It's very clear from the beggining of the FCC rulebook that "Advancing the State of the Art","Technical Skills", "Becoming technicians and electronic experts" is at the top of the desired effect of the Amateur Radio service! Let us never forget this important and fundamental philosophy of "HAM RADIO" !!!
Remember, experimentation and exploration of this electronic art is at the very core of Ham Radio...
The rules decare it so !!
Just What is "Hi-Fi" & "Extended SSB" (eSSB)?
These terms can be somewhat confusing since true "Hi-fi" is an old stereophonic audio term referring to true High-fidelity audio - e.g. 20Hz ~ 20kHz of flat frequency response with very low Total Harmonic distortion (THD) and good Signal-To-Noise (S/N) characteristics. By this definition, any Amateur Radio transmission hardly qualifies as true Hi-fi
However, speaking in a relative fashion as compared to standard SSB practice, I would like to define the terms we use as follows in the table below as a reference only:
eSSB = Extended Single Sideband
Note: "Extended SSB" or "eSSB" is any J3E SSB transmission that exceeds the audio bandwidth of standard or traditional 2.9kHz SSB J3E modes (ITU 2K90J3E) starting at 3kHz (ITU 3K00J3E), in order to support the fidelity required and desired for relative high fidelity, full range clean and articulate vocal audio. - See table below:
SSB & eSSB EXAMPLES
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".
Before diving into this, let's review a few basic fundamentals of received signals... Keeping in mind that the audio signals from your transceiver have been demodulated from your receiver's I.F. section, and that your receiver's I.F. signals have been demodulated from your transceiver's R.F. section, what you hear are the resulting demodulated R.F. signals your transceiver receives after filtering and several signal conversions. Therefore, anything you hear, has originated from R.F. as far as your transceiver is concerned and conversely, any R.F. within your receiver's filter and circuit passband will be demodulated to A.F. In other words, the A.F. spectrum analysis shown below is directly proportional to the R.F. spectrum that was demodulated to A.F., including any I.M.D. products, as discussed later.
A HYPOTHETICAL SCENARIO:
If an R.F. signal would have 10kHz artifacts, it would be demodulated to 10kHz artifacts in your receiver's audio section, that is, if it could hear a 10kHz wide signal. If your transceiver, for example can hear out to, say, 3kHz USB, and someone was transmitting a 10kHz wide USB signal, you could still hear their 10kHz USB passband, but only in 3kHz USB receiver passband segments. If you were zero-beat with them, you would hear from about 100Hz up to 3kHz of their total bandwidth. If you tuned up frequency (USB) by 3kHz, you would still be hearing a 3kHz segment of their passband... from about 3 ~ 6kHz of the original TX passband. With a 3kHz receiver listening to a 10kHz transmitter, the receiver would have to tune up 7kHz above the transmitter's fundamental frequency to hear the last full 3kHz segment of the 10kHz passband. You would have to tune up about 9.9kHz to hear the last 100Hz of the 10kHz passband. Beyond 10kHz, it would disappear as your receiver filter skirts and the transmit filter skirts would be to far apart to be demodulated by your receiver. For a 6kHz USB transmitted signal, the 3kHz USB receiver would loose the signal after tuning up by 6kHz as the receiver moves out of the total TX passband. This is assuming the original 6kHz wide TX signal is clean, the receiver has reasonable selectivity and the signal strength is not in excess of some ridiculous S9 +40dB level.
With this in mind and some fundamentals aside, and assuming you can hear a 3kHz passband, and I could transmit only up to a 6kHz passband, then you would hear the last 100Hz of my transmitted information at about 5.9kHz above my fundamental frequency as mentioned above. My extreme high SSSing frequencies at 6kHz would sound like a bassy 100Hz "chunk-chunk-chunk" sound to your receiver and this would be normal under perfect circumstances.
This is NOT splatter, I.M.D. or spurious radiation, but rather two station pass-bands overlapping in the A.F. - I.F. - R.F. - R.F. - I.F. - AF modulation to demodulation transmitter to receiver process. If I.M.D. were present, the demodulated RF to AF spectral display would reveal the I.M.D. in the audio base-band on a receiver with sufficient receive bandwidth. Harmonic content (3rd order, 5th order, etc...) fall well outside of the amateur bands, or at worst, on another amateur band... but not on the same band. All of the complaints that I and others have experienced have been based on what has been "heard", not what has been measured on an RF spectrum analyzer. And again, what is "heard" is what has been demodulated from the R.F. source. If there are any harmonically related issues, this would be a separate topic and not an artifact that anyone is hearing within 10kHz of the TX passband!
