DENKOThe Tests page
Three hardware self-tests at /test: the response sweep, the gain check and the alias survey. They inject a known signal into the station's own front end and measure what comes back — the only figures on the station that describe this board rather than the schematic.
Detection is paused while a diagnostic runs. The station cannot listen for lightning and inject test tones at the same time, so run these when a few seconds of quiet do not matter — not in the middle of a storm you care about.
One diagnostic at a time. Starting a second one while another is running is refused; wait for the progress bar to finish.
1. Run sweep: the frequency response
Choose a channel and press Run sweep. The station injects a tone ahead of the whole signal chain (the DAC block on the Signal chain diagram), steps it through 28 frequencies, and measures the amplitude that comes back — once through the LTC1569-7 filter path and once through the bypass. It takes about 22 seconds.
The result is drawn as a response (Bode) plot, with a dashed computed curve of the passive LC ladder from the netlist for comparison — a model of the board family, not a measurement of your board. For each path the table reports the peak, the −3 dB crossings, and the noise floor:
- Hollow rings mark points at or near the noise floor: there the dB figure is a limit, not a value — the true response is at least that low.
- CLIPPED means a sample hit the converter's rail, so attenuation below that point is compression, not filtering.
- Both paths are measured together because the comparison is the test: on a board with no filter chip fitted, the filtered path shows nothing while the bypass shows the tone — one path alone cannot tell “not fitted” from “fitted and attenuating”.
2. Check gains: the PGA ladder
The gain stages are write-only: nothing in the hardware reads a gain back, so every gain figure the station displays is what it believes it sent. Check gains is the evidence. It steps the stages through all 64 combinations of the two 8-step ladders (×1, ×2, ×4, ×5, ×8, ×10, ×16, ×32) at the strongest frequency in the passband, injecting at whatever level keeps each combination between the noise floor and the rails. It takes about 9 seconds.
The result is an 8 × 8 table of measured gains against the ladder. Cells more than 15 % off are flagged; a dash means no injection level could put that combination in range. A healthy board ends with all measurable combinations follow the ladder. A cell that is consistently wrong points at that gain stage; a board where nothing follows the ladder points at the injection path or the converter.
3. Alias survey
The alias survey captures the selected channel through the filter and the bypass at three slightly different sample rates (480, 500 and 525 kSPS). A real in-band tone stays at one frequency; an out-of-band tone that is only aliasing into the measurement band moves when the sample rate changes. Use it when the spectrum view shows a suspicious steady line: this is alias evidence, not source identification, but it tells you whether the tone is really in the band your filters claim to pass.
4. Reading and re-reading results
- Results stay on the page (and in the station) until the next run or a restart; the page reloads them when it opens, so you can leave and come back.
- The same results are available as JSON at
/api/resp(sweep and gain check) and/api/alias(alias survey) — see the endpoint list. - These tests measure the board, not the sky. Run the sweep and gain check after building or repairing a station, after changing the amplifier head, and whenever the Diagnostics page disagrees with what you expect.