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#81
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Why don't voice radio communications use FM?
Larry Dighera writes:
I would guess that noise-blanker and noise-limiting circuits are incorporated in the current radio designs. You can't actively remove noise over a radio channel because you have no unique identifier of noise vs. information. Noise-reduction headsets work because they know what is noise (outside sound) and what isn't (audio being played through the headset). Other than the occasional heterodyne squeal that occurs in the receiver when two transmitters are transmitting on the same frequency simultaneously, there shouldn't be any other noise. Ignition noise should be suppressed by Faraday shielding, and generator/alternator noise should be bypassed to ground. 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. What is the nature of the noise you are hearing? Can you describe it? Is it a hum, pulses, growling, squealing, what? White noise. It doesn't come from anything within the aircraft or station. Regardless of when it occurs, there will ultimately be an additional cost. Sure, but one that companies and individuals can assume on a phased basis at their convenience. The fact that transponders and VORs exist today (when they did not in the early days of aviation) proves that this works. And to expect the old (current) communications system to remain operational while the new system you are proposing is operating concurrently won't be feasible if they use the same frequencies. Presumably they would use different frequencies. If an new alternate frequency band is used for the new communications system you are proposing, it could work. But getting the FCC to allocate additional frequency spectrum will probably be opposed, because the frequency spectrum is a finite resource, and there are many more services desiring to use it than there is bandwidth available. Aviation is a pretty critical use of bandwidth. You really should read the information at some of the links I provided to get an idea of what has been tried, and what is on the FAA's horizon regarding aviation communications. This topic has been very thoroughly researched by government personnel and it's unlikely that you will hit upon a superior system to what the professionals have examined. How much of aviation was designed by "professionals"? -- Transpose mxsmanic and gmail to reach me by e-mail. |
#82
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Why don't voice radio communications use FM?
Dan Luke writes:
********. One has two syllables, the other only one. There's a lot more to human speech than syllables. Only a single phoneme separates the two in many pronunciations (particularly because restricted bandwidth can limit the intelligibility of fricative consonants), and that phoneme sounds very much like an unstressed central hesitation vowel, which means it may not be heard at all. This is especially true for non-rhotic speakers. You haven't spent much time communicating via aircraft radios, have you? How much time have you spent studying phonetics and linguistics? They are just as relevant here as experience with aircraft radios. However, I don't think a wealth or dearth of experience in any domain need be a prerequisite to discussion. And I think it more productive to discuss the topic at hand than to direct personal attacks at anyone with whom one disagrees. -- Transpose mxsmanic and gmail to reach me by e-mail. |
#83
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Why don't voice radio communications use FM?
Jim Logajan writes:
...honestly don't make any sense to me. In the first paragraph you see no problem with two transmitters being used to transmit the same thing using different frequencies and different modulation techniques, and in the second paragraph you do. The second instance involves additional or different information being transmitted over one channel, but not the other. The first instance involves only a reduction of noise; the information content is the same in both channels. I think you could turn the first paragraph into the second or vice-versa with appropriate special pleading - which is why I'm confused about why you find a switch from AM to FM a better transition than any other transition. I guess I just don't see what you see. I don't know if it's better than any other transition; I just think that something should be done to improve the archaic system that exists now. -- Transpose mxsmanic and gmail to reach me by e-mail. |
#84
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Why don't voice radio communications use FM?
Mxsmanic schrieb:
However, you're not supposed to listen to other pilots; you're supposed to listen to controllers. All conversations are air-ground, not air-air. You haven't ever actually flown a plane, have you? Stefan |
#85
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Why don't voice radio communications use FM?
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 |
#86
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Why don't voice radio communications use FM?
On Sat, 02 Sep 2006 20:19:15 +0200, Mxsmanic wrote:
Jim Logajan writes: details snipped Maybe someday the FAA and/or ICAO will consider replacing analog radios with a more capable digital system.... All very interesting, but one of the criteria that any new system would have to satisfy is that it would have to work in parallel with the existing system. Adding features to the new system that are not available in the old system would create dangerous differences between the two. Seeing fancy displays in the ATC or tower for the lucky digital users won't help deal with traffic from old AM users, and it might even confuse things enough to cause problems. A highly advanced solution would require replacing everything at once, which isn't going to happen. A simpler solution that just provides better quality audio could coexist with older systems without a problem. New systems (P25) already do this type of thing. I develop digital radio systems. Police, fire, FBI, CIA, DoD, DoE, various municipal utilities, and various branches of the military are all taking advantage of this technology. In many cases, the old analog systems must co-exist with the newer P25 systems. In some cases, more rural analog systems actually connect with a P25 network via a specialized repeated. Integration is not a problem. Last I read, an FAA study indicated they need lots and lots of money (sorry, don't remember the amount) to upgrade their infrastructure from analog to digital. The sad thing is, it does not appear Congress is going to give it to them. Worse, the same report indicates, over the next 10-years, the FAA will exceed their required conversion dollars by simply maintaining and repair their existing, archaic, analog infrastructure. In other words, the FAA needs to do something...even if they are simply updating their existing analog infrastructure. Regardless, the money does not appear to be available. Advantages of this technology include: o call queuing - meaning, PTT places you in a queue so you can get a word in, even when the controllers are very busy. BTW, this also means no more "walked on" transmissions. o call prioritization - All sorts of cool things can be done here - including, most recent exchange receives priority. Also, should IFR traffic receive higher priority over that of VFR? What about commercial traffic? Priority could be adjusted dynamically too. This means planes in distress could be assigned higher priority. So on and so on... o hang timer detection - a stuck PTT is not going to lock everyone out o caller id - imagine your tail number, altimeter, heading, and aircraft type provided to the controller on every PTT. o MUCHO better frequency utilization o Limited data services The list could go on and on...needless to say, digital has some neat features. The only con of digitial compared to analog is reception. With analog, you can hear a weak signal. It may sound like absoluete crap, but you can still hear it. With digitial, either you have a strong enough signal to hear it...and it sounds awesome...or you hear absoluetely nothing at all. Greg |
#87
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Why don't voice radio communications use FM?
