mckero
0889a3bd88
The mixer runs above unity for any ordinary input - the Hilbert kernel's L1 gain is 2.51, so amplitude 0.7 peaks at about 1.76 - and the output was hard clipped to fit. Clipping squares the waveform off and generates odd harmonics, which the widened waterfall would now put on screen. Measured, the harmonics happen to be harmless today: TARGET_HZ is a quarter of the sample rate, so 3f, 5f, 7f and 9f all fold back onto the tone itself and out-of-band energy stayed at 0.00%. That is a coincidence between two constants, not a property of the design. At a 700 Hz target the third harmonic folds to 1100 Hz - inside the analysis window, where no filter may remove it and the model would read it as a second tone. So two changes, because neither alone is enough. A peak-following gain scales the mixer output to fit rather than clipping it: measured 0 of 3200 samples on the rail, against a clipped waveform parking there for much of every cycle. And a 95-tap windowed-sinc band-pass over the model's window removes whatever the mix leaves outside it - images, harmonics, the far sideband - measured at 58-60 dB rejection with 0.09 dB of passband ripple and out-of-band energy down to 0.0002%. The gain is shared across chunks so it cannot step at a boundary, and the filter carries tap history for the same reason the Hilbert filter already did. The band-pass adds 47 samples of linear-phase group delay, 14.7 ms, which delays the keying envelope without distorting it - 4% of a dot at 40 WPM. CwToneShifterStreamingTest's boundary criterion was wrong, and the band-pass exposed it: distanceToBoundary measured only forward, so the first samples of a chunk came out 320 away from "the" boundary and counted as interior when they are the far side of the same seam. Both filters need samples ahead of the output they are producing - 32 for the Hilbert transform, 47 for the band-pass - and with the distance measured to the nearest boundary either way, interior divergence is 0.000116 against a 0.01 budget. Also: the CW transcript now follows the newest text, but only while the operator is already at the bottom, so scrolling back to read earlier traffic is not undone by the next decoded character.
Look4Sat: Satellite tracker
Radio satellite tracker and pass predictor for Android, inspired by Gpredict
Track satellite passes with ease!
Thanks to Celestrak and SatNOGS you have access to over 9000 active satellites.
You can search the entire database by NORAD Catalog Number or the satellite's name.
Orbital positions and passes are calculated relative to your location.
To get reliable data make sure to set the station position via the app Settings.
The application is built using Kotlin, Coroutines, Jetpack Compose and Navigation.
It is now and always will be completely ad-free and open-source.
Main features:
- Predicting satellite positions and passes for up to 10 days
- Showing the list of currently active and upcoming satellite passes
- Showing the active pass progress, polar trajectory and transceivers info
- Showing the satellite positional data, footprint and ground track on the map
- Custom TLE satellite data import is available via Three Line Element .txt files
- Offline first: calculations are made offline. Weekly TLE data update is recommended.
License
The Look4Sat application code is licensed under the GNU General Public License v3.0.
The CW decoder in feature/cw bundles the DeepCW
neural decoding model, licensed under the GNU Affero General Public License v3.0 only
(AGPL-3.0-only). Because the combined work incorporates an AGPL-3.0 component, the
combined work is distributed under the
GNU Affero General Public License v3.0 — GPL-3.0 Section 13 permits the
combination, and AGPL-3.0 Section 13 applies to the combined work as a whole.
Model provenance and attribution are documented in
feature/cw/licenses/NOTICE.md; the original GPL-3.0
text is preserved at feature/cw/licenses/Look4Sat-GPL-3.0.txt. The CW model runs
locally on-device and does not provide services over a network.