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Software-defined radio: Difference between revisions
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== Possibilities == | == Possibilities == | ||
SDR's have endless possibilities. Because all demodulation is done in software, no new hardware is needed to decode, for example, a new digital voice mode. All the programmer has to do is write code to convert the raw samples from USB to the correct format data. | SDR's have endless possibilities. Because all demodulation is done in software, no new hardware is needed to decode, for example, a new digital voice mode. All the programmer has to do is write code to convert the raw samples from USB to the correct format data. | ||
== SDR# FAQ == | |||
* I hear FM radio stations from 25-86MHz | |||
** That is your SDR being overloaded by FM broadcast signal, try installing an FM trap or lowering your gain. | |||
* I see signals that go the opposite way from where i'm dragging | |||
** That is interference, not an actual signal, lowering your gain solves this | |||
* I see a spike in the middle of the screen | |||
** This is the DC spike, a side effect of the RTLSDR, check the box that says Correct IQ | |||
* I see lots of interference in the 100-150MHz band | |||
** It's common to see interference when the antenna is placed near networking equipment, wireless routers and computers. Move the antenna away from these sources to lower the effect | |||
== Modulation guide == | |||
Some frequencies are used by only one type of modulation. For example 88-108 is broadcast FM, the modulation used is WFM. Using the correct modulation can help you decide what type of signals you are listening to. The table below lists the most common modulations. | |||
{| border="1" {{table}} | |||
| align="center" style="background:#f0f0f0;"|'''Frequency''' | |||
| align="center" style="background:#f0f0f0;"|'''Modulation''' | |||
|- | |||
| 0-50MHz||AM, SSB, USB, LSB | |||
|- | |||
| 88-108MHz||WFM | |||
|- | |||
| 120MHz||AM (Airband) | |||
|- | |||
| 120-980MHz||NFM | |||
|- | |||
|} | |||
== Getting Started with RTLSDR == | |||
== AM vs FM == | |||
== Points of interest == | |||
=== MF(Shortwave Radio) === | |||
An upconverter is required to listen to these frequencies | |||
=== HF (3-30MHz)=== | |||
An upconverter is required to listen to most of these frequencies | |||
=== VHF(30-300MHz) === | |||
=== UHF(300MHz-3GHz) === | |||
== Upconverters == | |||
== Software == | == Software == | ||
Revision as of 19:48, 25 February 2014
This article is written for beginners, higher level material can be found on using the links below
Software defined radio is the means of listening to radio waves using the combination of low level hardware, and software processing. While non-SDR techniques use physical hardware to demodulate FM and AM, In SDR raw data from the receiver gets sent into the USB port, and software is used to control the modulation. The only drawbacks of SDR are bandwidth constraints and processing. Since uncompressed unmodulated data is coming through a PC interface (USB mostly), a high speed connection and a computer with decent specs is required. A Single RTL-SDR May use up to 3.4MB/sec of USB bandwidth. CPU usage varies on the tuner software you use. Using software defined radio opposed to regular radio gives you the ability to see signals you would normally only hear. Your eyes can cover a very wide bandwidth of signals on a computer screen, while your ears can only comprehend a single spoken conversation at a time.
SDR models
SDRs come in many shapes in sizes, from the $8 RTL-SDR to $2000 USRP(with daughterboards) There are also many SDR's such as the HackRF, USRP, FunCube, etc.List of SDRs When you buy an SDR, you get what you pay for. More expensive SDR's are purpose built for receiving, and can handle things such as GSM spoofing, where an unencrypted GSM tower can be simulated to capture SMS in a cleartext fashion.
RTLSDR
A great beginner SDR is the RTL-SDR It features a receive frequency range of 25-1700MHz, 2.048MHz bandwidth and is priced low enough that beginners can see whether radio is a hobby they want to get into(R820T model).
RTL-SDRs come with various tuner chips, the most widely used tuner is the R820T, with the E4000 coming in a close second. The E4000 is a discontinued model and is usually priced higher than R820T models. R820T tuners are generally better for reception of trunked radio systems (digital police radio).
The RTLSDR began its life as a DVB-T OTA TV tuner (a tv tuner for europe). China began bulk manufacturing these TV tuners for the european market. It was later found that a hacked driver could be installed that let the user use the dongle as an SDR.
