He did, I guess, when he added a 500Hz-wide mode. The footprint of that
mode indicates it is probably FSK as he tried to claim for the 2200
Hz-wide mode. He says he submitted a technical description to the FCC
but will not release it until he gets an OK. Don't know what to believe
from him these days, though!
A further problem is the the new mode is included under the ROS name,
and the 2200Hz-wide mode still looks like spread spectrum, unchanged
from earlier. So if the FCC approves ROS on the basis of the new 500
Hz-wide mode, operators may think the 2200Hz-wide mode is now legal also.
Still not a good situation!
73 - Skip KH6TY
g4ilo wrote:
Skip.
Thank you for the comprehensive explanation. I understand why ROS is
illegal under your rules.
The point of my question was, if FHSS is illegal, why not simply
modify the mode (which after all is experimental and does not have a
large number of users) to use a non random way of generating the
tones? Instead of rewriting the description to falsely claim ROS is
not SS, why could he not have changed the mode so that it really was
not SS?
What does ROS gain by using SS over another mode that carries the same
amount of data at the same speed using the same bandwidth and the same
number of tones but uses an entirely predictable method of modulation?
Julian, G4ILO
--- In digitalradio@yahoogroups.com
<mailto:digitalradio%40yahoogroups.com>, KH6TY <kh...@...> wrote:
>
> Julian,
>
> By definition, it is SS "if" the pattern is independently generated
from
> the data. The original intent of FHSS was to make third-party decoding
> impossible without knowledge of the code that generated the tones or
> carriers. FCC rules disallow encryption because we are required to
> police the bands ourselves. As long as there is not a pattern to the
> frequencies generated, that is independent of the data, one of the
> necessary and sufficient conditions to qualify as FHSS is missing.
> However, in the case of ROS, the repeated pattern is not there, so,
> until the regulations are changed, ROS is illegal FHSS, even though the
> spreading is limited and capable of third-party monitoring. That is a
> result of a historical attempt to prevent encryption, but this can
> probably be changed through the petition process with public comment.
> Until then, hams in the US have no choice but to abide by the
> regulations as written.
>
> In the author's own words, three necessary and sufficient elements make
> it SS, and a search of the literature says the same:
>
> 1. The signal occupies a bandwidth much in excess of the minimum
> bandwidth necessary to send the information.
> 2. Spreading is accomplished by means of a spreading signal, often
> called a code signal, which is independent of the data.
> 3. At the receiver, despreading (recovering the original data) is
> accomplished by the correlation of the received spread signal with a
> synchronized replica of the spreading signal used to spread the
information.
>
> The operative phase here is "independent of the data".
>
