No, the shift on RTTY and other soundcard modes is not determined by a
pseudo random code but always known and predictable. Instead, the tones
on ROS are driven by a code signal. To quote from the ROS documentation,
"2. Spreading is accomplished by means of a spreading signal, often
called a code signal, which is independent of the data."
The original intent of spread spectrum was to make it impossible to
monitor without possessing the despreading code, but ROS can be monitored.
There is a good chance that the FCC will allow us to use ROS on HF - why
not! But as the rules are written right now, ROS is FHSS - by design,
and it does not matter if the description is changed or not, so it is
necessary to get a waiver or other FCC agreement that we can use it on
HF. ROS can be copied by third parties, and is no wider than a phone
signal, so I cannot think of any reason the FCC would decline, but they
have to give permission. That is just the way it works, because that is
how the rules happen to have been written in the past.
If the spreading is NOT actually "accomplished by means of a spreading
signal, often called a code signal, which is independent of the data"
then ROS is not spread spectrum and there is no problem.
73 - Skip KH6TY
jhaynesatalumni wrote:
--- In digitalradio@yahoogroups.com
<mailto:digitalradio%40yahoogroups.com>, "John" <ke5h...@...> wrote:
>
> Thanks Skip,
>
> Unfortunately, this really does not get to the crux of my
question(s). I understand how an SSB transmitter works, but that is
not really what I am after.
>
> What I am driving at is if like this. If I use DM780 to run some
version of digital mode via an SSB transceiver, it uses a tone or
series of tone modulation/shifting to create the output of the
transmitter, and not one single mode is called "spread spectrum"
output, but is called FSK or PSK, etc. Now, we get into the
aforementioned discussion regarding ROS, and suddenly, still via the
microphone input of the same transmitter, those shifted frequencies
are now called "spread spectrum" instead. I am having a great deal of
difficulty understanding, other than the author happened to call his
scheme "spread spectrum" in his technical documentation.
>
That's a good question. If we run RTTY with 850 Hz shift like we
did in the old days, has that turned into spread spectrum?
