21.03.2010 - La ESSB, nuova frontiera della sperimentazione OM?

We all need to be on the same page when referring to terms like this. 2.7 kHz of bandwidth will always sound like 2.7 kHz of bandwidth, no matter how aggressive we process it, or "enhance" it. Can it sound better than non-processed 2.7 kHz SSB? You bet! But it will NOT be "eSSB" that supports critical frequencies in human speech found above 3, 4, 5 or 6 kHz. Anyone can boost bass frequencies in a 2.7 kHz bandwidth... But that really doesn't produce the definition, fidelity and "openness" of a true "eSSB" signal as defined. That would only produce a modestly "Better Sounding Single SideBand" (BSSB)... HI.

To conclude, I just would like to keep the record straight regarding eSSB... I'm just concerned that what we all have been working hard for, doesn't end up in the toilet, where the ARRL can conclude that a 3k SSB bandwidth limitation (or less) would still support eSSB operations. IT WILL NOT !!!


Questions about eSSB

Should You Even Consider eSSB or Not?
If your desire is to have a more pleasing and natural sound than that of conventional SSB practice and a persona that is rich, smooth and highly defined, then you should consider eSSB. If you desire audio that does not sound like it originated from a tuna can, the bottom of a barrel or from the song "Winchester Cathedral, then eSSB may be for you.

However, if it is your desire is to "Cut" through QRM and bad band conditions, break a DX pileup or have contest grade audio, then forget about eSSB...it is definitely not for you! Stay with your Yaesu FT-1000-D and Heil HC-4... You will be much happier!


Are There Any Real Benefits To eSSB Hi-fi Transmissions and Reception?
eSSB Hi-fi has many benefits, the most noticeable being a very pleasing and highly defined sound not inherent with traditional SSB audio. Also, it only occupies 1/2 of the bandwidth required by AM for the same audio quality, since SSB is a Single Sideband Suppressed Carrier mode vs. AM, which is a Double Sideband with Carrier mode and is therefor a more efficient signal and less subjected to the phasing and selected fading problems inherent with its AM counterpart.

Additionally, if you will be pursuing eSSB, you will also inherently be pursuing a clean, low distortion signal with low I.M.D characteristics, simply because you will not want these artifacts on your hard earned audio since it sounds bad, and this is, after all, why you are pursuing eSSB audio in the first place... To sound good!. This dimension alone will make you a better operator through experimentation that leads to engineering practices and technical excellence throughout your station such as RFI suppression techniques, cabling, grounding and in-depth equipment adjustments as well as many other factors that lead to a high quality signal. This will definitely expand your knowledge and harness skills otherwise not realized with simple plug-and-play SSB operations practiced by most.


Why Use More Bandwidth Than 2.4 or 2.8 kHz?
The simple reality here is this: Audio fidelity is directly proportional to audio bandwidth. And, with a clean SSB signal with low distortion and I.M.D., SSB RF bandwidth will be directly proportional to audio bandwidth.

Because of the way that our ears work, and the different audio frequencies that are supported by wider bandwidths beyond 2.4 kHz, the ability to reproduce certain sounds (especially high frequencies) becomes more realized as the bandwidth of a signal increases. For example, with a 2.4 kHz wide signal with a carrier set point adjusted for 200 Hz (200 Hz being the lower end limit of the total bandwidth), the highest frequency that will be heard will be at 2.6 kHz. While 200 Hz ~ 2.6 kHz will arguably suffice in reproducing the main envelope of human speech for intelligence and for bare minimum communications requirements, it hardly qualifies as a way to communicate accurately with any of the inherent frequency components found in the original signal that entered the transceiver, let alone the original voice itself.

As the bandwidth of a signal increases, improvements can be heard, making the audio sound more like the original source audio. When the bandwidth is increased from 2.4 kHz to 3 kHz, 600 Hz of the upper voice energy is recovered. Likewise, when the bandwidth is increased from 3 kHz to say 4 kHz, 1000 Hz of the voice's energy is recovered.

