software defined radio (SDR) receivers

see also:

• transceivers - software defined radio (SDR)
• radio basics
• satellites and their radio signals
• radio signal intelligence (SigInt)
• radio antennas
• radio RF filters
• digital TV for portable devices - DVB-T USB dongles
• CB 2-way radio
• see Youtube articles:
  • The Coolest Radio You've Probably Never Heard Of

• SDR is an inexpensive, great way to get a much better understanding of radio and how it works
• can be used to listen to a wide range of audio radio:
  • AM/FM radio stations
  • DAB+ digital radio stations
  • Ham radio including SSB
  • CB radio
  • Air band - pilots and control tower communications as well as automated control tower current weather conditions and aircraft local advice
• can detect and analyze non-audio data that is being transmitted by radio waves such as:
  • aircraft or ship transponders containing call signs, heading, altitude, speed, barometer, wind speed, GPS location data and display the aircraft on a map
  • analyzing signals from remote control devices and other radio transmitting devices
  • downloading, decoding and viewing LRPT or HRPT satellite weather images via weather fax services (although NOAA has been moved to more complex transmissions to detect and decode, and only Russia's satellites still transmit these at lower frequencies)
  • tracking the source of a radio transmission (using a directional antenna)
  • detecting meteors and lightning
  • images sent from the International Space Station (ISS)
    • https://ariss-sstv.blogspot.com/ has times when the ISS sends images - doesn't seem to happen very often though!
    • see https://www.youtube.com/watch?v=HaAprfh9ZtM
• requires:
  • a SDR device (RTL-SDR Blog v4 USB dongles are < $100) to connect to a computer
  • a LNA amplifier dongle - may need USB power
  • an antenna - a basic dipole antenna will work OK for FM radio, DAB+, Airband, some AM
  • a device on which to load the SDR software eg. computer, tablet, smartphone (may need a USB to Go cable)
  • SDR software
  • as basic SDR dongles have restricted frequency range of 500kHz to 1.75GHz, these cannot access long wavelengths, Bluetooth, WiFi signals or high frequency satellites - however, the frequency range can be extended by using up-converter or a down-converter and appropriate antenna

• a normal radio is essentially analog with hard coded components designed so that you have to search for a station or a signal but can only listen to one frequency at a time and given that many signals are transient you are likely to miss tuning to that frequency unless you know it is there or you are lucky
• in contrast, a SDR device is plugged into your USB port and you can use software to not only apply variable programming such as gain and filters, but more importantly, you can visualise a whole range of frequencies (“spectrum”) at once and the “waterfall” visual display shows a longer time period not just real time so you can visualise patterns including intermittent signals
  • some software allows you to simultaneously monitor a range of bands
  • in the software you can choose which type of signal decoding to use for a given signal such as FM, AM, morse code, etc
  • in addition you can use a virtual audio out to input this into other software which is expecting an audio output from a radio such as a weatherfax software
  • furthermore, depending on the SDR device, you may be able to transmit (if legally permitted to do so in your country) as well as receive
• whilst SDR is great for visualising radio signals, it is not designed or easily able to be used for measuring local EMF as it outputs relative EMF signal values not absolute strength signals and would need a dedicated probe as well as calibration to measure absolute local EMF
  • if you need a field strength meter / spectrum analyzer (and don't need to listen to the audio) in the field, then a dedicated spectrum analyzer is probably the way to go
    • eg. "RF Explorer" models

• whilst SDR was developed in 1982, it was not generally available to the community as it was too expensive
• however, with the advent of USB DVB-T TV tuner hardware using the Realtek RTL2832U chipset in c2010, in 2012, hobbyists found that these chips could be repurposed into USB wideband software-defined radio receiver devices which could cover 500 kHz to 1.766 GHz and thus resulted in a range of very cheap products using this chip which cost around $US30

