Apex radio stations (also known as skyscraper and pinnacle) was the name commonly given to a short-lived group of United States broadcasting stations, which were used to evaluate transmitting on frequencies that were much higher than the ones used by standard amplitude modulation (AM) and shortwave stations. Their name came from the tall height of their transmitter antennas, which were needed because coverage was primarily limited to local line-of-sight distances. These stations were assigned to what at the time were described as "ultra-high shortwave" frequencies, between roughly 25 and 44 MHz. They employed amplitude modulation (AM) transmissions, although in most cases using a wider bandwidth than standard broadcast band AM stations, in order to provide high fidelity sound with less static and distortion.
In 1937 the Federal Communications Commission (FCC) formally allocated an Apex station band, consisting of 75 transmitting frequencies running from 41.02 to 43.98 MHz. These stations were never given permission to operate commercially, although they were allowed to retransmit programming from standard AM stations. Most operated under experimental licenses, however this band was the first to include a formal "non-commercial educational" station classification.
The FCC eventually concluded that frequency modulation (FM) transmissions were superior, and the Apex band was eliminated effective January 1, 1941, in order to make way for the creation of the original FM band, assigned to 42 to 50 MHz.
During the 1920s and 1930s, radio engineers and government regulators investigated the characteristics of transmitting frequencies higher than those currently in use. In the United States, by 1930 the original AM broadcasting band consisted of 96 frequencies from 550 to 1500 kHz, with a 10 kHz spacing between adjacent assignments. On this band, a station's coverage during the daytime consisted exclusively of its groundwave signal, which for the most powerful stations might exceed 200 miles (320 kilometers), although it was significantly less for the average station. However, during the nighttime, changes in the ionosphere resulted in additional long distance skywave signals, that were commonly reflected for up to hundreds of kilometers. [2]
Over time, technology was developed to transmit on progressively higher frequencies. (Although initially these were in general called "ultra-high shortwave" frequencies, radio spectrum nomenclature was later standardized, with 3 to 30 MHz transmissions becoming known as "High Frequency" (HF), 30 to 300 MHz called "Very High Frequency" (VHF), and 300 to 3,000 MHz called "Ultra High Frequency" (UHF)). [3] It soon became apparent that there were significant differences in the propagation characteristics of various frequency ranges. Signals from shortwave stations, operating roughly in the range from 5 MHz to 20 MHz, were found to be readily reflected by the ionosphere during both the day and at night, resulting in stations that sometimes could transmit halfway around the world.
Investigations of increasingly higher frequencies found that, above around 20 MHz, signal propagation by both groundwave and skywave generally became minimal, which meant that station coverage now began to be limited to just line-of-sight distances from the transmitting antenna. This was considered to be a valuable characteristic by the FCC, because it would allow the establishment of broadcasting stations with limited but consistent day and night coverage, that could only be received by their local communities. It also meant that multiple stations could operate on the same frequency throughout the country without interfering with each other. [4]
Because the standard AM broadcast band was considered to be too full to allow any meaningful increase in the number of stations, the FCC began to issue licenses to parties interested in testing the suitability of higher frequencies. Most Apex stations operated under experimental licenses, and were commonly affiliated with and subsidized by a commercially licensed AM station. Until the late 1930s, commercially made radio receivers did not cover these high frequencies, so early Apex station listeners constructed their own receivers, or built converters for existing models.
