Posted: 4/10/2026 10:29:24 AM EDT
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News article here: https://aviationa2z.com/index.php/2026/03/15/faa-orders-boeing-787-fix-after-radio-signal-flaw/ FAA Airworthiness Directive (AD) here: https://drs.faa.gov/browse/excelExternalWindow/FR-ADNPRM-2025-10759-00000000000.0001 TLDR: CW signals are occasionally causing the Mode S ATC transponders on 787 aircraft to fail to respond to normal ATC interrogation signals. This results in their disappearance from ATC radar displays. The FAA refers to this as "interference", but the issue is probably better termed "susceptibility", i.e. the onus is on the transponder. At any rate, for once the amateur radio community is not getting shit on. Instead it is Boeing, and the transponder manufacturer Collins Aerospace, that are getting the heat. Poor Boeing, this is yet another thing they have to take up their butthole  |
"Cogito, ergo armatum sum."
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Originally Posted By Phillbilly: What's CW? CW is a mode of communication using radio waves. It was the first mode ever used to communicate using radio. It was encoded by humans directly using a "code" the Morse Code or actually a modified version of Morse code that had been used on land line telegraph circuits for some 60 years prior. This was adopted for radio use and messages were sent by this encoding method for some years until "phone" or sending voices over a radio was perfected. But even after that was accomplished, CW was still a very viable method for sending messages (for some very complicated reasons) And is still in use even in this day. It is used by Amateur Radio Operators daily , not because they have to, but because they want to, and for its superior signal to noise ratio advantage over most voice operations AND more importantly for the celebration of the skill and knowledge required to use it. It is also used by a few other groups but not to the extent it was a few decades ago. The main reason is because there has to be a trained operator to decode it. There are many other modes, including digital modes that can outperform it, but all of these things require infrastructure to be able to work. A simple CW transceiver and a trained operator is an extremely simple "system" that is both efficient and minimalist in all respects at the same time. If you would like to learn more, we can help. Best Regards "73" James K0UA |
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I'm really curious about the frequency of the emitter. I'm skeptical it's amateur HF CW. I'm betting it's something near the transponder frequency or a harmonic, or it's just blanket RF susceptibility (e.g. desense.) To the "what is CW" question, it's an abbreviation for Continuous Wave, which is simply a signal with no modulation. To hams CW means morse code, where a continuous wave signal is turned on and off (which is modulation) with the morse code key or its equivalent. In the context of the 787 transponders, they're likely referring to always-on signal emitters other than transponder pings from FAA radars. |
| I mirror your skepticism. I made a casual search for a technical report but failed to find anything. Perhaps they want to keep that data confidential given the fragility of most of our RF infrastructure where deliberate interference is concerned. Only the cell systems have achieved a decent level of resistance to interference. |
"Cogito, ergo armatum sum."
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They're not talking about amateur morse code. "CW" as a designation for Morse code is not really correct. It's called that in the ham world as a historical artifact as a distinction from spark. Morse isn't continuous, it's intermittent pulses of a carrier. "CW" in the context of the reported issue with aircraft systems is literally "continuous wave", or continuous carrier transmissions. Radar, or something like a localizer or other beacon system most likely is the culprit. "CW" as opposed to modulated. |
This is...a clue - Pat_Rogers
I'm not adequately aluminumized for this thread. - gonzo_beyondo
CO, MI, OR - Please lobby your legislators to end discrimination against non-resident CCW permit holders
I'm not adequately aluminumized for this thread. - gonzo_beyondo
CO, MI, OR - Please lobby your legislators to end discrimination against non-resident CCW permit holders