• antenna Rx port
• antenna Tx port if it is a transceiver
• output digital port - usually USB but may be ethernet or WiFi
• power supply - usually via USB
• accurate timer
  • the oscillator / timer manages the timing of signal processing, data sampling, modulation, demodulation, and protocol handling.
  • these are usually temperature-compensated crystal oscillator (TCXO) with 0.5 PPM with 24 MHz internal reference clock - some can be synced to external clocks
  • accurate timing helps in synchronizing the radio’s operations with external signals or networks, ensuring correct signal acquisition, transmission timing, and processing intervals
  • SDRs often handle complex digital communication protocols that rely on strict timing and synchronization to decode and encode signals properly
  • the timer's PPM specification refers to the frequency accuracy or frequency offset of the device’s oscillator or clock and measures how much the oscillator’s frequency deviates from the desired or nominal frequency - a tolerance of ±10 PPM means the oscillator frequency can vary by 10 parts per million from the specified frequency
  • low PPM values indicate better frequency stability and accuracy, which is crucial for maintaining signal integrity, especially in applications like GPS, communications, and signal decoding (satellite GPS services use atomic clocks for better accuracy!)
  • the timing clock also has a timing clock frequency (eg. 10MHz or 24MHz) which sets the base rate at which the SDR samples or processes data and directly influences bandwidth and resolution.
• general analog to digital electronics
  • eg. Realtek RTL2832U DVT-T chipset
• DAC if they are transceivers
• some also have a dedicated internal microcontroller chip for SDR processing
  • eg. HackRF, HydraSDR
• a frequency range specification
  • basic ones with the Realtek RTL2832U DVT-T chipset usually are restricted to 500kHz-1.75GHz so these cannot access Bluetooth or WiFi signals (2.4/5GHz) and need HF upconverters for longer wavelengths
  • HackRF can do 100 kHz to 6 GHz but are tunable from 0 Hz to 7.1 GHz albeit with loss of dB at the extended ranges;
  • Blade RF 2.0 can do 47MHz to 6GHz hence cannot do MW (300 – 3000 kHz) or SW (3 – 30 MHz)
• adjusting gain
  • Low Noise Amplifier (LNA)
    • as its name implies, this attempts to increase the signal more than increasing the noise
  • Variable Gain Amplifier VGA)
    • this is much like adjusting volume levels - it generally increases both noise and the signal
  • Amp
    • a physical amplifier usually placed near the Rx antenna input
    • usually can be turned on or off
    • eg. Hack RF amp boosts the incoming signal by about 11dB but less than 1V of energy coming into the antenna port can destroy this amp eg. static whilst connecting an antenna or being close to a strong transmission - if your signal strength FALLS when you turn amp on, this means the amp has been damaged and is now acting as an attenuator instead of an amplifier - keep the amp turned off unless you need it, turn the device off when changing antennas and ground them first - the Clifford Heath modification remedies this issue ¹⁾
    • you can also use an external LNA (see below)
• ascertaining optimal gain settings
  • check the Rx saturation level
    • this should not be near 100% (too much gain which will cause noise, ghost signals, etc) or near 0% (this will make it hard to receive a signal)

• these are SDRs connected to an antenna that are accessible via your internet browser
• see http://kiwisdr.com/.public/
  • this one is in Melbourne: http://vk3fsk.proxy.kiwisdr.com:8073/

• use a USB dongle (with analog-digital converter) to connect to a computer and to a dipole antenna
• USB 2.0 are most common but these do have limited data bandwidth compared to USB 3.0 models
• basic models are based on the USB DVB-T TV tuner hardware using the Realtek RTL2832U chipset and have restricted frequency range of 500kHz to 1.75GHz so these cannot access Bluetooth or WiFi signals and need HF upconverters for longer wavelengths

