W2XF
A
brief
history
of
W2XF---subject
to
revision
as
I
learn
more
A Work In Progress
Additions, corrections and comments may be sent to frank at w2xf
dot com
( Remove "at" and "dot"; and substitute @ and . in the address)
please put W2XF in the subject line
The Empire State Building was
completed in May 1931 and, at the time the tallest building ever
built,
towered 1,250 feet over
New York City. The top of the building was designed to be
a mooring for dirigibles, but that was soon abandoned as
impractical
because of excessively high
wind
currents. David
Sarnoff, President of the Radio Corporation
of America, had a vision that was to include the top of that
building
for a
different purpose. He foresaw the future of
television; and what better
location for an antenna from which to broadcast television, than
the
top of the then
tallest
building in the
world!
RCA leased the 85'th floor of the Empire State Building for
a studio and transmitter location for experimental television
broadcasts. RCA, through its broadcasting division NBC, applied to
the
Federal Radio Commission on July 1,
1931 for construction
permits for the sight and sound
channels of a television station, which were issued on July 24,
1931. The call sign W2XF
was issued in
December 1931 for the "sight"
channel of that station
on an
assigned frequency of 44Mc.
The
transmitter had an input power to the final stage of
about 5Kw, giving an estimated power output to the antenna of
about
2Kw. The sound channel of
the TV station was
separately licensed as W2XK for a 2.5Kw transmitter to operate on
61Mc.
Both transmitters
were located on the 85'th floor and used separate
vertical dipole
antennas extending from the top of the
building.
Previously the W2XF call sign, and it's predecessor 2XF, belonged
to
the
Western Electric Company and Bell Laboratories, respectivly, which
later became a part of
the RCA group.
The
1932-1933
Television
Tests
The experimental television broadcasts from W2XF during 1932 and
1933 used a
mechanical Nipkow scanning
disk
to provide the video signal to the transmitter. (An electronic
video
camera, the Iconoscope, was under development at RCA's Camden, NJ
facility but was not yet ready
for field testing.) The early W2XF pictures were scanned
by using the "flying spot" method of producing a picture signal.
That
method employed an arc lamp behind a spirally
perforated disk to illuminate the subject in front of the disk
with a
bright spot of light. When the disk was rotated, the subject was
progressively illuminated by a spot of bright light moving in a
line
across it through each successive perforation of the disk.
Since
each perforation in the spiral was a little lower on the disk than
the
preceding one, the subject was sequentially illuminated by spots
of
light moving in a series of substantially
horizontal scan
lines from top
to bottom. A photocell picked up the variations in light
intensity reflected from the subject as
each moving
spot of
light illuminated it, and sent a modulating signal to the
transmitter corresponding with the variation in the light
intensity
during each scan line.
The video signals
received from the
transmitter were reproduced by
the newly developed cathode ray tube "kinescope," invented by
Vladimir Zworykin in RCA's Camden laboratories. The
variations in light
intensity along each scan line reflected from the subject, were
reproduced
as a corresponding
line on the face of the cathode ray tube. The image produced by the cathode ray
tube could then be viewed in a mirror or enlarged by optically
projecting it
onto a
viewing screen. W2XF
began its
testing in 1932 using a resolution of 120 lines
per frame and 24 sequential
frames per second.
In May 1932 RCA arranged a private demonstration of television
progress
from the W2XF transmitter for about one hundred executives and
engineers of it's licensees. The 4 by 5 inch pictures, using
live performers, were described by one of the guests as "fairly
clear."
Motion picture film reproduction was described as better, but not
comparable with "home
taking" pictures, which was the benchmark sought by TV engineers
at
the time.
RCA had an earlier experimental TV transmitter that was originally
located at Van Cortlandt Park and later moved to the
New Amsterdam theater on
42'd Street in 1930. That station was
originally
licensed in April 1928 as W2XBS to broadcast on 2100-2200 Kc. The first tests
using that transmitter were conducted
using a Nipkow disk that provided a resolution of 60 lines per
frame
and 20 sequential frames per second. Many of these tests consisted
of
transmitting an image of a 13 inch paper mache statue of Felix the
Cat
on a rotating phonograph turntable, and were reproduced as a 2
inch
picture at the receiver. Later, the resolution of the W2XBS signal
was
increased and eventually it was used for early tests the
Iconoscope
television camera tube.
