Also known as: HydraSDR, RFOne
HydraSDR RFOne is a high-performance VHF/UHF software-defined radio receiver in the lineage of the Airspy R2 — same 12-bit oversampling architecture and R820T2 front end, carried forward as an independent open project. It samples up to ~10 MHz of spectrum anywhere from ~24 MHz to 1.8 GHz.1
Overview
The RFOne is aimed squarely at the niche the Airspy R2 created: a receiver with the sensitivity, dynamic range, and capture bandwidth an RTL-SDR can’t reach, in the bands public-safety and business radio actually use. It is designed in France by Benjamin Vernoux and manufactured in the USA, which — with the recent rise in RTL-SDR dongle prices — makes it one of the better value high-performance receivers on the US market.1
How it works
Like the Airspy R2, the RFOne pairs a Rafael Micro R820T2 tuner with a 12-bit ADC driven by an NXP LPC4370, replacing the RTL2832U’s 8-bit ADC and USB bridge. Two design choices give it its edge over a dongle:
- 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 receiver 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 adds effective bits (process gain), so the delivered stream is quieter than the raw ADC alone.
It delivers up to about 10 MS/s of complex bandwidth and is receive-only — there is no transmit path.
Variants
- HydraSDR RFOne — the single current model: ~24 MHz–1.8 GHz, up to ~10 MS/s, 12-bit, with a clock reference and a bias tee for powering an inline LNA.
Compared with the Airspy R2 it is architecturally very close — a practical alternative in the same slot. Against an SDRplay RSPdx it trades the RSPdx’s 14-bit ADC and HF coverage for the R820T2 path’s simplicity and a pure-USB streaming model. As with any 12-bit direct-sampling receiver, put a broadcast-FM notch filter in front of it in a strong signal environment to keep the front end out of overload.
Relevance to SDR
GopherTrunk drives the HydraSDR over USB 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, so like the Airspy it is a strong choice for the role: wideband use.
It remains a receiver only, so it decodes clear and scrambled traffic, never keyed
encryption.
Where to buy
The RFOne is sold through DigiKey (~US$189) and listed on the manufacturer’s site at hydrasdr.com — it is not currently carried on Amazon.