NU9N SSB Audio News Editorial - July, 2004 |
| AMATEUR RADIO eSSB TELEPHONY  (What Is Wrong With "Hi-fi SSB" or "eSSB"?)A Brief Retrospect
Amateur Radio has enjoyed a rich history of technically minded individuals who have pursued their passions and aspirations through experimentation of both existing and non-existing technologies. Of all hobbies, Amateur Radio has arguably produced some of the most important technological break-throughs in the art and science of electronic communications, including AM, FM, Television as well as many digital modes of communication. If it were not for the experimental aspect of Amateur Radio and the freedom enjoyed to build, improve and simply "tinker", the science and art of the commercial electronic communications industry would more than likely not be as advanced as it is today. An Observation and Question The face of Amateur Radio has itself changed and adapted in part due to technological advances in electronic circuits (another benefit enjoyed via Amateur Radio experimentation) especially since the introduction of transistors. And more currently because of integrated circuits utilizing "Digital Signal Processing" (DSP) techniques in modern communications transceivers. Modern electronics has made it possible to pack millions of micro-transistors on the head of a penny which would have required a large room in the past, and even then could still not have achieved the results enjoyed today. Signal and audio quality no longer needs to suffer due to inherent deficiencies in electronics technology. So why does it suffer? Why does modern Amateur Radio SSB communications audio sound as bad now as it did 40 years ago? Stereos, recorders, televisions, microphones, processors and a whole host of electronically based products have progressively improved with new technologies... Why not Amateur Radio SSB telephony? Hi-fi eSSB (Extended Single Sideband) Objections There seems to be a built-in resistance by a few Amateurs against any high quality developments in modern SSB technology. This resistance has its roots based in a host of misconceptions about "Extended Single Sideband" (eSSB). Change itself is sometimes hard to accept because tradition is a comfort zone for us. The following is a list of commonly used objections used against Hi-fi SSB operations that I have compiled, numbered and will therefore respond to:
In the scheme above, 3 kHz of audio bandwidth was the chosen criteria or threshold qualifying a signal as eSSB. The reason for this, is that high frequency audio from 3 kHz and above starts to support a significant
difference in clarity, "openness" and fidelity of the audio signal that better reproduces natural energy found in the human voice. Even though vocal chord energy diminishes rapidly above 3 kHz, the all important high frequency
consonants such as the "S", "T", "SH", "CH" "K" and "Z" that are formed with various combinations of the tongue, roof of the mouth and teeth are well above 3 kHz and essential
for high definition speech with less listener fatigue. See the excellent Polycom White paper on: "The Effects of Bandwidth vs. Speech Intelligibility".
Some may argue that the FCC has defined what is "excessive" in Part 97.307. Has the FCC really defined it? Read Part 97.307 very carefully and you will notice language like "necessary", "information rate", "emission type being transmitted" and "good amateur practice" in the text. Let's look at Part 97.307(1) for example, which states the following: §97.307(a) No amateur station shall occupy more bandwidth than necessary for the information rate and emission type being transmitted, in accordance with good amateur practice. Now we must ask these questions: What is "necessary"? What is our "information rate"? "What is our "emission type"? What exactly is "good amateur practice" regarding the bandwidth issue? I will attempt to answer these questions from a Hi-fi SSB perspective: · What is "Necessary"? - More than 3kHz in order to reproduce the desired fidelity of articulate speech · What is the "Information Rate"? - 6000 Cycles / second (6kHz) for 6K00J3E SSB · What is the "Emission Type"? - 6K00J3E as defined in FCC Part 2-201 and ITU-2. · What is "Good Amateur Practice"? - Being considerate of others regardless of bandwidth It is clear to me that the real message of Part 97.307 in its entirety and in the context intended, including power and IMD observances, is simply keeping the signal clean and linear as well as being considerate of other operators already using a specific frequency as to not cause any uncessesary interference. An unnecessarily wide signal will occur if excessive power, excessive modulation or excessive processing is applied resulting in high IMD and distortion. However, any station, whether wide or narrow in audio, can be guilty of these unwanted properties. A well-controlled clean signal can still be 6kHz in RF bandwidth resulting from a clean 6kHz AF source signal feeding a transmitter that can reproduce it. Good amateur practice and 6kHz of bandwidth do not have to be mutually exclusive if the following guidelines are true: · The 6kHz AF source signal is clean and well controlled. · The transmitter can sufficiently transmit 6kHz of RF bandwidth with acceptably low IMD and distortion properties like any modern narrow-band transmitter. · The transmitter (whether stock or modified) has good carrier suppression and good opposite sideband suppression. · The operating frequency selected for a 6kHz transmission is not initially in use by another station within the desired 6kHz passband needed. · It is not operated in a passband where the signal may fall outside of the operator's band edge. · The band of operation is not overly crowded where 6kHz transmissions would not be courteous or practical. Excessive bandwidth problems are no more specifically inherent with Hi-fi SSB than with traditional narrow band SSB transmitters that are not properly adjusted. In fact, you can easily find stations using 2.4kHz transmit filters that in reality are occupying two or three times this in occupied RF spectra because of overprossesing, overmodulation, a mistuned amplifier and poor operating practice.
