Completely agree -- Virtually all commercial aircraft are monitoring 121.5 in flight and many of us private pilots monitor on cross country flights. With so many recievers out there, it's hard to believe any low power signal on the ground wouldn't be picked up very quickly.... I've heard beacons twice: once someone was testing an ELT and once the CG was involved in tracking it -- don't know the outcome......... Best Regards, Michael Hopkins Manager, Customer Technical Center Control Technology Division Compliance Test Solutions Thermo Electron Corporation One Lowell Research Center Lowell, MA 01852 Tel: +1 978 275 0800 ext. 334 Mobile: +1 603 765 3736 [email protected]
One Thermo, committed to integrity, intensity, innovation & involvement _____ From: [email protected] mailto:[email protected]] On Behalf Of jshinn Sent: Wednesday, October 20, 2004 1:21 PM To: [email protected]; [email protected]; [email protected] Subject: RE: ... And they wonder why we test...? The 121.5 MHz Beacon may be old, but just a carrier setting it off is enough. It does not rely on Satellite technology. Most towers monitor this guard frequency full time. Most commercial aircraft and many private aircraft monitor this frequency. The ELTs are allowed to be tested only at a certain time of the day. If an ELT, or other device sets up a carrier on 121.5 MHz, it will trigger a lot of alarms in many control towers if they are within range (i.e. – the transmitter is not down is some valley far from civilization). The response is generally much sooner than 1.5 Hrs. The system works quite well, everything considered. John Shinn (Pilot) From: [email protected] mailto:[email protected]] On Behalf Of [email protected] Sent: Tuesday, October 19, 2004 8:50 AM To: [email protected]; [email protected] Subject: RE: ... And they wonder why we test...? Patrick, a very interesting article. The 121.5 MHz beacon system is old and primitive. All it takes is a carrier to get noticed. And when you do get noticed it requires up to 90 minutes to get a fix on your location as it takes two passes of the satellite. This system will be phased out by 2009. The beacons run 100 mW. It would take a milliwatt or so to alert the satellite- this TV problem must have been more than just a bit of leakage. Perhaps the front-end amplifier oscillating? Got to make sure the amps are unconditionally stable. Radio Shack and Weingard, I believe, have had problems with TV antenna amplifiers oscillating. While designing some in-house test equipment, that operates around 120 MHz, we were careful to keep it away from 121.5 MHz and added spread spectrum for good measure. Dave Cuthbert Micron Technology From: [email protected] mailto:[email protected]] On Behalf Of Conway, Patrick R (HOU) Sent: Tuesday, October 19, 2004 8:21 AM To: [email protected] Subject: ... And they wonder why we test...? I thought this was worth sharing. http://www.cnn.com/2004/SHOWBIZ/TV/10/18/odd.television.reut/index.html How many people and how much money do you think were spent tracking this one down? …this reminds me of all the times I've had to justify to someone why we test, and why we fix something "that no one cares about" (not my quote - just one that I've heard many times at previous job sites). Thank goodness my present employer doesn’t think that way! But, I think I'll archive this article just in case I ever run into this question again. Best Regards, Patrick Conway, NCE Senior EMC Engineer Hewlett-Packard Company 281.514.2259 281.514.5473 (fax) <mailto:[email protected]> [email protected] _____________________________________________________________________________ Scanned by Sanmina-SCI eShield ________ ____________________________________________________________________ ---------------------------------------------------------------- This message is from the IEEE Product Safety Engineering Society emc-pstc discussion list. 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Website: http://www.ieee-pses.org/ To post a message to the list, send your e-mail to [email protected] Instructions: http://listserv.ieee.org/listserv/request/user-guide.html List rules: http://www.ieee-pses.org/listrules.html For help, send mail to the list administrators: Ron Pickard: [email protected] Scott Douglas [email protected] For policy questions, send mail to: Richard Nute: [email protected] Jim Bacher: [email protected] All emc-pstc postings are archived and searchable on the web at: http://www.ieeecommunities.org/emc-pstc
