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Men Overboard Retrival System - WAVEFINDER
On 26 Aug 2003 23:26:16 -0700, (Patrick) wrote:
Hello Larry,
You are not completely wrong, if every crew member own at any time a
waterproof VHF radio and a GPS, you have a good solution to the MOB
problem, but the boat VHF has to be turned on and the other crew
members have to be awake.
The size of the package you have to carry will be really not pleasant
!!
Concerning the range, the transmitter has a 500mW ERP power. The
receiver has a bandwith of only 1 Hz, with a 8th order filter !!! The
resulting sensitivity is better than -127dBm.
This high sensitivity is furthermore improved by a strong digital
signal processing.
I have an 8-pole CW filter of 250 Hz with about 60db/octave sides on
it in my Yaesu FT-990AC transceiver. How do you get the bandwidth to
1 hz? If you had 10 identical crystals in a row you'd never reach 1
Hz! Is this the IF bandwidth or some digital trick to make it LOOK
like a 1 Hz BW?
As to the 127 dBm receiver sensitivity, that might work great in deep
space, but I live on planet EARTH. The noise from the sun, thermal
noise from every surface Sun beats on is higher than that.
The propagation on a sea is absolutely not completely guided by the
line of sight rules, in fact, you have a big refraction factor on the
top of the waves. The measurements we have achieved have always been
better in strong sea conditions.
No matter....500mw ERP isn't going 10 miles except maybe in space if
you have a big enough dish to collect enough energy cryogenically
cooled.....
Larry W4CSC
Isn't it becoming more practical by the day to make
Iraq's desert the new World Nuclear Waste Disposal Site?
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