Scott wrote:
brian whatcott wrote:
Since satellite cover has been withdrawn for 121.5
(High false alert rate, poor localization)
406.0 and 406.1 ELTs will be needed, following a recent FCC
determination.

Brian W

I can see the 406 units providing better localization, but how do they
lower the high false alert rate? I assume they still use a "G Switch"
to activate?

I would think that localization could be good on the 121.5 units if they
would be made to accept GPS data and transmit lat/long data when they go
off...

The rationale seems to go like this: the 406 spec is for 4 watts min on
the UHF (Oh, alright = 17dBm) pulsed for nearly 1/2 second per 50 secs
or so for the following 48 to 50 hours... It emits a traceable
signature, which can quickly be associated with a particular aircraft,
so that tracing a likely route is enabled.
The 121.5 continuous signal can help with close in location.
There are apparently as many as nine G-switches built in.
They say the rescue rates on 406 alerts have been MUCH better than 121.5
alerts.

Brian W