It was apparent by the middle of 1933 that the
resolution of Nipkow disks would not provide a satisfactory
picture,
and that flicker in
the image at 20 or even 30 sequential frames per second was a
serious
problem. RCA
sent its television development program back to the laboratory for
further
work.
New
technology to electronically scan the picture with higher
resolution
and a greater frame rate
would be required to provide a picture that would be
commercially practical.
The tests made from W2XF in 1932 and 1933
were of significance, however, because they were successful in
proving
that the
use
of very high frequencies
for television broadcasting was
feasible in spite of their limited range. These tests were also
the
first major field tests to use the cathode ray Kinescope for
viewing
television images.
The
Frequency
Modulation
Tests
Edwin Armstrong made at least four
major
inventions in the field of radio during his lifetime. His first
major
invention,
regeneration, revolutionized radio transmitters and greatly
increased
the sensitivity of radio receivers. This invention
was instantly embraced by the radio industry, as was his
later invention of the superheterodyne radio. Armstrong sold both
of
these inventions to Westinghouse which became a part of the RCA
group
until its breakup on antitrust grounds. His invention of
super regeneration, which was discovered by him almost by
accident, greatly increased the sensitivity of regenerative
radios. At the time
of
its invention, super regeneration was thought to be a
significant advance in radio.
RCA
had rights under Armstrong's prior inventions through it's
association with Westinghouse, and
was determined to obtain the patent
rights to super regeneration.
When RCA purchased
Armstrong's super regeneration patent, he received a substantial
sum of
cash and sixty thousand shares of RCA stock, making him the
largest
individual
stockholder in the company.
But super regeneration had serious technical problems and did not
became
commercially successful on other than a limited scale. One can
wonder
whether Sarnoff
may have resented in later years the excessive price RCA paid to
Armstrong for that invention. But RCA also received another
important
right as a part of that
agreement, namely, the first right of refusal to acquire rights
under
any future
inventions made by Armstrong.
Armstrong had worked for a
number of years to develop a system of wide
band Frequency Modulation. The work was conducted
at the Marcellus
Hartley Research Laboratories in the basement of Philosophy Hall
at
Columbia University, where he was a professor of electrical
engineering. His wide band FM invention offered the promise of
eliminating static,
which was the major drawback of conventional AM radio at that
time. By
the end
of 1933 his work had reached the point
that he was ready to demonstrate his new "static eliminator"
invention
to David Sarnoff and other
executives and engineers of RCA. These demonstrations took place
in
December 1933 and
January 1934. The laboratory demonstrations were transmitted over
only
about
fifty feet and were greeted with considerable
skepticism about how well the system would work in actual
field
tests.
Since the previous mechanically scanned TV tests at the Empire
State
Building were ending, RCA offered to make the W2XF transmitter and
antenna
available to Armstrong for field tests of his FM invention.
RCA
obtained the license W2XDG from the Federal Radio Commission in
May
1934 to enable
Armstrong to use the W2XF transmitter for those FM tests.
Actually, Armstrong's wide band Frequency Modulation invention did
not
fit well into
Sarnoff's vision of the future of broadcasting. Sarnoff had hoped
that
someone would invent a cheap little "black box" that could be
attached
to an existing radio to eliminate static. Armstrong's invention
eliminated
static, but involved a whole new
system of radio. RCA had a huge investment in conventional AM
radio,
had
three profitable national radio networks and was heavily invested
in
cranking out inexpensive radios for the general public.
Commercializing
FM would involve replacing conventional transmitters and radios
with more
expensive equipment in
the middle of a depression, when discretionary money was scarce.
But
even more importantly, Sarnoff's vision was that television would
be
the next major advance in broadcasting. FM radio not only didn't
fit
into his plan, but could
detract from it. It is perhaps ironic that commercial
television
broadcasting would employ FM as its audio transmission mode into
the
early part of the next century.
For the early tests, Armstrong set
up
a receiving
facility about 70 miles
from
New York City,
at the home of an old friend, George Burghard, at Westhampton
Beach,
Long
Island. The first recorded reception
at that location was on June 16,
1934. In Armstrong's words:
"The
initial
tests
in
the
early
part
of
June
surpassed
all
expectations....The
margin
of
superiority
of
the
frequency
modulation
system
over
amplitude
modulation
at
forty-one megacycles was so great that it
was at
once obvious that comparisons of the two were principally of
academic
interest."
