I am no radio expert, but I do know that receivers do emit some radio energy, and different radios emit it in different bands. Maybe airlines are trying to protect against that?
Many radio receivers use an oscillator to shift received signals down to a lower frequency, the "intermediate frequency" (IF), before demodulating the signal. Sometimes the oscillator "leaks" a small amount of signal onto the air through the antenna. The leakage is not very great because, for one thing, the antenna is not usually "tuned" to the IF. But the leakage is great enough that countermeasures against eavesdropping are built to detect IF. Radar-detector detectors may detect IF, also. So, maybe airlines are trying to protect radio bands where the IF for FM/GPS/WWVB receivers is found, but neither the UHF nor IF parts of a WiFi card concern them? Dave On Thu, Jan 16, 2003 at 12:26:49PM -0800, Gordon Arnold wrote: > That sounds really cool, but you know what has me rolling on the floor > laughing? The airlines say we can't use even radio receivers for fear > that the low level EM fields they generate will trigger a false alarm in > the cockpit, but now that there financial benefits to allowing the use > of transmitters, they're for it! Curiously, though, the use of a GPS > receiver is permitted 'cept for takeoff and landing. I wish I could get > a handle on the spirit of the rules, since the letter makes no sense! > How is a WWVB watch going to goof up the avionics? Or a walkman? Or a > scanner? What is the crucial difference between that and a GPS receiver > or a WiFi card? > > Gordon Arnold > > > -----Original Message----- > From: [EMAIL PROTECTED] > [mailto:[EMAIL PROTECTED]] On Behalf Of > [EMAIL PROTECTED] > Sent: Thursday, 16 January 2003 12:00 > To: [EMAIL PROTECTED] > Subject: wireless digest, Vol 1 #20 - 1 msg > > Send wireless mailing list submissions to > [EMAIL PROTECTED] > > To subscribe or unsubscribe via the World Wide Web, visit > http://lists.bawug.org/mailman/listinfo/wireless > or, via email, send a message with subject or body 'help' to > [EMAIL PROTECTED] > > You can reach the person managing the list at > [EMAIL PROTECTED] > > When replying, please edit your Subject line so it is more specific > than "Re: Contents of wireless digest..." > > > Today's Topics: > > 1. Anyone heading to Germany next month? (Tim Pozar) > > --__--__-- > > Message: 1 > Date: Thu, 16 Jan 2003 11:42:11 -0800 > From: Tim Pozar <[EMAIL PROTECTED]> > To: [EMAIL PROTECTED] > Subject: [BAWUG] Anyone heading to Germany next month? > > http://siliconvalley.internet.com/news/article.php/1570531 > > January 15, 2003 > Lufthansa and Cisco Put Wi-Fi in the Plane > By Eric Griffith > > At last, the days of your laptop being nothing more than a method > of playing Minesweeper on airline flights may be coming to an end. > > Deutsche Lufthansa AG is currently doing passenger trials of in-flight > Wi-Fi- and Ethernet-based access to the Internet. Partnered with > Boeing Company (Quote, Company Info) and Cisco Systems (Quote, > Company Info), the Lufthansa flight -- part of a project called > FlyNet -- will travel from Frankfurt, Germany to Washington D.C and > back for the next three months. > > The plane in use is a Boeing 747-400 equipped with Connexion By > Boeing, a system for providing high-speed, real-time data services > via satellite. The network from Cisco includes five Cisco Aironet > 350 Access Points, a Cisco 3640 Router, and nine digital switches > for the hardwired Ethernet connections found in some seats in First > Class and Business Class. The wireless, obviously, reaches everyone > on the plane. The data throughput for users on the plan is about 3 > Megabits per second (Mbps) downstream and 128Kbps for uploads. > > The service is initially free to any one on the Germany to US > flights; Jonathan Hindle, strategic technology manager for the World > Wide Mobile Team at Cisco, says that this trial is, in part, about > finding out what people will pay for the service. > [...] > > > > --__--__-- > > -- > general wireless list, a bawug thing <http://www.bawug.org/> > [un]subscribe: http://lists.bawug.org/mailman/listinfo/wireless > > End of wireless Digest > > -- > general wireless list, a bawug thing <http://www.bawug.org/> > [un]subscribe: http://lists.bawug.org/mailman/listinfo/wireless -- David Young OJC Technologies [EMAIL PROTECTED] Engineering from the Right Brain Urbana, IL * (217) 278-3933 -- general wireless list, a bawug thing <http://www.bawug.org/> [un]subscribe: http://lists.bawug.org/mailman/listinfo/wireless