Of course, there are more variables in this scenario as well... signal strength, and receiver performance. If relative signal strengths exceed S9 + 30dB, receiver "front-end's" have a harder time dealing with the overload characteristics. And this is where receivers vary from manufacturer to manufacturer. Some are better than others regarding selectivity vs. sensitivity.
After doing a complete real-time spectral analysis of my on-air station, I have documented the resulting data below with some explanations and philosophies regarding the relevant issues at hand. Click here to hear an MP3 demonstration of the attenuation properties of the transmit audio above 7kHz.
Note: the spectral information provided below was obtained via a TEN-TEC RX340 commercial DSP receiver using a flat 10kHz receiver bandwidth selection.
Here are the test results, graphs and data, of my spectral measurements using my complete audio rack system, Kenwood TS-850S and Kenwood DSP-100 into my Heathkit SB200 amp (500w) and TH7 antenna on transmit and a borrowed commercial TEN-TEC RX340 receiver with a dead-flat 10kHz receive bandwidth so that my entire TX passband can be viewed in it's entirety:
1kHz ~ 10kHz Close-up of above graph
AF Spectral Analysis
Based on a 100Hz, 0dB measuring reference point:
If I would have choose 1kHz (as is most often done) as my 0dB measuring reference point, then the table data would look like this:
As observed from the graphs, my AF/RF energy falls steeply after 6kHz and well into the average noise floor by 7kHz depending on the intensity of the noise floor. To hear this, listen to the mp3 file demonstration I recorded with a second receiver with no noise floor. This is well within any spectral requirements as vaguely (and arguably) defined by FCC Part 97 rules and regulations for the United States. 6kHz and beyond SSB bandwidths are not illegal !!! (Outside of the United States, check your local communications management authority or ITU region agreements.)
In creating these graphs, there was absolutely no noise floor because of the direct transmitter to receiver setup I used to do direct measurements. The average noise floor would be at -50dB relative to these graphs scales and the way in which I calibrated.
The problem is how the wider SSB transmitter pass-bands are interpreted by the receiving station, listening in 3kHz or less. The average listener has not been educated to understand this wide/narrow scenario, although some common sense will apply here. This overlapping TX/RX passband effect would essentially be the same as a 2.4kHz transmitting station and 2.4kHz receiving station only 2kHz apart in frequency. Everyone has experienced this at one time or another, and is frustrating for both parties involved. (See the illustration below)
I have had a few listeners, using ICOM's with the spectral pan displays, report to me that I was occupying as much as 10kHz of bandwidth. The popular ICOM rigs with the spectral pan displays are anything but accurate in determining precise frequency and amplitude relationships and were only designed to give the operator a general idea as to where the band activity is at. These displays cannot measure relative amplitude like a true RF analyzer in the $20,000 price range, or even a good computer based audio spectrum analyzer where frequency and amplitude measurements are excellent! And to make matters worse, these ICOM pan displays are probably subject to the same AGC properties found in the receivers that will always try to show equal amplitude even with signals that have real +20dB signal differences! In fact, I know of a 3kHz transmitting station that was told by someone using an ICOM pan display that he was in excess of 4kHz wide... That's an amplitude - frequency measurement error of 25% and probably displays even greater errors logarithmically as true bandwidth increases! It has also been reported to me that these displays will display a pure unmodulated carrier (virtually 0Hz wide) as being 2kHz wide! These pan displays are certainly no way to properly analyze a signal's frequency and amplitude, as they are nothing more than relative visual aids for band activity, not measuring tools!
As explained above, the "Chunk Chunk Chunk" sounds, as a listener tunes 5 to 6kHz above the fundamental frequency (if USB is used), is nothing more than their receiver capturing and demodulating part of the upper passband segment of the transmitting station's high frequency content in their receiver's lower passband limit. Simply put, the transmitting and receiving stations are overlapped.