Broken down, "J3E" means the following: J - Single sideband, suppressed carrier 3 - A single channel containing analog information. E - Telephony (Phone / Voice) No mention of occupied bandwidth is included in this naming scheme. However, a trip to Part 2-201 expands the designator by four more digits that precede the three above. Example of a full alphanumerical designator is as follows: 3K00J3E In this example, the first four characters: 3, K, 0 and 0 represent the specific bandwidth of the mode being used which in this case means 3.00 kHz. The number before the "K" represents the number of thousands of Hz and the numbers after the "K" represents the number of hundreds and tens of Hz, with the "K" representing the decimal separating the thousands from the hundreds as a decimal place holder. A 4kHz SSB mode would be designated as 4K00J3E. A 4.5kHz signal would be designated as 4K50J3E, etc... Therefore, J3E could have a number of different bandwidth possibilities. In other words, the mode designator does not determine the bandwidth, but rather the reverse! The bandwidth determines the alphanumeric designator for mode specific identification purposes!
There is no inconsistency using Hi-fi SSB (eSSB) when the attitudes above are employed. It is no more "immoral" or "unethical" generating a high quality eSSB signal than it is generating a highly processed narrow "DX" signal if the attitudes of the operators are peaceful. Good amateur practice is the use of the VFO to find peace instead of the PTT to start World War III.
The "minimum necessary bandwidth" rule, as reviewed earlier, is again dependent on what you consider is "necessary". This terminology is open to a variety of interpretations based on presuppositions about where you already stand on the bandwidth issue. It is always tempting to interpret rules according to a personal position rather than vice-versa.
A properly aligned transceiver and filter combination, when fed with a properly pre-emphasized audio signal will perform exceptionally well without any added IMD, distortion or splatter. The transceiver and filter(s) used will be the most important factor in determining natural bandwidth and how aggressively it can be manipulated with EQ cleanly. Again, common sense should be used when processing the pre-transmitter audio.
All Hi-fi SSB operations I have monitored and measured have not exceeded 6kHz in one direction or the other depending on which sideband was being utilized. This is perfectly acceptable in ITU-2 emission standards as well as in Canada where 6kHz is specifically mentioned as being "acceptable" and in the spirit of "good amateur practice". 6kHz is the widest bandwidth that any Hi-fi SSB operator would want to use anyway since any bandwidth beyond 6kHz for SSB would not be heard in most amateur receivers! What I am convinced is happening when someone makes a claim that an eSSB signal is 9 or 10kHz wide is an error when calculating the total bandwidth. They erroneously include their receiver's passband width in the count. Let me explain using an example: If you put your receiver on say 14.100 USB and zero-beat a CW signal and then tune up frequency until the signal disappears, you will find the CW signal gone after about 32Hz at 14.103. This would determine the total bandwidth of the signal in question. However, if you tune down in frequency, you will hear the CW signal as far as the filter width in your receiver will allow. So, if you had a filter bandpass of 4kHz selected, you would hear the CW signal 4kHz below zero beat. Does this mean then that the CW signal is 32Hz plus 4kHz wide totaling 4032Hz? No Way!!! Your receiver's band pass is allowing you to hear it, but this is not how to measure the bandwidth of the signal. The receiver's bandpass in the opposite direction does not count when measure the bandwidth of an SSB signal any more than it does when measuring the bandwidth of a CW signal as demonstrated above! So, when measuring an SSB signal's bandwidth, you MUST ONLY measure what you can hear in the direction of the selected sideband; If measuring USB, then tune up and do not count what is below the suppressed carrier baseline. For LSB, it is the reverse. The "10k" report occurs when someone is including the 4kHz bandpass of their receiver in the opposite direction of the 6kHz signal being measured. They think that this therefore means they are measuring 10kHz, when in fact they are only measuring 6kHz plus the 4kHz of their own receiver's bandpass selection. Quite honestly, I have not ran across to many operators who even know how to accurately determine someone's RF transmit bandwidth. Again, when I hear someone tell me that I am "9kHz wide", I know that they are including their 3kHz of receiver bandwidth when they tuned the extra 3kHz on the opposite side of the carrier frequency. Also, signal strengths above S9 in the order of 20dB/9 or above complicate matters when receiver rejection (or the lack of it) comes into the equation. A good quality HP RF spectral analyzer can cost thousands of dollars. And even with an accurate measuring device, great care must be exercised when doing measurements and evaluating the RF bandwidth of someone's signal. I'm sorry, but an ICOM band "pan" display is not even close to being any type of a serious RF spectrum analyzer. It's pretty and gives you a rough idea where band activity is occurring, but that's about it.
