In Part 2 of this narrative, we asked "Who Invented Cable TV?" and examined the claims of three contenders ― Davidson, Parson, and Walson ― all of whom established CATV systems during the 1948-50 time period. But their efforts are but a small part of the larger story of the technological progress in the years following World War II. During these years, technology was exploding: new devices and new techniques appeared in every issue of the trade press. Better antennas, better transmission lines, and by 1951, better amplifiers.
Blonder-Tongue Laboratories, Inc.
In our discussion of Walson, we noted that he utilized a cascade of Electro-Voice Model 3000 amplifiers in the headend run at his CATV system in Mahanoy City, Pennsylvania. The E-V 3000 was one of the first "broadband" amplifiers, capable of carrying Channels 2-13 without individual channel tuning. According to the Radiomuseum, it was capable of amplifying "US VHF TV bands" (i.e., Channels 2-13), but the actual passband specification is not known.
But the E-V 3000 wasn't the first such amplifier. Our research indicates that the first amplifier capable of carrying Channels 2-13 was Model HA-1 "Antensifier" settop booster amplifier designed by Ben Tongue and manufactured by Blonder Tongue Laboratories of Yonkers, New York. Although intended for indoor use as a settop booster, the HA-1 could be modified for outdoor use just as Walson had done with the E-V 3000.
| Advertisement for the Blonder-Tongue Model HA-1L "B-T Antensifier" from Radio & Television News, October 1950, p. 171.
Ben Tongue and his partner Isaac Blonder had established Blonder-Tongue in Mount Vernon, New York in 1950. Tongue had based the "Antensifier" on a design originally patented by the engineering and manufacturing arm of the British firm EMI and licensed to the Boston firm SKL (Spencer-Kennedy Laboratories) in 1946. SKL designated the amplifier as the Model 202 series.
But SKL was not in the business of building amplifiers for television signals. SKL's 202-series amplifiers were commonly called servo drives — specialized amplifiers intended to drive electric motors in applications where precise control of speed, torque, and angular position were required. For this application, an amplifier capable of providing substantial power over a broad range of frequencies was required.
High power over a broad frequency range? Just what Ben Tongue was looking for!
Well, almost. Tongue wanted an amplifier that would cover a wide passband, but he also wanted an amplifier that would be a better fit the requirements of fringe-area home viewers and dealer showrooms:
|A passband wide enough to amplify the two VHF frequency bands (Channels 2-6 and 7-13), but only those bands.
Improved Noise Figure.
Lower maintenance costs. The SKL design employed twelve 6AK5 pentode vacuum tubes ― a tube with a life expectancy of 90 days and an advertised price of $1.09 each. (Radio-Electronics, July 1961) A quick mathematic calculation shows that it would cost over $50 per year just for replacement tubes, per amplifier, excluding labor and overhead costs.
Substantially lower manufacturing costs.
And, of course, he wanted to avoid infringing on the EMI patent and the SKL license.
He accomplished this with a design that used three (or, in some versions, four) 6J6 dual-triode vacuum tubes and a unique coupling circuit design.
(patent). The "Antensifier" amplifier consisted of two amplification circuits in one cabinet ― one amplifier for channels 2-6 (54-88 MHz) and the other for channels 7-13 (174-216 MHz). See B-T Addendum.
Two versions of this amplifier were released:
Model HA-1, a three-tube version.
Model HA-1L, a four-tube version.
According to Tongue's Cable Center oral history, he introduced this amplifier in May 1950 at the Chicago Parts Show (now EDS). This amplifier could serve two markets: as a booster for fringe-area reception and as a distribution amplifier for TV dealer showrooms. Articles about this booster appear in the October 1950 issues of
"Radio & Television News" and "Radio-Electronics." These are the first known published references.
Industrial Television Incorporated
Ben Tongue's broadband amplifier was soon followed, in March 1951, by the 'Auto-Booster' amplifier manufactured by Clifton, New Jersey-based Industrial Television Incorporated (ITI). This amplifier incorporated two RF inputs, one for the low band (channels 2-6) and one for the high band (channels 7-13), so that two separate antennas could be used.