"...perfectly
quiet
reception
being
secured
through
the
heaviest
thunderstorms
when
all
the
standard
broadcast
services
had
been
rendered
utterly
useless."
But, it was felt that Westhampton was too favorable a location to
give an accurate
indication of typical reception conditions. Consequently,
the
receiver was moved at the end of June 1934 to the home of Harry
Sadenwater at Haddenfield, NJ,
about eighty five miles from New York City.
The
results at the Haddenfield location were reported to be equally
impressive. The W2XF transmitter, broadcasting FM with
approximately
two
kilowatts, was reported to produce a signal at the Haddenfield
location
that was
superior to the existing fifty kilowatt AM stations
under
all conditions.
The
Buzalski
Paper
An interesting
paper was published in
Volume 1 of
the Antique Wireless Association Review, written by Thomas
Buzalski, Chief Transmitter Engineer, NBC, New York. He
writes
that he worked along side of Armstrong to assist him during those
early
tests at the
Empire State Building.
Buzalski takes pains to specifically
point out that it was the NBC technical staff's responsibility to
make
sure that the FM tests
were made in accordance with the license granted for FM tests by
the FRC.
Buzalski states that the record of visitors showed that Armstrong
first visited the W2XF transmitter site on January 12, 1934, and
again
on January 19, 1934 "...to get information on W2XF for
experimental
work
he is to do on it in the near future." Preliminary testing was
conducted at Armstrong's request on the W2XF transmitter in
February
1934 to test it's audio response and in March 1934 to check
whether
it's frequency bandwidth was sufficient for the FM tests. According to Buzalski, Armstrong
moved
his FM exciter equipment
to the Empire State Building site in May 1934, the same month that RCA obtained the
W2XDG license to enable him to use the
W2XF transmitter for FM tests. However, according to another
source, Armstrong actually moved his equipment to
the Empire State Building in March 1934 which, if true, may shed
additional light on the sequence of events that later transpired.
Buzalski states that the FM
tests from W2XDG started on June 2, 1934 on 41 MHz, and
on the evening of June 20, 1934 a special demonstration of organ
music
was transmitted for observation by the Chairman of the Board of
RCA.
The
Armstrong
Paper
Armstrong described the FM
tests from the Empire State Building
transmitter in detail in a paper he delivered to the Institute of
Radio
Engineers in March of 1935. This was the first full public
exposition
of his FM invention after his original announcement in April of
that
year. He goes into much detail in his IRE paper about the
frequencies used by his
modulator to excite the transmitter.
The modulation equipment
that
Armstrong
brought to the Empire State Building was
designed to operate the W2XF transmitter on 44 megacycles, which
was
the
frequency used for the
television experiments. But the W2XDG license granted by the FRC for the FM tests, was
restricted to
testing on 40.6
and/or 41.0 Mc. Armstrong
mentions in
his paper that,
"Considerable trouble was caused
during
the early stages of the
experiments by an order of the Federal Radio Commission
requiring the
changing
of the frequency of the Empire State transmitter from forty-four to
forty-one
megacycles; thus necessitating the realignment of the large
number of
interstage transformers in the modulating equipment...and also
retermination of
the antenna."
Were
all
FM
tests
made
in
accordance
with
the
FRC
license?
Careful reading of
the
two
papers leaves a question whether some
early FM tests may have been conducted from the W2XF transmitter
before
the modulator was modified to operate on 41 Mc.
The W2XF transmitter,
according to
Buzalski, had three doublers
and one trippler which produced a 24X
frequency multiplication of the input signal. Armstrong states in
his IRE
paper that,
“The frequency
of the system was
ordinarily controlled by a master oscillator operating at 1733
[sic]
kilocycles which
was multiplied by a series of doublers and triplers to forty four
megacycles”
“The crystal
control oscillator was
replaced by the output of the modulation system shown in Fig. 20
in
which an
initial frequency of 57.33 kilocycles was multiplied by a series
of
doublers up
to the input frequency of 1733 [sic] kilocycles.”