Currently R820T RTLSDRs can be bought for as low as $8 on eBay with free shipping R820Ts on eBay
Funcube Dongle
As part of AMSAT-UK’s FUNcube satellite project, the FUNcube Dongle is the “ground segment”, or a radio receiver designed to allow anyone to try their hand at reception of satellites like FUNcube anywhere on Earth as part of a global educational collaboration project collecting information from space. The original has a frequency range of 64MHz to 1.7GHz. The Pro + has a frequency range of 150kHz to 240 MHz and 420MHz to 1.9GHz.
HackRF
The HackRF is a DARPA funded project, it aims to provide innovation and research in the SDR field. It's much more powerful than the RTL-SDR, much more sensitive, covers a greater frequency range. The HackRF starts at $300, has both RX and TX functionality from 30 MHz to 6 GHz, bandwidth of 20MHz. During DARPA funding, beta units, the HackRF Jawbreaker were given to hundreds of testers for free. The production version was funded through KickStarter. The campaign was successfully funded on September 4th 2013 and will be available to the public after donators get their HackRF's. KickStarter Page
- Transmitting
- TX functionality on the HackRF is limited in power because RF theory says you must have an antenna length that corresponds to the wavelength you are sending. For example sending 5Watts over the wrong size antenna will cause a buildup of standing waves, and may fry the transmitter. To prevent this, the antenna build into the breadboard of the HackRF is only designed for ultra low power, good enough for experimentation, but not for serious broadcasting.
Possibilities
SDR's have endless possibilities. Because all demodulation is done in software, no new hardware is needed to decode, for example, a new digital voice mode. All the programmer has to do is write code to convert the raw samples from USB to the correct format data.
SDR# FAQ
- I hear FM radio stations from 25-86MHz
- That is your SDR being overloaded by FM broadcast signal, try installing an FM trap or lowering your gain.
- I see signals that go the opposite way from where i'm dragging
- That is interference, not an actual signal, lowering your gain solves this
- I see a spike in the middle of the screen
- This is the DC spike, a side effect of the RTLSDR, check the box that says Correct IQ
- I see lots of interference in the 100-150MHz band
- It's common to see interference when the antenna is placed near networking equipment, wireless routers and computers. Move the antenna away from these sources to lower the effect
Modulation guide
Some frequencies are used by only one type of modulation. For example 88-108 is broadcast FM, the modulation used is WFM. Using the correct modulation can help you decide what type of signals you are listening to. The table below lists the most common modulations.
| Frequency | Modulation |
| 0-50MHz | AM, SSB, USB, LSB |
| 88-108MHz | WFM |
| 120MHz | AM (Airband) |
| 120-980MHz | NFM |
Getting Started with RTLSDR
AM vs FM
Points of interest
MF(Shortwave Radio)
An upconverter is required to listen to these frequencies
HF (3-30MHz)
An upconverter is required to listen to most of these frequencies
VHF(30-300MHz)
UHF(300MHz-3GHz)
Upconverters
Software
Software is available for Windows, GNU/Linux and OSX.
