DVB-T Dongles in Amateur Radio
Transcription
DVB-T Dongles in Amateur Radio
DVB-T Dongles in Amateur Radio Or, Extra Cheap Software Defined Radio Al Floyd, W8ADF What is a Dongle? A USB Stick originally designed for European Television Contains a I/Q decoder chip, that can be used to decode I/Q radio signals Covers the spectrum from approximately 60 MHZ to 1700 MHZ. Some devices have slightly different coverages. QST, January 2013 The article that introduced me to DVB-T Dongles. This article is great background information, and lists sources for the various pieces of computer software required to use the device. The DVB-T dongle was designed for European television. Antti Palosaari first noticed that the device contains a Realtek RTL2832 quadrature decoder chip, and that this might have possibilities as a general radio receiver. With a team of other developers. Antti wrote a driver that accesses these capabilities, and made this driver open source software. Since then, numerous developers have generated applications using this driver and these cheap, but very sophisticated devices. How cheap? Under $15.00 from China, including shipping. Two Dongles, with various antenna cords. The plug for the dongle is the tough one to find! The DVB-T dongle is a VHF/UHF device. To make it useful for the HF amateur bands, an upconverter is required. The original W9RAN article in QST described such a converter, and suggested that a circuit board was available from FAR Circuits. While assembling parts to put together one of these upconverters, I found a “W9RAN Kit” at the Dayton Fleamarket in 2013. The kit was also available this year. Commercial Upconverter, NooElectric Commercial Upconverter, NooElectric Performance of the commercial Upconverter The DVB-T is not the most sensitive receiver! As with any receiver, the better the antenna, the better the signal (so what's new about that?). This is a lesson we all learned from our earliest days in radio. One solution is to add a low noise wideband amplifier. There are numerous designs for these, and the simplest is to use a device such as a MAR-6 with input and output filters. Simple LNA with suggested PC board. There is a commercial version of this type of device available in Europe, either as a finished device, or as a circuit board only. Software to use the DVB-T SDR#, simple, flexible, and free HDSDR, the old Winmor. Also Free SDR-Radio, steep learning curve, but free Linrad, Advanced features, difficult to learn, but also free GQRX, Mac and Linux, but free ShinySDR, based on GNU radio, free SDRTouch, for Android devices. Not free CuSDR, used also with HPSDR hardware, free And many others, both free and paid SDR# screen showing both frequency display and waterfall. Some DVB-T Applications Receiving unencrypted Police/Ambulance/Fire/ EMS Aircraft control communications Tracking Aircraft positions with ADSB decoder Decoding aircraft ACARS messages Trunking radio conversations Unencrypted digital voice transmissions Maritime boat positions with AIS decoding Decoding POCSAGFLEX pager traffic Cordless phones and baby monitors Meteorological weather balloon data Wireless temperature sensors and wireless power meters VHF amateur radio Uses, continued Decoding Amateur radio APRS packets Sniffing GSM signals Using RTL-SDR on Android as portable scanner Receiving GPS signals and decoding them Using RTL-SDR as spectrum analyzer Receiving NOAS weather images Listening to satellites and the International Space Station Radio Astronomy Monitoring meteor scatter Listening to FM broadcast and decoding RDS information Use as a panadapter for traditional radio hardware Decoding taxi mobile data terminal signals Use RTL-SDR as a true random number generator QST, January 2014 W9RAN article on tracking aircraft using the DVB-T. QST. April 2014 Using a DVB-T dongle as a panadapter with a commercial SDR, and a small color display. The software for this application was developed using the Python libraries that have been developed for the DVB-T devices. Software Plugins for SDR# Unitrunker Trunking Plugin Orbitron - Satellite tracking with Doppler shift correction Frequency Manager + Scanner and frequency entry package Easy Scanner - similar to standalone radio scanning Auto Tuner - sort of a level control ADSB# - Aircraft tracking DDE - DDE interface so programs like WXTrack and use Audio FFT ScopeView Audio EQ Balance Other Applications One individual has demonstrated using a DVB-T dongle with a Raspberry Pi computer, attached to a network. This makes all of the functions of the dongle available to any computer on the network Another individual has demonstrated use of up to seven DVB-T dongles on a single computer, and being able to monitor seven different frequencies or bands at a time. To use this idea for the HF bands would also require duplicate upconverters. Future dream - I would like to use the Python libraries that are available to write a software application using a single DVB-T with upconverter as a HF/VHF band activity monitor. As the bandwidth of the device is sufficient to cover an entire HF band, and the relevant portions of the VHF bands It should be possible to create a small window on the computer desktop that displays a single band spectrum. The window would scroll through each of the bands of interest, dwelling only long enough for the display to be seen. A refinement would be to set a signal level detect, and sound an alarm when activity was detected. This feature would be useful for sparsely populated bands, but would need to be disabled for more active bands. The advantage of such an application would be that it would indicate when signals were being received at the location of interest, not just those sites that post to the Internet. Other sources of information One of the best sites on the Internet is RTL-SDR.com. This site has links to many of the plugins available, and also links to other sites with information. A good place to start in RTL-SDR is with the original W9RAN article in January, 2013 QST. The information in that article alone will get you receiving signals with your DVB-T dongle. A Google search using the terms DVB-T and RTL-SDR will generate hundreds of leads. New applications appear almost daily using the DVB-T, so frequent returns to sites, and frequent searches will help to keep you up to date. Have fun, and hope you all are inspired to acquire a Dongle!