Hi All.
Just a question, and please, be patient if I'm asking this...
I'm a SWL and I decoded ros in last days, but HOW MUCH is large its
bandwidth ?
In other words, which is the minimun value of bandwidth enough to
receive/decode ros ?
Best regards and thanks in advance for any reply.
73 de Ugo - SWL 1281/VE
(sent with iPhone)
Il giorno 22/feb/2010, alle ore 22.33, KH6TY <kh...@comcast.net> ha
scritto:
Hi Jose,
Of course we start that way (using a SSB filter), but then a Pactor
station will come on, cover the upper fourth of the ROS signal, and
decoding becomes garbage until it leaves. With a more narrow mode,
the Pactor station can just be filtered out at IF frequencies and
not affect either the AGC or the decoding of something like MFSK16
or Olivia 16-500, as long as those signals are sufficiently away
from the Pactor signal (even if they are still within the bandwidth
of a ROS signal).
In the case of CW stations, during the contest, they just appeared
in the SSB filter bandwidth, and therefore among the ROS tones, and
some of those also stopped decoding until they left.
Let's say a MT63-500 signal appears at 2000 Hz tone frequency (i.e.
covering from 2000 to 2500 Hz) at the same signal strength as the
ROS signal. Will ROS stop decoding? If a MT-63-1000 signal appears
at 1500 Hz tone frequency, will ROS stop decoding? If this happens
and there is a more narrowband signal like MFSK16, for instance,
covering from 500 Hz to 1000 Hz, the MFSK16 signal can coexist with
the MT63 signal unless the MT63 signal has captured the AGC and
cutting the gain. If it has, then passband tuning can cut out the
MT63 signal, leaving only the MFSK16 signal undisturbed and
decoding. In other words, there is less chance for an interfering
signal to partially or completely cover a more narrow signal that
there is a much wider one, unless the wider one can still decode
with half or 25% of its tones covered up. The question posed is how
well ROS can handle QRM, and that is what I tried to see.
If ROS can withstand half of its bandwidth covered with an
interfering signal and still decode properly then I cannot explain
what I saw, but decoding definitely stopped or changed to garbage
when the Pactor signal came on.
73 - Skip KH6TY
jose alberto nieto ros wrote:
Hi,
You must not filter anything in the transceiver. You must pass all
bandwith in your receiver because filter are doing by the PC better
than you transceiver.
De: KH6TY <kh...@comcast.net>
Para: digitalradio@yahoogroups.com
Enviado: lun,22 febrero, 2010 18:31
Asunto: Re: [digitalradio] ROS Advantage?
Howard,
After monitoring 14.101 continuously for two days, I find the
following:
1. CW signals (of narrow width, of course) during this past weekend
contest often disrupted decoding, and it looks like it was not
desensitization due to AGC capture, as the ROS signals on the
waterfall did not appear any weaker.
2. Pactor signals of 500 Hz width, outside the ROS signal, that
capture the AGC, do desensitize the receiver and cause loss of
decoding, as expected. Passband tuning takes care of that problem
however.
3. Pactor signals which have the same degree of darkness as the ROS
carriers, and occur within the upper third of the ROS signal, cause
loss of decoding, and it is not possible to fix the problem with
passband tuning, as trying to do that appears to take away enough
of the ROS signal that the degree of frequency hopping used is
insufficient to overcome. Receiver is the IC-746Pro.
4. If more than one ROS signal is present on the frequency, ROS
will decode one of them - apparently the strongest one - and the
weaker one is blanked out until the stronger one goes away and the
the weaker one is decoded.
5. Compared to Olivia 16-500, for example, the width of the ROS
signal seems to be a disadvantage as far as handling QRM is
concerned. Five Olivia 16-500 signals will fit in the same space as
one ROS signal needs, so QRM, covering the top 40% of the ROS
signal, for example, would probably not disrupt any of three Olivia
signals in the bottom 60% of the ROS signal bandwidth.
In other words, the wide bandwidth required for ROS to work is a
disadvantage because IF filtering cannot remove narrower band QRM
signals that fall within the area of the ROS signal, but IF
filtering can remove the same QRM from the passband that has been
narrowed to accept only an Olivia signal. A much wider expansion or
spectrum spread might reduce the probability of decoding
disruption, but that also makes the signal wider still and more
susceptible to additional QRM. The advantage of FHSS appears to be
more in favor of making it hard to copy a traditional SS signal
unless the code is available, than QRM survival, but on crowded ham
bands, it looks like a sensitive mode like Olivia or MFSK16,
because it is more narrow, and filters can be tighter, stands a
better chance of surviving QRM than the ROS signal which is exposed
to more possibilities of QRM due to its comparatively greater width.
The mode sure is fun to use and it is too bad it does not appear to
be as QRM resistant as hoped, at least according to my observations.
Another problem is finding a frequency space wide enough to
accommodate several ROS signals at once so there is no cross-
interference. It is much easier to find space for five Olivia or
MFSK16 signals than for even two ROS signals.
These are only my personal observations and opinions. Others may
find differently.