• no legality issues with ownership and use in Australia as they cannot transmit
• the original DVB-T dongle usually did not have a TCXO (Temperature Compensated Crystal Oscillator) and thus overheated resulting in unstable frequency
• example dongles:
  • NooElec RTL-SDR v5
    • made in USA; ?same chip as RTL-SDR Blog V3
    • frequency capability of 100kHz to 1.75GHz and up to 3.2MHz of instantaneous bandwidth
    • HF reception below 25MHz is accomplished with direct sampling and requires a suitable antenna (eg. a Balun One Nine to make a DIY long wire or dipole antenna) and for improved HF, add an upconverter like the Ham It Up
    • compatible with Windows, Mac OS, Linux, and Android
    • preferred software is usually SDR-Sharp
    • https://www.amazon.com.au/dp/B01GDN1T4S/ $AU85 with 3 antennas for 433MHz, UHF and VHF operation
  • AirSpy Mini or Airpsy R2 plus Spyverter
    • https://airspy.com/airspy-mini/
    • Airspy R2 uses a R820T2 tuner
    • see https://www.youtube.com/watch?v=50NdrHLWcNc
  • HydraSDR RFone
    • made in USA;
    • uses a NXP LPC4370 microcontroller as its main chipset
    • Rafael R828D tuner chip
    • 12-bit ADC for signal sampling;
    • 24 MHz to 1800 MHz and can sample up to 10 MHz of spectrum
    • https://hydrasdr.com/ ~$US189
  • SDRplay
    • https://www.strictlyham.com.au/browse-by-type/receivers/sdrplay-rsp-1568#.YRkZm98RVhE
    • 1 kHz to 2 GHz; 14-bit ADCs
    • RSP2 and RSP2PRO include additional features like notch filters and Bias-T power. They use a 24 MHz reference clock internally, which can be synchronized to an external 24 MHz clock for improved timing accuracy.
  • RTL-SDR Blog V3 R820T2 RTL2832U 1PPM TCXO HF Bias Tee SMA Software Defined Radio with Dipole Antenna Kit
    • see https://www.rtl-sdr.com/review-airspy-vs-sdrplay-rsp-vs-hackrf/
    • Rx only;
    • Works on Windows, OSX, Linux, Android, Raspberry Pi;
    • https://www.youtube.com/watch?v=am5DsZvmlSs Turn your Android phone into a radio scanner
    • v3:
      • 500 kHz to 1.7 GHz and has up to 3.2 MHz of instantaneous bandwidth (2.4 MHz stable)
      • R820T2/R860 tuner; basic diplexer;
      • 1 PPM TCXO (Temperature Compensated Crystal Oscillator); 250-300mA power usage over USB; bias-tee;
      • https://www.amazon.com.au/dp/B0BMKZCKTF ~$AU88
    • v4:
      • requires a driver update and does not support direct sampling!
      • better for HF and for urban environment compared to V3, the V3 may be better in quieter rural environments especially where older software is used
      • R828D tuner;
      • 500 kHz up to 1.766 GHz and adds built in automatic overload-resistant HF upconverter circuit for improved signals for below 24MHz;
      • can handle up to 3.2 MHz of bandwidth, with 2.4 MHz being stable
      • reduced interference by using a triplexer circuit that separates the input signal into HF (0-28MHz), VHF (28-250MHz), and UHF bands and by using the open drain pin on the R828D tuner for notch filters
      • less prone to the V3 images which occurred at 14.4MHz and less susceptible to strong AM/FM overload without filtering
      • for satellite, ADS-B, combine 1090MHz filters, LNA, and outdoor collinear or QFH antennas for best results
      • for HF, use AM notch or band-pass filters, long wire or dipole antennas and a 1:1 choke to minimise noise
      • for VHF/UHF, may need to add FM notch filter, modest LNA to boost weak signals and avoid desense
      • advantage of the Blog V4 over the v3 or the Nooelec V5, is at HF is it upconverts through the RF tuner. The RF Tuner is where the gain control is, so you have gain control on the HF bands, that you do not have in the Nooelec V5
      • https://www.amazon.com.au/RTL-SDR-Blog-RTL2832U-Software-Defined/dp/B0CD745394/ ~$AU92
    • avoid clones which may be identified by:
      • flat enclosure rather than rounded; 4 screws per side panel instead of 2; missing SMA nut or washer;
      • no logo on back; do not have “Blog” in the name; do not have the official URL printed on them;
      • board inside is yellow or blue instead of green and may lack thermal pad on bottom;
      • sold but unofficial stores;
      • features may not work such as Bias Tee, HF, TCXO (incorrect frequencies); may have higher noise floor, more noise spurs, signal distortion such as too wide, and high pitched audio spurs;
  • RX888 Plus RX-888 MKII
    • 16bit ADC;
    • Dual RF input, HF frequency range: 1kHz-64Mhz, maximum real-time bandwidth 64M. VHF frequency range: 64M-1700Mhz, maximum real-time bandwidth 10M
    • https://www.aliexpress.com/item/1005006856211779.html ~$AU236

• may have legal issues in Australia
• see transceivers - software defined radio (SDR)

• these usually have ethernet and WiFi connectivity rather than going through USB to connect to devices
• KiwiSDR 2 HF SDR
  • 10-30MHz only; 14bit 65MHz ADC; Xilinx/AMD Artix-7 A35 FPGA; ethernet; OpenWebRX via browser; GPS antenna; ext. clock input;
  • http://kiwisdr.com/
  • https://www.youtube.com/watch?v=QvkZ_1xCBeA
• Web-888:
  • inherits design of the RX-888 but with Wifi/ethernet / web based user interface and a new RF frontend and FPGA implementation
  • 1kHz to 62MHz; 16-bit ADC DDC; supports 24kHz and 36kHz RX bandwidth in additional to original 12kHz;
  • Zynq7010 FPGA with dual A9 ARM cores; fast in-chip bus to deliver 13 channels with waterfall enabled for all channels;
  • built-in High-Performance GPS; HF/VHF Dual Antenna Input; external clock input;2 USB-C Ports
  • https://www.rx-888.com/web/
• SDR Play nRSP-ST
  • 3 configurable antenna inputs; 24MHz clock ref input port; USB-C power supply;
  • 1kHz - 2GHz
  • Wifi, ethernet, as well as USB; internet streaming options; automatic scheduled recordings;
  • https://www.youtube.com/watch?v=Zn0LaYCMeks
    • software SDRConnect or just the web client any where in the world via an internet browser
  • https://www.youtube.com/watch?v=7xnrt6sSxKA
    • can save and store all SDR signals to UGREEN DXP4800 Plus NAS as either audio files (only records the one set frequency) or IQ files which contain an entire bandwidth which can be played back on SDRConnect
    • in the UGREEN DXP4800 Plus NAS software you need to enable SMB Service and create Shared storage folders with a user name and password
      • to access the files on the NAS via a Windows computer, you will need to map a network drive to the IP address of the NAS
    • saving files is via the nRSP admin tool's Recording Schedules feature without any need for a computer to be running during recording but you first need to create a Profile on SDR Connect by tuning to the middle of the band you want, create profile and give it a bandwidth and Profile name
    • in the nRSP admin tool's Storage Configuration, you enter in the SMB Server IP address, and then you can define a SMB Server folder (SMB Share) for saving the files to - you will need the user name and password you set on the NAS