The ITI Autobooster. From the collection of The Old CATV Equipment Museum. More photos here.
Over the 1951-54 period there would be several variations of this device, some using only two tubes (6J6 and/or 6AK5) while others employed as many as five.
The first major differences between the ITI and B-T amplifiers are shown in the following table:
||High Band: 14 dB.
Low Band: 19 dB.
Note that both devices passed the two VHF frequency bands through separate amplifiers, then combined the ouputs. There is a clue here when we note that ITI had separate input connections. Given this approach, it makes sense why the ITI's amplifier was rated for 14 dB gain on the high band channels (7-13) but 19 dB on the low band channels (2-6), when logically high-band channels would have needed higher gain than low band.
Ben Tongue worked around the EMI/SKL-licensed 40–220 MHz circuit by breaking the TV channels into two separate groups (2-6; 7-13) while ITI worked around Tongue's pending patent by further providing two inputs rather than just one, treating 2-6 and 7-13 as separate amplifiers.
By using two inputs, ITI also offered individual gain controls for each band. In fact, however, they were 'peaking adjustments' to adjust the frequency response of the circuit ― what we'd call tilt controls today.
Gain controls would become standard practice for others but any design using a single input and single output also required a tilt contort to create the slope between the lowest channel and highest channel. But this feature was not yet available in 1951.
ITI designed and manufactured a variety of related products In early 1949, ITI built and installed five television monitors at the Louden-Knickerbocker Hall Sanitarium in Amityville, New York, a privately-owned 36-bed facility for mental patients. The monitors were protected with thick Plexiglas covers, and all operating controls [channel, volume, video settings] were located in an administrative office.
As TIME reported at the time:
|Dr. George E. Carlin installed five television sets for his mental patients at Louden-Knickerbocker Hall, a 63-year-old private sanatorium. Said Owner John F. Louden: "We're using TV as a form of occupational therapy, to take the patients' minds off themselves and to let them live nearer to a normal life." TIME, 4-Apr-1949
Not to be outdone by its upstart competitor, General Electric created a 'juke-box-TV set' which they tested in a luncheonette in Hoboken, New Jersey. Three minutes of TV for a nickel, 30 minutes for a quarter.
The Twinlead Loss Problem
But if you lived in Jenkins or Hazard, Kentucky, and were on a hilltop capturing a channel or two from Cincinnati or Huntington to be 'wired' down into your 'hollow' at the base of the hill, even $77.50 (list price of B-T's top-of-line CA-1-M) was a big number.
But had you started back in 1948, the ITI amplifier wasn't yet available. Nor was any other broadband (channels 2-13) amplifier (or signal booster) capable of operating unattended for extended periods of time. Single-channel, whether by design or by user tuning, yes; broadband amplifiers, no.
As for the cable, your best option would have been twinlead ("flat line"), the 300-ohm answer to residential TV antenna installations through at least the '70s. It was inexpensive (as little as 1.3 cents a foot in 1950) and reasonably durable, although when exposed to sun, wind and rain – not to mention snow and ice – it would become brittle or split apart, significantly shortening its life. Furthermore, loss-per-foot doubled or trebled when wet or, worse still, was caked in ice.
Various types of 300-ohm twinlead
But the biggest problem with twinlead was lack of shielding. If the twinlead was installed too close to (or worse, in contact with) any metallic surface, other forms of signal degradation arose. The presence of metal disrupted the electromagnetic and electrostatic fields surrounding the line, resulting in frequency-dependent signal loss. The signal of one channel might be completely lost, whereas another channel would be unaffected.
In short, a 500-foot run of twinlead between amplifiers, such as Walson claimed, would have involved a variety of mechanical and electrical challenges. Even if you had enough signal at the top of the hill, the signals often just disappeared when the cable got wet. The flatline-wet-loss simply ate up your original signal before it reached the base of the hill, even if you somehow could afford the cost of the amplifiers.