On March 18, 1934, W8XH in Buffalo, New York, a companion station to AM station WBEN, became the first Apex station to air a regular schedule. [5] Although most of these stations merely retransmitted the programs of their AM station partners, in a few cases efforts were made to provide original programming. In 1936, The Milwaukee Journal's W9XAZ, which initially had relayed the programming of WTMJ, became the first Apex station to originate its own programming on a regular basis. [6]
While monitoring the first group of stations, it was soon realized that, due to the strengthening of the ionosphere during periods of high solar activity, at times the lower end of the VHF frequencies would produce strong, and undesirable, skywave signals. (The December 1937 issue of All-Wave Radio reported that W6XKG in Los Angeles, transmitting on 25.95 MHz, had been heard in both Asia and Europe, while W9XAZ, 26.4 MHz in Milwaukee, Wisconsin had "a strong signal in Australia", and W8XAI, 31.6 MHz in Rochester, New York, "is another station that is often heard in Australia.") [7] This most commonly occurred during the summer months, and during peaks in the 11-year sunspot cycle. This determination led to the FCC moving the developing broadcasting service stations, which by now began to include experimental FM radio and TV stations, to higher frequencies that were less affected by solar influences.
In October 1937, the FCC announced a sweeping allocation of frequency assignments for the various competing services, including television, relay, and public service, which covered 10 kHz to 300 MHz. Included was a band of Apex stations, consisting of 75 channels with 40 kHz separations, and spanning from 41.02 to 43.98 MHz. [8] The 40 kHz spacing between adjacent frequencies was four times as much as the 10 kHz spacing on the standard AM broadcast band, which reduced adjacent-frequency interference, and provided more bandwidth for high-fidelity programming.
At the time it was estimated that there were about 50 Apex-style stations currently in operation, although transmitting on a variety of frequencies. [8] In January 1938 the band's first 25 channels, from 41.02 to 41.98 MHz, were reserved for non-commercial educational stations, [9] with the Cleveland City Board of Education's WBOE in Cleveland, Ohio, [lower-alpha 1] the first station to begin operation within this group. [10] [11]
Frequency | Station assignments |
---|---|
41.02MHz | W8XH – Buffalo, New York: Buffalo Evening News /WBEN (1934 –1939 ) |
41.06MHz | n/a; unused |
41.10MHz | WCNY/WNYE – Brooklyn, New York: New York City Board of Education (1939 –1941 ) |
41.14MHz | n/a; unused |
41.18MHz | n/a; unused |
41.22MHz | n/a; unused |
41.26MHz | n/a; unused |
41.30MHz | n/a; unused |
41.34MHz | n/a; unused |
41.38MHz | n/a; unused |
41.42MHz | n/a; unused |
41.46MHz | n/a; unused |
41.50MHz | WBOE – Cleveland, Ohio: Cleveland City Board of Education (1938 –1941 ) |
41.54MHz | n/a; unused |
41.58MHz | n/a; unused |
41.62MHz | n/a; unused |
41.66MHz | n/a; unused |
41.70MHz | n/a; unused |
41.74MHz | n/a; unused |
41.78MHz | n/a; unused |
41.82MHz | n/a; unused |
41.86MHz | n/a; unused |
41.90MHz | n/a; unused |
41.94MHz | n/a; unused |
41.98MHz | n/a; unused |
42.02MHz | n/a; unused |
42.06MHz | W8XWJ – Detroit, Michigan: Evening News Association/WWJ (1936 –1940 ) |
42.10MHz | n/a; unused |
42.14MHz | W3XIR – Philadelphia, Pennsylvania: WCAU Broadcasting Co./WCAU (1938 –1941 ) [12] |
42.18MHz | W2XWF – New York, New York: William G. H. Finch (1940 –1941 ) [13] |
