Coherent arrays

An array processes several antenna signals together. Shared clocks determine whether those signals can support direction finding, beamforming, or passive radar.

A shared clock is required. Independent receivers drift apart even when tuned to the same frequency.

Radios that are already an array

Add one Device for a multi-lane receiver such as KrakenSDR, CR-8, RSPduo in dual-tuner mode, or a multi-channel SoapySDR radio. Its driver reports the coherence tier. Connect its iq, iq2, and subsequent outputs directly to processing nodes.

KrakenSDR

KrakenSDR has five lanes; KerberosSDR has four. Their shared clock provides time_sync coherence, but tuner phases change after every retune.

Set Cal source to Noise. SDR-- switches the built-in noise source on when calibration is needed, including after a retune or a press of Calibrate, then returns to the antennas. During calibration, the display shows noise source in and suppresses bearings.

Use fixed gain and equal-length antenna cables. Calibration pauses while scanning or hunting.

Radios you wired together yourself

Use an Array node for separate receivers physically connected to a shared clock.

1. Add a Device for each receiver.
2. Set matching sample rates and, for shared tuning, matching centre frequencies.
3. Connect each Device's iq output to an Array input. Inputs expand as members are added.
4. Set Wired as to match the hardware: shared clock, or shared clock and local oscillator.
5. Connect the Array outputs to your processor, channels, or recorders.

Input order sets antenna numbering. Use fixed gain on every receiver; calibration can correct different fixed gains, but AGC changes invalidate it.

Tuning and membership

Tune and change sample rate through Array to keep members aligned. Independently tuned arrays provide a frequency control per lane. Disconnect the array before scanning or hunting.

Device nodes keep ownership of their radios and existing outputs. Removing Array leaves those running. Removing a member removes the dependent array. A disconnected member faults the array; processing reconnects when all members recover.

Calibration

Press Calibrate on the coherent processor. It measures delay, amplitude, and phase corrections for each lane.

A time_sync array needs injected noise or a specified pilot frequency to resolve phase after retuning. Built-in noise sources switch automatically. Inject an external reference before pressing Calibrate. On phase_coherent hardware, calibration corrects cable and other path differences.

The display reports solved, still solving, or phase unknown. Phase unknown means the reference is insufficient for bearings or beamforming.

Combining antennas

Connect one coherent source to a Combiner, then connect its beam output to an ordinary channel.

For cancellation, place the wanted signal on the first antenna and receive the local noise on the others. Both modes need known relative phase; time_sync arrays require a pilot or noise reference.