Phil
One of the thing that I have found with DSS is that multi-path is not as big of a problem as it is with constant carrier.
With constant carrier if the directly transmitted signal arrives at the receiver and there is no multi-path every thing is fine however if there is multi-path due to buildings or something for the signal to reflect off of and the reflected signal arrives at the receiver out of phase with the directly transmitted signal then you can have all kinds of problems.
With DSS by the time the reflected signal arrives at the receiver the transmitter and receiver have hopped to a new frequency and the receiver will not see the reflected signal.
This is all depend on how fast the hopping sequence is and how long it takes for the the reflected multi-path signal to arrive at the receiver.

Dave Jones
AUAV.net