A aviation & planes forum. AviationBanter

If this is your first visit, be sure to check out the FAQ by clicking the link above. You may have to register before you can post: click the register link above to proceed. To start viewing messages, select the forum that you want to visit from the selection below.

Go Back   Home » AviationBanter forum » rec.aviation newsgroups » Piloting
Site Map Home Register Authors List Search Today's Posts Mark Forums Read Web Partners

Why don't voice radio communications use FM?



 
 
Thread Tools Display Modes
  #1  
Old September 2nd 06, 01:40 PM posted to rec.aviation.piloting
Mxsmanic
external usenet poster
 
Posts: 9,169
Default Why don't voice radio communications use FM?

Perhaps this is a naive question, but: Why don't voice radio
communications for aviation use FM radio instead of AM radio? I
realize there's substantial inertia in the installed base of AM
equipment, but surely one could allocate some new frequencies to FM
and use them in parallel for some years to ease the transition.

The reason I ask is that improper and misunderstood radio
communication is a leading cause of accidents, and so it seems that
anything that can make that communication clearer would greatly
improve safety. I can barely understand what I hear on the radio. It
is true that the communication is very standardized, making it easier
to guess what is being said, but the results are pretty unpleasant if
one guesses wrong.

On a related note, it has occurred to me that one could develop
voice-recognition systems that understand the speech of a pilot and
then repronounce what he says in an extremely standard synthetic
voice. This could also improve understanding, especially for
non-Anglophone pilots who speak with heavy accents. The same systems
could clean up the speech so that it is absolutely standard, with no
missing or added words. Of course, the issue here is that the system
would be stuck if it cannot recognize what is being said, or if a
completely non-standard utterance is made by the pilot. A natural
extension of this would be systems that recognize standard phrases in
one language and translate them to another, but that would be even
more dangerous if the system ever failed.

Still another idea is special training systems that listen to a
pilot's speech and transcribe it, and point out any problems with
understandability. Again, this would be most useful for
non-Anglophone pilots, but it would work for anyone. If a machine can
understand a pilot's speech clearly, then a human being should
certainly be able to understand it that much more easily.

--
Transpose mxsmanic and gmail to reach me by e-mail.
  #2  
Old September 2nd 06, 01:43 PM posted to rec.aviation.piloting
Steven P. McNicoll[_1_]
external usenet poster
 
Posts: 660
Default Why don't voice radio communications use FM?


"Mxsmanic" wrote in message
news

Perhaps this is a naive question, but: Why don't voice radio
communications for aviation use FM radio instead of AM radio?


Wouldn't that reduce the available frequencies?


  #3  
Old September 2nd 06, 02:12 PM posted to rec.aviation.piloting
Peter R.
external usenet poster
 
Posts: 1,045
Default Why don't voice radio communications use FM?

Mxsmanic wrote:

The reason I ask is that improper and misunderstood radio
communication is a leading cause of accidents,


A leading cause of accidents? Where did you get this statistic?

but the results are pretty unpleasant if
one guesses wrong.


Guess? If a pilot or controller is not able to comprehend the other side's
transmission, there is no guess. "Say again?" is the phrase of choice and
it is used all over the frequencies.



--
Peter
  #4  
Old September 2nd 06, 02:13 PM posted to rec.aviation.piloting
James Robinson
external usenet poster
 
Posts: 180
Default Why don't voice radio communications use FM?

Mxsmanic wrote:

Perhaps this is a naive question, but: Why don't voice radio
communications for aviation use FM radio instead of AM radio?


I understand it is because of a characteristic of FM called "capture
effect" that blanks out weaker transmissions when two radios transmit at
the same time. The listener would have no idea that a second, weaker
transmission was being made.

With AM, when two radios transmit on close frequencies, you either hear
both signals poorly, or you get squeal, which is the sum of the two
signals. This characteristic is considered important when you have elevated
transmitters that can be hundreds of miles away, like on aircraft.
  #5  
Old September 2nd 06, 02:38 PM posted to rec.aviation.piloting
Larry Dighera
external usenet poster
 
Posts: 3,953
Default Why don't voice radio communications use FM?

On Sat, 02 Sep 2006 14:40:40 +0200, Mxsmanic
wrote in :

Perhaps this is a naive question, but: Why don't voice radio
communications for aviation use FM radio instead of AM radio?


I presume the reason stems from AM radio's introduction into aviation
after CW was used prior to and during WW-I. The cost of re-equipping
all aircraft with new radios is also not insignificant.

I realize there's substantial inertia in the installed base of AM
equipment, but surely one could allocate some new frequencies to FM
and use them in parallel for some years to ease the transition.


AM frequencies are currently 25 kHz wide. FM would require more
bandwidth. Regardless, where would you place these newly allocated
frequencies?

The reason I ask is that improper and misunderstood radio
communication is a leading cause of accidents,


What is the source of that questionable statistic?

and so it seems that anything that can make that communication clearer
would greatly improve safety.


Hence the popularity of Active Noise Reduction headsets.

I can barely understand what I hear on the radio.


Do you use an ANR headset?

It is true that the communication is very standardized, making it easier
to guess what is being said, but the results are pretty unpleasant if
one guesses wrong.


Request 'say again' if in doubt.

On a related note, it has occurred to me that one could develop
voice-recognition systems that understand the speech of a pilot and
then repronounce what he says in an extremely standard synthetic
voice.


What would you estimate the cost of re-equipping all aircraft with
such a system might be?