The transmitter input and
modulator
output frequency of 1733 Kc mentioned above,
appears to be a mistake, and probably was
1833 Kc, which would have produced a transmitter output frequency
of
almost exactly
44 Mc (43.992 Mc) from the
transmitter's 24X multiplication factor. (The W2XF transmitter would have
produced
a 41.6 Mc output if
the input was 1733 kc.)
At
another point in the paper, Armstrong specifically
states that his modulator had to have an output of 1708 Kc to
produce a
transmitter output of 41 Mc, which reflects that 24X
multiplication
factor.
Armstrong also states
that his
modulator used a fundamental frequency of 57.33kc, and had a
series of
doublers to multiply its fundamental
frequency to provide its output frequency. The modulator would
have to
have had five doublers for a
frequency multiplication of 32X to provide a suitable output
frequency
for the W2XF transmitter to operate on about 44 Mc from a 57.33 Kc
input.
Hence the
modulator's
fundamental frequency of 57.33 kc would
result in an input to the transmitter of a little less than 1835
Kc
instead of 1733 Kc as stated in his paper, and would result in a
transmitter
frequency
of 57.33 X32 X 24 or 44.029 megacycles. It seems likely that
the modulator output was actually closer to 1833
Kc so as to produce an output of almost exactly 44 Mc.
It is somewhat strange that
Armstrong
describes these facts in
his IRE paper, which he
explains would result in a transmitter
frequency of 44 Mc, if at least some FM tests weren't
conducted on
that
frequency. This leaves the possibility that
Armstrong may have
run some early tests using his original FM
modulator to drive the W2XF transmitter on 44Mc, before the
equipment
was
converted to broadcast on 41Mc in accordance with the W2XDG
license,
and perhaps
even before that license was obtained.
It is also interesting
that several American and European sources state that Armstrong
began broadcasting FM signals using the call
W2XF
on 42.1 Mc, in May, 1934, and that the first
comparison test with AM took place on June 9, 1934.
Unfortunately, they do not give the source for this
assertion.
The
Low
Power
Frequency
Modulation
Tests
Another interesting aspect of Armstrong's IRE paper is the mention
that
he had a 50 watt breadboard FM transmitter at the Empire State
Building. That transmitter is shown at the Empire State Building
site
in
Fig. 23 of his paper. The final stage of it is presently on
display at the AWA Museum at Bloomfield, NY and uses a pair of 852
tubes in the final stage of its amplifier. The description accompanying the
transmitter at the Museum specifically describes it as producing
50
watts at 44 Mc. Armstrong describes in his IRE paper some FM
tests
that were made using 50 watts from the Empire State
Building. He writes:
"It was noted by C.
M. Burrill of the RCA
manufacturing Company who
made the observations at Arney's Mount that with fifty watts
in the
antenna
frequency modulated (produced by pair of UX 852 tubes), a
signal-to-noise ratio
of the same value as the two-kilowatt amplitude modulation
transmitter
(eight
kilowatt peaks) was obtained."
Armstrong states that these 50
watt FM
tests were made with his breadboard 50 watt transmitter and it is
apparent that he was comparing that transmitter, on FM,
to the 2Kw W2XK transmitter on AM at that point in time. The
paper
does not state whether those tests were conducted before or after
the
W2XDG license was granted for FM tests, and no mention is made of
the
frequency on which they were conducted. However, it is known that
the
Arney's Mount
relay station was designed to receive and relay the 44 Mc
television
signals from
W2XF to Camden, NJ.
The
End
Of
The
Frequency
Modulation
Tests
RCA
requested Armstrong in
April
1935, to remove
his equipment
from the Empire State Building so that the transmitters could be modified for
new
television tests that were to
be undertaken later that year. Actually, the FM tests apparently
continued into
October while the W2XK sound transmitter was being rebuilt, but,
by
then the studio space being occupied by Armstrong was needed for
construction work on the W2XF sight transmitter.
The
1936
Electronic
Television
Tests
On May 7, 1935 David
Sarnoff
made the startling announcement at RCA's
Annual Stockholders Meeting that the company would begin a one
million
dollar test program to bring television out of the laboratory
and into
the
field. He further told his stockholders that regular television
broadcasting would start by June of the following year. However,
he was
quick to
point out,
"... while television
promises to
supplement the present service of
broadcasting by adding sight to sound, it will not supplant or
diminish
the
importance and usefulness of sound broadcasting."
