airtraffic

Author Topic: Scanner on commerical flight compared to wi-fi  (Read 8016 times)

Offline jeffcyn

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Scanner on commerical flight compared to wi-fi
« on: November 19, 2009, 08:47:34 PM »
I saw an old post in this forum about using a scanner while on board.  The post stated something regarding "oscillators" in regards to why scanners cannot be used.

I wanted to get the forums updated opinion and knowledge on this subject.  Especially wanted to know why computers and devices can use wi-fi on-board and a scanner cannot.




Offline Dave_B

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Re: Scanner on commerical flight compared to wi-fi
« Reply #1 on: November 23, 2009, 05:13:38 PM »
Receivers of ANY kind generally emit RF. Wi-Fi- is included. If they are letting you use Wi-Fi it is laregely because of the design of the system and that the frequencies used are unlikely to affect aircraft systems. Depending on the design of the scanner, it can be a pretty good transmitter right on NAV/COM frequencies.

IMO all of these are overblown and the evidence is based more on anecdote than science. But why risk it for the sake of a few? BTW many regs are FCC-mandated - not FAA. Aside from those, airlines are free to have whatever restrictions they wish.

Offline PHXCONXrunner

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Re: Scanner on commerical flight compared to wi-fi
« Reply #2 on: November 23, 2009, 10:01:14 PM »
Receivers of ANY kind generally emit RF. Wi-Fi- is included. If they are letting you use Wi-Fi it is laregely because of the design of the system and that the frequencies used are unlikely to affect aircraft systems. Depending on the design of the scanner, it can be a pretty good transmitter right on NAV/COM frequencies.

IMO all of these are overblown and the evidence is based more on anecdote than science. But why risk it for the sake of a few? BTW many regs are FCC-mandated - not FAA. Aside from those, airlines are free to have whatever restrictions they wish.

Wi-fi (IEEE 802.11) currently uses the 2.4-2.5 GHz band.  Radios and navigation equipment use 108-137 MHz, neither of which will conflict with each other.

Cell phones use a range of frequencies between 850 and 1900 MHz, which will cause slight interference, usually manifested as a buzzing in the speakers.

Offline n8zrp

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Re: Scanner on commerical flight compared to wi-fi
« Reply #3 on: November 24, 2009, 05:46:08 PM »
Receivers of ANY kind generally emit RF.

I think you mean 'tunable' when you say 'generally'.

There are passive designs that don't have an oscillator so they don't create potentially harmful interference. (i.e. a crystal detector that amplifies the demodulated audio.)
http://www.edn.com/article/CA529386.html
http://www.techlib.com/electronics/aircraft.htm
http://www.ramseyelectronics.com/cgi-bin/commerce.exe?preadd=action&key=ABM1

Of course they're not tunable and only usable to receive strong transmissions very near to you.

BTW, has anyone tried the Ramsey unit?

Wi-fi (IEEE 802.11) currently uses the 2.4-2.5 GHz band.  Radios and navigation equipment use 108-137 MHz, neither of which will conflict with each other.

I don't necessarily disagree with you, but here are a couple of points for some more depth on the topic...

1. Modern scanners/etc have super-heterodyne tuners, which by definition generate RF on multiple frequencies as part of the mixing process prior to demodulation.  It's very possible that a super-heterodyne receiver will generate RF on the additional frequencies on which aeronavigation systems utilize. (see #2).

The worst case here is a receiver that is leaking 'too much' RF and causing reception issues on the navigation/communications equipment.

This problem probably doesn't surface with well-designed, properly functioning, type-accepted receivers; but what about malfunctioning or questionable consumer-grade equipment brought on board by a passenger?  It's just easier for the governing body to issue a blanket restriction to prevent any possible scenario where a radio receiver could interfere with critical navigation/communications.

http://abcnews.go.com/Technology/AheadoftheCurve/story?id=6833039&page=1

I haven't been on any of the new aircraft with the 802.11 capability, but I'm willing to bet that they turn off the 802.11 access points prior to final approach/landing.  Any one know if this is true?

