Also known as: Airspy R2
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The Airspy R2 is a high-performance VHF/UHF software-defined radio receiver with a 12-bit ADC, capture up to about 10 MS/s, a clock output for chaining, and a 4.5 V bias tee — the flagship of the Airspy line and GopherTrunk’s recommended wideband, multi-site channelizer.1 It carries far more dynamic range and wider bandwidth than an RTL-SDR.
Key takeaways GopherTrunk’s recommended wideband radio. The Airspy R2’s 12-bit ADC (~72 dB dynamic range vs an RTL-SDR’s ~48 dB) and ~10 MS/s capture let one dongle channelize several control channels — including multiple sites of one P25 system — out of a single IQ capture. Adds a clock output and a 4.5 V bias tee for an inline LNA. Receive-only, ~$150–185. Airspy is distributor-sold, so Amazon stock is intermittent — the button tracks live listings. For most of the quality cheaper, see the Airspy Mini; like every receiver it can’t decode AES encryption. New here? See best SDR for GopherTrunk.
Overview
The R2 is the radio you reach for when an RTL-SDR’s 8-bit ADC or ~2.4 MHz of usable bandwidth is the thing standing between you and a decode. Its ~10 MS/s capture is useful when a system’s channels are spread across a band, or in tough RF where a strong neighbour would push an 8-bit front end into clipping. For the lower bands, the Airspy HF+ Discovery is the specialised choice; the smaller Airspy Mini is the same design in a cheaper dongle.
How it works
An R2 shares the front-end tuner with an RTL-SDR — a Rafael Micro R820T2 — but replaces everything behind it. Instead of the RTL2832U’s 8-bit ADC and USB bridge, the Airspy digitises the tuner’s IF with a 12-bit ADC driven by an NXP LPC4370 microcontroller, then streams the samples over USB 2.0. Two design choices give it its edge:
- More bits. A 12-bit ADC carries roughly 72 dB of theoretical dynamic range against the RTL2832U’s ~48 dB — the headroom that lets a weak signal survive next to a strong one without the front end clipping.
- Oversampling and real-to-complex conversion. The Airspy samples the IF at a high real rate and digitally converts it to complex baseband on the way out, decimating to the requested rate. Averaging many high-rate samples into each output sample adds effective bits (process gain), so the delivered stream is quieter than the raw ADC alone.2
The R2 is receive-only — there is no transmit path. The HydraSDR RFOne is an independent successor built on the same 12-bit R820T2 architecture, and an SDRplay RSP1B is the closest 14-bit alternative in a similar niche.
Relevance to GopherTrunk
GopherTrunk supports the R2 for demanding reception where an RTL-SDR’s bandwidth or
sensitivity falls short — a congested band, a distant control channel, or a multi-site system
whose control channels are spread too far apart to fit one RTL-SDR capture. The extra ADC bits
and wider capture are exactly what a wideband, multi-tap channelizer wants, which is why the R2
is GopherTrunk’s recommended device for the role: wideband use. GopherTrunk drives it over
USB with a pure-Go backend (no libairspy needed); it remains a receiver only, so it decodes
clear and scrambled traffic, never keyed encryption.
Wideband multi-site monitoring
An R2 pinned to role: wideband can channelize several control channels — including multiple
sites of one P25 system — out of a single IQ capture, all decoded in parallel. Every tap
shares one antenna, one centre frequency and one gain, and the channelizer is gain-flat
across taps. So if one site decodes cleanly while others sit at the noise floor, the cause is
RF, not the DDC:
- Front-end overload. A strong (often hilltop) site can drive the shared ADC into
clipping, raising the noise floor and burying weaker sites. Gain is in tenths of a dB
(
gain: 600means 60 dB). If the input clip ratio is non-zero, lower the gain or add attenuation — do not raise it. In a metro the usual culprit is broadcast FM; an FM broadcast notch filter inline is often the cheapest fix. - A genuinely weak/distant site may not survive a capture optimised for a stronger one. Give it a dedicated dongle if it matters.
Where to buy
Airspy is sold through its own distributor network, so Amazon stock comes and goes — the button is a tagged search that always resolves to current listings rather than a single page that may be out of stock. Get the R2 for the full ~10 MS/s wideband capture, clock output and bias tee; for most of the quality at a lower price, the Airspy Mini tops out around 6 MS/s.
Deciding between radios? See best SDR for GopherTrunk, compare against the RTL-SDR and HackRF One, or, for shortwave/low-VHF, the Airspy HF+ Discovery. Then grab GopherTrunk from the downloads page.
As an Amazon Associate, GopherTrunk earns from qualifying purchases — at no extra cost to you. It never changes what we recommend.
Sources
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Software-defined radio — Wikipedia, for background on Airspy-class high-performance VHF/UHF SDR receivers. ↩
-
Airspy R2 — Airspy, on the R2’s R820T2 front end, 12-bit oversampling architecture, up-to-10 MS/s capture, clock output and bias tee. ↩
Frequently asked questions
Is the Airspy R2 worth it over an RTL-SDR for GopherTrunk?
For tough or busy RF, yes. The R2’s 12-bit ADC carries far more dynamic range than an RTL-SDR’s 8-bit converter, and its ~10 MS/s capture lets one dongle channelize several control channels — including multiple sites of one P25 system — at once. For a first radio on a clean single-site system, a $30 RTL-SDR is still the cheapest thing that works.
Airspy R2 or Airspy Mini?
Same 12-bit architecture. The R2 captures up to ~10 MS/s and adds a clock output and a 4.5 V bias tee; the Mini tops out around 6 MS/s in a smaller, cheaper dongle. Choose the R2 for wideband multi-site channelizing and inline LNA power; the Mini for most of the quality at a lower price.
Does GopherTrunk need libairspy or SoapySDR for the R2?
No. GopherTrunk drives the Airspy R2 directly over USB with a pure-Go backend — no libairspy, no SoapySDR. It’s the recommended device for GopherTrunk’s wideband, multi-tap channelizer role.
Can the Airspy R2 decode encrypted police channels?
No. The R2 is a receiver and GopherTrunk is receive-only. It decodes clear P25/DMR/NXDN/TETRA, but no radio or scanner can decode AES-encrypted transmissions.