Colleagues and friends of Leonard Kahn
unanimously agree that the gifted engineer’s life would make for a remarkable
|Leonard Kahn is in white at left, with his engineers Robert R. ‘Bob’ Gordon in red and Ira M. Salzman in blue. Herb Squire dates the photo to the early morning hours of Oct. 3, 1983. They were installing the AM stereo exciter at WQXR(AM) New York. The Westinghouse 50HG-2 transmitter went on the air in 1956. A Continental 317C-2 rig would arrive on site in 1983. WQXR Chief Engineer Zaven ‘Doc’ Masoomian took the photo. Squire became CE when Masoomian retired in 1986.
| A Kahn Symmetra-peak brochure from the 1960s.
Kahn, who died in Florida in June at age
86, certainly lived a life worthy of documentation, they said.
The inventive Kahn, former chief executive
officer of Kahn Communications, was described with words like determined,
eccentric, brilliant, argumentative, unique and, in his later years, litigious.
Colleagues said he was a man of many layers wrapped into one body of genius.
Kahn was well known for his Kahn AM stereo
system and later the Compatible AM Digital system, known as CAM-D. Colleagues
remembered his legal attempt to block Motorola from using its C-QUAM system in
the United States in the 1980s — saying C-QUAM violated FCC emission bandwidth
specifications — and his later bitter lawsuits against iBiquity Digital Corp.
Broadcast Devices Inc. President Bob Tarsio
said, “Leonard was not crazy or eccentric, which I have seen written. He was a
driven engineer only interested in what was right both in engineering, business
and his personal dealings.”
Tarsio, who met Kahn in 1983, points to the 1960
edition of the NAB Engineering Handbook as evidence of the kind of engineer
In the handbook, continues Tarsio, “is Leonard’s
paper on compatible single-sideband operation for AM broadcasting. You will
find real explanations of system operation and most importantly the mathematics
of how it all worked.
“Many so-called white papers that are written today are nothing more
than sales pitches without science to back them up,” Tarsio said. “Verity in
science and life — that was the kind of man Leonard Kahn was.”
Kahn held many key patents in HF transmission
and worked on shortwave and single-sideband transmission for RCA Labs early in
his career. Tarsio considers Kahn to be one of the “legends of broadcasting” because
of his contributions, including his work with Envelope Elimination and
Restoration, or EER, “which eliminated and then restored the carrier in a
linear modulation system that allowed for the use of a Class C amplifier to be
used in a more or less linear mode, which saved power and reduced electrical
“He’s right there with Armstrong, de
Forest, Hertz and Maxwell,” Tarsio said.
EER, sometimes referred to as the Kahn Method, is
used in many digital transmission schemes worldwide, Tarsio added.
“Leonard’s impact was
that he was one of the last broadcast innovators who believed that technology
for technology’s sake was not enough. If you developed a system it had to have
efficacy and provide a true improvement and it had to be the best solution.”
Kahn Research Laboratories proposed the concept
of AM stereo in 1958 and 1959, according to earlier Radio World coverage. About
that same time, Philco Corp. and Radio Corporation of America proposed
competing systems. However, the FCC stalled on a rulemaking procedure, citing a
lack of interest in AM stereo at the time.
By the 1980s, five companies, including Kahn
Communications, had developed AM stereo systems. The others were Harris,
Motorola, Magnavox and Belar Electronics.
The FCC originally picked the Magnavox AM stereo
system as the U.S. standard in April 1980, based on a complicated matrix of
performance attributes to which the agency assigned scores, said an observer
familiar with the selection process. Magnavox had the highest total of the five
AM systems considered. However, many in the industry protested, calling the
commission’s research and decision-making process incomplete and partially
flawed. So the agency backtracked and decided to let market forces determine
However, by 1993, it became clear there needed
to be one AM stereo standard in the United States. Other countries began
adopting Motorola’s C-QUAM, and that’s what the FCC chose. At the time, of the
660 radio stations using AM stereo, 591 were using Motorola’s system. Fewer than
20 were using Kahn’s system, according to the agency.
AM stereo ultimately did not flourish in the
marketplace; over time, for many in radio, the experience would come to be seen
as a poorly handled technical rollout and regulatory debacle.
Kahn also created Symmetra-peak while
working at RCA. This was a passive device that equalized the positive and
negative audio peaks being sent to a station’s transmitter and helped increase
modulation density before the days of sophisticated multiband audio processing
systems, according to long-time acquaintance Herb Squire, vice president of
engineering for DSI RF Systems Inc.
