Technical articles on engineering, scientific Python, embedded systems, and power systems.https://alpisto.eu/en-ushttps://alpisto.eu/blog/how-a-flybeeper-vario-decides-when-to-beep/https://alpisto.eu/blog/how-a-flybeeper-vario-decides-when-to-beep/Between a climb tone and a sink alarm there is a band where a vario has to make up its mind, and pilots disagree about what it should do there. Some want silence the moment a thermal fades, some want to keep hearing a weak core, some want a tone almost all the time. This is how a FlyBeeper vario makes that decision, step by step: the averaging, the tone curve, two thresholds on each side, a memory of which tone is playing and an early exit on a weakening climb. Every example plays in the page, and opens in the configurator with one click.Tue, 06 Oct 2026 00:00:00 GMTflybeeperfanet-variosun-variovariometeraudiofirmwareconfiguratorparaglidinghttps://alpisto.eu/blog/one-radio-two-networks/https://alpisto.eu/blog/one-radio-two-networks/My vario has one radio and two networks to serve. Every second it has to decide which network to listen to and when to transmit, and that decision affects who you see on the map. Bench results: if the vario listens to ADS-L for the whole second, FANET reception drops to zero; if it stops listening to ADS-L, it receives 40 to 140 % more FANET frames; if the ADS-L listening window is cut from 550 to 300 ms, the share of seconds in which another maker's transmitter is heard falls from 61 % to 34 %.Wed, 23 Sep 2026 00:00:00 GMTflybeeperfanetads-lfanet-variosx1262softrfogntime-syncparaglidinghardwaremeasurementhttps://alpisto.eu/blog/thermal-top-from-competition-tracks/https://alpisto.eu/blog/thermal-top-from-competition-tracks/In 11,046 competition thermals the lift hardly fades: pilots climb at full rate almost to the top, so your own vario cannot warn you. The pilots who left before you and the day's earlier tops can, about a minute ahead.Sun, 20 Sep 2026 00:00:00 GMTflybeeperfanet-variofanetads-lthermal-soaringparaglidingigccompetitiondata-analysismeteorologymeasurementpythonhttps://alpisto.eu/blog/thermal-axis-from-competition-tracks/https://alpisto.eu/blog/thermal-axis-from-competition-tracks/From the tracks of 28 competitions I rebuilt 8,409 thermals. Near mountain terrain the column stays put and leans at 45°; higher up and over flat land it stands nearly straight and drifts at two thirds to three quarters of the wind.Sat, 19 Sep 2026 00:00:00 GMTflybeeperfanet-variofanetads-lthermal-soaringparaglidingigccompetitiondata-analysisransacmeteorologymeasurementpythonhttps://alpisto.eu/blog/vario-piezo-tone-measured/https://alpisto.eu/blog/vario-piezo-tone-measured/Small varios beep in a way nobody would call pleasant, and it is not because nobody cared. A piezo disc is a bell with one note of its own, and a vario plays a tune on it by feeding it square waves and letting the bell pick what it likes. I put one in a desk drawer with a microphone: at 1000 Hz the note that was asked for comes out 33 dB below its own third harmonic, loudness swings 16 dB across the tone table, and the obvious way to soften a beep turns out to make it sharper.Thu, 10 Sep 2026 00:00:00 GMTflybeeperfanet-variosun-variovariometerpiezoaudiopwmfirmwarenrf52zephyrmeasurementparaglidinghardwarehttps://alpisto.eu/blog/flyability-model-training/https://alpisto.eu/blog/flyability-model-training/The technical story of the Flyability forecast on the FlyBeeper map: five million XContest flights, GFS weather, cumulative XC-distance probabilities, confident learning against self-reported logs, isotonic calibration, and an honest evaluation protocol. From a binary classifier and an attention network to three gradient-boosted trees that ship inside the package and refresh a map layer four times a day.Sun, 06 Sep 2026 00:00:00 GMTflybeepermachine-learningparaglidemlgfsxcontestparaglidingforecastgbmcalibrationhttps://alpisto.eu/blog/barometer-thermal-drift-measured/https://alpisto.eu/blog/barometer-thermal-drift-measured/Everyone who builds these devices knows you must not solder near the barometer, and that the third rework kills it. Nobody says by how much. This one came off the bench at 470 Pa/K against a rated 0.5, inventing 14.5 metres of climb while sitting still. Thirty lines of firmware removed 95 % of that and every bench test agreed — until somebody picked the device up and the vario