42.22MHz | W1XKA – Boston, Massachusetts: Westinghouse E. & M. Co./WBZ (1940 –1941 ) |
42.26MHz | W9XAZ – Milwaukee, Wisconsin: The Journal Co./WTMJ (1940 –1941 ) [14] |
42.30MHz | W6XDA – Los Angeles, California: Columbia Broadcasting System/KNX (1940 ) |
W6XRE –Los Angeles, California: Ben S. McGlashan/KGFJ (1940 ) | |
W9XHW – Minneapolis, Minnesota: Columbia Broadcasting System/WCCO (1939 –1940 ) | |
W1XEQ – New Bedford, Massachusetts: E. Anthony & Sons/WNBH (1940 ) | |
W2XDV –New York, New York: Columbia Broadcasting System/WABC (1940 ) | |
42.34MHz | W1XER – Mount Washington, New Hampshire: Yankee Network (1940 –1941 ) |
W8XNT –Cleveland, Ohio: United Broadcasting Co./WHK (1940 ) | |
42.38MHz | W1XKB – Springfield, Massachusetts: Westinghouse E. & M. Co./WBZA (1940 ) |
42.42MHz | n/a; unused |
42.46MHz | W1XEH – Hartford, Connecticut: Travelers Broadcasting Service Corp./WTIC (1940 –1941 ) |
W9XER – Kansas City, Missouri: Midland Broadcasting Co./KMBC (1940 –1941 ) | |
42.50MHz | n/a; unused |
42.54MHz | n/a; unused |
42.58MHz | n/a; unused |
42.62MHz | n/a; unused |
42.66MHz | n/a; unused |
42.70MHz | n/a; unused |
42.74MHz | n/a; unused |
42.78MHz | n/a; unused |
42.82MHz | n/a; unused |
42.86MHz | n/a; unused |
42.90MHz | WBKY – Beattyville, Kentucky: University of Kentucky (1940 –1944 ) [15] [16] |
42.94MHz | n/a; unused |
42.98MHz | n/a; unused |
43.02MHz | n/a; unused |
43.06MHz | n/a; unused |
43.10MHz | n/a; unused |
43.14MHz | n/a; unused |
43.18MHz | n/a; unused |
43.22MHz | n/a; unused |
43.26MHz | n/a; unused |
43.30MHz | n/a; unused |
43.34MHz | n/a; unused |
43.38MHz | n/a; unused |
43.42MHz | n/a; unused |
43.46MHz | n/a; unused |
43.50MHz | n/a; unused |
43.54MHz | n/a; unused |
43.58MHz | n/a; unused |
43.62MHz | n/a; unused |
43.66MHz | n/a; unused |
43.70MHz | n/a; unused |
43.74MHz | n/a; unused |
43.78MHz | n/a; unused |
43.82MHz | n/a; unused |
43.84MHz | n/a; unused |
43.92MHz | n/a; unused |
43.96MHz | n/a; unused |
43.98MHz | n/a; unused |
At the time the Apex band was established, the FCC noted that "The Commission at an early date will consider carefully the needs and requirements for high-frequency broadcast stations using both conventional [AM] modulation and frequency modulation". [8] As of January 15, 1940, only 2 non-commercial [17] and 14 experimental stations held Apex band licenses, all of which were assigned operating frequencies in the bottom half of the band. (A similar number of experimental stations held grants for frequencies in the 25–26 MHz region.) In addition, at this same time 20 experimental FM stations had been assigned slots within the top half of the Apex band frequencies. [18]
The commission's studies soon found significant advantages to FM transmissions over the Apex AM signals. Sound quality, and especially resistance to interference from static, including from lightning, was found to be far superior for FM. Although FM assignments required five times the bandwidth of Apex stations (200 kHz vs. 40 kHz), the "capture effect" allowed FM stations operating on the same frequency to be spaced closer together than Apex stations. By 1939 the FCC began encouraging Apex stations to consider changing to the technically superior FM transmissions. In May 1940, the FCC decided to authorize a commercial FM band effective January 1, 1941, operating on 40 channels spanning 42–50 MHz. [19] (This was later changed to 88–106 MHz, and still later to 88–108 MHz, which increased the number of channels to 100.)
