ELT antenna in composite planes.

ELT normally uses an externally mounted antenna. But in composite
planes it may be advantageous to use a ducky.

1. On crash the external antenna may be destroyed - brushing against
trees, whatever. An attached ducky on the ELT will likely stay on.

2. A ducky radiates nearly isotropically - i.e. near equal in all
directions. If the standard externally mounted ELT antenna survives
the crash, a half wave or a quarter wave radiation pattern is mostly
perpendicular to the antenna - in normal situations that would be
horizontal. But on the ground after the crash, horizontal directions
are often obscured by terrain - one reason why HAMs use VHF repeaters
- and the signal is weak above where the search planes are. This is
where the ducky may have an advantage and will send signals in all non-
obscured directions equally. Note that a plane crash does not
guarantee any orientation of the plane/antenna or after crash
worthiness of the antenna.

Even if Fosett's ELT worked its antenna may have radiated horizontally
against mountain obscurations or was broken off.

You can get a 121.5MHZ tuned ducky (low SWR) for only $16 bucks from
http://www.smileyantenna.com/ I don't work for them.