Nevertheless, even in 1948, Albert Warren of Television Digest, whom you'll remember from our discussion in Part 2, would have heard about your efforts. He was compiling a list of every 'community antenna' system. You'd be on his list. You had to solve the signal problem. But how?
Enter The Gonset Company.
The Gonset Company
Some (not all) of these problems would disappear when Gonset, a California company based in Burbank, announced a type of transmission line called 'Gonset Line.' Gonset line consists of a pair of wires separated by insulating spacers at intervals.
Gonset line (conceptual sketch)
Unlike twinlead, the spaces between the spacers are open so that water and snow cannot affect the transmission characteristics of the line. It's sometimes called "ladder line" or "open wire feed line."
For CATV applications, the significance of Gonset line is its substantially lower loss when compared to twinlead, as the following table illustrates:
Approximate loss at 200 MHz (VHF Channel 10)
(dry, no nearby metal
(rain, snow, nearby metal)
|Loss in dB.
Per 100 feet
Per 500 feet
Per 100 feet
Per 500 feet
|| 2.0 dB
||Greater than 2.0 dB.
(possible complete signal loss)
|Greater than 10.0 dB.
(possible complete signal loss)
|| 0.5 dB.
|| 2.5 dB.
|| 0.5 dB. (or slightly greater)
|| 2.5 dB. (or slightly greater)
The above chart is based on losses at 200 MHz ― Gonset's reference frequency ― a frequency that falls a bit above VHF Channel 10 (192-198 MHz). As always, even in coaxial cable, losses increase as the square of the frequency, so the losses at Channel 13 would be somewhat greater. Thus it appears that Gonset's claim ("less than 1/6 the loss of new molded ribbon") is justified under actual field conditions.
At this point, we should note one other factor that would have affected transmission line loss: characteristic impedance. The characteristic impedance of Gonset line was 450 ohms (Gonset, 1952), resulting in impedance mismatches at both ends, where it connected to 300-ohm devices. These mismatches introduced additional loss. Although Gonset could have produced a product with a characteristic impedance of 300 ohms, it chose not to do so for two reasons:
Bottom line: the slight additional loss caused by the impedance mismatches were deemed to be negligible in comparison with the substantially lower per-foot-loss of Gonset line.
- The wire-to-wire spacing would have been only 0.3 inches. This product would have been difficult to manufacture, and virtually impossible to use under actual field conditions. By contrast, 450-ohms line was easier to manufacture and install.
- Very few antennas, and even fewer amplifiers or receivers, were actually 300-ohm devices themselves.
Nevertheless, except for the advertisement cited above (Gonset, 1952), Gonset generally avoided mentioning the line impedance in advertising or literature, choosing instead to refer to simply as "Gonset Line."
The advantages of Gonset line quickly caught on among early CATV operators, and TV Digest's Al Warren was well aware of the situation. He seemed to have an 'inside line' to the Gonset organization. Whenever some entrepreneur purchased a few thousand feet of Gonset Line to activate TV sets in a shadowed reception area, Warren added a tick to his 'community antenna television' roster.
For its part, Gonset (which, you'll recall, was based in Burbank) was quick to capitalize on this fact. Gonset created 'success stories' that they spread far and wide: "No TV? Install Gonset Line!" This fit California perfectly because Californians were building homes in canyons surrounded by hills and ridge tops. Put the TV antenna 'up there' and run Gonset Line!
Where Gonset faltered was east of the Rockies. Perhaps it was a lack of savvy distributors, or perhaps it was 'eastern fear' that all of this California hype was just that: 'hype.' Articles in respected publications didn't help: an article in the April 1951 issue of Radio & Television News titled Novel Antenna Installation Overcomes Mountain Terrain merely fueled the hype.
Or perhaps it was the timing. Gonset Line was not introduced to the trade until early fall 1950, and by then John Walson and hundreds like him had allegedly strung their 300-ohm twinlead from hilltop to tree to tree to town.