SDR Software (The stuff you listen with)
| Software | Supported Modes | OS | Cost/License | Features/Limitations |
| SDR Touch | AM, WFM, NFM, SSB, DSB, CW | Android | Freemium, Closed | supports RTL_TCP and USB OTG, FFT times out after 30 seconds on free version |
| glSDR | AM, WFM, NFM, SSB, DSB, CW, DIG(?), SPEC(?), SAM(?), DRM | Android | Free, GNU/GPL | UI for ghpsdr servers |
| SDR-Radio | Windows | Free, Closed | Feature packed, harder to get set up | |
| SDR-Radio v2 | Windows | Free possibly paid out of beta, Closed | Beta, Feature packed, supports RTL_TCP | |
| SDR# | Windows | Free, MS-RSL/MIT | Most popular and easiest to use | |
| HD-SDR | Windows | Free, Closed | ||
| PowerSDR | Windows | Free, GNU/GPL | Does not support RTL-SDR | |
| GQRX | AM, WFM, NFM, SSB, CW, AFSK1200 | Win,Lin,Mac | Free, GNU/GPL | Runs on GNU Radio |
| GNU Radio | Win,Lin,Mac | Free, GNU/GPL | Tools to build your own receiver. Versatile, larger learning curve. | |
| Linrad | Win,Lin,Mac | Free, OSS | ||
| Studio1 | Paid,Closed Source | Formerly WRPLUS |
Plugins for SDR#
| Purpose | Software | Cost/License |
| Scan and log various frequencies | Frequency Manager + Scanner plugin | Free, OSS |
| Tune SDR# to the approprate voice channel | Trunking plugin for SDR# | Free, OSS |
HF decoders (shortwave 0-30MHz)
| Purpose | Mode | Software | OS | Cost/License | Common Frequency |
| Digital decoding on HF | CW, Domino, Hell, MFSK, PSK, OLIVIA, RTTY, Throb, Thor, WWV | Fldigi | Win,Lin,Mac | Free, GNU/GPL | 0-30MHz AM |
| HF amateur radio codec | FreeDV, Codec2 | FreeDV | Win,Lin,Mac | Free, GNU/GPL | 0-30MHz AM |
| Digital broadcast shortwave | DRM | Dream | Win,Lin,Mac | Free, GNU/GPL | 0-30MHz AM |
| Sending images over HF, commonly QSLs | Robot, AVT, Scottie, Martin | MMSSTV | Windows | Free, OSS | 0-30MHz AM |
ADS-B Airplane tracking software
| Purpose | Mode | Software | OS | Cost/License | Frequency |
| Plane-spotting, decoding ADS-B | ADS-B | ADSB# | Windows | Free, MIT | 1090MHz AM |
| Decodes ADSB# data + Plot planes on a map | AVR-BEAST | VirtualRadar Server | Windows | Free, OSS | 1090MHz AM |
| Alternative to ADS-B# | ADS-B | RTL1090 | Windows | Free, Closed | 1090MHz AM |
| Decodes ADSB (S Mode) | ADS-B | Dump1090 | Linux | Free, BSD | 1090MHz AM |
APRS (like GPS, hams use it)
| Purpose | Mode | Software | OS | Cost/License | Frequency |
| Amateur packet radio incl. GPS location | AX.25, AFSK, APRS | AFSK1200 | Win,Lin,Mac | Free, GNU/GPL | 144-145MHz FM, Varies |
Trunked Radio (police fire and EMS in urban areas)
| Purpose | Mode | Software | OS | Cost/License | Frequency |
| Decode control channel data | P25, EDACS48, EDACS96, Motorola, MPT1327 | Unitrunker | Windows | Free, Closed | Usually 400MHz, 760,860,933MHz FM |
| Decode digital voice | P25p1, ProVoice, X2-TDMA, DMR/MOTOTRBO, NXDN | DSD | Win,Lin,Mac | Free, BSD | Usually 400MHz, 760,860,933MHz FM |
| Decode LTR data | LTR | LTR Analyzer | Windows | Free, Unknown | ~400-500MHz |
NOAA weather satellite
| Purpose | Mode | Software | OS | Cost/License | Frequency | Other |
| Decode NOAA WX images | APT, WEFAX | WxtoIMG | Win,Lin,Mac | Freemium, Closed | ~137MHz FM | Track Live |
| Decode NOAA Satellite | APT | Atpdec | Linux | Free, GPL | ~137MHz FM |
Television (non digital kind)
| Purpose | Mode | Software | OS | Cost/License | Frequency |
| Analog television decoder, no sound | NTSC, PAL | TVSharp | Windows | Free, OSS | Any AM (including ISM security cameras) |
Pagers
| Purpose | Mode | Software | OS | Cost/License | Frequency |
| Decode various pager formats | POCSAG, FLEX | PDW | Windows | Free, GNU/GPL | 35-45MHz, 152-160MHz, 455-463MHz, 928-932MHz FM |
| Decode various including pager | POCSAG | multimon-ng | Linux | Free, GPL | various |
Audio routing software
| Purpose | Software | Cost/License |
| Routes audio from the receiver to a decoder software above | Virtual Audio Cable | Shareware, Closed $35 |
| Routes audio from the receiver to a decoder software above | VB Audio Cable | Donationware, Closed ($5 donation gets you more cables) |
Video Tutorials
Other SDR resources
Scanner centric SDR discussion forums on RadioReference
FCC website, every RF transmitter registered registered with the FCC resides in this database
An online SDR receiver that covers the HF band (shortwave, worldwide transmissions)