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Watch a sweep live

chirp-view makes TX1 play a sweep from a cyclic buffer and shows RX1 receiving it: live spectrum, waterfall, the loop's response, and the sound.

chirp-view running: on the left the live spectrum, a waterfall with one slanted line per sweep from 864.5 to 871.5 MHz, the response curve and the transmitted sweep; on the right the control panel.

It transmits: read before you transmit first

TX1 must reach RX1 through at least 20 dB of attenuation. The board puts out about +19 dBm and RX1 survives +2.5 dBm.

You need
TX1 → 20 dB attenuator → RX1 never without one: the board puts out about +19 dBm and RX1 survives +2.5 dBm
the board on Ethernet, the Debian root
zc-stream on the board for the default 20 MS/s (how); without it, --rate 4.8e6 --span 1e6 --period 3
no other program receiving the board has one receive buffer 
# run from: tools/chirp-view on your PC
python3 -m venv .venv
.venv/bin/pip install -r requirements.txt
.venv/bin/python chirp_view.py --fullscreen

You should see: a 7 MHz up-sweep from 864.5 to 871.5 MHz every 0.8 s, one slanted line per sweep in the waterfall. It sets RX1's gain by itself within a couple of seconds. Esc or Q quits, muting TX1 first.

Also
--channel 2 the same on TX2 → pad → RX2, TX1 muted
Pulsed chirp mode radar-style pulse compression: 123 ns peak (theory 127 ns) for 7 MHz × 100 µs pulses
--reference loops ranging timed against RX2, so lost samples cannot move it; at most 5.5 MS/s

chirp-view's signal path: the PC computes one period of the sweep and uploads it once; the FPGA replays it as a cyclic buffer; it goes round the loop TX1, 20 dB pad, RX1; zc-stream sends it back as 8-bit samples at 20 MS/s; a receiver process on the PC draws the window and plays the sound. chirp-view's signal path: the PC computes one period of the sweep and uploads it once; the FPGA replays it as a cyclic buffer; it goes round the loop TX1, 20 dB pad, RX1; zc-stream sends it back as 8-bit samples at 20 MS/s; a receiver process on the PC draws the window and plays the sound.

The modes, the controls, the mirror and ranging: chirp-view.