This new assignment also resulted in the elimination of the Apex band, and the Apex stations were informed that they needed to either go silent or convert to FM. [20] With this change, a few of the original Apex stations were converted into some of the earliest FM stations. The three educational stations were allowed some leeway in making the conversion to FM, with WBOE switching over in February 1941, [21] WNYE receiving permission to continue as an Apex station until June 29, 1941, [22] and WBKY receiving a series of authorizations to continue using its AM transmitter until May 1, 1944. [16] Currently, the frequencies that had been used by the Apex band are allocated for land mobile communication. [23]
There would be at least one attempt to revive the Apex band concept. Beginning in May 1946, consulting radio engineer Sarkes Tarzian operated a 200-watt experimental AM station, W9XHZ, on 87.75 MHz in Bloomington, Indiana. After two years of successful operation of what he referred to as his "HIFAM" station, [24] in 1948 he proposed that the FCC allocate a small high-frequency broadcast band, 400 kHz wide with 10 kHz spacing between frequency assignments. Tarzian promoted this as a low-cost alternative to expensive FM transmitters and receivers, saying that a $5.95 converter could be added to existing AM radios that would allow them to pick up the HIFAM stations. [25] He continued to operate his experimental station, which eventually became KS2XAP, until 1950, although by then its transmitting hours were greatly restricted, as the FCC required the station to remain off the air whenever nearby WFBM-TV in Indianapolis was broadcasting. This was due to the fact that the TV station's audio transmitter used the same frequency as Tarzian's station. [26] Moreover, after his station's final license expired on June 1, 1950, the FCC denied Tarzian any further renewals, [27] concluding it would not reverse its earlier determination that there was no need for a second AM broadcast band.
Shortwave radio is radio transmission using radio frequencies in the shortwave bands (SW). There is no official definition of the band range, but it always includes all of the high frequency band (HF), which extends from 3 to 30 MHz ; above the medium frequency band (MF), to the bottom of the VHF band.
FM broadcasting in the United States began in the 1930s at engineer and inventor Edwin Howard Armstrong's experimental station, W2XMN. The use of FM radio has been associated with higher sound quality in music radio.
AM broadcasting is radio broadcasting using amplitude modulation (AM) transmissions. It was the first method developed for making audio radio transmissions, and is still used worldwide, primarily for medium wave transmissions, but also on the longwave and shortwave radio bands.
Radio broadcasting is the broadcasting of audio (sound), sometimes with related metadata, by radio waves to radio receivers belonging to a public audience. In terrestrial radio broadcasting the radio waves are broadcast by a land-based radio station, while in satellite radio the radio waves are broadcast by a satellite in Earth orbit. To receive the content the listener must have a broadcast radio receiver (radio). Stations are often affiliated with a radio network that provides content in a common radio format, either in broadcast syndication or simulcast, or both. The encoding of a radio broadcast depends on whether it uses an analog or digital signal. Analog radio broadcasts use one of two types of radio wave modulation: amplitude modulation for AM radio, or frequency modulation for FM radio. Newer, digital radio stations transmit in several different digital audio standards, such as DAB, HD radio, or DRM.
A radiotelephone, abbreviated RT, is a radio communication system for conducting a conversation; radiotelephony means telephony by radio. It is in contrast to radiotelegraphy, which is radio transmission of telegrams (messages), or television, transmission of moving pictures and sound. The term is related to radio broadcasting, which transmit audio one way to listeners. Radiotelephony refers specifically to two-way radio systems for bidirectional person-to-person voice communication between separated users, such as CB radio or marine radio. In spite of the name, radiotelephony systems are not necessarily connected to or have anything to do with the telephone network, and in some radio services, including GMRS, interconnection is prohibited.
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A subcarrier is a sideband of a radio frequency carrier wave, which is modulated to send additional information. Examples include the provision of colour in a black and white television system or the provision of stereo in a monophonic radio broadcast. There is no physical difference between a carrier and a subcarrier; the "sub" implies that it has been derived from a carrier, which has been amplitude modulated by a steady signal and has a constant frequency relation to it.
The FM broadcast band is a range of radio frequencies used for FM broadcasting by radio stations. The range of frequencies used differs between different parts of the world. In Europe and Africa and in Australia and New Zealand, it spans from 87.5 to 108 megahertz (MHz) - also known as VHF Band II - while in the Americas it ranges from 88 to 108 MHz. The FM broadcast band in Japan uses 76 to 95 MHz, and in Brazil, 76 to 108 MHz. The International Radio and Television Organisation (OIRT) band in Eastern Europe is from 65.9 to 74.0 MHz, although these countries now primarily use the 87.5 to 108 MHz band, as in the case of Russia. Some other countries have already discontinued the OIRT band and have changed to the 87.5 to 108 MHz band.