Another observer called Symmetra-peak “Kahn’s
single biggest contribution to broadcasting. The technology later went on to
become standard in nearly every name brand audio processor you can think of.”
Squire said, “Symmetra-peak restored the
symmetry and balance between positive and negative peaks of voice signals,
which tend to be asymmetric. It made the stations louder.”
According to Kahn’s marketing materials at the
time, the Symmetra-peak “redistributed unequal positive and negative peaks symmetrically
about the zero axis.”
Squire, who knew Kahn since 1969,
testified as an expert witness on behalf of Kahn in some of the lawsuits.
Squire worked with Kahn’s AM stereo system at WQXR(AM) and WQEW(AM) in New
“I was in regular contact with Leonard
[during that time]. He and his guys would come out and tweak the system.
WNBC(AM) also had his AM stereo system. He was right there with the technology.
He lived his work. That was his life,” Squire said.
Squire and other observers believe Kahn’s
development of his AM stereo system, which dates to the early 1960s, was complicated
at first by the FCC’s reluctance to adopt a standard while hoping the
marketplace would settle the issue. Kahn used independently modulated upper-
and lower-level sidebands for the Kahn-Hazeltine AM stereo system, used at one
time by WLS(AM) Chicago.
Kahn’s Powerside, a system to minimize
distortion of selective fading such as skip conditions, eventually led to
CAM-D, which was an in-band, on-channel technology for AM digital radio,
several observers noted. However, his legal dealings against iBiquity and Clear
Channel — chronicled in Radio World at the time — had him mired in court for
years beginning in 2006.
Kahn touted CAM-D as a major improvement over
iBiquity’s digital AM system. Kahn claimed his system did not increase adjacent
or co-channel interference, Kahn told Radio World then.
“I think he was extremely frustrated by that
time, but he was so dedicated to his work,” Squire said. “His years in the
business overlapped so many generations. He knew Major Armstrong, of course,”
he continued, referring to FM pioneer Edwin H. Armstrong, “and when you look at
those two lives, there were a lot of similarities at the end, with the lawsuits.”
Kahn would often send Squire cassette tapes of
various recordings to get his opinion on sound quality. He was notorious for
balking over any constructive criticism of his products. Rather “thin-skinned”
is how one former colleague recalled Kahn.
Kahn’s opinions and comments were published in Radio World, but he was
critical of its coverage. During industry debate over AM IBOC operation, he wrote
on his website that columns by “masked engineer” Guy Wire had taken his
statements out of context. He called this “yet another example of Radio World
type reporting and the reason we never send RW our press releases or authorize
my associates at KCI to grant interviews to Radio World reporters.” He did talk
to Radio World reporters at other times.
But in a letter to its then-parent IMAS Publishing, he stated that Radio
World had staged an interview with a radio corporate director of engineering
and displayed a “willingness to participate in a plan to deceive the
broadcasters and the public they serve” regarding engineering characteristics
of the IBOC system.
Robert Meuser, chief technical officer for
design engineering company Engineaux, described Kahn as “a very complex figure.
You either loved him or hated him. He could push very hard, but single-sideband
technology was truly dear to his heart.”
Meuser read Kahn’s technical writings before
meeting him in the 1970s; he described the period of the AM stereo wars in the
1980s as the time “when I first saw the cantankerous side of Kahn. You were
either with him or against him. He was kind and generous to those who was on
his side. There was no middle ground.
“As brilliant as he was, he really liked to keep
the technology to himself. His AM stereo equipment (STR-77 and STR-84) was very
difficult to adjust. We told him it needed to be more solid mechanically. This
annoyed Leonard, very much so,” Meuser said. “I fell out of his favor around
that time. But that is the way he was.”
Still, Meuser acknowledged Kahn’s work
with the EER concept as “incredibly important” in the history of wireless
Meuser said so many things in communications can
be attributed to Kahn, from low-power digital devices to the way that HD Radio
in the United States and Digital Radio Mondiale technology in Europe is used on
“They all basically use the EER concept. When
you look at European technical papers they actually refer to it as the Kahn Method,”
Meuser said. “So deploying that and getting people to recognize EER is probably
his biggest single contribution.”
Kahn’s wife, Ruth, preceded him in death in
2004, according to various reports. The couple had no children.
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