The longer version of my response would be to point out how ineffective narrow band SSB really is. Or, going positive, to point out how effective eSSB can be. Any credible audiologist would agree that 2.4kHz or even 3kHz is barely enough bandwidth to accurately and easily interpret speech. While it is true that 2.4kHz SSB bandwidths have been used somewhat successfully for years (with added phonetics required for communication accuracy) we take for granted what that success is largely attributed to... Our brains! (See an excellent "Polycom White Paper" on this subject!) The human brain is wonderful at deciphering low bandwidth speech audio into meaning. With narrow bandwidths being used, the brain must work extra hard to fill in the missing audio gaps and give the speech some meaning. While our brains are great about doing this, it is also quite fatiguing and after awhile, quite frustrating! If you have ever wondered why listening to a wider and more natural sound is calming, it is because your brain is not constantly trying to figure out if it just heard a "C", "T" or "P". This is why we have resorted to a "phonetic" alphabet. Have you ever had to use phonetics when talking with someone in person? Of course not! We could go into a phonics discussion here in great detail, but I think it is sufficient to make a point using a hypothetical scenario - If your life depended on a critical communication without any time for repeats and lengthy phonetics, wouldn't you want a Hi-fi communication to take place? I sure would!
What is ironic about these kind of remarks is the fact that I receive dozens of e-Mail's a week from those interested in becoming FCC licensed amateur radio operators so that they can experiment with high quality audio. The ARRL should be thrilled about attracting new blood to keep this hobby of ours alive since there are more hams becoming silent keys than those entering the fraternity. And with stiff competition from other forms of communications media like voice over IP, cell phones and chat-rooms via the Internet, there needs to be something that creates excitement other than DXing since these young people can virtually "DX" on their Internet connections every day!
Another possibility is that a station listening to a Hi-fi SSB transmission may be slightly off frequency. Even 10Hz of miss-beat can cause a strange sound due to the low frequency energy being transmitted and received. Miss-tuned low frequencies sound strange indeed. Without explaining why, simply re-tuning to "zero-beat" the signal will more than likely solve the problem. I find that many amateurs need a lesson in properly zero-beating SSB signals anyway. Tuning in a Hi-fi SSB station is a perfect way to practice! A well-processed Hi-fi SSB signal, when heard in the proper bandwidth and tuned properly, will sound outstanding! You really have to hear it to believe it and appreciate it. As I once heard it put, "It's like comparing an old 19'' black and white television set with a modern 60'' plasma HDTV home theater system!"
I will argue to the day that I die that Hi-fi SSB modulation is a worthy and credible cause toward improving the quality of the amateur radio experience. Furthermore, it has gained wide acceptance, as can be heard on any band, where operators are becoming more critical of their audio quality than ever before. Additionally, the art and science of developing a well controlled high fidelity SSB signal employing modern audio processing makes for a better rounded amateur radio operator. Not everyone will be interested in this aspect of the hobby, and that's fine. But for those who want to be better educated in the art and science of audio processing, the journey is a rewarding one and one that will bring back a sense of pride knowing that everything possible has been accounted for in producing a fine signal. This includes proper grounding, cabling, RFI suppression, AC distribution, antenna orientation, feedline maintenance, oscilloscope waveform monitoring and analysis, etc... Is this not in keeping with the spirit of amateur radio?