You may ask why 4 kHz of bandwidth or beyond is needed when arguably the voice can be sufficiently reproduced at 2.4 kHz as mentioned above? Hasn't 2.4 kHz been good enough for years? ... Well my answer would be a question; Is 2.4 kHz sufficient to produce the human voice accurately? My answer to that would be an emphatic NO! And just because is has been "good enough", doesn't mean that we shouldn't pursue some improvements. Isn't that, after all, in the true nature and spirit of Amateur Radio?

There are certain consonants that are very frequency dependent. For example, "S" and "F" will sound almost identical in a 2.4 kHz bandwidth limitation, as well as letters like "M" and "N" and also "C" and "E". When we look closely at the speech characteristics of a letter like "C" or "S" for example, there are natural components generated that are much higher in frequency than what the vocal cords are producing because of the "SSSing" sounds made by the tongue and roof of the mouth, producing high frequency air making up part of the speech process. If these frequencies contained in letters like "S" and "C" are suppressed, what we are left with are words that sounds like "shame" instead of "same" and "hey ho" instead of "say so", "hell" instead of "tell" or "J3AEM" instead of "KT8TN". Get the picture? For more on this, an excellent "White Paper" article on this by Polycom is available. Also see "Broadcast Chain Tutorial" by Martin Wolters.

There is even more however... There are those who claim that there is no appreciable energy in the human voice beyond 3 kHz. I guess it would depend on how we define "appreciable". However, there is definitely energy above 3 kHz, and it is more than just harmonic energy as opposed to what some would argue. Look at the spectral graph below where I measured my own voice in a flat 20 Hz ~ 20 kHz environment using a good flat condenser microphone. You will see the energy content in my voice well above 3 kHz... Also notice that the human voice is not flat, but rather decreasing in amplitude as frequency increases.

As you can see, I have some natural and dominant high frequency excitation occurring at 4kHz and 7.5 kHz due to the "SSSing" sounds as described above. If we remove these frequencies, especially the 5 kHz components of my voice, the 3 kHz component must carry the information by itself. Is a 5 kHz bandwidth required for the communication to be understood? Of course not. If I would have included the word" accurately" in my question, then the answer would be yes. I am only pointing out how we take for granted the natural energy that is really inherent with normal and natural speech! In my case (as with most male voices), a bandwidth of 4 ~ 5 kHz would catch the lower end of "SSSing" intelligibility before using the full bandwidth necessary for accurate reproduction that occurs at about 7.5 kHz. This is where the AM mode has it hands down when accurately reproducing full speech characteristics. The problem with AM however, is that to reproduce 7.5 kHz of audio with accuracy, the RF bandwidth would be required to be 15 kHz wide! (7.5 kHz x 2 sidebands = 15 kHz). For this site, we will stick to eSSB and RF bandwidths at or less than 6kHz.


Is Any RF SSB Bandwidth Beyond 3 kHz Legal?
The simple answer to this is YES! There has been much debate over this one. Debate it all you want. The simple fact is, THERE ARE CURRENTLY NO BANDWIDTH RULES stating hard numbers for the HF Amateur Radio service concerning A3A, J3E etc...! Look at Part 97 a thousand times if you like. YOU WILL NOT FIND A BANDWIDTH FORMULA OR RULE in place. All you will find, are some very subjective and gray guidelines regarding "minimum bandwidth necessary". We could debate the meaning of words like "necessary", "quality desired", etc... all day long and not reach an agreement. This is where the vagueness of Part 97 gets a bit sticky. I have seen Amateurs debate this until Hell itself dropped 1000 degrees in temperature! HI. Let's stop this debate for awhile and just use some common sense...
Read on...

The real questions is this... Is it always a good idea or acceptable to use more than 4kHz of bandwidth? Again the answer to this is simple... NO! If a band is very crowded, and there is nowhere to squeeze in a signal that is 6 or 5 kHz in bandwidth without interfering with someone else, then common sense and common courtesy would obviously apply here. Narrow it down to 4 kHz or less and I'm sure that most operators will be okay with this. We do have to compromise at times and Amateur Radio is no different than any other area of life where people are involved. If you can produce a good clean 4 kHz of RF and audio bandwidth, you will already be narrower than most SSB stations using 2.4 kHz of audio who's splatter and I.M.D. occupy twice that or more!


