Also known as: Airspy
Airspy is a line of high-performance VHF/UHF software-defined radio receivers (the R2 and the smaller Mini) offering better sensitivity, dynamic range, and wider bandwidth than an RTL-SDR.1
Overview
Airspy R2 captures up to ~10 MHz, useful when a system’s channels are spread across a band or in tough RF environments. For the lower bands, the Airspy HF+ is the specialised choice.
Relevance to SDR
GopherTrunk supports Airspy receivers for demanding reception where an RTL-SDR’s bandwidth or sensitivity falls short.
Wideband multi-site monitoring
An Airspy 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. List each site’s control channel as its own channels:
entry (see config.example.yaml).
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 the 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, very high for a wideband capture. Ifgophertrunk_sdr_wideband_input_clip_ratiois non-zero (a throttled WARN also fires), lower the gain or add attenuation — do not raise it. - A genuinely weak/distant site may not survive a capture optimised for a stronger one. Give it a dedicated dongle if it matters.
Diagnostics: each tap’s level is on gophertrunk_sdr_iq_power_dbfs labelled
<system> @ <freq> MHz; the whole capture is on
gophertrunk_sdr_wideband_input_iq_power_dbfs{serial} and
gophertrunk_sdr_wideband_input_clip_ratio{serial}. Compare a tap against the
whole-capture power to tell a weak site apart from a decode problem, and watch
the clip ratio for overload.
Sources
-
Software-defined radio — Wikipedia, for background on Airspy-class high-performance VHF/UHF SDR receivers. ↩