• these are all in one devices that act as a radio receiver but with a SDR display and controls
• you cannot load your own software onto these - it is dependent upon the firmware
• Malahit / Malachite DSP2
  • High Z and 50 Ohm antenna ports
  • 10kHz-380MHz 404MHz-2GHz
  • modulation types: AM, SSB, DSB, LSB, CW DEC, NFM, WFM, FT8, RTTY
  • display bandwidth options of 192kHz, 96kHz, 48kHz; built-in preamplifier; Bias Tee;
  • 3.5“ touch screen; 5000mAh battery;
  • generally available for around $AU540
  • sensitive, selective, the NR (Noise Reduction) circuit is one of the best in the industry
  • can use it via PC with HDSDR or SDR Uno
  • https://www.youtube.com/watch?v=S34bo5OmoD0
• see also transceivers - software defined radio (SDR)

• great interface but Windows only and need to ensure you choose correct 32bit or 64bit version
• can also transmit if you have a transceiver and this is legal for you
• https://www.sdr-radio.com/download free download, donation, but the download page is full of confusing ads - take care - see guide here: https://hamradiodx.net/sdr-console-download-link
• see https://www.youtube.com/watch?v=kAiGlIJdhbw
• can purchase optional software to allow use of virtual audio cables to connect output to other software - see https://vac.muzychenko.net/en/

• can be used on Android devices as well as Win/MacOS/Linux
• https://www.sdrpp.org
• compatible devices include Airspy, HackRF, RTL-SDR, SDRPlay (if API installed)
• see https://www.youtube.com/watch?v=EhN8NZU1DtY How to install and use SDR ++ on Android tablet using an HackRF dongle

• Airspy

• https://www.sdrplay.com/start-here/ - Introduction to the software
• https://www.sdrplay.com/sdruno/ - Windows only
• https://www.sdrplay.com/sdrconnect/ - multiplatform version - Windows/MacOS/Linux and in future Android/iOS
• this is required to be installed if using SDRPlay dongles on Windows as this provides the device driver

• often the preferred software for RTL-SDR devices
• ability to use software plugins eg. Inmarsat decoding

• ensure the SDR device driver has been installed for that USB port (eg. with Zadig on Windows)
• ensure you are using an appropriate antenna (this is the most important part) and cable for your use
  • consider having two types:
    • one for UHF/VHF - eg. CoLinear or Discone (although these may not work well)
    • one for high frequencies such as LoRa, 1GHz
    • for < 30MHz a long piece of wire will do as long as you can install it as high as possible
    • see radio antennas
  • if using the supplied dipole from RTL-SDR, it should be vertical, preferably with the active arm upwards (the active element is the one connected to the center conductor) and each dipole arm should be:²⁾
    • Large Antenna, 5 Sections, 100cm + 2cm is resonant @ ~70 MHz
    • Large Antenna, 4 Sections, 80cm + 2cm is resonant @ ~87MHz (NB. FM radio is 88-108MHz)
    • Large Antenna, 3 Sections, 60cm + 2cm is resonant @ ~115 MHz (NB. Airband in Melbourne is mainly 118-132MHz and weather sats are 137.9MHz, 2m Ham is 144-146MHz)
    • Large Antenna, 2 Sections, 42cm + 2cm is resonant @ ~162 MHz (eg. marine AIS transponders, DVB-T 184-227MHz, DAB radio 202-207MHz)
    • Large Antenna, 1 Section, 23cm + 2cm is resonant @ ~ 285 MHz
    • Small Antenna, 4 Sections, 14cm + 2cm is resonant @ ~445 MHz (eg ISM 433MHz; CB radio 476-477MHz)
    • Small Antenna, 3 Sections, 11cm + 2cm is resonant @ ~550 MHz
    • Small Antenna, 2 Sections, 8cm + 2cm is resonant @ ~720MHz
    • Small Antenna, 1 Section, 5cm + 2cm is resonant @ ~1030 MHz. (eg. ADS-B aircraft 1090MHz; LoRa 915MHz)
• ensure you select the correct bandwidth and modulation for what you are trying to listen to:
  • FM radio stations = wideFM 192kHz bandwidth
  • AM radio stations = AM
  • Airband - AM (usually)
  • 2m Ham = 12.5kHz narrowFM
  • CB Radio = narrowFM
  • Ham SSB = 2.7Khz or 3kHz bandwidths are common but some use 5kHz
  • 80m as well as the 40m Ham band is usually LSB
  • 20m (14MHz) tends to be USB but can be LSB or AM
  • be aware of the digital modes
• consider time of day for longer wavelength radio (ie < 50MHz):
  • 10MHz works best at night when the blocking D and E ionosphere layers disappear and you just have the F layers to bounce off
  • 80m band (3.5Mhz) works well in early morning and in evenings as the disappearing D layer allows it to reach the E layer which is still there and bounce off it
  • 20m (14MHz) often works well during the day for both local and long distance DX but get poor by early evening unless there is a peak solar maximum in which case it may work all night
• optimise your gain settings
  • too high a gain will overload the receiver and cause false signals from harmonics, etc as well as causing potential damage - SDRUno can show if you are doing this
  • too low a gain and you won't get much if any signal
  • an option is to use the autogain control

• HF requires a different antenna (and potentially, attachment to an upconverter to access frequencies < 35MHz) to VHF/UHF and thus you either need a dongle with dual antenna inputs or you need a manual low-loss coaxial switch.

