You mention thick forest.
Foliage loss in dB is roughly proportional to freq^0.77, so higher frequencies are more lossy than lower frequencies. True plb's work at 400 MHz or so, SPOT at ~1.6GHz. So that is what, (0.4/1.6)^0.77~.34dB down in gain from SPOT to true plb, all else equal. But its not, Spot operates at 0.5W (1'st gen.), or 1W maybe, they're not saying on the specs page. plb's operate at 5W. Antenna efficiencies are not in anyone's specs.
SPOT is claiming they have more satellites than anyone. I find that hard to believe when compared to the SARSAT constellation of LEO and geosynchronous satellites.
Don't know anything about DeLorme thingy, but I suspect it is like SPOT.
Last edited by huskyrunnr; 06/03/12.
