El 06/03/2010 9:01, KH6TY escribió:
The other possible problem is "wide-spreading" spread spectrum. There was a failed attempt about 5 years ago by the ARRL HSMM (High Speed Multi-Media) proponents to allow spread spectrum on the HF bands with the argument that the signal is spread so widely, each carrier appears at any given frequency only a short time, so it would not significantly interfere with other users of the frequency, and could, for example, be allowed to cover the entire 20m band. However, that assumes only "one" FHSS signal at a time. I think if you put on many at one time, in the resulting aggregate, there could be continuous interference over the entire width of the spectrum spread, since the spreading is pseudorandom. You can see what happens when just more than one ROS user tries to use the same frequency. They interfere with each other.
That is affectively a limit with CDMA cellphones. Even when using different codes, they are not 100% orthogonal and the result is a degradation of SNR. It requires a multiplicity of non overlapping cells and automatic power control to be viable.
Using a single coding sequence, access method such as those used in packet to share the channel should be enforced as well. Not a simple matter, as the hidden station is a concrete fact.
73, Jose, CO2JA