• generic Chinese 100Khz-1.7Ghz RTL-SDR Receiver Upconverter RTL2832U+R820T2
  • https://www.aliexpress.com/item/1005009089390893.html ~$AU69
• Airspy SpyVerter R2
  • ~$US49
• Nooelec Ham It Up Plus v2
  • https://www.amazon.com.au/dp/B076CYK8XZ ~$AU117

• Ku band LNBs
  • RF input range generally 10.7-12.7GHz
  • the Local Oscillator (LO) value will determine the output range so a 9.75GHz LO will essentially give a RTL-SDR a range of 9.775-11.516 GHz although the precision of this LO may change with temperature, etc and may result in some slight variation to actual frequencies found due to drift
  • unlike most other dongle attachments for the RTL-SDR which take a 4.5V Bias Tee to power them, these devices usually require 13V or 18V via coax cable hence you will also need a coax Bias Tee device with DC power input and a built-in capacitor to block current to the RTL-SDR (just don't connect it in reverse else you will blow the RTL-SDR), such devices are available as those used to power TV antenna amplifiers
  • you will also need an attenuator before the signal gets to the RTL-SDR
  • you will also need a F to SMA adapter to connect the coax to the RTL-SDR and a satellite dish antenna or similar device
  • if your SDR software has a “shift” input value option, you can put in the LO value and the software will display the adjusted frequencies
  • the RTL-SDR only has a narrow bandwidth of 2.5MHz and many transmissions is Ku band are 10x that so will only display as an increase in noise level as you can't see the whole bandwidth, but many TV satellites also send narrow band beacons which can be seen well
    • Starlink transmits internet data at 12-18GHz with bandwidths up to 250MHz so this method is not going to be useful but you may be able to see narrow band “beacons” which are incidental “leakage tones” every 125MHz starting at 10825MHz and ending at 12575Mz (most commonly seem to be 10950MHz and 11450MHz) which is most of the downlink range of Starlink internet and you can see the doppler effect of the frequency change on the waterfall as the satellite is moving³⁾
  • the LNB will need to be rotated according to vertical vs horizontal transmissions and also for skew adjustment to account for satellite elevation - there are online calculators for this such as SatLex Digital AZ/EL calculators
  • see https://www.youtube.com/watch?v=eDGEGndEQUg

• sometimes a nearby FM station can overload your SDR dongle and thus one of these device placed in-line with the antenna can mitigate this
• eg. 88-108MHz BandStop Broadcast FM Reject Filter

• this are optional extras to boost the signal and reduce noise
• they generelly have female SMA input and output so you will also need a male-male connector probably
• various versions of these are available such as 20dB amp 10Mhz-6Ghz versions, 100kHz-6GHz versions
• don't leave these in-line if you are not turning them on as they can upset your impedance match when turned off
• typical in-line set up is Antenna > Filter > LNA > SDR
• Nooelec Lana - Ultra Low-Noise Amplifier (LNA) Module for RF & Software Defined Radio (SDR)
  • https://www.amazon.com.au/dp/B07XNLJ9X2 ~$AU60
  • HF-low VHF:50kHz-150MHz BiasTee & USB Power Options; designed mainly for HF https://www.amazon.com.au/Lana-HF-Low-Noise-50kHz-150MHz-Capability/dp/B08XX3NYL3
  • wideband 20MHz-4GHz BiasTee & USB Power Options
  • UHF only: 300MHz-8000MHz: BiasTee & USB Power Options https://www.amazon.com.au/Nooelec-Lana-Accessories-300MHz-8000MHz-Capability/dp/B0CN1JWTLQ $AU99
• combined filter and LNA units such as:
  • https://www.aliexpress.com/item/1005009652903267.html
    • 433MHz BPF+ 23dB LNA Module
    • 868MHz BPF+ 20dB LNA Module
    • 915MHz BPF+ 22dB LNA Module
    • 1090MHz BPF+ 20dB LNA Module
    • 2.4GHz BPF+ 18dB LNA Module
  • Nooelec SAWbird iO Premium Dual Ultra-Low Noise Amplifier (LNA) & Saw Filter Modules:
    • 1090MHz (ADSB) and 978MHz (UAT)
    • 1542MHz for Inmarsat
    • 1620MHz for Iridium and Inmarsat
    • 1688MHz for NOAA (GOES/LRIT/HRIT/HRPT)