What happened next is less well documented. By the end of 1948, many 'hilltop antennas' were feeding multiple TV sets in lower elevation communities. The geographic concentration of this activity would turn out to be Kentucky and Maryland, north and northeast through Pennsylvania, southern New York, and into New England. Most of these antennas were operating on a 'co-operative' basis: two or more homeowners pooled money to build the antenna and run the wire. In most cases, there was no monthly charge: these were co-ops, not businesses. When something broke, the original investors ponied up funds to fix the problem.
Unfortunately, such failures were not uncommon. Most of these co-ops utilized inexpensive components — twinlead and consumer-grade antennas — and located them on hilltops and similar elevated locations. West Virginia is an example here: some hilltops had a dozen or more separate antennas, each feeding one or a few homes.
Eventually, some energetic entrepreneur, tired of the constant maintenance, decided to 'do it right.' Articles by Jerrold and others, published in the contemporary trade press, showed the way. Utilizing appropriate wire and electronics, our entrepreneur offered a higher grade of service. In due time, the other one- two- or three-home antenna owners abandoned their antennas and connected to the entrepreneur's antenna — for a fee. Our entrepreneur had created a business.
A hilltop sprouting ten antennas in 1951 would, by 1955, have only one antenna — a 'community antenna television' antenna. By attrition, the last antenna standing became the CATV operator for the community. Bill Turner's system in Welch, West Virginia is an example here (for a description of this antenna, see Television's Pirates, pages 84+).
The Growing Demand for Television Service
"It's one of those." "Radio-Electronics," October 1949.
For an entirely different – but related – reason, antenna systems feeding multiple TV sets became popular in multi-story apartment buildings in larger cities. In point: in 1948, New York City had only six operating TV stations, but by the end of that year, TV set penetration had already reached 50%.
A resident in an apartment that faced towards the Empire State Building (where some, but not all, transmitters were located), and high enough above other obstructions, might have acceptable (although seldom blemish-free) reception by using some form of indoor or window-ledge antenna. But even this resident rarely received all six channels.
But a resident in a lower apartment, or on the wrong side of the building, had only one choice: install an appropriate antenna on the roof, and drop a length of 300-ohm twinlead down the side of the building to the apartment window. Rooftops soon became forests of antennas.
Uncaptioned cartoon suggested by Arthur A. Henrikson. "Radio-Electronics," July 1951, p.91.
Occasionally, some resident would venture up to the roof at night with a length of 300-ohm line and attach it to an already-existing antenna. This, of course, created technical problems, which, in turn, precipitated contentious disagreements among neighbors — and even rooftop brawls according to police records. (Radio-Electronics April 1949).
The technical problems were numerous. TV sets of that era were so poorly shielded that they often radiated spurious signals from their local oscillators or other circuits. Radiation passed through walls, floors and ceilings, creating interference to neighbors' reception. Given the unshielded nature of the twinlead, this problem was even worse when two or more receivers were connected to a single antenna.
Apartment dwellers were up in arms (and on the roof). Something better had to be done. A Master Antenna TV system would have been the answer, but only after apartment operators had engaged security personnel to stand guard on the rooftops. The age of television had arrived with a vengeance.
The City of Detroit had an answer: the City's public-housing authority simply prohibited television sets in public housing residences. An infamous public notice read: "If you can afford a television set, you can afford to leave public housing!" TV sets were banned in all public housing units including thousands of units constructed during the early years of World War II to accommodate automobile-factory workers. Residents were not pleased.
Other cities took different courses, even affecting privately-owned housing.
Notwithstanding such efforts, television had arrived, and no political entity could stop it. At the end of 1946, 14,000 TV sets had been operating in the United States. By 1951, that number had exploded to 14,003,500 sets in use, a 1000-fold increase in five years.
- Rochester, New York: "No antenna shall extend more than 16 feet above the roof line" (thereby limiting reception to Rochester's WHAM which, at the time, was operating on Channel 6), but preventing reception of stations in Buffalo and Syracuse.
- Cleveland, Ohio: "Only one antenna per rooftop."
- Wisconsin: The state legislature enacted a law limiting antenna heights on private homes, a law aimed directly at communities just north of the Illinois state line, where an antenna mounted on 50-foot steel mast would receive Chicago stations. The justification: "We do not want to turn housing districts into forests of metal masts!"