went the wrong way. The number behind the folklore, and why the fix helps an altimeter and provably cannot help a variometer.Wed, 26 Aug 2026 00:00:00 GMTflybeepersun-variovariometerbarometerspl07sensorsfirmwarenrf52zephyrmeasurementparaglidinghardwaresolderingreflowhttps://alpisto.eu/blog/teaching-a-lora-vario-to-hear-ads-l/https://alpisto.eu/blog/teaching-a-lora-vario-to-hear-ads-l/An ADS-L receiver must know when each UTC second starts, and receivers normally get that from GNSS. My vario has no GNSS on purpose: its position comes from the pilot's phone. So I took the time from the phone too, over Bluetooth, and measured how accurate that is. It is accurate enough, with room to spare: the share of frames the device caught went from 15 % to between 50 and 100 %.Tue, 25 Aug 2026 00:00:00 GMTflybeeperfanetads-lsx1262gfskbletime-syncnrf52zephyrognparaglidinghardwarehttps://alpisto.eu/blog/vario-current-usb-tester/https://alpisto.eu/blog/vario-current-usb-tester/I spent eight hours per data point measuring a solar variometer through its own capacitor. Then I measured the same device directly with a USB tester and got a full consumption curve in twelve minutes — along with a 420 µA floor that belonged to the cable, not the device. What both methods agree on, where they don't, and how to read a WITRN tester from Linux.Thu, 20 Aug 2026 00:00:00 GMTflybeepersun-variovariometermeasurementlow-powernrf52zephyrsupercapacitorusbreverse-engineeringhardwarehttps://alpisto.eu/blog/flybeeper-sun-vario/https://alpisto.eu/blog/flybeeper-sun-vario/A solar audio variometer the size of a matchbox that runs off a lithium-ion capacitor instead of a battery. Thirty minutes of morning sun fills it from empty; a minute on USB-C is enough for a flying day. 29 × 34 × 12 mm, 9.8 g, one button, Bluetooth to your phone.Tue, 18 Aug 2026 00:00:00 GMTflybeepersun-variovariometerbluetooth-lesolarsupercapacitorparaglidinghardwarehttps://alpisto.eu/blog/sun-vario-energy-budget-measured/https://alpisto.eu/blog/sun-vario-energy-budget-measured/Eight hours of discharge logs on a solar variometer running off a 10 F lithium-ion capacitor. The current isn't constant, the buzzer isn't the main consumer, the barometer is — and the runtime formula that falls out of it. Plus what the enclosure had to become once the electronics stopped changing.Tue, 18 Aug 2026 00:00:00 GMTflybeepersun-variovariometersolarsupercapacitorlicenergy-harvestingnrf52zephyr3d-printingparaglidinghardwarehttps://alpisto.eu/blog/flarm-fanet-ads-l-where-the-line-is/https://alpisto.eu/blog/flarm-fanet-ads-l-where-the-line-is/Why I won't ship FLARM on hardware that could technically transmit it, what the licence actually permits, why FANET's adaptive interval matters in a gaggle, why LoRa means FANET can never be the EU conspicuity standard — and why ADS-L is a better bet than it looks.Thu, 30 Jul 2026 00:00:00 GMTflybeeperfanetflarmads-lloraconspicuityognparaglidinghardwarehttps://alpisto.eu/blog/why-no-accelerometer-in-my-vario/https://alpisto.eu/blog/why-no-accelerometer-in-my-vario/A phone's barometer isn't bad — it's read badly, and that's most of why phone-only varios feel laggy. Why I poll a dedicated baro at 60 Hz instead, why an IMU costs more than it gives, how it lies to you in a spiral, and where sensor fusion actually belongs.Wed, 29 Jul 2026 00:00:00 GMTflybeepervariometerbarometeraccelerometerimusensor-fusionbluetooth-leparaglidinghardwarehttps://alpisto.eu/blog/flybeeper-fanet-vario/https://alpisto.eu/blog/flybeeper-fanet-vario/The FlyBeeper FANET Vario is a wireless, solar-powered FANET beacon and barometric variometer in one. No GPS inside — it reuses your phone's, works as a plain radio driven by the app, and puts you on the map for nearby pilots. Full app, BLE protocol and specs. A quiet pre-order at €149 with free shipping.Tue, 21 Jul 2026 00:00:00 GMTflybeeperfanet-variofanetvariometersolarbluetooth-lenrf52loraparaglidinghardwarehttps://alpisto.eu/blog/deep-learning-for-n-1-security/https://alpisto.eu/blog/deep-learning-for-n-1-security/Neural networks can screen contingencies 300× faster than full AC power flow — at 98%+ accuracy. A survey of CNN, GNN, and DCNN approaches, the data problem, and where the field still struggles.Sun, 24 May 2026 00:00:00 GMTpower-systemsmldeep-learningn-1contingency-analysishttps://alpisto.eu/blog/ml-thermal-soaring/https://alpisto.eu/blog/ml-thermal-soaring/A