Rein,
You can decide for yourself if ROS is spread spectrum or not, just be
observing it with any audio spectrum analyzer, or program like fldigi or
Digipan that has a waterfall. Just observe the behavior with data and
without data at idle and you will see.
You find that the carriers of the 16 baud and 1 baud variations bear no
relationship to the imposed data, but "hop" around randomly - a sure
sign of spread spectrum or frequency hopping. Instead in FSK and PSK,
the carrier frequencies are fixed and modulated with the data. MFSK16 is
a FSK mode and MT63 is a PSK mode (modulation applied to 64 fixed
frequencies).
Here is a comparison I made, similar to what you can make yourself:
http://home.comcast.net/~hteller/SPECTRUM.JPG
There is indisputable randomness to the ROS tone frequencies, even if
you watch it for a long enough time. Applied to modulate a SSB
transmitter, the resulting RF frequencies are also indisputably random.
The FCC engineers have performed the same spectral analysis and informed
the ARRL that the mode is truly spread spectrum.
ROS now has some more narrow modes added, which I have not inspected,
but maybe only the wide 1 baud and 16 baud varieties are spread
spectrum, or frequency hopping, and the narrow ones are FSK - I don't
know. Even if those narrow modes are not frequency-hopped, they are
still grouped under the same umbrella, "ROS", which means any approval
of "ROS" for narrowband modes would wind up also approving the wide
versions, which have all the appearance of being spread spectrum, or
frequency hopped. For this reason, it did not work to include some
narrow FSK modes to try to get overall approval by the FCC engineers. In
fact it probably was an insult to their intelligence!
The distinction of spread spectrum, or frequency-hopping, is simply that
the carrier frequencies are determined independently of the data.
Originally this was done in order to encrypt the signal unless you
possessed the de-hopping code. It does not matter if the de-hopping code
is sent along with the data, or the frequency spread is unusually narrow
- frequency hopping is still frequency hopping - and that happens not to
be allowed under 222 Mhz in FCC jurisdictions. A petition to modify the
regulations can be submitted, but that has not been done, to my
knowledge - just repeated attempts to fool the FCC with untruths.
If a SSB transmitter is fed audio tones and the carrier is adequately
suppressed, then the output is pure RF at the suppressed carrier
frequency plus the individual tone frequency (for USB) and if the tones
are frequency-hopped, it makes no difference if the RF generation is by
frequency shift of an oscillator or by means of tones - the FCC is only
interested in the emitted RF and its behavior. The advantage to
frequency hopping, if you have the de-hopping code, is that the noise is
random, but the signal has a known autocorrelation function, so
integration by looking for the correlation can make the weak signal
stand out from the random noise background - something I am sure you are
aware of that has been long used in deep space communications.
Splitting off the frequency-hopped modes from the same program that
contains the narrow FSK modes might result in approval to use a separate
program that has no frequency-hopped modes. The remaining program would
only be allowed in the US above 222 Mhz.
73 - Skip KH6TY
Rein A wrote:
Hello All,
http://www.youtube.com/watch?v=lOmrgJkFY40
<http://www.youtube.com/watch?v=lOmrgJkFY40>
I found this interesting YouTube video, interesting to me at least.
It is going a to be a big help watching waterfalls at 14.103 kHz and
other channels such as
http://etgd2.ewi.utwente.nl:8901/ <http://etgd2.ewi.utwente.nl:8901/>
73 Rein W6SZ