• whilst the RTL-SDR USB dongle does have the chip to tune DVB-T signals (which are still used in Australia), they cannot tune in to DVB-T2 signals and they cannot act as an SDR at the same time as a DVB-T device which makes their use problematic
  • due to the limitations of the RTL-SDR chip, in SDR mode, bandwidth drops to ~3 MHz, when in DVB-T mode it is equal to 6-8 MHz thus you cannot fully decode the DVB-T signal in SDR mode
  • in Windows you will have used Zadig software to configure the Windows USB driver for the dongle to an SDR dongle
    • you would need to change this to a DVB-T driver for digital TV to work with software such as VLC's “Open Capture Device” Mode, HDTV Player or SDRSharp and GNU Radio
    • if you want to switch back to DVB-T mode, you would need to reinstall the original DVB-T driver manually or let Windows reinstall it automatically, and then you would need to use zadig to change it back to SDR - ths didn't work for me - perhaps easier to just buy a separate DVB-T dongle
• on Android, Google Play has a SDR driver and a separate DVB-T driver as well as Aerial TV by the same creator as the DVB-T driver however as of Aug 2025, it does not support RTL-SDR V4 - perhaps you need v3
• in Melbourne, the frequencies used are:
  • Seven Network (HSV6): 177.5 MHz (VHF)
  • SBS (SBS7): 184.5 MHz (VHF)
  • Nine Network (GTV8): 191.625 MHz (VHF)
  • Network Ten (ATV11): 219.5 MHz (VHF)
  • ABC (ABC12): 226.5 MHz (VHF)
  • Channel 31 (MGV32): 557.625 MHz (UHF)

• welle.io
  • Windows, MacOS, Linux, but android no longer updated although still runs
  • despite having the option, it doesn't seem to support Bios Tee for the RTL-SDR V4 dongle
• SDRAngel
  • seems to be buggy for DAB
• SDRPlay DAB/DAB+ Plugin
  • see https://sdrplay.com/docs/DABPluginHelp.pdf
  • uses the Freeware Advanced Audio Decoder (FAAD2) for DAB+ channel playback

• Universal Radio Hacker
  • https://github.com/jopohl/urh#Installation
  • see videos: https://www.youtube.com/watch?v=kuubkTDAxwA&list=PLlKjreY6G-1EKKBs9sucMdk8PwzcFuIPB&index=1&pp=iAQB
  • allows recording of a radio signal eg. remote control, visualisation of the wave form modulation, analysis to ascertain the messaging protocol, then reverse engineer the signal for transmitting via transceivers - software defined radio (SDR)

• these allow listening in on public domain non-encrypted emergency services comms
• not sure why you would really want to bother doing this other than curiosity that it could be done - there are better things to do if you are bored
• trunk decoding requires two SDR devices - one for the constant muted fixed frequency control signal channel (eg. 179.4625MHz) and the other for the trunking voice channel
• digital voice protocols include:
  • P25 Phase 1 (Project 25 Phase 1) is a digital radio standard widely used for public safety radio communications (such as police, fire, and emergency services). It uses a 12.5 kHz channel and Frequency Division Multiple Access (FDMA). The digital voice audio is encoded using the IMBE (Improved Multi-Band Excitation) vocoder, and data is transmitted using C4FM (Continuous 4-Level Frequency Modulation) digital modulation. This results in a data rate of 9,600 bits per second, with 4,400 bps allocated to voice, 2,800 bps to error correction, and 2,400 bps to signaling and control data
  • ProVoice is a proprietary digital radio protocol developed by Ericsson (and later, M/A-COM, now part of L3Harris). It was mainly used in public safety and utility radio networks, as a successor to their older “EDACS” digital voice implementations. ProVoice uses IMBE vocoding, just like P25 Phase 1, but is not a P25 standard. Its digital voice signal uses a different modulation and trunking architecture compared to P25, based on EDACS systems rather than P25's protocols. It cannot directly interoperate with P25 systems without special gateways.
• needs a tall, elevated antenna!?
• SDR decoders:
  • UniTrunker
    • decodes P25 Phase 1 and ProVoice audio. It does not decode P25 Phase 2 audio.
    • Windows only
    • need to adjust the warp setting of the control SDR to give a Window value near 0 and a .. value near 100 - can use the scope function to visualise this, and apply the warp value to the voice SDR as well
    • see https://www.youtube.com/watch?v=ZLaBQgomOR4
    • best used with DSD Plus and a Virtual Cable to route the digital audio
      • see https://www.youtube.com/watch?v=g9KJrtIO8_4&list=PL1fGEpsCNIpYAVyTZrIl2wc4nazYiY0ob
  • SDRTrunk
    • Java-based app; Win/MacOS/Linux
    • decodes P25 Phase 1 and 2 and others - see https://github.com/DSheirer/sdrtrunk/wiki
    • https://github.com/DSheirer/sdrtrunk/releases
    • https://www.youtube.com/watch?v=jy_INdGBTM0

• ACARS (Aircraft Communications Addressing and Reporting System) is a digital data link system used in aviation for transmitting short text messages between aircraft and ground stations.
• ACARS allows aircraft to send and receive various types of messages, including air traffic control clearances, operational data, maintenance reports, and weather information. The system integrates with aircraft avionics to automate the sending of reports about flight status and other key data, reducing the need for voice radio communication
• typically uses VHF between 129-137 MHz
• examples:
  • Acarsdec for Linux

