NU9N eSSB Audio News Editorial - April, 2008
eSSB — Somewhere Between SSB and AM

NU9N News Blog - April, 2008

Quality AM Audio

Those who remember "The Good Old Days" of AM, should also remember generally how good it sounded.

AM is still a viable mode for many and the only mode of preference for some. There are many reasons for this, but the one that I would like to focus on for the moment is the quality of the modulated audio on AM.

It is generally accepted and expected (for whatever reasons) that AM audio response will occupy more bandwidth per sideband than that of SSB. It is not uncommon to find AM stations occupying 8kHz of RF bandwidth (4kHz of audio on each sideband) or even considerably more. An AM transmitter capable of 6kHz of audio bandwidth will occupy 12kHz of RF bandwidth when adding up the sidebands.

This is fine with me and quite refreshing, to be honest, just to hear quality audio that is easy on the ears and reminiscent of the old-time broadcast sound that a lot of us grew up with. AM has been a fixture in the amateur radio community and one that has been kept alive by some very knowledgeable and talented people. I envy the technical expertise that some of these fine operators bring to our hobby. May they always be there keeping the vintage (and new) rigs alive with the unmistakable sounds of AM.


Old SSB Limitations and Traditions

For most of the rest of the amateur radio community using SSB phone, there seem to be a general mind set that 3kHz of audio bandwidth should be the maximum bandwidth that anyone should use who has any good sense or who desires to be accepted as being reasonable and conforming. I suppose that this mentality was originated when overcrowding of the bands was an issue in the 80's and part of the 90's, as well as the fact that most SSB amateur radio equipment was manufactured with narrow 2.4kHz filters installed.

This filter selection used by manufacturers was a cheap and effective way to avoid certain problems with analog equipment invading the undesired opposite sideband on both transmit and receive. So a 2.4kHz filter would be installed, and the carrier point would be set at about 200Hz above the suppressed carrier (insuring no bleed-over on the opposite sideband) and then cut off by the filter's shape factor at around 2.6kHz. Any I. F. filters used beyond 3kHz would have been a problem since the carrier point adjustments were not versatile enough to keep the opposite sideband suppressed. So, because of engineering deficiencies and cheap parts, a 3kHz bandwidth maximum, through tradition only, became the status quo of SSB bandwidth—Not any FCC or ARRL rule or law.


Quality SSB Audio — The Extended Single Sideband (eSSB) Alternative

Things have changed! It is no longer an engineering issue to accomplish more than 3kHz of audio bandwidth on a single sideband, and do it cleanly and efficiently. Modern DSP transceivers (and some analog models) no longer have the inherent limitations of their old counterparts. In fact, even most older analog transceivers can accomplish single sideband beyond 3kHz if some careful modifications and adjustments are performed. Other than on heavily used portions of certain bands, there is no reason that SSB cannot sound as good (and even better in some cases) than AM.

eSSB (Extended Single Sideband) has been making inroads in the amateur radio community and has slowly been gaining acceptance as an alternative to both narrow SSB and wide AM. It can be considered a middle-ground solution that offers the best of both worlds. It is much better sounding than narrow SSB since a greater frequency response is supported and much less wide than good sounding AM since it only occupies one sideband instead of two.

There are many modes of operation in amateur radio, from analog to digital, from narrow to wide, and from one mode designator to another. It is only natural that eventually, there would be a mode developed that was something in-between AM and SSB, between painfully narrow and ultra wide. eSSB is this mode. It's perfect for those who want high quality modulation, but do not want to invest in vintage AM equipment that occupies 12kHz or more of bandwidth. It's perfect for those who want to use modern equipment, but who do not get into DXing or contesting. It is perfect for those who enjoy transmitting and receiving using a mode that is easy on the ears. It is perfect for those who want to experiment with the art of processing and crafting their audio to yield a beautiful, natural sounding way of communicating, without the need for using the phonetic alphabet to distinguish "K1SFC" from "K1FST".

There is indeed a place and a purpose for eSSB on our amateur radio bands. And, many are taking advantage of it. Generally, operators are becoming more and more careful about their SSB audio and vast improvements in modulation quality have been realized in the last ten years.

Those who insist that eSSB is not an acceptable mode of operation, are not being open and sensitive to the changing needs, interests, and practices of their amateur radio brothers. The hobby is changing (as is the world around us) and drawing a new breed of operator who wants an alternative to their high-quality audio internet experience. They have no desire to sound like Donald Duck "quacking" away for some equally bad sounding station who is "tinny" and hard to understand. I know of several new operators who became interested in amateur radio specifically because of interest in good sounding audio and the art, challenge, and experimentation of processing it.

Let's keep the hobby interesting and innovative, and most of all accessible to newcomers who desire a quality audio experience. It just may keep ham radio, and the spirit of it, alive and viable for years to come.

73,

-John, NU9N

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