I still plan to find out if ROS can withstand the extreme Doppler
shift and flutter on UHF which just tears up even moderately strong
SSB phone signals. Olivia appears to be the best alternative mode
to SSB phone we have found so far and sometimes provides slightly
better copy than SSB phone, but for very weak signals, CW still
works the best. Even though the note is very rough sounding, as in
Aurora communications, CW can still be copied by ear as it
modulates the background noise.
73 - Skip KH6TY
Howard Brown wrote:
Aside from the legal aspect, does anyone have an opinion as to
whether the limited hopping (within the 3khz that it hops) helps
the robustness of the waveform? If it makes a tremendous
difference, maybe we should all work to get it accepted.
Howard K5HB
From: J. Moen <j...@jwmoen.com>
To: digitalradio@ yahoogroups. com
Sent: Sun, February 21, 2010 9:13:50 PM
Subject: Re: [digitalradio] FCC Technology Jail: ROS Dead on HF
for USA Hams
Bonnie's note describes the US/FCC regulations issues regarding
ROS and SS really well. It's the best description of the US
problem I've seen on this reflector.
After reading what seems like hundreds of notes, I now agree that
if ROS uses FHSS techniques, as its author says it does (and none
of us has seen the code), then even though it 1) uses less 3 kHz
bandwidth, 2) does not appear to do any more harm than a SSB
signal and 3) is similar to other FSK modes, it is not legal in
FCC jurisdictions.
As Bonnie points out, ROS "doesn't hop the VFO frequency," but
within the 2.5 bandwidth, it technically is SS. This would be
true if ROS used 300 Hz bandwidth instead of 2.5 kHz, but hopped
about using FHSS within the 300 Hz bandwidth. So I have to agree
the FCC regs are not well written in this case.
Regarding the corollary issue of US/FCC regulations focused on
content instead of bandwidth, I'm not competent to comment.
Jim - K6JM
----- Original Message -----
From: expeditionradio
To: digitalradio@ yahoogroups. com
Sent: Sunday, February 21, 2010 5:09 PM
Subject: [digitalradio] FCC Technology Jail: ROS Dead on HF for
USA Hams
Given the fact that ROS Modem has been advertised as Frequency
Hopping Spread Spectrum (FHSS), it may be quite difficult for USA
amateur radio operators to obtain a positive interpretation of
rules by FCC to allow use of ROS on HF without some type of
experimental license or waiver. Otherwise, hams will need an
amendment of FCC rules to use it in USA.
Sadly, this may lead to the early death of ROS among USA hams.
If ROS Modem had simply provided the technical specifications of
the emission, and not called it "Spread Spectrum", there would
have been a chance for it to be easily adopted by Ham Radio
operators in USA.
But, the ROS modem designer is rightfully proud of the design, and
he lives in a country that is not bound by FCC rules, and probably
had little or no knowledge of how his advertising might prevent
thousands of hams from using it in USA.
But, as they say, "You cannot un-ring a bell, once it has been
rung".
ROS signal can be viewed as a type of FSK, similar to various
other types of n-ary-FSK presently in widespread use by USA hams.
The specific algorithms for signal process and format could simply
have been documented without calling it Frequency Hopping Spread
Spectrum (FHSS). Since it is a narrowband signal (using the FCC
and ITU definitions of narrowband emission = less than 3kHz)
within the width of an SSB passband, it does not fit the
traditional FHSS description as a conventional wideband technique.
It probably would not have been viewed as FHSS under the spirit
and intention of the FCC rules. It doesn't hop the VFO frequency.
It simply FSKs according to a programmable algorithm, and it meets
the infamous 1kHz shift 300 baud rule.
http://www.arrl. org/FandES/ field/regulation s/news/part97/
d-305.html# 307f3
This is a typical example of how outdated the present FCC rules
are, keeping USA hams in "TECHNOLOGY JAIL" while the rest of the
world's hams move forward with digital technology. It should come
as no surprise that most of the new ham radio digital modes are
not being developed in USA!
But, for a moment, let's put aside the issue of current FCC
"prohibition" against Spread Spectrum and/or Frequency Hopping
Spread Spectrum, and how it relates to ROS mode. Let's look at
"bandwidth".
There is the other issue of "bandwidth" that some misguided USA
hams have brought up here and in other forums related to ROS. Some
superstitious hams seem to erroneously think that there is an over-
reaching "bandwidth limit" in the FCC rules for data/text modes on
HF that might indicate what part of the ham band to operate it or
not operate it.
FACT:
"There is currently no finite bandwidth limit on HF data/text
emission in USA ham bands, except for the sub-band and band edges."
FACT:
"FCC data/text HF rules are still mainly based on "content" of the
emission, not bandwidth."
New SDR radios have the potential to transmit and receive wider
bandwidths than the traditional 3kHz SSB passband. We will see a
lot more development in this area of technology in the future, and
a lot more gray areas of 20th century FCC rules that inhibit
innovation and progress for ham radio HF digital technology in the
21st century.
Several years ago, there was a proposal to FCC to provide
regulation by bandwidth rather than content. However, it failed to
be adopted, and ARRL's petition to limit bandwidth was withdrawn
http://www.arrl. org/news/ stories/2007/ 04/27/101/ ?nc=1
Thus, USA hams will continue to be in Technology Jail without
access to many new modes in the foreseeable future :(
Best Wishes,
Bonnie Crystal KQ6XA