Frequencies above 3kHz play a major part in articulating the "S", "T" and "C" sounds as high frequency air passes through the top of the tongue and roof of the mouth. The "K" sound is produced between the back of the tongue and the roof of the mouth. And the "F" sound is produced between the lower lip and bottom of the front teeth. While it is true that the vocal chords do not produce any appreciable energy above 3kHz (other than some high frequency air that slips through) the sounds from the vocal chords are only a part of the overall speech process. The other sounds mentioned above rely on different parts of the mouth containing very important fundamental high frequency components. There has been much research done on this topic. If some Internet investigations are done, we can find many articles on the subject. (View an excellent "Polycom White Paper" on the subject by clicking here.. One additional note about "Useful Bandwidth"; If it were true that speech frequencies above 3kHz were non-existent, or not evident enough to be concerned about, then transmitting a 4 to 6kHz bandwidth should not cause any interference right?. If my useful speech components ends at 3kHz, and someone is listening 4kHz away, then they should not be bothered by frequencies transmitted beyond 3kHz, (regardless of how wide I have my transmitter bandwidth set) since they do not exist or are attenuated by 30dB or more. Obviously, this is not the case, since someone only 4kHz away would certainly hear my 6kHz passband, since I do have substantial speech information in the overlapping 2kHz. One additional note about "Useful Bandwidth"; If it were true that speech frequencies above 3kHz were non-existent, or not evident enough to be concerned about, then transmitting a 4 to 6kHz bandwidth should not cause any interference right?. If my useful speech components ends at 3kHz, and someone is listening 4kHz away, then they should not be bothered by frequencies transmitted beyond 3kHz, (regardless of how wide I have my transmitter bandwidth set) since they do not exist or are attenuated by 30dB or more. Obviously, this is not the case, since someone only 4kHz away would certainly hear my 6kHz passband, since I do have substantial speech information in the overlapping 2kHz.
What hs happened to the amateur radio spirit of exploration, experimenation and just making things better or at least interesting?
An interference problem occurs when an eSSB QSO has been in progress and someone else moves into the operating passband. The eSSB operator that initially secured the frequency is told by the station that moved into the passband that they are being interfered with. If the station that moved in doesn't happen to approve of eSSB, they will argue that they should not have to move more than 3kHz away to avoid interference, therefore claiming rights to the frequency they selected. I have seen this scenario too many times! eSSB operators NEVER intentionally interfere with existing QSO's. Great care by eSSB operators is taken to find a clear 3, 4, 5 or 6kHz non-occupied frequency segment. Because this is a shared service, a little common sense must be used to avoid these kinds of conflicts. The best solution I can think of is one that has been in place ever since the humble beginnings of amateur radio; Turn the VFO knob until the QRM disappears! Profoundly simple, but extremely effective! Besides, no one has ever guaranteed that this would be an interference free service.
a) Define or even find "Communications Grade Audio" in the FCC Part 97 Rule Book. b) The FCC has defined broadcast audio bandwidth at 9.7 kHz of audio or 20 kHz RF @ -30dB point c) Broadcast Radio in the medium wave band is for communications... what else? d) What's wrong with improving communications accuracy and lessening listener fatigue? e) As long as we are "Communicating" with one another, we're using "communications audio" ... Duh! f) "Broadcasting" is a one-way communication - we receive also so there's no "Broadcasting" involved. g) "Broadcast Audio" has many bandwidths... 9.7kHz, 4.5kHz, etc... So does amateur radio! So what? 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! A Closing Argument What is wrong with "Hi-fi SSB" or eSSB? - Nothing at all. It is legal. It can coexist with current operations if given a chance. It can be clean and beautiful sounding. It promotes research and careful execution of the modulation process and demands good engineering practice as to avoid distortion, RFI and Hum problems. eSSB operators focus on audio quality so distortion is certainly not desirable or acceptable at all anyway. You will find the most spectrally clean amateur stations on earth where you find eSSB stations! Hi fi SSB bandwidth is going to be somewhat wider than traditional SSB bandwidth to support the fidelity required for articulate speech and natural vocal reproduction. This is a normal requirement for those pursing extended fidelity and is not a result of splatter, distortion or IMD artifacts. Remember, based on the definition of "distortion" as given above, it can be argued that a 2.4kHz or even a 3kHz SSB bandwidth is inherently a distortion of the original speech source. The distortion is quantified by the enormous differences between the natural voice entering the microphone and the resulting demodulated audio on the receiving end. Therefore, it can be said that Hi-fi SSB transmission and reception is a worthy attempt to restore, in a practical manner, some of the original fidelity of the source speech by using equipment and techniques to keep distortion to an absolute minimum. How can this be a negative attribute or an unworthy cause for the betterment of amateur radio? In summarizing, I think that FCC Part 97:1(b), (c) and (d) speaks for itself: FCC Part §97.1 - Basis and Purpose of the Amateur Radio Service (b) Continuation and extension of the amateur's proven ability to contribute to the advancement of the radio art. (c) Encouragement and improvement of the amateur service through rules which provide for advancing skills in both the communications and technical phases of the art. (d) Expansion of the existing reservoir within the amateur radio service of trained operators, technicians and electronic experts. It is time to bury the anti-SSB Hi-fi audio hatchet and get out the diplomatic hammer and nails to start building each other up instead of hacking each other apart. We are all in this together... Let's choose to respect and have tolerance for each other, or at least agree to disagree without being disagreeable! And, therein lies the real definition of "good amateur practice"! 73, -John Anning, NU9N |
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John M. Anning - NU9N
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