• these use the ADS-B transponder signals from aircraft on 1090MHz
• i you have internet access, you don't really need an SDR for this - AirNav has already mapped them for you: https://www.airnavradar.com/
• see https://www.rtl-sdr.com/adsb-aircraft-radar-with-rtl-sdr/
• a properly tuned antenna is required to get decent range but a simple dipole may work but ADS-B uses a vertically polarized signal
  • see https://www.amazon.com.au/dp/B07K7YW1XJ $AU99 for this 1090 antenna
• ensure that your coax feed line (the length of coaxial cable between the antenna and dongle) is high quality (use coax cable intended for satellite installations, such as RG-6) and as short as possible
• add a low noise amplifier (LNA) and a 1090 MHz filter can also help by blocking out interfering signals on other frequencies that could cause your RTL-SDR to overload
  • see https://www.amazon.com.au/AirNav-RadarBox-FlightStick-Advanced-Receiver/dp/B07K47P7XD/ $A49 for filter, LNA and SDR in one unit
• software like Virtual Radar Server (VRS) is commonly used alongside these decoders to visualize aircraft data on maps
• RTL1090 - needs two dongles?
• SDR# (SDRSharp): Has plugins available that can decode ADS-B directly when used with Airspy SDRs
• SDRUno: has an ADS-B decoding plugin
• Dump1090 for Android
  • https://ebctech.eu/faq-dump1090/ works on my Android using a RTL-SDR v4 with the SDR Driver by Martin

• of course you could just do this on the internet without using your own radio antenna such as:
  • https://www.n2yo.com
  • GPredict application - Linux only, but can be used in Windows: https://sourceforge.net/projects/gpredict/
• track satellites and access their signals
• ideally needs a 2m and 70cm Yagi antenna installed on a rotator but you could get by with a dual band fixed antenna
• SkyRoof
  • Windows only - open source
  • https://ve3nea.github.io/SkyRoof/index.html
  • https://www.youtube.com/watch?v=NNwuJhMzPUY&t=414s

• you will need an appropriate antenna and a band filter with LNA
• weather maps
  • SDR software such as SatDump does support many geostationary weather satellite protocols (HRIT/LRIT, APT, HRPT) and receives images from satellites like NOAA, GOES, Meteor-M, and Elektro-L—all of which operate in frequency ranges accessible by common SDR equipment.
    • NOAA, Meteor-M, and Elektro-L satellites all provide weather images covering Australia, although with different resolution and regional accuracy
      • NOAA polar-orbiting satellites (like NOAA 15 137.62, 18 137.9125, and 19) pass over Australia several times daily, offering moderate-resolution images of cloud cover and weather fronts as they sweep across the region
        • you probably also need https://www.amazon.com.au/Nooelec-SAWbird-NOAA-Ultra-Low-Applications/dp/B07TWPR871 NooElec SAWbird+ NOAA - Premium Satellite Tuner with Ultra-Low Noise LNA & SAW Filter for NOAA Applications. 137MHz Center Frequency but the 30dbi gain might be too high for the dongle even with a V dipole antenna, so the 20bl gain version may be better: https://www.amazon.com.au/Nooelec-SAWbird-NOAA-Satellite-Applications/dp/B0D1CTGZZH/
      • Meteor-M satellites (Russian polar orbiters, M1 137.1, M2 series 137.9 ) also regularly pass above Australia and provide similar coverage with high-resolution multispectral images.
      • Elektro-L satellites (Russian geostationary weather satellites 1691-1693 MHz) include Australia in their hemisphere-level imagery, though resolution is lower compared to Himawari
      • GOES satellites are geostationary above the Americas; their view of Australia is very limited and not operationally useful for Australian weather monitoring
  • SDR and SDR software will NOT be able to decode the primary Australian weather map mainly as the frequency is too high:
    • The primary satellite providing weather images for Australia is Himawari-9, a geostationary satellite operated by the Japan Meteorological Agency (JMA) on Ka-band (18.1–18.4GHz) although the data relayed is from environmental data collection platforms using frequencies around 402MHz for both international and domestic channels. Himawari-9 is positioned at longitude 140.7°E, giving excellent coverage of Australia and surrounding regions. For end-users such as meteorological agencies, data is mostly received via commercial satellite rebroadcast (HimawariCast), internet service (HimawariCloud). HimawariCast (the rebroadcast of Himawari data for the Asia-Pacific region) is sent via DVB-S2 protocol on the C-band (approximately 3.7–4.2GHz), which also typically requires a satellite dish and a C-band LNB, not just an SDR stick.
• other satellite data includes:
  • Inmarsat Aero provides secure and reliable voice and data communication services for aviation worldwide.
    • best with a small satellite dish and L band helix antenna - see https://www.youtube.com/watch?v=aLsOZbsGJ1Q
    • only Immarsat 3,4 (“Alphasat”) and 6 satellites transmit in L band:
      • 1530 MHz to 1660 MHz for the full Inmarsat Aero service coverage including uplink and downlink bands
      • 1545 MHz to 1547 MHz (forward link, ground station to aircraft)
      • see https://www.youtube.com/watch?v=uq4BwsPcQrE
      • https://www.youtube.com/watch?v=mRXWhk9Gf1g
    • 3685 MHz to 3687 MHz (additional frequencies)
    • standard modulation types used include phase shift keying such as OBPSK and OQPSK at different bit rates: 600, 1200, and 10500 bps.
    • you would probaby also need:
      • https://www.amazon.com.au/Nooelec-Inmarsat-Patch-Antenna-Connector/dp/B07YYMVFQV Nooelec Inmarsat Patch Antenna
      • https://www.amazon.com.au/Nooelec-SAWbird-iO-Ultra-Low-Applications/dp/B07K1PBJ4X/ Nooelec SAWbird iO - Premium Dual Ultra-Low Noise Amplifier (LNA) & Saw Filter Module for Inmarsat Applications. 1542MHz Center Frequency
  • Inmarsat-C STD-C EGC messages are emergency warning broadcasts sent via satellite to deliver critical safety and weather information to aircraft and ships.
    • 1545-1547 MHz in L-band for communications with aircraft
    • 3685-3687 MHz are additional frequencies
    • uses various digital modulations at bit rates suited for voice and data
  • OrbComm
    • 31 LEO satellites for machine-to-machine and IoT
    • transmit around 137-148MHz on narrow FM sending ASCII data?
    • see https://www.youtube.com/watch?v=vEha9se62NQ
• SatDump
  • can track satellites automatically and download the signal and decode it eg. NOAA weather images if you are in USA or Europe
  • can decode weather maps from NOAA, etc
  • see also: https://www.youtube.com/watch?v=8mo_KVSkgb8
  • https://www.youtube.com/watch?v=CrMdsfKu5Ys
• Jaero
  • can decode Inmarsat Aero signals
• Skytal-C
• GPS signal decoding
  • not sure why you would want to do this as your phone will do it automatically for you but it can be useful to gain a better understanding of what is happening
  • you will need:
    • a GPS antenna
    • https://github.com/rtlsdrblog/rtl-sdr/releases/tag/v1.1 Bias T driver for RTL-SDR v3 to power the GPS antenna
    • https://github.com/taroz/GNSS-SDRLIB GNSS-SDRLIB-GUI
    • https://www.rtklib.com/rtklib.htm RTKNAVI
  • see https://www.youtube.com/watch?v=YG2fJRTAoHA

