Talkback: New Fast Find Emergency Beacon Launches

Moel Hebog

10/05/2012 at 17:33

Interesting article. However, I can just imagine the headlines when a tired walker decides to use it inappropriately in order to get a lift off the hill!!!

The use of PLBs such as this are quite common in other parts of the world. For some long distance trails in Australia, it is a requirement that you hire one for your trip and when you sign on to start your trip, it is checked by a Park Ranger.

Jon Doran

10/05/2012 at 17:40

I wonder if there's a legal sanction against such a thing... some sort of implied contract when you start using it.

It's an odd one. It'd be nice to try one out, but I'm not sure we could actually use it without being plucked off the top of Kinder by Thunderbird 2. Looking into it.

OutdoorsMagic Editor | jon@outdoorsmagic.com

captain paranoia

10/05/2012 at 18:47

> McMurdo, the brand behind Fast Find, says that the unit will transmit continuously for a minimum of 24 hours with a 5-watt output

Okay, so assuming it has a 3V battery, that requires a current of 5/3A, assuming 100% efficient transmitter (hah!).

For 24hr transmission, that needs a battery of 24*5/3=40Ahr. The unit looks a bit small for that...

So I suspect it's not continuous transmission, but it will repeatedly send messages at some defined rate for 24hours. Looking at the unit, I think you'd be hard pressed to get more than 3Ahr of battery in it, so we have a transmit duty cycle of no more than 7.5%. Realistically, probably 1%. But then, if all you're trying to do is send an emergency message, you don't want to be splattering the band continuously; that would make you very unpopular (a potential denial of service, effectively), and would probably a violation of the SARSAT specification.

Okay, as you were. Just thinking aloud...

On the other hand, doing a little googling (which can be a dangerous thing), I note a number of hits refering to the phasing out of COSPAS-SARSAT monitoring of the 121.5MHz beacons; for instance.

Aha! Reading their product website, it uses the 406MHz COSPAS-SARSAT signal to transmit position and the old skool 121.5MHz homing signal for use by SAR teams equipped with RF triangulation devices.

Right; as you were (2)...

Jon Doran

11/05/2012 at 16:04

Thank you, I think

OutdoorsMagic Editor | jon@outdoorsmagic.com

Slioch

14/05/2012 at 13:39

Re the freq thing:

As I understand it, new PLB/EPIRB units have been compelled to use the UHF freq for several years; the phasing-out of monitoring of 121.5 by SARSAT has been planned for quite some time. Effectively, in the UK, the VHF freq would only be of use to RAF helicopters equipped to monitor/triangulate on it. [Well, it would have worked with Nimrods too, but that was then]. I don't know of any MRT equipped to pick up the 121.5 signals.