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| | |-+  This is scary - crew cannot understand plain instructions from Shanwick
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Author Topic: This is scary - crew cannot understand plain instructions from Shanwick  (Read 12275 times)
55brianb
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« on: July 05, 2013, 06:39:36 PM »

I was testing my new cheapo SDR and heard this exchange at 22h56 UTC on 4 July 2013 on 6547kHz USB between TAM8085 and Shanwick Oceanic.  It was going on when I tuned into the frequency and I heard it for over a minute before I started my recording software!

Checking showed it to be TAM8085 (TAM Linhas Aereas) from London Heathrow (LHR) in the UK to Sao Paulo, Guarulhos (GRU) in Brazil.  Departed LHR on the evening of 4 July 2013.

Scary.....
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flyflyfly
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« Reply #1 on: July 05, 2013, 07:30:58 PM »

Nice catch. Amazing patience. I guess the controller desperately needed a break after this one  grin.
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55brianb
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« Reply #2 on: July 05, 2013, 09:21:01 PM »

Yea, and probably a few stiff Jamesons too!  cheesy
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frcabot
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« Reply #3 on: July 06, 2013, 06:29:31 PM »

I can't understand a word that the TAM crew is saying. Can someone transcribe?
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svoynick
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« Reply #4 on: July 06, 2013, 08:24:50 PM »

Something to consider here - because of the uncertainties in HF propagation, you can't be at all sure, from sitting at the spot where you are receiving, how the Shanwick controller is being received at the aircraft.  He may well be coming in weak and covered with noise, much like the aircraft is apparently being received - essentially unreadable - at your end. 

So I don't know if your statement that it was "scary" that the crew couldn't understand "plain instructions" was an implication that there was some incompetence there in the cockput, but put it this way:  if all you could hear was something like what was coming back from the airplane (e.g. essentially a nearly unreadable signal-to-noise ratio), you might well transmit "in the blind" and just repeat your current flightplan back to them, just to try to be sure they had your current flightplan confirmed. 

Propagation changes often, sometimes by the minute, so it may be that a few minutes later, the propagation path shifted just so, so that they were able to read Shanwick well enough to finally understand the instructions. 

I can't say this was the scenario for sure, but likewise, we also don't know with any certainty that they were able to receive those "plain instructions" with any decent readability in the cockpit.

(Since you talked about using a "cheapo" SDR, can I assume you're using one of those DVB-T USB sticks with an RTL2832 device in it?  If so, what are you using for an up-converter from HF into the VHF passband of the tuner device?  One of those homebuilt NE-602-based mixers?)
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55brianb
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« Reply #5 on: July 08, 2013, 11:12:13 AM »

Yea, the propagation point is fair enough, but that's why there's a backup frequency  wink  Shanwick asked the pilot if he could copy him and the reply was "Yes sir", but that was maybe 30 seconds - one minute before I was able to start recording.

Yep, it's an RTL2382U/R820T-based dongle, but the converter's a commercially available one - the NooElec "Ham it Up", and the combination of these is providing me with generally better results than my Eton E5 does - it's not as portable as the E5 though!  A mate has the same setup (which is where I first saw it) and says his outperforms his Sony ICF7600 receiver.  Cheap SDR it may be, but it's quite impressive.  I just wish I could afford something like a WinRadio or Perseus  smiley
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