• spherics are usually 3-30kHz VLF
• you don't need special SDR software for this as lightning can be seen on the SDR software by a general transient rise in the noise floor across all frequencies
• can be done with simple electronic circuit, an antenna, a ground and a audio recorder or headphones and no need for SDR at all
• https://www.youtube.com/watch?v=5azk0unfptg
• https://techlib.com/electronics/VLFwhistle.htm

• meteor trails briefly ionize the atmosphere and transiently increase signal strength of powerful FM transmissions
• frequencies below 40 MHz may have interference from other ionospheric propagation modes and are less commonly used specifically for meteor scatter
• meteor scatter reflections are most prominent between 40-50 MHz
• you will need a 6m or 2m dipole or yagi antenna
• monitoring software generally targets signals around 140 MHz in Europe while in Australia, there are digital meteor scatter modes like MSK144 and FSK441 commonly operating at 50.220–50.280 MHz in the 6m band as well as the more challenging 144.230–144.330 MHz 2m band for high-speed meteor scatter modes such as FSK441. In Melbourne, there is a meteor scatter beacon at 49.3MHz;
• Echoes
  • Windows/Linux
  • https://www.rtl-sdr.com/echoes-an-rtl-sdr-tool-for-meteor-scatter-detection/
• Meteor Logger:
  • https://www.rtl-sdr.com/meteor-logger-a-tool-for-counting-meteor-detections-with-an-rtl-sdr/

• DragonOS
  • has hundreds of tools for learning how hackers do their thing
  • create a Linux virtual machine and looks a bit like Ubuntu
  • works with RTL-SDR, Hackr One, Blade
  • can create your own cellular network if you have a full duplex SDR like Blade (as you would need to send and receive at the same time) - but this may not be legal in Australia as with a lot of other radio transmissions so CHECK what is legal - if you stick with RTL-SDR which is a receiver only, you are probably not going to do anything illegal!

• this analyses the FST4, FST4W, FT4, FT8, JT4, JT9, JT65, Q65, MSK144, and WSPR signals on a given band and can provide a number of functions such as
  • logging time, dB, DT, Freq, Message
• https://wsjt.sourceforge.io/wsjtx.html - only available on Windows, MacOS, Linux (eg. Raspberry Pi)
• can be visualised on Android via browser interface to WiFi-connected computer running it
• has WSPR mode (Weak Signal Propagation Reporter) which is handy for sending and receiving beacon signals to test antennas, determining when bands open

• Digital Speech Decoder “Florida Man Edition” (DSD-FME)
  • https://github.com/lwvmobile/dsd-fme
  • https://www.youtube.com/watch?v=ZtSLWTX7TKY