survey of deep learning and reinforcement learning for autonomous thermal soaring — LSTM/GRU/TCN/Transformer architectures, POMDP and PPO/TD3 formulations, Kalman + ML hybrid filtering, and a concrete five-stage plan for an on-board AI co-pilot for paragliders.Mon, 23 Feb 2026 00:00:00 GMTflybeepermachine-learningreinforcement-learningthermal-soaringparaglidinglstmtransformertcnkalman-filterliterature-reviewhttps://alpisto.eu/blog/flybeeper-fanet/https://alpisto.eu/blog/flybeeper-fanet/An always-on BLE bridge to the 868 MHz FANET data network. No on-board GPS — the smartphone provides position, the device just radiates. Solar-powered, years of standby, full radio configuration over GATT so apps can transmit FANET, ADS-L or anything else on the same radio.Wed, 08 May 2024 00:00:00 GMTflybeeperfanetlorabluetooth-lenrf52paraglidinghardwarehttps://alpisto.eu/blog/flybeeper-tas/https://alpisto.eu/blog/flybeeper-tas/A purpose-built BLE true-airspeed sensor for paragliders and hang gliders up to 103 km/h IAS. Custom CFD-designed pitot tube with a 4% correction coefficient versus 50% for hobby tubes, four PCB revisions ending in USB-C supercap charging, and standards-compliant BLE GATT services.Sat, 30 Dec 2023 00:00:00 GMTflybeepertasairspeedpitot-tubebluetooth-lenrf52paraglidinghardwarehttps://alpisto.eu/blog/flybeeper-pressure-sensor/https://alpisto.eu/blog/flybeeper-pressure-sensor/An external BLE pressure sensor for paragliding flight apps like xcTrack and SeeYou Navigator. Always on, pair once and forget — wakes the moment the app subscribes to ESS pressure notifications. ±2 cm/s vertical-speed resolution from an SPL06, 5-year standby on a single CR2032.Sun, 24 Dec 2023 00:00:00 GMTflybeeperps1pressure-sensorbarometerbluetooth-lenrf52paraglidinghardwarehttps://alpisto.eu/blog/flybeeper-remote-control-4/https://alpisto.eu/blog/flybeeper-remote-control-4/An always-on four-button BLE remote for paragliding flight apps. No power switch, deep-sleep when idle, automatic wake when an app connects — battery life measured in years from a single CR2032. Built on Nordic nRF52, exposes the standard Automation IO Service.Fri, 22 Dec 2023 00:00:00 GMTflybeeperrc4remote-controlbluetooth-lenrf52paraglidinghardwarehttps://alpisto.eu/blog/flybeeper-mini-bt/https://alpisto.eu/blog/flybeeper-mini-bt/A dwarf-sized BLE 5 variometer on nRF52 + Zephyr RTOS, exposing pressure, temperature, altitude, four-button remote and OTA updates through standards-compliant GATT services. The entire stack — GPIO, SPI, PWM, ADC, FLASH, OTA, DFU, BLE, GATT, plus the OS — fits in 200 kB.Wed, 09 Aug 2023 00:00:00 GMTflybeepermini-btvariometerbluetooth-lenrf52zephyr-rtosparaglidinghardwarehttps://alpisto.eu/blog/canflybot-soaring-forecast/https://alpisto.eu/blog/canflybot-soaring-forecast/A Telegram bot that wraps the Paraglidable AI forecast and Meteoblue thermal soundings for paragliding pilots. Tracks 10,000+ take-off and landing spots, pings you when probabilities exceed your thresholds, and serves detailed thermal diagrams on demand.Sat, 25 Feb 2023 00:00:00 GMTflybeepercanflybottelegram-botweatherparaglidablemeteobluethermal-forecasthttps://alpisto.eu/blog/flybeeper-f1-test-report/https://alpisto.eu/blog/flybeeper-f1-test-report/Five hours, three F1 units, two GPS antennas, one RF interference incident over Cividale. Notes on GPS lock quality, vario behaviour, BLE companion app, and a Tagliamento-crossing flight across the Julian Alps.Mon, 16 May 2022 00:00:00 GMTflybeeperf1test-flightparaglidingfield-testgnsshttps://alpisto.eu/blog/flybeeper-f1/https://alpisto.eu/blog/flybeeper-f1/A pocket-sized paragliding flight instrument with GNSS, barometer, 868 MHz LoRa FANET, BLE 5.0 and on-board logging. Built as both a FANET tracker and the main vario, with a long development log covering hardware, firmware, FAI-recognised IGC validation and a Web BLE configurator.Thu, 21 Apr 2022 00:00:00 GMTflybeeperf1fanetparaglidinggnssblehardwarehttps://alpisto.eu/blog/flybeeper-horn/https://alpisto.eu/blog/flybeeper-horn/The smallest variometer in the FlyBeeper line, doubling as an emergency whistle and acoustic distress beacon. A demanding miniature project that combines tight PCB design, a composite CR2032 holder, and a 3D-printed enclosure that has to actually whistle.Mon, 07 Mar 2022 00:00:00 GMTflybeeperhornvariometerparaglidinghardware3d-printing