RCA
was much concerned that premature rumors of television being
available soon, would diminish sales of conventional radios. This
announcement was also incorrectly heralded as lifting the heavy
secrecy
that
had
surrounded RCA's television developments up to that time.
RCA was actively
testing at it's research
facility in Camden, NJ, a
new
TV
technology, making use of the electronic "Iconoscope"
camera tube, developed by Vladimir Zworykin, to
replace the scanning disk. The
Iconoscope
used
a
tube,
similar
to
a
cathode
ray
tube,
having
a
matrix
of
photoelectric
spots
on
which
an
image
was
focused.
The charged spots
were then
scanned with a beam of electrons, moving in lines, to produce a
current
corresponding with the image. The current was amplified and used
to
modulate the
transmitter. The signal from the transmitter was reconstructed as
a
image by a cathode
ray tube "kinescope" at the receiver.
A great advantage
of the Iconoscope was that the number of scanning lines, and hence
the
resolution, could be increased significantly over the practical
limitations of
the Nipkow scanning disk. In addition, the camera-like Iconoscope
allowed much greater flexibility of lighting and subject
matter, especially for outdoor scenes.
By 1934 the Iconoscope experiments at
Camden
employed a
resolution of 343 lines, which produced a much superior picture.
Just
as importantly, they used a frame rate of thirty frames
per
second
with
a
field
frequency
of
60
frames
per
second,
interlaced,
which
fully
overcame
the
flicker
problem.
These tests involved transmitting from the Camden research labs
with
nominal power on 49 and 50 Mc. Similar tests
were also being conducted
at this time from RCA's W2BXS transmitter at the New Amsterdam
Theater.
By
the middle of 1935, Zworykin's Iconoscope camera was
ready for full scale field
testing from the Empire State Building.
To accommodate the new tests, the
W2XF video transmitter was rebuilt as
a 10
Kw transmitter,
having an
output of about 7.5 Kw, designed to transmit on 49.75 Mic, and the
W2XK
sound
transmitter was rebuilt to operate on 52 Mc. W2XF was now able to
provide an all-electronic
video signal
from an Iconoscope source
having
343
lines and 30 interlaced frames per second. The Iconoscope cameras were located
in
the RCA studios at Radio City and linked to the Empire State
Building
transmitter by both an underground coaxial cable and a microwave
link.
Page 63 of the
Second Annual Report of the Federal Communications Commission to
Congress for the
fiscal year 1936 describes this event as follows:
"On
June
29
television
broadcast
station
W2XF
began
operating
in
the
Empire
State
Building,
New
York,
on
an
experimental
basis
for
public
reception.
A few receivers were distributed to selected
observers.
It was reported that the operation would continue as the experimental
work
permitted."
Actually, only about 90 television
receivers became available and all were in the hands of RCA
executives and
engineers. None were
available to
the public. Strict secrecy still surrounded the results of the
transmissions. The New York Times headlined the event with:
"Test Of Television Started In
Secret"
"...observations
on the quality of
the images will be kept secret.
The
only indication that the tests reveal signs of success is
found in the
fact
that licensees of the Radio Corporation of America will be
invited to
see the
'show' and apparatus on July 7."
In fact, the engineers had
encountered
serious noise problems in the amplifiers, and it was not until the
early morning hours of July 7 that the pictures were reported as
being
worth showing. These first, green phospor images were reproduced
by 9
inch round tubes
having 5X7 inch masks, which were deemed by most viewers to be too
small for wide
acceptance. The receivers had a total of 33 tubes and 14 control
knobs at that time.
However, the June 29 event represented a major milestone in
the
development of television in the United States. An all-electronic,
a
343 line "high
resolution" television signal was now being broadcast to home
viewers
throughout
the New
York
City
area, by W2XF, on a somewhat regular basis. These broadcasts were the first major
field tests to
use
the Iconoscope camera and, arguably, may have been the first
regular
broadcasts
of all-electronic television in the United States. In a statement to the Press
on
November 6,
1936, David Sarnoff said:
"That
date
[June,
29,
1936] marked the beginning in
this
country of
organized television experiments between a regular transmitting
station
and a
number of homes."
