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#51
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Why don't voice radio communications use FM?
Larry Dighera wrote:
Because it is unlikely the FCC will agree to allocate additional frequency spectrum for the proposed new communications system. The frequency allocation would need to be changed or added to on an international scope, so I believe the operative organizations would be the ITU and the ICAO or IATA - the FCC would simply enforce the change within the U.S. Like you, I would have thought new allocations or changed allocations would be hard, but changes are made every four years and in the GHz range they seem to been more readily done; e.g.: http://www.boeing.com/connexion/news...r_030707j.html |
#52
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Why don't voice radio communications use FM?
"Mxsmanic" wrote: With regards to aviation communication, "niner" is the proper phonetic pronunciation of nine and "fife" is the proper pronunciation of five, although admittedly "fife" is not as widely used as it should be. They still sound very much the same. ********. One has two syllables, the other only one. You haven't spent much time communicating via aircraft radios, have you? -- Dan C172RG at BFM |
#53
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Why don't voice radio communications use FM?
Mxsmanic wrote:
Switching from AM to FM doesn't involve incompatibilities. You can run both in parallel indefinitely, providing identical services (just as some commercial radio stations have broadcasts on both AM and FM simultaneously). Introducing FM doesn't obsolete any of the AM equipment. Regarding your argument in the paragraph above and the one below... Adding all sorts of digital gadgets is quite a different matter. Now you are adding functionality that will be available only to the FM/digital community. This introduces potential safety and usability issues. Stacking transmissions digitally isn't going to work when the same transmissions must be mirrored on analog AM--and they have to be if you want to maintain safety and keep controller workload reasonable. ....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. 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. |
#54
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Why don't voice radio communications use FM?
"Peter R." wrote: With regards to aviation communication, "niner" is the proper phonetic pronunciation of nine and "fife" is the proper pronunciation of five, There is newsreel footage from the fifties of a nuclear bomb test that includes scenes from the control room. The guy calling the countdown actually says "fiver". Talk about unclear on the concept! -- Dan C172RG at BFM |
#55
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Why don't voice radio communications use FM?
Mxsmanic schrieb:
I don't see why it would be so objectionable. It isn't even necessary that the AM be phased out. The FM would simply be available to those who wish to use it, for the added clarity it provides. Yeah. One pilot talks on AM and the other listens to FM. Great idea. Adds a lot of clarity to the communication. Stefan |
#56
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Why don't voice radio communications use FM?
On Sat, 02 Sep 2006 21:08:49 GMT, B A R R Y
wrote: On Sat, 02 Sep 2006 18:03:31 +0100, wrote: With FM the signal remains much clearer until the point where it suddenly becomes unreadable when itl becomes weak. With AM is that readability gradually reduces as the signal gets weaker. If you open the squelch you can often still read AM when FM would be unreadable. That's the way I always understood it. AM transmissions can be pulled out of background noise. FM is more difficult, as it cuts out before it's unreadable. I would imagine digital would be the worst. Digital is either decodable and there or nothing and silence. This is all based on my experiences with aircraft AM radios, FM business radios, broadcast and satellite TV, and radio, so it might be all wrong. G You're spot on with your comments. My experience is amateur radio with AM/FM & SSB plus business radios, broadcast radio & TV FM/AM from longwave to SHF. Given the choice SSB gives best low signal readability but not very suitable for normal aviation. The problem with comparisons is a 10watt AM transmitter puts out 2x sidebands of 2.5watts (max). All of the intelligence is available in one 2.5watt sideband, the rest is to make the signal easier to decode. The equivalent 10watt FM transmittter uses the full 10 watts but that's getting too technical:-) At the end of the day if AM equipment is working properly there's not a problem and there's no reason to change every transmitter in the world. Probably the main problem is aircraft noise and poor hearing along with microphone technique and peoples accents! I've flown mamy aircraft in a number of countries and can't say there's a problem with AM. More likely to have a problem with a controller rattling out an instruction too fast. I doubt I've had more than a handful of transmissions, in 15 years, I'd give worse than readability 4. Almost always 5. Normal communication quality is up to 4KHz audio response. As you get older you loose the high frequencies anyway so forget hi-fi! My hearing is only good to around 6KHz but when I was younger was around 16KHz. You only require 3KHz audio bandwidth and if pushed for maximum readability and least bandwidth 2KHz but it sounds very harsh though very readable. The worst transmissions in the UK are the military who sometimes sound like they're using throat mikes. Myself and another aircraft were working one military controller who was almost impossible to understand. I could just make him out but the commercial aircraft gave up. I'd say readability 2. David |
#57
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Why don't voice radio communications use FM?
"Dan Luke" wrote:
There is newsreel footage from the fifties of a nuclear bomb test that includes scenes from the control room. The guy calling the countdown actually says "fiver". Talk about unclear on the concept! Maybe he did it because unclear is an anagram of nuclear? ;-) |
#58
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Why don't voice radio communications use FM?
Stefan wrote:
Mxsmanic schrieb: I don't see why it would be so objectionable. It isn't even necessary that the AM be phased out. The FM would simply be available to those who wish to use it, for the added clarity it provides. Yeah. One pilot talks on AM and the other listens to FM. Great idea. Adds a lot of clarity to the communication. Huh? How is that problem different from something transmitting on 121.5 MHz and someone else listening on 406 MHz? Why is having multiple channels all using AM not a problem but if one added more channels using a different modulation now suddenly presenting a communication problem? |
#59
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Why don't voice radio communications use FM?
"Jim Logajan" wrote in message .. . "Vaughn Simon" wrote: But changing to FM would require a new radio to be simultaneously installed in every cockpit in the world. The only way to accomplish that would be for every plane with a new radio to transmit in "parallel" (as someone already suggested) for a period of years on both the new mode and the old mode. That need not be the case, as evidenced by dual-mode cell phones that allow access to analog and digital cell sites, The problem I was thinking of that is solved by parallel operation is where you have two planes in the same pattern who can't hear each other because their radios are not compatible. The only way I know to solve that is dual (parallel) operation. A good example of that concept is what they are doing with TV today. Many TV stations are transmitting in both analog and digital (HD) so that we are covered no matter what type of receiver we happen to own. Vaughn |
#60
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Why don't voice radio communications use FM?
In article ,
Jim Logajan wrote: That would definitely be a great solution, but that page was last updated January 4, 2000. Do you or anyone else know if any further progress been made or have the efforts died? (The links I could find all seemed to dead- end.) VDL mode 2 will be coming Real Soon Now. Like all the recent CNS/ATM mandates/changes (RVSM, 8.33, TCAS, FM immunity, TAWS, BRNAV, RNP-4, etc etc), the move to VDL is happening way way WAY later than originally planned by the Big Thinkers. -- Bob Noel Looking for a sig the lawyers will hate |
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