When I was in the Marine Corps I repaired the control tower equipment including the transmitters and receivers. One of the perks of the job was to grab the DF and begin the hunt when an ELT went off.
In some cases it could take 2-3 hrs to find the exact location of the offender. So just because it may be noticed with in minutes doesn't mean it doesn't take time to find it. The other thing to remember is the dispatch to find it was usually a few minutes later. This is because most of the time it happened when the Pilot would accidentally turn the switch on the personal ELT (mounted to the flight jacket) one click too far. Josh jshinn wrote: > 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) > > > > > > -----Original Message----- > *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 > > > > -----Original Message----- > *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) > [email protected] <mailto:[email protected]> > > > > _____________________________________________________________________________ > Scanned by Sanmina-SCI eShield > _____________________________________________________________________________ > > ---------------------------------------------------------------- This > message is from the IEEE Product Safety Engineering Society emc-pstc > discussion list. 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 > ---------------------------------------------------------------- This > message is from the IEEE Product Safety Engineering Society emc-pstc > discussion list. 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 > This message is from the IEEE Product Safety Engineering Society emc-pstc discussion list. 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 This message is from the IEEE Product Safety Engineering Society emc-pstc discussion list. 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