This could also improve understanding, especially for
non-Anglophone pilots who speak with heavy accents. The same systems
could clean up the speech so that it is absolutely standard, with no
missing or added words. Of course, the issue here is that the system
would be stuck if it cannot recognize what is being said, or if a
completely non-standard utterance is made by the pilot. A natural
extension of this would be systems that recognize standard phrases in
one language and translate them to another, but that would be even
more dangerous if the system ever failed.


Pilot: "Oh ****!"

Electronically rephrased: "Mayday!"

Still another idea is special training systems that listen to a
pilot's speech and transcribe it, and point out any problems with
understandability. Again, this would be most useful for
non-Anglophone pilots, but it would work for anyone. If a machine can
understand a pilot's speech clearly, then a human being should
certainly be able to understand it that much more easily.


I can understand you frustration with non-standard phraseology and
foreign accents, but given the current state of the art, such a voice
recognition/synthetic voice system as you suggest would probably be
unworkable not to mention costly and short lived. I would expect to
see data-link equipment (ACARS* or more likely ATN** or NEXCOM***)
available for GA aircraft soon.

* http://en.wikipedia.org/wiki/ACARS
** http://www.tc.faa.gov/act300/act350/
*** http://www.faa.gov/nextgen/nexcom/Publib/aboutnc2.htm
  #6  
Old September 2nd 06, 02:52 PM posted to rec.aviation.piloting
Emily[_1_]
external usenet poster
 
Posts: 632
Default Why don't voice radio communications use FM?

Mxsmanic wrote:

The reason I ask is that improper and misunderstood radio
communication is a leading cause of accidents


Really? Can you cite some statistics? I'd be very interested in
reading them.
  #7  
Old September 2nd 06, 05:00 PM posted to rec.aviation.piloting
RST Engineering
external usenet poster
 
Posts: 1,147
Default Why don't voice radio communications use FM?

Yeah, Steve, it would. But I think we might be able to swap (on a long term
swap basis) the VHF com band for stuff up between 600 and 900 MHz. that have
very limited usage. Not only could we get way more bandwidth, but the
antenna size is cut by a factor of 6 or so.

Jim


"Steven P. McNicoll" wrote in message
nk.net...

"Mxsmanic" wrote in message
news

Perhaps this is a naive question, but: Why don't voice radio
communications for aviation use FM radio instead of AM radio?


Wouldn't that reduce the available frequencies?



  #8  
Old September 2nd 06, 05:02 PM posted to rec.aviation.piloting
John Gaquin
external usenet poster
 
Posts: 170
Default Why don't voice radio communications use FM?


"Mxsmanic" wrote in message

....that improper and misunderstood radio
communication is a leading cause of accidents,


Cite, please.

... I can barely understand what I hear on the radio.


I suspect the reasons for this relate more to the environmental effects and
quality of the speakers, etc., than to the nature of AM transmissions.


  #9  
Old September 2nd 06, 05:04 PM posted to rec.aviation.piloting
John Gaquin
external usenet poster
 
Posts: 170
Default Why don't voice radio communications use FM?


"James Robinson" wrote in message

With AM, when two radios transmit on close frequencies, you either hear
both signals poorly, or you get squeal, which is the sum of the two
signals. This characteristic is considered important when you have
elevated
transmitters that can be hundreds of miles away, like on aircraft.


Sounds plausible. Marine radios also operate in the VHF band, but are FM.
They are also almost always at or very close to sea level.


  #10  
Old September 2nd 06, 05:05 PM posted to rec.aviation.piloting
RST Engineering
external usenet poster
 
Posts: 1,147
Default Why don't voice radio communications use FM?

Red herring, again. AM radio does the same suppression effect if the
signals are widely differing in power (google "AGC" or "AVC" for an
explanation). The odds of two signals being absolutely equal in time is
close to zero. True, they can start simultaneously, but the ending time is
generally measured in multiseconds. One side or the other always gets the
tag end of one conversation or the other and can figure out that a second
station is trying to get a message across.

The squeal when two nearly equal power signals is not the sum of the
frequencies, it is the difference.


Jim



"James Robinson" wrote in message
. ..
Mxsmanic wrote:

Perhaps this is a naive question, but: Why don't voice radio
communications for aviation use FM radio instead of AM radio?


I understand it is because of a characteristic of FM called "capture
effect" that blanks out weaker transmissions when two radios transmit at
the same time. The listener would have no idea that a second, weaker
transmission was being made.

With AM, when two radios transmit on close frequencies, you either hear
both signals poorly, or you get squeal, which is the sum of the two
signals. This characteristic is considered important when you have
elevated
transmitters that can be hundreds of miles away, like on aircraft.



 




Thread Tools
Display Modes

Posting Rules
You may not post new threads
You may not post replies
You may not post attachments
You may not edit your posts

vB code is On
Smilies are On
[IMG] code is On
HTML code is Off
Forum Jump

Similar Threads
Thread Thread Starter Forum Replies Last Post
UAV's and TFR's along the Mexico boarder John Doe Piloting 145 March 31st 06 06:58 PM
Air Force One Had to Intercept Some Inadvertent Flyers / How? Rick Umali Piloting 29 February 15th 06 05:40 AM
terminology questions: turtledeck? cantilever wing? Ric Home Built 2 September 13th 05 09:39 PM
I Hate Radios Ron Wanttaja Home Built 9 June 6th 05 05:39 PM
AirCraft Radio Communications [email protected] Rotorcraft 0 November 13th 03 01:48 AM


All times are GMT +1. The time now is 01:13 PM.


Powered by vBulletin® Version 3.6.4
Copyright ©2000 - 2024, Jelsoft Enterprises Ltd.
Copyright ©2004-2024 AviationBanter.
The comments are property of their posters.