"Mxsmanic" wrote: ********. One has two syllables, the other only one. There's a lot more to human speech than syllables. Only a single phoneme separates the two in many pronunciations (particularly because restricted bandwidth can limit the intelligibility of fricative consonants), and that phoneme sounds very much like an unstressed central hesitation vowel, which means it may not be heard at all. This is especially true for non-rhotic speakers. That is why we say "niner." In practice, it works very well to distinguish nine from five.. You haven't spent much time communicating via aircraft radios, have you? How much time have you spent studying phonetics and linguistics? They are just as relevant here as experience with aircraft radios. One semester in college. My guess is that's a lot longer than you've spent talking to ATC. However, I don't think a wealth or dearth of experience in any domain need be a prerequisite to discussion. And I think it more productive to discuss the topic at hand than to direct personal attacks at anyone with whom one disagrees. When it becomes apparent that an argument is born of ignorance, it is appropriate to point that out. That is not a personal attack. I did not impugn your character, merely noted the obvious: WRT aircraft radio communications, you do not know what you are talking about. You began this thread with the unfounded assertion that "improper and misunderstood radio communication is a leading cause of accidents." When Emily challenged you for evidence, you used the old, lame usenet dodge of telling her to look it up herself. Since then, you have attempted to create an argument based on phonetics to support a faulty premise. Your five vs. niner attempt is the weakest yet, and you would not even have tried it if you had any experience on the radio. -- Dan C172RG at BFM |
#88
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Why don't voice radio communications use FM?
"Mxsmanic" wrote: I would guess that noise-blanker and noise-limiting circuits are incorporated in the current radio designs. You can't actively remove noise over a radio channel because you have no unique identifier of noise vs. information. ******** again. I have a radio that does actively remove noise--it has a button to turn the feature on and off, and it works quite well. I'll say one thing for you, you are fearless in your ignorance. -- Dan C172RG at BFM |
#89
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Why don't voice radio communications use FM?
Greg Copeland writes:
New systems (P25) already do this type of thing. I develop digital radio systems. Police, fire, FBI, CIA, DoD, DoE, various municipal utilities, and various branches of the military are all taking advantage of this technology. In many cases, the old analog systems must co-exist with the newer P25 systems. In some cases, more rural analog systems actually connect with a P25 network via a specialized repeated. Integration is not a problem. So why wouldn't it extend to aviation? Last I read, an FAA study indicated they need lots and lots of money (sorry, don't remember the amount) to upgrade their infrastructure from analog to digital. They need not upgrade it all at once. The sad thing is, it does not appear Congress is going to give it to them. Congress, like most of America, is hysterical about imaginary human threats these days, and has probably lost track of the much more mundane but much more serious safety risks associated with infrastructure, aircraft, and crews. Advantages of this technology include: o call queuing - meaning, PTT places you in a queue so you can get a word in, even when the controllers are very busy. BTW, this also means no more "walked on" transmissions. Do other aircraft hear the transmission when you make it, or when the controller hears it? Granted, they are only supposed to listen to the controller, but in practice they will be listening to other aircraft as well. How do you make this work in parallel with analog systems that cannot queue? o call prioritization - All sorts of cool things can be done here - including, most recent exchange receives priority. Also, should IFR traffic receive higher priority over that of VFR? What about commercial traffic? Priority could be adjusted dynamically too. This means planes in distress could be assigned higher priority. So on and so on... It's best not to jump off the deep end with gadgets. Just because something can be done doesn't mean that it should be done. o caller id - imagine your tail number, altimeter, heading, and aircraft type provided to the controller on every PTT. Where does this leave people with analog equipment? o Limited data services What kind of data services do pilots need? Are they going to be surfing the Web? The list could go on and on...needless to say, digital has some neat features. Neat features aren't necessarily desirable features. There is too much of a tendency to bloat digital systems with features that have been hastily designed, inadequately analyzed, and barely tested at all. The only con of digitial compared to analog is reception. With analog, you can hear a weak signal. It may sound like absoluete crap, but you can still hear it. With digitial, either you have a strong enough signal to hear it...and it sounds awesome...or you hear absoluetely nothing at all. If the digital threshold is set where the threshold of intelligibility would be in analog, there's no net loss. -- Transpose mxsmanic and gmail to reach me by e-mail. |
#90
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Why don't voice radio communications use FM?
"Thomas Borchert" wrote: Mxsmanic, 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. Sorry, but that's just plain BS. He's got a ton of it to spread around. -- Dan C172RG at BFM |
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