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#101
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Why don't voice radio communications use FM?
On Sun, 03 Sep 2006 13:39:09 +0200, Mxsmanic
wrote: Larry Dighera writes: --- cut----- Anything that isn't signal is noise. AM transmissions are fuzzy and hard to hear. In fact, aviation AM radio is probably the noisiest type of radio voice communication still in use. Most other types of radio communication today are FM. This thread is becoming a lot of guessing and not based on facts! I doubt anybody has evaluated AM compared to FM in an aircraft so won't know what the effects are when tried side by side. There is absolutely no difference in qualilty between AM & FM if they are designed to the same specification. If you modulate an AM or FM transmitter with up to 3KHx of audio they will sound identical. What you put into the transmitter comes out of the receiver assuming there isn't a fault. FM maintains a low background noise longer than AM and the only difference is at low signal levels when FM very quickly becomes totally unreadable. AM can still be heard and understood, depending on the ability of the person listening. With all the noise in an aircraft a little bit of low level background noise is not significant. Digital has some merit but again when the signal reaches a threshold it stops completely. The whole thread is futile as the centre of the 'aviation universe' may well be the US but you aren't going to get the rest of the world to change. Even having regultions which are supposed to be accepted worldwide doesn't work. Most counties have exceptions. About the only thing which is standard is the use of the English language. Even then the locals will use their own language! Have you ever worked controllers with Spanish English, Finnish English, Canadian English, New Zealand English, Cyprus English, Bahamian, Caribbean or even Amereican English. That's where the differences can be heard. AM radio is adequate for the job and if you don't think so then get your installation checked out by a qualified engineer, you may be suprised. As for increasing the number of frequencies Europe has introduced 8.3KHz spacing. Fortunately at the lower GA flight levels it's not required but the higher commercials now require new radios. Most radios are dual NAV/COM so not only would you need a new COM but a new NAV too... It isn't going to happen...! |
#102
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Why don't voice radio communications use FM?
James Robinson wrote:
Emily wrote: The tower told the KLM aircraft to stand by at the same time the Pan Am aircraft transmitted, which resulted in a blocking of both transmissions. There were many other steps in the accident chain, but Tenerife was most certainly not caused by a pilot hearing what he wanted to hear. Then why did the aircraft start its takeoff roll, if the pilot didn't hear what he wanted to? The tower only issued the ATC clearance, and the KLM captain seems to have taken that as permission to take off. What else is that but hearing what he wanted to? He didn't hear ANYTHING but a heterodyne. If you want to say he heard the heterodyne as clearance to take off, fine, but that's not what we're talking about. The OP stated that AM results in poor transmission quality and therefore pilots will hear what they want to hear. In this case, the pilots heard nothing, and a high ranking captain blatantly ignored both ATC and his own f/e. |
#103
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Why don't voice radio communications use FM?
Mxsmanic wrote:
Vaughn Simon writes: Actually, not much does change in aviation compared with other fields of human endeavor. I don't think that is necessarily a bad thing. It does worry me that the things that change in aviation are things that I'd rather see stable. I have my doubts about fly-by-wire systems or glass cockpits, which seem to be increasingly designed for the convenience of programmers who grew up with Windows rather than for the convenience of pilots. Do you have any connection to aviation at all? |
#104
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Why don't voice radio communications use FM?
Mxsmanic wrote:
Emily writes: They were misunderstood a) because people were stepping on other people and b) because the KLM crew had heavy Dutch accents. The reasons why they were misunderstood have never been ascertained, and there are several possibilities. It's not even clear how much was understood or misunderstood, since a number of the people involved are dead. The common point to all the possible scenarios is misunderstood radio communication. Because of a heterodyne, NOT poor radio transmission quality. As someone else already pointed out, FM doesn't even have this useful quality. And yes, the official probable cause lists the heterodyne. I thought you would have known that, seeing as you know allegedly read all these accident reports. (And since one full flight crew survived, that's pretty good eyewitness account) |
#105
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Why don't voice radio communications use FM?
Mxsmanic wrote:
Thomas Borchert writes: Sorry, but that's just plain BS. Famous last words. Speaking as someone who works for an OEM that works with the latest cutting edge technology, Thomas is entirely correct. |
#106
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Why don't voice radio communications use FM?
Stefan wrote:
Emily schrieb: There were many other steps in the accident chain, but Tenerife was most certainly not caused by a pilot hearing what he wanted to hear. Actually, the KLM captain hearing what he wanted to hear was most certainly the main cause for that accident. As a consequence of this misunderstanding, the word "take-off" shall now only be used in "cleared for take off" and in the read-back of this clearance, or, at uncontrolled airfields, when a pilot says that he is taking off. No more "ready for take off", "stand by for take off" and the like, and no taking off before you are absolutely positively sure that you have heard and read back the word. But all this had nothing to do with the readability of the radio transmissions. Stefan That was my point. He heard what he wanted to hear, but not because of jarbled radio transmission. |
#107
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Why don't voice radio communications use FM?
Mxsmanic wrote:
Larry Dighera writes: You'll have to cite a source for this nugget of knowledge. FAA AIMs and CFRs make it pretty clear that communications involving a controller are pilot-controller exchanges, not pilot-pilot exchanges. Are you familiar with Common Traffic Advisory Frequency (CTAF)? Yes, but it and similar schemes don't involve a controller, so obviously the communication is between aircraft directly. But you just said that all communications are air-ground. You can't back pedal. |
#108
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Why don't voice radio communications use FM?
Emily schrieb:
He didn't hear ANYTHING but a heterodyne. Wrong. Please read the NTSB report before making such statements. 1705:53.4 APP KLM eight seven * zero five uh you are cleared to the Papa Beacon climb to and maintain flight level nine zero right turn after take-off proceed with heading zero four zero until intercepting the three two five radial from Las Palmas VOR. (1706:08.2) 1706:09.6 KLM Ah roger, sir, we're cleared to the Papa Beacon flight level nine zero, right turn out zero four zero until intercepting the three two five and we're now (at take-off). (1706:17.9) Of course this has nothing to do with the readablility of the transmission. Stefan |
#109
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Why don't voice radio communications use FM?
"Mxsmanic" wrote in message ... Wait and see. I try to remain civil here on the Usenet, but you have proven all through this thread to not be someone worth wasting time on. You get the last word, but thanks to technology I won't be seeing it. Bye Vaughn Transpose mxsmanic and gmail to reach me by e-mail. Why would I want to do that? |
#110
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Why don't voice radio communications use FM?
Stefan wrote:
Emily schrieb: He didn't hear ANYTHING but a heterodyne. Wrong. Please read the NTSB report before making such statements. I have read the report, and I don't see where readability came in. 1705:53.4 APP KLM eight seven * zero five uh you are cleared to the Papa Beacon climb to and maintain flight level nine zero right turn after take-off proceed with heading zero four zero until intercepting the three two five radial from Las Palmas VOR. (1706:08.2) 1706:09.6 KLM Ah roger, sir, we're cleared to the Papa Beacon flight level nine zero, right turn out zero four zero until intercepting the three two five and we're now (at take-off). (1706:17.9) I think there was some confusion here. I wasn't saying that he never heard ATC at all, just that the transmission confusion was due to the heterodyne, not static or poor transmission quality. |
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