2. 108-137Mhz is only one part of the radio spectrum that the modern aircraft uses for navigation and communication.  (Also regarding 802.11 in the US; 'a' and 'n' can also operate 5Ghz, and recently 'a' will be allowed to use 3.7Ghz as well)

Here's a few other parts of the radio spectrum I've identified that modern aviation uses for navigation/communication.  I'm still building a list but here's what I have so far...


329.15-335.0Mhz - GlideSlope/GlidePath
960Mhz-1215Mhz - Distance Measuring Equipment (DME)/TACAN
1176.45MHz, 1379.913Mhz, 1381.06Mhz, 1227.60Mhz, 1575.42Mhz - GPS
1030-1090Mhz - ADS-B 1090ES
978Mhz - ADS-B UAT 
75Mhz - ILS Outer Beacon
145-530Khz - Non Directional Beacons (NDB), DGPS

Offline mhawke

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Re: Scanner on commerical flight compared to wi-fi
« Reply #4 on: November 27, 2009, 09:03:41 PM »
From the flights I have been on, I believe the wi-fi shuts off at 10,000 ft during decent.


My understanding (as shallow as it may be), is that the FCC was more behind the cell phone rule then the FAA.  They were/are concerned that the rate at which a cell phone moving in a plane will hop towers would confuse the cell phone circuits.

Overseas there are now areas where cell phone use in the plane is allowed. 

However, as a frequent business traveler, I hate the idea, and hate it when I am overseas.  Nothing worse then listening to 200 people all try to discuss their personal problems while you are sitting next to them.  Its also the last place of sanctuary I have where I can honestly say "sorry I couldn't use my cell phone, I was on a plane".


Offline bluecrewfan08

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Re: Scanner on commerical flight compared to wi-fi
« Reply #5 on: November 27, 2009, 11:01:27 PM »
"However, as a frequent business traveler, I hate the idea, and hate it when I am overseas.  Nothing worse then listening to 200 people all try to discuss their personal problems while you are sitting next to them.  Its also the last place of sanctuary I have where I can honestly say "sorry I couldn't use my cell phone, I was on a plane"

Amen brother, Amen.

Rob

Offline sykocus

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Re: Scanner on commerical flight compared to wi-fi
« Reply #6 on: November 28, 2009, 01:39:11 AM »

My understanding (as shallow as it may be), is that the FCC was more behind the cell phone rule then the FAA.  They were/are concerned that the rate at which a cell phone moving in a plane will hop towers would confuse the cell phone circuits.


I've actually heard the opposite. The FAA said it would be virtually impossible to be sure cellphones would be safe to use, because it was require testing of nearly every single phone still in use.

Offline mhawke

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Re: Scanner on commerical flight compared to wi-fi
« Reply #7 on: November 30, 2009, 09:18:34 AM »
Apparently there are two separate bans on using cell phones on planes.  One from the FAA and one from the FCC.

FCC ban is based on intereference with the cell phone network because of hopping so fast.  FAA is based on interference with insrumentation.

http://www.msnbc.msn.com/id/17935297/

Quoted from article

"The agency has been considering lifting its ban on cell phone usage on airplanes since 2004. Unlike the Federal Aviation Administration, which bans the use of cell phones and other portable electronic devices for fear they will interfere with navigational and communications systems, the FCC’s concern is interference with other cell phone signals on the ground."




Offline CVG

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Re: Scanner on commerical flight compared to wi-fi
« Reply #8 on: October 28, 2010, 02:33:20 AM »

BTW, has anyone tried the Ramsey unit?


Indeed I recently purchased the Passive Air Band Monitor ABM1 from Ramsey.  Nice change from big $$$ complex radios.  Enjoyable and I would recommend to anyone.