- New York: In 1951, the state legislature enacted a law making it illegal "to attach radio, television or other wires" to fire escapes or side-of-building or rooftop vent (sanitary or kitchen) pipes.
Meanwhile, real estate developers embraced television and used it as a sales tool. Starting in 1947, Levitt & Sons, Inc., of New York, built a planned community on Long Island, still known today as Levittown, New York. To encourage sales, Levitt included a television antenna and twinlead inside wiring with each home. The company constructed hundreds of homes on a mass-production basis, reaching a total of over 17,000 homes by 1951.
Nationally, homebuilders were doing the same thing: they were installing TV antennas and twinlead inside wiring in new homes. Some, including Levitt, even included a television receiver with each home. In a housing development in Paramus, New Jersey, 16-inch sets were included under a contract from a firm we've encountered previously in the narrative: Industrial Television, Incorporated.
For large scale developers, television wiring was approaching the same must-have status as electric wiring and indoor plumbing.
In 1949, a clever person by the name of Robert Wright installed a television set in his car, positioned on the driveshaft 'hump' so he could watch it while driving. Prompted by the National Safety Council, legislatures across America reacted swiftly, banning TV sets from vehicles. Wright's defense: "I'm not allowed to have a TV aerial on my apartment so I moved the receiver to the car!" The National Safety Council called it "suicide on wheels!"
If the homebuilders had solved the television-reception problem for potential buyers, apartment dwellers were still at the mercy of their landlords. And many building owners continued to resist the installation of building-wide distribution systems.
Antenna manufacturers, included Jerrold, were quick to capitalize on this situation. Jerrold offered an array of devices including one called the "TV-FM Receptor" that claimed to turn your electrical wiring into a TV reception antenna ("slides over the line cord of TV or FM set"). Jerrold's second device was a flat roll-up doormat-like device called "The Magic Carpet" that could be laid on or tacked to a flat surface – floor or ceiling for example.
Neither of these approaches worked particularly well. Other firms created window-ledge antennas: lift up the window (assuming that was possible in your apartment unit), move a pair of adjustable wedges, and lower the window sandwiching the attached lead-in wire to the sash. Some of these antennas worked some of the time, provided that the window was located on the side of the building facing the TV transmitter.
And provided that neighbors above, below and on either side, were not watching certain television channels at the same time. For some combinations of channels, radiation from one TV set would interfere with a neighbor's TV set.
This situation resulted from two factors:
Consider, for example, the following situation. Residents of one apartment wish to watch Channel 5, but neighbors next door are watching channel 2. Thus, the local oscillator in the neighbor's TV set is tuned to:
Note that 81.00 MHz falls withing the passband of TV Channel 5 (76-82 MHz). Thus, radiation from the Channel 2 local oscillator causes interference to the Channel 5 receiver.
- Television sets of the day were notoriously poorly shielded, resulting in radiation from their local oscillator circuits.
- The intermediate frequency of most television sets of the day was set at 27.75 MHz (visual) and 21.25 MHz (aural).
The following photograph illustrates the how such interference would affect the picture on the set tuned to Channel 5. Note the diagonal light-and-dark bars.
Defects in television picture produced by interference from another source.
Interference of this type can occur with several channel combinations:
MATV - Free or for a price?
By the end of 1952, consumer demand for television service was growing rapidly. Television receiver manufacturers responded to this growing demand by offering better quality products. They began providing TV sets with better shielding to reduce the effects of interference, and they developed 12-channel detent tuners (Channels 2-13) to simplify tuning. Most significantly, they began using a higher intermediate frequency standard: 41.25 MHz (aural) and 45.75 MHz (visual) to eliminate the interference problem described above.
Meanwhile, cable TV was growing rapidly in rural areas across the country and some operators were building systems in smaller TV markets already served by a broadcast television station or two.
But Master Antenna Television was slow to develop. We'll continue this story in Part 4.
Continue to Part 4...