Alan, please carry on the debate with someone else. I have spent a huge
amount of time on this issue, trying to help in whatever way I can,
although I do not have all the answers, obviously. I need to do
something other than sit in front of this computer all day!
Have fun,
73 - Skip KH6TY
Alan Barrow wrote:
KH6TY wrote:
>
>
> Alan, though we may disagree as to the amount or nature of FHSS in ROS,
Actually, I think we agree, just for different reasons. I really don't
care about ROS. But do care about dangerous precedents. :-)
> the bottom line is that the FCC engineers, as well as the ARRL
> engineers, reviewed both the documentation and the signal footprint,
> and have concluded it is FHSS.
I think we all agree it's a micro form of FHSS. I'm not sure I agree the
FCC engineers have "ruled". If Bill Cross or similar commented, that'd
be definitive. But the ARRL interpretation of the FCC dialog still is
pretty ambiguous. Lot's of "the author stated" and "each operator has
to"....
Compare it with the ruling on Pactor 3 when challenged on a similar
crusade. That's clear & unambiguous, it was not FDM, even though it
could be construed as such on a micro scale. And that crusade had
similar arguments & mis-statements.
> While their opinion might be changed through dialog, that is unlikely
> at this point, so the most sure approach is just to agree it is FHSS
> and petition for a variance with necessary limitations.
Again, I think the real area to petition is not about ROS itself. That
has been so badly handled from all sides it's probably tainted. And to
be clear: Amateur radio was the net loser.
The real issue is around applying macro definitions (like ITU SS,
traditionally broadband, wide spreading factor) to a micro (SSB, non
broadband) implementation like ROS.
Put another way, what would an HF optimized SS mode do that other modes
do not? What would be the negative? And factor in the potential (done
right) of improved interoperation with other modes, signal processing
gain, etc. And potential channel sharing (concurrent users).
> I think we have beat this horse to death at this point and should move
> on to another topic.
Well, that would be great, except you keep refering to the "must have
idle tones like my grand-dad's rtty" test.
Again, I don't really care about ROS. This dialog is about the idea of
using carrier patterns at idle or steady zero's/ones (like ancient RTTY)
as a test for SS. That's just not it. We *are* allowed to encode data in
a pseudo-random pattern, as long as the other SS tests are not triggered.
Instead of concocting our own definitions, let's refer to the standards.
ITU, which is referenced by NTIA, which is referenced by Fed Std, which
is also reference by some FCC commercial definitions. It's the closest
we have and is attached below.
What's still not 100% is whether a SSB signal with a fixed dial
frequency (and implied fixed carrier frequency) would be considered SS
just because the audio sent changed in a SS fashion. It's back to is FSK
& AFSK the same mode, or just happen to look the same.
Which is becoming tiresome, and makes me think reminisce about the
traditional anti "new mode" (PSK, Pactor, ALE, whatever) crusades. :-)
Remember, PSK was going to ruin the world as well. So was SSB in it's day!
Have fun,
Alan
km4ba
Here are the ITU definitions. Note the spreading factor definitions, etc:
*Term* : spread spectrum (SS) system *Definition* : System in which the
average energy of the transmitted signal is spread over a bandwidth
which is much wider than the information bandwidth (the bandwidth of the
transmitted signal is wider than the information bandwidth by at least a
factor of two for double sideband AM and typically a factor of four or
greater for narrow-band FM, and 100 to 1 for a linear SS system).
*Term* : Direct sequence (DS) spread spectrum *Definition* : signal
structuring technique utilizing a digital code spreading sequence having
a chip rate 1/Tsin much higher than the information signal bit rate
1/Ts. Each information bit of the digital signal is transmitted as a
pseudo-random sequence of chips, which produces a broad noise-like
spectrum with a bandwidth (distance between first nulls) of 2 Bsin ?
2/Tsin. The receiver correlates the RF input signal with a local copy of
the spreading sequence to recover the narrow-band data information at a
rate 1/Ts.
***Term* : Frequency-hopping (FH) spread spectrum *Definition* : signal
structuring technique employing automatic switching of the transmitted
frequency. Selection of the frequency to be transmitted is typically
made in a pseudo-random manner from a set of frequencies covering a band
wider than the information bandwidth. The intended receiver
frequency-hops in synchronization with the transmitter in order to
retrieve the desired information.
Here's the NTIA "redbook" definitions, which is also reference in
Fed-Std 1037c:
Spread Spectrum: A signal structuring technique that employs direct
sequence, frequency hopping
or a hybrid of these, which can be used for multiple access and/or
multiple functions. This technique
decreases the potential interference to other receivers while achieving
privacy and increasing the
immunity of spread spectrum receivers to noise and interference. Spread
spectrum generally makes use
of a sequential noise-like signal structure to spread the normally
narrowband information signal over a
relatively wide band of frequencies. The receiver correlates the signals
to retrieve the original
information signal.
Direct Sequence Spread Spectrum: A signal structuring technique
utilizing a digital code sequence
having a chip rate much higher than the information signal bit rate.
Each information bit of a digital
signal is transmitted as a pseudo-random sequence of chips.'
Here's a widely used industry definition:
FHSS
Acronym for frequency-hopping spread spectrum. FHSS is one of two types
of spread spectrum radio, the other being direct-sequence spread
spectrum. FHSS is a transmission technology used in LAWN transmissions
where the data signal is modulated with a narrowband carrier signal that
"hops" in a random but predictable sequence from frequency to frequency
as a function of time over a wide band of frequencies. The signal energy
is spread in time domain rather than chopping each bit into small pieces
in the frequency domain. This technique reduces interference because a
signal from a narrowband system will only affect the spread spectrum
signal if both are transmitting at the same frequency at the same time.
If synchronized properly, a single logical channel is maintained.
The transmission frequencies are determined by a spreading, or hopping,
code. The receiver must be set to the same hopping code and must listen
to the incoming signal at the right time and correct frequency in order
to properly receive the signal. Current FCC regulations require
manufacturers to use 75 or more frequencies per transmission channel
with a maximum dwell time (the time spent at a particular frequency
during any single hop) of 400 ms.
Frequency-Hopping Spread Spectrum: A signal structuring technique
employing automatic
switching of the transmitted frequency. Selection of the frequency to be
transmitted is typically made in a
pseudo-random manner from a set of frequencies covering a band wider
than the information band-width.
The intended receiver would frequency-hop in synchronization with the
code of the transmitter in order
to retrieve the desired information.
