On 2/20/2010 10:28 PM, Mark Langford wrote:
> What you may have missed on Sam Buchanon's site is that there are ham
> operators with systems set up that are constantly looking for "emergency"
> packets, and help would be on the way very shortly after broadcasting them,
> especially after a quick Google Maps search showed the plane flying along at
> 160 mph, then losing speed and altitude, and "landing" at somewhere other
> than an airport.
The fundamental issue is that with amateur operators you are relying on
their good will and periodic checks of the system when they get around
to it. I'm not putting down hams, I've been one myself for some 25+
years or so, but things get done when the volunteers have time to do it.
The 406Mhz ELTs and PLB are part of a network that is monitored
24/7/365 with multiple redundancies built in. Plus, APRS relies on
ground stations that may or may not be within range of your packets
being transmitted, whereas the ELT/PLB satellites are always there.
As much as I like APRS, it just does not provide the same coverage and
function that ELTs do. ELTs and PLBs are specifically for emergency
situations, and have the infrastructure behind them to support this.
APRS simply doesn't.
> I've had a 406 MHz ELT in my plane for about a year a half, but what
> worries me is what kind of shape it and it's vital antenna connection will
> be in after I go into the trees somewhere.
Not sure I understand - how will the APRS antenna be any different if
it is installed in the same aircraft as the ELT? How will APRS be any
better than a PLB, which is generally carried either on your person or
in your nearby flight bag while in flight (ie, somewhat protected inside
the cabin)?
>
> I'm not saying a 406 MHz ELT is worthless or a PLB is worthless, but I think
> an APRS has an equal place in the triad, especially for the price and
> minimal weight penalty. It's hands off, and always working...no thinking or
> "good luck" required.
I think there is more good luck involved with the APRS system then
either the ELT or the PLB. First, if you are going down, you may not
have time to activate the "emergency" switch on the APRS or the PLB, so
in that regards they are equal. If you crash, the ELT at least has a
sensor that should start it transmitting, so the ELT wins over PLB and
APRS in this case. Once on the ground, if you are capable, you can
activate the APRS "emergency" switch and the PLB. The chances are much
higher that you are going to be able to hit a satellite with the PLB
signal than you are going to be in range of an APRS ground receiver, so
the ELT and the PLB win over APRS here. Assuming that both the APRS
signal and the ELT/PLB signal gets though, the APRS system is now
relying on a volunteer to notice the signal, and take action to notify
the appropriate entity, whereas the PLB/ELT is talking to the entity
directly and is monitored 24/7, so I think the ELT/PLB wins here too.
APRS is awesome, and has MANY useful features (2 way messaging is very
cool, easy for friends to track you, etc), but it is not on par with
PLB/ELT units for emergency response. I think it is very useful *in
addition* to a PLB and ELT, but does not replace either.
-Dj
--
Dj Merrill - N1JOV
Glastar Sportsman 2+2 Builder #7118 N421DJ - http://deej.net/sportsman/
Grumman Yankee Driver N9870L - http://deej.net/yankee/
