Fergus Kyle wrote:
> and ELTs are insufficient enough without stifling the signal
> further.
You may be amused by my running a 160 milliwatt ELT thru Jim Weir's (RST
Engineering) RF calculator spreadsheet. It will have a theoretical
reception area of 980 thousand square miles! It doesn't help if you've
engineered a perfect antenna install, but with the antenna oriented
vertically, because there will be a big void overhead in the center of
the "donut." That's why previous posts mentioned tilting it 20-degrees
to fill in the void.
Our gov't also says typical location accuracy is 12 miles even at
required 100 milliwatts (lesser the better for this purpose). A variety
of reasons make it difficult to find you within the center of the
radiation pattern, if it's anything close to circular at all. Thus
mythology that high signal strength is always good and that it's easy to
home in on the signal. Fastest and most assured rescue, if a cell phone
won't work, is direct VHF comm with passing overhead aircraft, ideally
with GPS coordinates. Also the 121.5 mHz ELT's will be phased out in a
few years.
Fred F.
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