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Software-defined radio — edited Aug 31, 2026 by Unknown editor
This is the first recorded version, so every line is shown as added. Note: Imported from content/wiki
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In a software-defined radio, the hardware digitizes a slice of spectrum and software does the
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filtering and demodulation. Practically, that means you see the band instead of tuning blindly
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across it — and you can change what the radio *is* by changing the program.
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## Receive-only, for about $30
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An RTL-SDR dongle (RTL2832U with an R820T2 or R828D tuner) covers roughly 500 kHz to 1.7 GHz. With
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a good antenna it will let you:
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- Watch a whole band at once and see where activity is.
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- Decode [APRS](/wiki/operating/digital-modes/aprs), [SSTV](/wiki/operating/sstv-and-atv), FT8,
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aircraft ADS-B, NOAA weather satellite images and pagers.
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- Diagnose your own station — find birdies, harmonics and
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[noise sources](/wiki/station/rfi-and-noise).
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- Learn modulation by looking at it. This is the cheapest education in radio there is.
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Buy from a reputable source (rtl-sdr.com's v3/v4), add an upconverter or use direct sampling for
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HF, and fit a bandpass filter if you live near broadcast transmitters.
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## Better receivers
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- **Airspy HF+ Discovery**, **SDRplay RSPdx** — real HF performance, good dynamic range, $200–400.
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- **KiwiSDR** and the public WebSDR network — free receivers around the world in your browser.
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Listen to your own signal from another continent; nothing else tells you as much about your
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antenna.
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## Transceivers
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- **Hermes-Lite 2**, **HackRF**, **LimeSDR**, **ADALM-Pluto** — open, experimenter-oriented.
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- **FlexRadio**, **Apache ANAN** — direct-sampling HF transceivers run entirely from a PC client.
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- Most modern mainstream radios (IC-7300, IC-7610, FTdx10, TS-890) are SDRs internally with a
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built-in spectrum display; you get the benefits without a computer.
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## Software
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SDR++, SDRangel, GQRX, SDR# and CubicSDR for general use; GNU Radio if you want to build the signal
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chain yourself. See [software](/wiki/operating/software).
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## Practical notes
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- Panadapter output from a conventional radio (an IF tap or the IC-7300's USB stream) gives you the
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waterfall without replacing the radio.
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- Keep the dongle away from the transmit antenna, or fit a receive-protection relay — a few watts
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will destroy the front end.
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- USB noise is real: use a shielded cable, a ferrite choke and, if needed, a powered hub.