For an illustration of this, look at the following scenario where a receiving station with a 3kHz receiver passband is tuned 4.5kHz above a 6kHz wide transmit station on USB...
If you could slide the green receiver passband over to the right by another 1.5kHz, placing the receiver at 14.206, only a small overlap region would remain and very little pickup by the receiving station due to passband selectivity. If you were to slide the green receiver passband to the left by 1.5kHz, placing the receiver at 14.203, the full 3kHz passband of the receiver would hear the upper 3kHz passband of the 6kHz transmitting station. In either case, if the receiver passband is overlapped with this red area, the receiver will hear the lower, mid or upper portion of the 6kHz TX passband as the receiver travels through the red area.
Regarding opposite sideband suppression, (or energy in the 'wrong sideband' as some have said) I find that the 850S w/DSP100 achieved better than - 60dB of opposite sideband suppression. The correct way to measure this is to zero-beat a station that's on USB, then change to LSB and note your relative signal strength of the LSB as compared to USB and then do the math. Example: S9 + 40dB on USB, S6 on LSB would be a -58dB difference, using the 6dB/S unit methodology. That would be -40dB + ( -6dB x 3 ) = -58dB. The Kenwood TS-850S with the optional Kenwood DSP-100 well exceeds any ITU/FCC regulations for true SSB criteria. Doing this on a 4kHz + transmitter with analog only filters would result in terrible opposite sideband and carrier suppression due to the way that carrier points are handled in the analog domain. This is not to say that a 4kHz + wide analog rig wouldn't sound great... It would. But, to really accomplish a wide analog SSB signal with good carrier and opposite sideband suppression would not be practical or very affordable by time you had the special filters cut and the engineering done by someone who really knows what their are doing! Transmitter/Receiver Digital Signal Processing (DSP) can truly accomplish some amazing feats that simply cannot be done easily or cheaply with analog equipment.
MOTIVATION FOR EXTENDED-BAND SSB vs. AM
There are those of us who are experimenting with 6kHz wide-band SSB and enjoying near AM quality audio via Single Sideband without the AM artifacts, (i.e. Double Sideband with Carrier). We could, legally, do 6kHz wide (or more) AM anywhere on 20m if we wanted to, but then other stations would have to contend with annoying carriers and heterodyning effects that SSB was designed to eliminate in the first place. By the way, SSB was not developed specifically to be narrow in order to squeeze more stations on the band (although this was one of the attractive attributes about it) but rather developed to relieve the bands of the annoying heterodyning and poor efficiency of AM. It has been argued that SSB was developed as a "spectrum conscious mode" Again, this was not the original intent, but certainly has this benefit since a given SSB signal requires only one half of the RF bandwidth of AM for the same audio bandwidth response. See the illustration below:
Additionally, SSB technology presented some cost benefits over AM as well. AM requires twice the RF bandwidth to achieve the same audio bandwidth of that generated by SSB. However, original pre-DSP analog
SSB technology was inherently deficient in exceeding 3kHz because of opposite sideband and carrier suppression problems due to carrier-point placement and cost of the filters and engineering needed to achieve wider bandwidths. This is no
longer the case due to advancements in technology, a.k.a. DSP! Also, wide band digitally processed SSB is a much more efficient way of amplitude modulation than AM ever was! Again, for a true AM signal to have the same
audio information and quality as a 6kHz wide SSB signal, it would have to be 12kHz wide! ... 6kHz USB plus 6kHz LSB and a carrier, which would, by the way, be perfectly legal to do.
Receiver Bandwidth of the receiving station is critical to how the listener will perceive what they are hearing. Those who try to listen to the wider SSB signals in their 3kHz or narrower receivers will, unfortunately, not hear or appreciate the higher fidelity audio achieved by the wider transmitting stations. Those of us who engineer our Hi-fi TX audio can also receive it. Those who cannot receive it will probably not appreciate what we're doing... or why, most likely. The best they can do is respect this aspect of the hobby, allowing for enthusiasm and experimentation, even though they are not participants, and/or agree with activities they don't personally endorse, like many other aspects of the Amateur Radio hobby.
No filters have been "ripped out" of the Kenwood TS-850S, nor has the equipment been "hacked-up" electrically to produce wide transmitter characteristics. The 850/DSP100 combination can do this easily, as per the instruction manual (even 12kHz Double Side Band - which is also legal) and has been FCC type accepted and approved!
