jamesbuk
Posts: 3712
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Why Is There Still Aircraft Radio Splutter?

Wed Dec 27, 2006 11:50 pm

Hi guys and girls,

Well here i am, i'm in the room were we have the pc in the house, and in the next room is a normal radio, picking up the local radio station and its playing some music in nice good quality, nothing unusual right? so why is it that aircraft radio transmissions are always very low quality? its very hard to make out what they are staying over the fizzing of the radio unless your experienced. So why has this quality not been introduced into aviation? It could save runway incursions as it would be clearer and no reason not to hear your callsign etc.

I understand you may not get the quality at 36k feet, but radio transmissions (as in music radio) works quality wise very well up to 6000 feet i believe, so it would be useful for when the most talking is done (approach and departue)

So why isnt it used?

Rgds --James--
You cant have your cake and eat it... What the hells the point in having it then!!!
 
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Starlionblue
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RE: Why Is There Still Aircraft Radio Splutter?

Thu Dec 28, 2006 12:20 am

Interesting question. So here is my theory:
- Still analog with potential for distortion.
- "Good enough" for the purpose so not much incentive to make it better.
- Moving transmitter/receiver makes exact modulation tricky.
- Interference from atmospheric effects and terrain coupled to the above.

In theory, if everyone went to digital satellite comms this would all improve, but I don't see traditional radios going away anytime soon.
"There are no stupid questions, but there are a lot of inquisitive idiots." - John Ringo
 
SPREE34
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RE: Why Is There Still Aircraft Radio Splutter?

Thu Dec 28, 2006 12:24 am

Perhaps it's your Airband receiver or antenna? With a few exceptions, I've heard mostly clear transmissions from aircraft over my 30+ years as an ATCer and Flyer.
You won't ever get FM quality sound from AM, but AM is fine for voice.
I don't understand everything I don't know about this.
 
SlamClick
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RE: Why Is There Still Aircraft Radio Splutter?

Thu Dec 28, 2006 12:31 am

There is? I always wondered why the controllers were always frying fish!

One factor could be horsepower so to speak. Even my hokey local station boasts "fifty thousand pots of wower" (watts of power) Our Cessnoid doesn't.
Happiness is not seeing another trite Ste. Maarten photo all week long.
 
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Starlionblue
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RE: Why Is There Still Aircraft Radio Splutter?

Thu Dec 28, 2006 12:40 am

Quoting SlamClick (Reply 3):
Even my hokey local station boasts "fifty thousand pots of wower" (watts of power)

Are you sure that isn't 50k milliwatts? I loved it when my local station in Stockholm went "TEN THOUSAND MILLIWATT MUSIC POWER!!!!" with an echo sound effect.
"There are no stupid questions, but there are a lot of inquisitive idiots." - John Ringo
 
jamesbuk
Posts: 3712
Joined: Mon May 02, 2005 11:52 pm

RE: Why Is There Still Aircraft Radio Splutter?

Thu Dec 28, 2006 1:04 am

Quoting SPREE34 (Reply 2):

I dont have an airband. I went up in a tower at an airfield (Cranfield/EGTC) and they had big overhead speakers and it was still fuzzy, and in the cessna's (yes i know there old) it was fuzzy as well.

Quoting SPREE34 (Reply 2):
I've heard mostly clear transmissions from aircraft over my 30+ years as an ATCer and Flyer.

Yeh but if you look at my original post it was "If you arent used to it" you've been on the end of it for 30 years, you'd make it out perfect, when you started you have to admit maybe for the first week or so of working as ATC it was understandable but you had to think.

Quoting Starlionblue (Reply 1):
In theory, if everyone went to digital satellite comms this would all improve, but I don't see traditional radios going away anytime soon.

Yeh it would, the only problem would be a 2-3 second delay from the signal going to the sattelite and back (if you have SKY Tv turn it on and a normal terrestrial tv, on the same channel the sky will come through a couple seconds later)

Rgds --James--
You cant have your cake and eat it... What the hells the point in having it then!!!
 
AAR90
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RE: Why Is There Still Aircraft Radio Splutter?

