the range of frequencies. It then connects to Gqrx, and the scanning begins.
I wanted to share this here because there are some advantages over traditional ghost boxes:
- Traditional ghost boxes can be expensive. With SDR, the extra hardware needed is a cheap USB device.
- Traditional ghost boxes are limited in range by the device, but generally support AM and/or FM scanning. Using SDR the limits are defined by the device, opening up the potential for exploring results elsewhere in the spectrum.
- Gqrx shows visualizations of the spectrum that may provide other useful information when receiving EVP.
- Gqrx has options to help control the incoming signal, such as gain, demodulation, noise filtering, and squelch controls.
- The scanning program has options and modes that aren't supported on most ghost boxes, such as random and bounce scanning modes. The tool is open source, and adding more modes and features is possible.
- The underlying scanning program is command-line based, and this makes it very easy to save and share the settings that work for you.
- With SDR it is easy to swap out antennas, and research which types of antennas and what layouts work best.
A big downside, and one that everyone should take note of is that this requires more technical skill to set up than a standalone ghost box device. Setting up SDR and the Gqrx program can be tricky. The gqrx-ghostbox tool itself uses the command line. A certain level of comfort with these types of things is needed, as is a willingness to tinker and figure them out. To anyone who isn't somewhat familiar with these things, I do caution you it could be a pain to get it setup.
As for operating system support, I've only run it on Linux. Running on Windows would require installing Perl. (Using Cygwin should work.) If the versions of Gqrx for Windows and MacOS are relatively up to date, it should work there as well, but I have not tested those environments. Again, I caution anyone who attempts that path, it is uncharted territory, and may take some effort to get going.
I do think this style tool has interesting potential for researchers. I hope that someone finds this useful, and if you do, please share the results back so that others can learn from them, and attempt to repeat them.
- gqrx-ghostbox - Application for using SDR as a ghost box
- Gqrx - SDR Receiver application, required by gqrx-ghostbox
- results sharing - A page for sharing successful results and details of the setup and configuration used to achieve them
Edited by doug, 30 October 2016 - 03:12 PM.