ORIGINAL: erauskydiver
My understanding of Spread Spectrum was that it just searches for a clear and most ideal channel. It only has something like 80 possiblities. I'm talking of actually encrypting the signal sent by the TX and decrypting it at the RX. This gives you infinite possiblities because it all relies on digital algorithms.
The system discussed in the cited thread uses a 32-bit codeword (GUID) to bind the Rx to the Tx. Not as long as GUIDs typically used to uniquely identify scraps of s/w and database elements (MS Windows system s/w includes a GUID generator that gins up pseudo-random 128 bit words, IIRC), but even the short 32-bit codeword along with the possible permutations of channel slots gives 4.2 billion unique combinations. That enough?
BTW, spread spectrum does much more than search for a clear channel - in fact that function isn't a necessary part of the signaling mode, though it often is. The essence of it is to spread signal energy across a wide bandwidth to improve signal to noise ratio - remember the concept of time-bandwidth product? It has been around for a long time. Broadcast FM spreads signal energy into multiple sidelobes. In order to accommodate those sidelobes and allow the Rx to recover signal energy from them, the signaling bandwidth must be increased. That's why 15 KHz is allocated to FM, as compared to 5 KHz for AM. Lots of people kid themselves into thinking FM is superior to AM for R/C, based on the performance differences in broadcast radio. It isn't, because both (all) modes in the R/C allocation are limited to the same bandwidth.
Abel