A few months later, on November 6, 1936 a
major demonstration from W2XF was
held for the press before about 250 invited guests assembled in
Radio
City. It was the first time that RCA had
demonstrated a practical working television station to the Press
under
actual
field conditions. This event also introduced receivers having a
much
improved 12 inch kinescope tube that provided 71/2 x 10 inch
pictures.
Fifteen of
these new receivers were set
up at Radio City for the demonstration. The program included talks
by
the President of NBC and David Sarnoff, President of RCA, on the
progress
and challenges of television development, as well as entertainment
features.
The New York Times reported on January 3, 1937 that the Empire
State
Building transmitter would be shut down early that year for
conversion
to 441 line pictures. The Third Annual Report of
the FCC to Congress for the fiscal year 1937 states:
"One
television
station
in
New
York
City
broadcast for public
reception using a high picture definition of 343 lines, until
December
1936
when operations were discontinued in order to alter the
equipment to
transmit
definition of 441 lines. Demonstrations of this definition in
April
1937 were
successful, and the improvement in the picture detail was very
noticeable."
It is highly probable that this
FCC statement refers to the Empire State Building operation. It is
also
likely that the W2XBS
call
was transferred to that operation at about this
time. The 441 line standard had
been recommended by the Radio Manufactures Association for TV
broadcasting. Later
the NTSC
group was formed and recommended the finally adopted 525 line
standard. It is not clear
whether those first 441
line pictures from the Empire State Building were
broadcast as W2XF or W2XBS.
Confusing
History
Researching the history of
W2XF
has led to a number of omissions and contradictions in the
literature. Some
references state
that the 1933 television tests from the Empire State Building were
made
from
RCA's earlier experimental
station,
W2XBS. However, Thomas BuzalskI, who was NBC's chief transmitter
engineer at the Empire State Building,
clearly states in his AWA paper that those 120 line tests were
broadcast
from W2XF. Similarly,
many
references state that the all-electronic television
broadcasts that were begun on June 29, 1936 were made from W2XBS.
However, the
1936 FCC Report to Congress clearly states that these broadcasts
emanated
from
W2XF, as does an article in the August, 1936 issue of Radio Craft
Magazine.
Part of the problem may
stem from the heavy secrecy that surrounded the TV experiments
from W2XF.
Confusion may also have come about because some of the programming
being
broadcast by W2XF originated from television studios in Radio City
which were
associated with W2XBS. By 1936, these studios were connected to
the
Empire
State
Building site by both a coaxial cable and a microwave link. In
addition, it may have served the cause
of historical simplicity to trace RCA's television history
directly
back to its
original 1928 TV station, which eventually took over the Empire
State
Building location. The
history on the Internet of its successor, WNBC, does not
specifically
mention the involvement of W2XF at the Empire State
Building, and
if not read
carefully, could be
misunderstood to imply that the 1931 and 1936 television
broadcasts
from
the Empire
State Building were made from W2XBS.
Other
articles state that Edwin Armstrong broadcast FM transmissions on
42.1Mc using the call
W2XF,
but there does not seem to be any clear evidence of that. It is clear that W2XDG would have been
the
proper call sign
under which the broadcasts
should have been made after that license was granted.
Epilogue
Eventually, the W2XBS
call sign was
transferred to the Empire State Building TV operation. The call
W2XF
seems to have disappeared sometime after February 1937, when it
still
appears
in a New York Times listing of one of the twenty currently
licensed
experimental TV stations. W2XBS became NBC's premier
television
station and was
introduced to the public at the 1939 World's Fair with the famous
broadcast of the opening remarks by FDR on April
30
of that
year. On the same day RCA model TRK-12 television sets first
became available to the public in New York City stores for $600.
W2XBS eventually received a commercial television license
with
the call WNBT, and became one of the first two
television stations in the United States to began
commercial operation on July 1, 1941. Through a succession of call
sign
changes,
WNBT became the present
WNBC
in 1992. It
also appears that RCA may have continued
to operate a low power station with the call W2XDG (the license
obtained for the Armstrong tests) as an
experimental, high frequency, AM station from November 1935 to
early
1940 according to one source.
Finally, in June 2007 the Call W2XF was assigned by the FCC to me.
I
feel extremely fortunate to have received a call with such a rich
and distinguished history in the fields of both television
and FM
broadcasting.
Frank Decker
