AIRCRAFT SIGNALS TRACKED 27 JANUARY 2020
Here at The Peppermint Lounge I like to dabble in several things radio. One of which is to see what signals I am able to pull out of the ether, or to be more precise, the ionosphere. Yesterday I set up one of my receivers to detect High Frequency Direct Link, or HFDL for short, signals which are transmitted by aircraft.
Aircraft have several navigational systems on board and HFDL is one of those systems which operates on the high frequency radio spectrum. For those not technically inclined think shortwave radio bands. HFDL is a coded transmission from the aircraft to a series of ground stations located around points on the globe, and vice versa. The aircraft is able to transmit location and other information such as fuel load to the ground station as it makes its way.
The system is automated and typically the plane will transmit a short burst of data of less than one second duration to the ground station. To receive these messages I run a software defined receiver plugged into an antenna outside at one end and my PC at the other. I then run software which decodes the message, which is turn relays this to another piece of software which sorts it out further. I am also able to send the information to Google Earth which plots the aircraft's flight path.
If you look at the image above you will see a series of lines and their corresponsding flight numbers. The little red markers are the ground stations - you can see one of these on Guam which is to the right of the image. These signals were detected on 17.919 MHz and if you look closely the most distant signal was picked up from a plane beyond India.
Here is an example of message received from an aircraft:
27/01/20 14:50:03 UTC
Mode: 2 Identifier: VH-VQK Ack.: {NAK}
Message type: 2L
Block: 1 (Downlink)
Message: M47AJQ0671DAT 27JAN20
UTC (Universal Coordinate Time) 1449
REG (Regulator) VHVQK
FLT (Flight) JST671
GWT 0
ZFW (Zero Fuel Weight) 567
FOB (Fuel on Board) 152
CAP (Capture) 149430
FO (Flyover / First officer) 210108
LOG 345318
LDR 0
DRT 1437
Now this is a bit pedestrian as it's a local flight from Darwin to Sydney. We can see that the aircraft registration is VH-VQK and it was Jetstar flight JST671. There's some information about fuel load and the time and date information. We can even find a picture of this aircraft on line.
Here's an example of a transmission from the Hong Kong ground station to an aircraft.
----------------------------------------------------------[27/01/2020 12:37]
HACARS mode: 2 Aircraft reg: .JA824P
Message label: A9 Block id: G [Uplink]
Message content:-
/HKGATYA.TI2/VHHH ARR ATIS H
0233Z HONG KONG ARRIVAL INFORMATION H AT TIME 0233
ARRIVAL RUNWAY 07L
WIND 020 DEG 11 KT
VISIBILITY 10 KM
CLOUD FEW 2500 FT
TEMPERATURE 12 DEWPOINT 5
QNH 1019 HPA
ACKNOWLEDGE
This was a Peach Airlines flight from Osaka to Hong Kong and here is a picture of the plane:
There are more signals we can monitor from aircraft, but I think that's enough for today. Until next time - peace and love.
