4 ms·

I was thinking along the same exact lines: Why do we still rely on analog narrowband AM voice over VHF to do vital comms like air traffic control? Same way as

by lxe 2y ago

I was thinking along the same exact lines: Why do we still rely on analog narrowband AM voice over VHF to do vital comms like air traffic control? Same way as we did in the 1940s! We should be transcribing the messages and relaying them digitally with signatures and receipt acknowledgement.

jimnotgym 2y ago
Isn't it because AM audio is still understandable under very suboptimal conditions where digital might not get through? Digital narrowband data modes tend to pass very small amounts of data
- lxe 2y ago
  Quite the opposite. For short messages digital modes can employ layers of redundancy, auto carrier recovery, error correction at all layers all while yielding lower power requirements, and longer distance.
  - EricButton 2y ago
    FAA actually tried moving to digital voice (has benefits wrt airband congestion) but it didn't go anywhere. I believe a lot came down to the minimal benefit over current solutions, plus the coordination and safety implications of actually making the switch. Tough for an FAA official to pull the trigger on a rollout that has even 0.1% chance of an aircraft crashing.
- dehrmann 2y ago
  A lot of ATC seems to use lowest common denominator tech so that you an fly a Cessna into JFK.
  - kristian1109 2y ago
    But only after 1am when you're not fighting a 15 knot headwind with an A320 cleared number two.
DF1PAW 2y ago
AM modulation is perfectly justified in this context: if two (or more) stations accidentally transmit at the same time, this will be noticed. Using FM, only the stronger signal wins and the other signal remains undetected. The advantage over digital transmission is the lack of coding overhead - the voice reaches the receiver without any time delay.
- jlewallen 2y ago
  This is true, for anybody curious about this: https://en.wikipedia.org/wiki/Capture_effect https://en.wikipedia.org/wiki/Capture_effect
- lxe 2y ago
  The justification still holds, but better tech with the same benefits exists nowadays. As far as digital decoding delay is concerned, this is a negligible number if implemented correctly.

by lxe 2y ago

jimnotgym 2y ago

Isn't it because AM audio is still understandable under very suboptimal conditions where digital might not get through? Digital narrowband data modes tend to pass very small amounts of data

lxe 2y ago
Quite the opposite. For short messages digital modes can employ layers of redundancy, auto carrier recovery, error correction at all layers all while yielding lower power requirements, and longer distance.
- EricButton 2y ago
  FAA actually tried moving to digital voice (has benefits wrt airband congestion) but it didn't go anywhere. I believe a lot came down to the minimal benefit over current solutions, plus the coordination and safety implications of actually making the switch. Tough for an FAA official to pull the trigger on a rollout that has even 0.1% chance of an aircraft crashing.
dehrmann 2y ago
A lot of ATC seems to use lowest common denominator tech so that you an fly a Cessna into JFK.
- kristian1109 2y ago
  But only after 1am when you're not fighting a 15 knot headwind with an A320 cleared number two.

DF1PAW 2y ago

AM modulation is perfectly justified in this context: if two (or more) stations accidentally transmit at the same time, this will be noticed. Using FM, only the stronger signal wins and the other signal remains undetected. The advantage over digital transmission is the lack of coding overhead - the voice reaches the receiver without any time delay.

jlewallen 2y ago
This is true, for anybody curious about this: https://en.wikipedia.org/wiki/Capture_effect https://en.wikipedia.org/wiki/Capture_effect
lxe 2y ago
The justification still holds, but better tech with the same benefits exists nowadays. As far as digital decoding delay is concerned, this is a negligible number if implemented correctly.