Friday, January 16, 2009

More PLB Discussion

Rebute:
It's only $650! The way it works is that it transmits the emergency signal to the GEOSAR satellites on 406MHz. This particular model also incorporates a GPS receiver (not one that you can see or use for regular navigation). The PLB will send out your coordinates on the 406MHz frequency to help SAR find you even faster. I was hoping to never use it, but if needed, it would be nice to have. I'm assuming I can buy the SAR insurance (excellent idea) if/when I bought this PLB.

I still have the Garmin III+, which still works fine for what I use it for, hiking and such. I have the built in GPS in the Prius, so I don't need to use the III+ for driving purposes anymore.

The SPOT thing is interesting, but it's $150 plus $99/year to use their service. After 5 years, it's the same price as the PLB. Plus I've read that it takes roughly 30 minutes for it to acquire and transmit to the satellite. The other problem is that coverage is limited: http://www.globalcomsatphone.com/spot/coverage.html
Plus I've heard that globalstar sat system is in financial trouble and who knows what will happen with them.



Second Reply
And more PLB articles for you:

PLB article
http://www.equipped.org/406_beacon_test_background.htm
PLB faq
http://www.equipped.org/faq_plb/default.asp
PLBs Legal in US
http://www.equipped.org/plb_legal.htm


One more article, but I don’t have an account.

RADIO RESOURCES

Personal Locator Beacons Upload GPS Positions!
by Gordon West, WB6NOA

It’s been three years and over a thousand “saves” since the personal locator beacon (PLB) was authorized by the FCC for use by the general public for land, sea, and air applications. These lightweight handheld distress beacons transmit a 25-milliwatt undulating warble on 121.5 MHz, and more important a 5-watt data burst on 406 MHz to low earth orbit (LEO) satellites and one of three geostationary satellites. These satellites are part of the search and rescue satellite-aided tracking system called COSPAS-SARSAT. Currently, there are six LEO satellites and five geostationary satellites, all listening in on 406 MHz frequencies (406.025 MHz, 406.028 MHz, and 406.037 MHz).

LEO satellites, on February 1, 2009, will turn off their simultaneous relay of received 121.5-MHz signals. More than 95 percent of 121.5-MHz high-power emergency beacon signals were false activations, and the signal itself carries no user identification.

Meanwhile, the 406-MHz Emergency Position Indicating Radio Beacons (EPIRBs) still include a 121.5-MHz homing signal, but this signal is only 25 milliwatts and is intended specifically for local search and rescue tracking. The main 5-watt signal is a 406-MHz data burst containing your unique identification number (UIN) that would allow a rescue coordination center to access the NOAA beacon database and immediately determine the beacon’s country of origin and the registered owner along with a phone number.

The six LEO satellites monitoring the 406-MHz data burst will also begin downloading Doppler shift measurements for an approximate position of the activated 406-MHz data burst signal. While the signal is immediately detected by the geostationary satellite and transponded to a local user terminal (LUT) ground station, it takes nearly an hour of Doppler shift calculations from the LEO satellites to develop a position fix within 2.3-nautical-mile radius of the activated beacon. This is infinitely faster and more precise than an older 121.5-MHz calculated position, 12-nautical-mile radius, over a six-hour period, requiring a search area of 452-square-nautical miles!

Technology That’s Come Into Its Own

The 406-MHz calculations cut the search area dramatically. Equipment has also improved over the first issue personal locator beacons, produced by ACR Electronics in Florida and McMurdo in Europe. The personal locator beacon acceptance among skiers and hikers was modest for the first couple of years after the FCC authorized the equipment, but with the new development of built-in GPS, the PLB life-saving beacon’s popularity has exploded.


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