sjg
2c1df75d19
Auto took the spectrum's noise floor and added 6 dB, but the threshold is compared against the channel level the meter reports, and the two sit a long way apart: the gap is set by the FFT size and window, the channel bandwidth, the decimation, and peak-versus-mean statistics. Measured on white noise it runs +22.1 dB at 48k/8k/3k, +18.7 dB at 240k/24k/12k and -1.2 dB at 1.92M/24k/12k — a 23 dB swing across ordinary configurations. Only the last of those is anywhere near right, so on a narrow span Auto set the gate some 20 dB below the noise and it never closed. It now reads the same number the DSP compares: the 20th percentile of the meter over the last ten seconds, plus 5 dB. The percentile keeps a burst of traffic inside the window from dragging the estimate up, and 5 dB clears the meter's own jitter, which measured 0.9-1.6 dB. Nothing in it converts between scales, so no part of the signal chain can put it out again. With no history yet — a fresh connection, a rig switch — it listens for a moment rather than refusing. The fixture gained a streaming /meter, without which there is nothing to measure, and the spectrum test pins auto to the meter it serves. Signed-off-by: Stan Grams <sjg@haxx.space>