Operators who complain that we "hacked-up" our radios to produce broad signals have a weak argument. Capable bandwidth is a manufactures issue, not the users. We hams must follow part 97 of the FCC regulations. However, building and modifying gear is the very soul of ham radio experimentation. How many operators have built their own transmitters, receivers, linear amplifiers and tuners? - Many!
In all fairness to the Amateur Radio fraternity, I try to be sensitive to those who are operating close to my frequency as to not cause interference. If an operator has occupied a frequency above me within 6kHz (USB) before me, I will narrow my TX bandwidth accordingly, or look for a clear 6kHz window before I operate wide. But I must point out, that if I secure a clear 6kHz window, and someone moves into my TX/RX passband, they are interfering with me! Amateur Radio frequencies are still "First Come First Serve" and should be respected by all... wide or narrow. There is no definitive, maximum 3kHz SSB limitation rule found anywhere in the FCC Part 97 rules and regulations! The FCC rule of relevance here is FCC Part 97.307(a) which states:
FCC Part 97.307(a)
"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." (Emphasis mine)
This text is very subjective and has been left wide open on how the phrase "necessary bandwidth" is interpreted. To better understand this definition, we need to travel to FCC Part 2 which defines "necessary bandwidth" as:
FCC Part 2
"...the width of the frequency band which is just sufficient to ensure the transmission of information at the rate and with the quality required under specific conditions." (Emphasis mine)
As you can see, there is a "quality" criteria variable here, which for some may be interpreted differently than by others. This FCC verbiage can be very tricky to interpret at best and almost impossible to ultimately standardize for everyone!
This is why we need to work out the details and conflicts among ourselves - leaving the legal experts to spend their time in the courtrooms, and letting us spend our time enjoying Amateur Radio instead! I'm confident that we can all get along, while at the same time enjoying our individual interests and aspects of the Amateur Radio service. I'm certainly willing to try! Life is just to short and Amateur Radio to rewarding to waste time complaining and arguing with one another about such trivial issues.
Also, the "Emission Type" is another one of those terms that can be very ambiguous in definition. Technically, SSB is referred to as J3E. 3kHz wide SSB is referred to, technically as 3K00J3E. 4kHz wide SSB is referred to as 4K00J3E. 4.5kHz wide SSB audio would referred to as 4K50J3E, etc...
For more on emission standards, click here to see the FCC Part-2-201 PDF document.
After reading the whole document, it is clear that the interpretation of 47 CFR 2.202(b) is to reflect the *minimum* necessary bandwidth sufficient to "... ensure the transmission of information at the rate and with the quality required for the system employed." So, it would appear that this rule simply establishes a *minimum* threshold, not a *maximum* bandwidth for the desired communications. It also appears to me that the "Table Of Necessary Bandwidths" gives us a criteria for determining the correct alpha-numerical designator as seen in the table reference.
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:
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!
THE BOTTOM LINE
Hi fi SSB / eSSB has been missunderstood by many. The intent and passion we have for Extended-band Hi-fi is derived from the desire to produce the highest quality, cleanest pure SSB modulation within reason. It's very exciting to me, that the quality issue is once again being addressed as opposed to the quantity (i.e. - lets jam as many people on the band as possible no matter how bad it sounds) philosophy. If we really wanted to jam as many operators on the band as possible, then maybe we should all narrow our transmit bandwidths to 2kHz, or even 1.5kHz! Heck, why stop there, let's just abandon phone altogether and work CW in a 250Hz bandwidth!!! I don't think this would be a very attractive solution to attract newcomers, or for those who think "The More The Merrier" is the way to reach Amateur Radio nirvana... We all know better!
None of us want to intentionally or maliciously interfere with anyone, but simply enjoy high quality modulation and the experimentation that has been at the heart of Amateur Radio since it's humble beginnings.
The following is a repeated excerpt from my "Introduction" page regarding this philosophy:
73, and may you enjoy your personal preferences and aspects of this wonderful world of Amateur Radio, no matter how different or unacceptable they may seem to others.
I would like to thank the following gentleman for their input, assistance, critique and technical skills.
They have been a tremendous help to me in the final revision of this document:
W9AC - Paul
W5JAY - Jay
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