Thu Dec 28, 2006 1:09 am

Quoting Jamesbuk (Thread starter):
its very hard to make out what they are staying over the fizzing of the radio unless your experienced. So why has this quality not been introduced into aviation?

You do not specify what receiver you are using and what location(s) you are using it at. Primary reasons for poor reception are antenna locations and atmospheric interference within the radio frequency bands being used. Within my current aircraft (B738) my perception of radio clarity was greatly improved with the switch to BOSE QCII headset. I had previously used Telex & Sundhousen ANR headsets (and other non-ANR sets) which were "okay" but not exceptional. My current FO uses a Lightspeed earplug style boom-mic set that he loves as well.
*NO CARRIER* -- A Naval Aviator's worst nightmare!
 
FredT
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RE: Why Is There Still Aircraft Radio Splutter?

Thu Dec 28, 2006 1:23 am

It's an AM vs. FM thing. Then it is an issue of station output power.

We still use AM rather than FM as

a) It is proven, relatively simple technology

b) If one FM transmission steps on another, you get nothing at all. If one AM transmission steps on another, you'll know it.

c) AM uses less bandwidth, so you can jam more frequencies into the same spectrum.
I thought I was doing good trying to avoid those airport hotels... and look at me now.
 
jamesbuk
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RE: Why Is There Still Aircraft Radio Splutter?

Fri Dec 29, 2006 2:39 am

Another question guys,

Now if i turn my radio onto AM mode, would i be able to pick up ATC? or do they have some sort of blocker to stop this?

Rgds --James--
You cant have your cake and eat it... What the hells the point in having it then!!!
 
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Starlionblue
Posts: 17208
Joined: Fri Feb 27, 2004 9:54 pm

RE: Why Is There Still Aircraft Radio Splutter?

Fri Dec 29, 2006 2:50 am

Quoting Jamesbuk (Reply 8):
Now if i turn my radio onto AM mode, would i be able to pick up ATC? or do they have some sort of blocker to stop this?

If you can receive the correct frequencies, sure. There is no specific blocker in any radio equipment I have heard of.
"There are no stupid questions, but there are a lot of inquisitive idiots." - John Ringo
 
zenarcade
Posts: 84
Joined: Mon Nov 27, 2006 11:08 am

RE: Why Is There Still Aircraft Radio Splutter?

Fri Dec 29, 2006 3:32 am

I have heard something about all transmissions going digital soon. Is this true?

Adam
If a plane falls on the tarmac and no one is there, does it make any sound? - Starlionblue
 
KELPkid
Posts: 5247
Joined: Wed Nov 02, 2005 5:33 am

RE: Why Is There Still Aircraft Radio Splutter?

Fri Dec 29, 2006 3:38 am

Quoting Jamesbuk (Reply 8):
Another question guys,

Now if i turn my radio onto AM mode, would i be able to pick up ATC? or do they have some sort of blocker to stop this?

Rgds --James--

Air band uses AM modulation, not FM (unlike most other VHF communications...)

AM will overdrive the FM filtration circuits, and work it's way into the amplifier section, so you will get (somewhat distorted, but still readable) audio...as a matter of fact, many scanners take advantage of this phenomena when receiving the VHF air band frequencies Basically, the manufacturers don't want to engineer a small AM demodulation (which would make the unit more costly to mass produce) section into their scanners when it covers such a small portion of the VHF frequency band (which is why air band sounds so crappy on a cheap scanner). Air band sounds much cleaner on a genuine airband radio than it does on many radio scanners for this reason. Sporty's pilot shop sells a $99 desktop airband scanner, but I have no idea what the audio is like (i.e. if it allows the FM filter to be overdriven, or uses a dedicated AM demodulation circuit).

EDIT: if you want a cheap, homemade airband scanner, purchase a walkman-type AM/FM radio (with an analog slider type tuner), and open the case. Find the inductor coils, little tiny coils of wire (used for filtration Wink ), and stretch them apart with a jewelry screwdriver. This will allow airband harmonics to overload the FM broadcast band, and voila! a homemade, portable airband scanner. The audio will be pretty bad, but it works...I did this when I was in high school (late 1980's) to listen to ATC  Smile

[Edited 2006-12-28 19:46:32]
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