Digital Radio Mondiale is a set of digital audio broadcasting technologies designed to work over the bands currently used for analogue radio broadcasting including AM broadcasting—particularly shortwave—and FM broadcasting. DRM is more spectrally efficient than AM and FM, allowing more stations, at higher quality, into a given amount of bandwidth, using xHE-AAC audio coding format. Various other MPEG-4 codecs and Opus are also compatible, but the standard now specifies xHE-AAC.
Digital radio is the use of digital technology to transmit or receive across the radio spectrum. Digital transmission by radio waves includes digital broadcasting, and especially digital audio radio services.
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Sarkes Tarzian was an Ottoman-born American engineer, inventor, and broadcaster. He was ethnic Armenian born in the Ottoman Empire. He and his family immigrated to Philadelphia, Pennsylvania, United States in 1907, following their persecution by Ottoman Turks. "His father escaped to America from the Turkish massacres of Armenians, and got a job as a weaver." In 1918, he was the top high school graduate in the city of Philadelphia, earning him a four-year, all-expenses-paid college scholarship to the University of Pennsylvania where he received an undergraduate degree in 1924 and a graduate degree in 1927. Tarzian worked for the Atwater Kent company and then for RCA in Bloomington, Indiana.
W8XH was a Buffalo, New York radio station, authorized by the Federal Communications Commission (FCC) as an "experimental audio station", which was owned by the Buffalo Evening News, and which operated from 1934 to 1939. It was the first apex band station, i.e. the first to transmit programming intended for the general public over what was then known as "ultra-high short-wave" frequencies. W8XH primarily simulcast programming originating from a co-owned AM radio station, WBEN, but it also aired some original programs. It ceased broadcasting in July 1939, after the newspaper began to focus on operation of an experimental facsimile broadcasting station, W8XA, which in turn shut down shortly prior to World War II and was succeeded after the war by the establishment of an FM station.
W8XWJ was a Detroit, Michigan "experimental audio broadcasting station", owned by the Detroit News, which operated from 1936 to 1940. It was classified as an Apex broadcasting station, i.e. it provided programming intended for the general public over what was then known as "ultra-high short-wave" frequencies. W8XWJ primarily broadcast unique programming, although it sometimes simulcast programs originating from co-owned AM station WWJ. In April 1940, W8XWJ was shut down, in order to be converted to a commercial FM station.
W4XA was an "experimental audio broadcasting station" operated by The National Life and Accident Insurance Company in Nashville, Tennessee, from 1939 to 1940. It was part of a group of stations informally referred to as "Apex" stations, because it transmitted programming intended for the general public over what was then known as "ultra-high short-wave" frequencies. Although co-owned with AM station WSM, it primarily originated its own programs. W4XA ceased broadcasting in 1940, as station management prepared to inaugurate a new FM station, W47NV.
WMNE was a pioneer commercial FM radio station, which was the second of two mountain-top broadcasting stations established by the Yankee Network. It began regular programming, as experimental station W1XER, in December 1940. In 1941 it was licensed for commercial operation from studios in Boston, initially with the call sign W39B, which was changed to WMTW in 1943. In late 1946 the station's designated community of license was changed to Portland, Maine, and its call letters became WMNE.
WTMJ-FM was a pioneer commercial FM radio station, owned by the Journal Company, publishers of The Milwaukee Journal, and located in Milwaukee, Wisconsin. In the late 1940s, it was one of the first FM stations in America and among the most powerful. Although heavily promoted, the station was unprofitable and ceased operations in April 1950. Management foresaw a limited future, especially in contrast to recently introduced television broadcasting.
HIFAM" was a contraction of "high frequency amplitude modulation