dasi2 bringup: probe for the TS-1 time-sync signal (and GPS) and surface a missing-signal indicator to the operator

[rrobinett]

Requested by rob 2026-07-24. A dasi2 system is expected to have the TS-1 BPSK PPS time-sync signal injected into its RF (45.375 MHz carrier, GPSDO-disciplined). Today B4 came out of greenfield with the hf-timestd config at the template's rtp/minimal defaults — T6 disabled, no metrology — and nothing told the operator that a live time-sync signal was present in the RF going unused (or conversely, would warn if the expected signal were absent, e.g. injector unplugged / GPS antenna missing).

Ask

During smd bringup dasi2 (and/or smd admin validate), probe for the expected time-sync signal and surface the result to the user:

• Signal present + T6 disabled in config → "time-sync signal detected at 45.375 MHz but [timing.t6_pps] is disabled — run …" (misconfiguration indicator)
• Signal absent + dasi2 topology → "expected TS-1 time-sync signal NOT found — check injector/GPS RF path" (hardware indicator)
• Similarly for the GPSDO/GPS presence (gpsdo-monitor already knows).

Validated probe method (used live on B4 today)

Create a temporary IQ channel on the running radiod and poll its spectrum with ka9q powers:

tune --radio <status> --ssrc 99045375 --frequency 45375000 --mode iq --samprate 12000
powers -s 99045375 -f 45375000 -w 40 -b 300 -c 2 <status>
tune --radio <status> --ssrc 99045375 --frequency 0   # delete probe

Decision rule that worked: max bin within ±100 Hz of 45,375,000 Hz vs median of the 12 kHz window; B4 showed the carrier 79 dB over the noise floor with the ±40/±80 Hz sidebands of 1 Hz BPSK phase flips. A ≥20 dB threshold is comfortably robust.

Context

• B4 full-chain bring-up 2026-07-24: T6 enabled at 45375000 (bee1-parity params minus bee1's chain_delay_calib_s), locked immediately (costas_locked=1, chain_delay ≈105.743 ms stable to ±200 ns).
• Related greenfield gap: greenfield/reinstall leaves sigmond's own systemd units uninstalled (shm-precreate, timing-reconcile, storage-trim, decode-health) #39 (baseline sigmond units not installed). The same bringup pass that asserts the unit baseline could run this probe.

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