FCC-DA-04-3661A1 Ruling on RM-10470
The FCC Rules on Occupied Bandwidth:
The following is an exert taken directly from the FCC ruling "FCC-DA-04-3661A1" regarding the ruling on "RM-10470" that was a petition filed by W4MDL (ex W0YR) and W6FDR who wanted a ruling made that would limit SSB bandwidth at 2.8kHz and AM at 5.4kHz. The FCC response was as follows:

I. BACKGROUND

9. We have carefully considered all comments filed, including comments filed in support of the Petition, and some alternative proposals. We conclude that Petitioners' request for an amendment of our rules is inconsistent with the Commission's objective of encouraging the experimental aspects of amateur radio service. The Petition also fails to demonstrate that a deviation from the Commission's longstanding practice of allowing operating flexibility within the amateur service community is either warranted or necessary. In this regard, we note that most operators use the amateur service spectrum in a manner consistent with the basic purpose of the amateur service. Further, we believe that our existing rules -- including the provisions that no amateur station transmission shall occupy more bandwidth than necessary for the information rate and emission type being transmitted, in accordance with good amateur practice, and that emissions outside the necessary bandwidth must not cause interference to operations on adjacent frequencies -- are adequate to address any noncompliant practices by amateur operators.

10. Regarding Petitioner's request that amateur stations transmitting emission type A3E not be authorized to occupy more than 5.6 KHz bandwidth on amateur frequencies below 28.8 MHz, we agree with commenters who note Petitioners have not demonstrated there to be a particular problem with stations that transmit AM emissions. Moreover, the Commission has previously declined to restrict bandwidth for AM because to do so would be inconsistent with the basic purpose of amateur service and our desire to offer amateur operators the opportunity to experiment with various types.

11. We continue to encourage amateur operators to act in good faith in the exercise of their operations as required by Section 97.101(d) of the Commission's rules,41 which provides that no amateur operator shall willfully or maliciously interfere with or cause interference to any radio communication or signal. The Commission's Enforcement Bureau will continue to monitor nonconforming activities of operators not abiding by the Commission rules through its complaint process. In instances of willful and malicious interference, the Enforcement Bureau will not hesitate to take appropriate action. In sum, we are not persuaded by Petitioner's claims that bandwidth restrictions are necessary, and, therefore, deny the Petition.

12. IT IS ORDERED that the Petition for Rulemaking, RM-10740, submitted by Michael D. Lonneke and Melvin J. Ladisky on May 27, 2003, IS DENIED. This action is taken under delegated authority pursuant to Sections 0.131 and 0.331 of the Commission's Rules, 47 C.F.R. §§ 0.131, 0.331.

FEDERAL COMMUNICATIONS COMMISSION
Michael J. Wilhelm
Chief, Public Safety and Critical Infrastructure Division
Wireless Telecommunications Bureau

As indicated above, the petition died a horrible death not only with the FCC, but with 85% of the amateurs who responded in the comment filing period. This was the correct decision made by the FCC and amateurs. This documented decision restored my faith that the Commission has not lost site of the basic purpose and mandate of the amateur radio service. Good call guys!


Is eSSB Really Necessary?
eSSB Hi Fi Audio is not absolutely necessary unless you consider accurate speech absolutely necessary. But other than emergency communications, is anything we do in Amateur Radio really necessary? No! Is DXing necessary? No! Are contests necessary? No! Is SSTV, FSTV, FSK, RTTY, Packet, AM, FM, SSB, Moonbounce, Satellite communications, Rag Chews, Nets or CW really necessary? No No No !!! So, who decides what has priority? I may be getting a bit philosophical here, but it seems to me that other than an emergency communication, NO ONE SHOULD HAVE SPECIAL PRIORITY OVER SOMEONE ELSE. And if they do, by what authority do they get their special privileges or priority? This is a shared service folks. I'm willing to share, I just hope that others not involved with eSSB are as well, despite their non acceptance of it. It's just another aspect of this great hobby of ours that should be treated as valid and with the same respect and credibility as any other interest in Amateur Radio!.

eSSB - Love it or hate it, it's here to stay! - If you have never experienced eSSB, you might be suprised with how much enjoyment you could receive with this extended mode we call eSSB.

Fonte: http://www.nu9n.com