Ok Skip Yes .. but .. looking at it from over here .. Technically the situation looks a little quaint ..
What happens between 145 and 220 meg to enable the mode ..the concept is the same . so it cannot be based on intercept ability ..that only leaves bandwidth ? Something must of driven the 'need' for the clause in the first place ? (my licence bans pulse tx below 10 GHz .. but all these mfsk systems transmit pulses .. long ones , but pulses just the same) How old is the FFC 220 meg rule on SS , what is the actual text of the clause ? Yes your right and as originally posted , the frequency allocation is randomised by a PG string added to the data , obvious way to go really .. but 'we' where locked into psk at the time but data manipulation cannot be the reason for the 220 clause as the system may be used over this frequency ... I suspect that in the mind of the 220 author , spread spectrum equated to high spectrum usage , hence the high vhf allocation to what i assume (in those days) was an experimenters band ? To quote from wiki Spread" radio signal over a wide frequency range several magnitudes higher than minimum requirement. The core principle of spread spectrum is the use of noise-like carrier waves, and, as the name implies, bandwidths much wider than that required for simple point-to-point communication at the same data rate. Pure tone bursts within a audio channel 500 Hz , 100 Hz or 50 Hz , do not quite compare to what is normally associated with SS ? .. May be its time for some one to ask again ,? , G .
