You can check out the Technical Manual for an ELT manufactured by Dukane, answers to many of your questions may be found there...
http://www.rjeint.com/pdf/DK100Series_15.pdf
anyhow, to contact the satellite , the antenna must be out of the water.
Im just wondering what h3dxb is talking about when he mentioned about ELT receiving satellite signal
My mistake, I was referring to ULB not ELT, sorry for that...