#ads-l.
Posts on the Alpisto engineering blog filed under #ads-l.
- 01#flybeeper #fanet #ads-l
One radio, two networks: how a FANET vario shares every second with ADS-L
My vario has one radio and two networks to serve. Every second it decides which one to listen to and when to speak, and that choice decides who you see on the map. The numbers from the bench: listen to ADS-L for the whole second and FANET goes to zero; stop listening to ADS-L and FANET comes back 40 to 140 % stronger; cut the ADS-L window from 550 to 300 ms and another maker's transmitter drops from 61 % of its seconds heard to 34 %.
12 min read - 02#flybeeper #fanet-vario #fanet
The lift does not fade: where 11,046 competition thermals end, and how to know before you get there
The usual advice is to leave a thermal when it weakens. In 11,046 thermals from competition tracks it hardly weakens at all: pilots climb at full rate to within a hundred metres of the top, and the last fifty metres still give most of it. The top is a ceiling, and your own vario cannot see a ceiling coming. The pilots around you can: the ones who have already left, and the tops of the day's earlier thermals, tell you how much is left to within about a hundred metres, a minute before you get there.
9 min read - 03#flybeeper #fanet-vario #fanet
The thermal leans, then it drifts: 8,409 thermals rebuilt from competition tracks
Every pilot knows a thermal drifts with the wind. How much, and in what way, a single pilot cannot tell: climbing and drifting happen at the same time. A competition gaggle can — a hundred pilots in one thermal at different heights in the same minute. From the published tracks of 28 competitions on 18 sites I rebuilt the axis of 8,409 thermals. In the mountains, near the ground, the column stays put and the wind lays it over at 45°; over flat land, and higher up everywhere, it stands nearly straight and the whole thing drifts at two thirds to three quarters of the wind. And the radio a FANET vario already listens to is enough to see it from the air.
21 min read - 04#flybeeper #fanet #ads-l
Teaching a LoRa vario to hear ADS-L — and finding the time to do it
Every ADS-L receiver takes its clock from GNSS. My vario has no GNSS by design — the position comes from the phone in your harness. So I took the UTC second from the phone too, over Bluetooth, and measured how bad that channel really is. Good enough with room to spare: the share of frames the device caught went from 15 % to between 50 and 100 %.
16 min read - 05#flybeeper #fanet #flarm
FLARM, FANET and ADS-L — where the line actually 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.
8 min read