It is a NECESSARY AND SUFFICIENT requirement (out of three). The point
is that if that is not the way the spreading is done in ROS, ROS is NOT
spread spectrum. PROVE, not just claim, that it is not, and the battle
is won.
73 - Skip KH6TY
Rik van Riel wrote:
On 02/23/2010 09:00 PM, KH6TY wrote:
> The distinguishing characteristic of spread spectrum is spreading by a
> code INDEPENDENT of the data. FM for example, creates carriers depending
> upon the audio frequency and amplitude. SSB creates carriers at a
> frequency dependent upon the tone frequency, and RTTY at a pair of set
> frequencirs depending upon the shift or the tones used to generate
> shift. In spread spectrum, as Jose has written, an independent code is
> used for the spreading, one of the requirements to classify it as spread
> spectrum.
One of the requirements - not the single determining
characteristic by any means.
>From a quick look through the fldigi source code,
MFSK and Olivia appear to use a pseudo-random code
as well, to provide robustness against narrow band
interference.
>From several places in src/include/jalocha/pj_mfsk.h
static const uint64_t ScramblingCode = 0xE257E6D0291574ECLL;
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