Decoding DME aircraft radio navigation system with the LimeSDR
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Re: Decoding DME aircraft radio navigation system with the LimeSDR
#2VORs are pretty interesting. At first i thought every plane had a small antenna array on board to check the direction to the VOR.
But the direction is just calculated by the phase shift between an omnidirectional and a directional signal. So it can be implemented very cheaply on every plane.
Re: Decoding DME aircraft radio navigation system with the LimeSDR
#3VORs are pretty interesting. At first i thought every plane had a small antenna array on board to check the direction to the VOR. But the direction is just calculated by the phase shift between an omnidirectional and a directional signal. So it can be implemented very cheaply on every plane.
ADF uses radio direction finding techniques. It's not very accurate and is all but deprecated except for some corner cases where the legislation hasn't yet allowed for overlay approaches (replacing a real radio beacon with its true position via GPS / IRS).
There are some convincing reasons for being cautious on general on that front. Accidents have happened because some beacons have been substituted for the wrong location or even things like slant range being different from true range. In general ADF is so inaccurate that its protected areas are massive.
Re: Decoding DME aircraft radio navigation system with the LimeSDR
#4If you want some in-depth technical details on how VORs work, I found this video very helpful. It goes into many of the details of the analog radio engineering:
Re: Decoding DME aircraft radio navigation system with the LimeSDR
#5VORs are pretty interesting. At first i thought every plane had a small antenna array on board to check the direction to the VOR. But the direction is just calculated by the phase shift between an omnidirectional and a directional signal. So it can be implemented very cheaply on every plane.
Easiest to understand with a flashing + rotating light analogy.
When a rotating, say one turn in 10 seconds, green light is pointing north, a red light flashes.
If you see a green flash 1 second before a red flash, you're on the 36 degree radial.
Re: Decoding DME aircraft radio navigation system with the LimeSDR
#6If you want some in-depth technical details on how VORs work, I found this video very helpful. It goes into many of the details of the analog radio engineering: https://www.youtube.com/watch?v=tZ2gG1v9Xg8
You can also compare and contrast how VOR/DME and TACAN works, to see two different solutions to one problem (polar coordinate measurement in 3D space.)
The mechanical differences are quite obvious when you look at a VOR, a TACAN, and a VORTAC, but the engineering behind them is interesting.
Re: Decoding DME aircraft radio navigation system with the LimeSDR
#7If you want some in-depth technical details on how VORs work, I found this video very helpful. It goes into many of the details of the analog radio engineering: https://www.youtube.com/watch?v=tZ2gG1v9Xg8
Animats wrote a great comment on the topic here [1] as well.
Re: Decoding DME aircraft radio navigation system with the LimeSDR
#8VORs are pretty interesting. At first i thought every plane had a small antenna array on board to check the direction to the VOR. But the direction is just calculated by the phase shift between an omnidirectional and a directional signal. So it can be implemented very cheaply on every plane.
Easiest to understand with a flashing + rotating light analogy. When a rotating, say one turn in 10 seconds, green light is pointing north, a red light flashes. If you see a green flash 1 second before a red flash, you're on the 36 degree radial.
Wouldn't you be on the 324 degree radial
Re: Decoding DME aircraft radio navigation system with the LimeSDR
#9VORs are pretty interesting. At first i thought every plane had a small antenna array on board to check the direction to the VOR. But the direction is just calculated by the phase shift between an omnidirectional and a directional signal. So it can be implemented very cheaply on every plane.
ADF uses radio direction finding techniques. It's not very accurate and is all but deprecated except for some corner cases where the legislation hasn't yet allowed for overlay approaches (replacing a real radio beacon with its true position via GPS / IRS). There are some convincing reasons for being cautious on general on that front. Accidents have happened because some beacons have been substituted for the wrong loc…
There's also a very real chance that commercial aviation may find itself operating in a GPS-denied environment, at least in various edge cases. For example, combat zones often employ GPS spoofing and jamming, and because radio waves don't exactly respect borders, this can sometimes affect civilian equipment outside of the combat zone. This has happened at least near Israel, Iraq, and Ukraine in the last few years. In other cases, truckers or rideshare drivers that want to spoof their company trackers end up parking too close to an airport and impacting planes on an RNAV approach.
Re: Decoding DME aircraft radio navigation system with the LimeSDR
#10Earlier quoted context omitted.
ADF uses radio direction finding techniques. It's not very accurate and is all but deprecated except for some corner cases where the legislation hasn't yet allowed for overlay approaches (replacing a real radio beacon with its true position via GPS / IRS). There are some convincing reasons for being cautious on general on that front. Accidents have happened because some beacons have been substituted for the wrong loc…
There's also a very real chance that commercial aviation may find itself operating in a GPS-denied environment, at least in various edge cases. For example, combat zones often employ GPS spoofing and jamming, and because radio waves don't exactly respect borders, this can sometimes affect civilian equipment outside of the combat zone. This has happened at least near Israel, Iraq, and Ukraine in the last few years. In…
> There's also a very real chance that commercial aviation may find itself operating in a GPS-denied environment, at least in various edge cases.
Yea, it's kind of terrifying that we are slowly putting all of our eggs in the GPS basket. I love GPS but when lives are at stake, you need a redundant backup navigation system that is robustly deployed and reliably works.