in our modern age, we tend to choose gadgets with as many features as possible, and we get goosebumps at the thought of a single-use item – which is why umbrellas can be so frustrating to carry around. But sometimes, a single use is exactly the right level of functionality.
This is something we’ve thought about recently after getting our hands on quite a big one that has literally one function: You turn it on and a specific station playsand there is no way to do anything else with it.
It’s a strange gadget, but for its niche, this device, called subcarrier radius, it was perfect. And it was one of the many niches that subcarrier radios made possible.
But… What is a subcarrier radio signal?
In 1985, an article in the American Sun-Sentinel newspaper in South Florida spoke of a potentially lucrative offer for the owners of FM radio stations: from parts of the authorized signal that they were not using.
This phenomenon was not unusual at the time; the practice had existed for decades. But what the article highlighted were the numerous ways to use radio signals that the average listener probably wasn’t aware of: for background music, stock reports, even for streaming.
And while station owners didn’t make much extra money (a single lease brought in $1,400 a month), about $3,500 today), for a struggling broadcaster, additional revenue could mean the difference between being in the red or the green.
What allows many radio stations to monetize their signals in this way is essentially a technical gap within the FM broadcast signal. These holes, or subcarriers, are frequencies that are not used for the main signal, but could find secondary uses in more specialized contexts.
At first, subcarrier signals were used in two ways:
First, allowed to obtain additional bandwidth to reinforce the primary technology. The best examples are the analog form of color television, which carried color information via the subcarrier, and the stereophonic capabilities of FM, which take advantage of subcarrier signals to make room for additional broadcast bandwidth. .
Some of the secondary signals could not be used to enhance the primary signal because they were not directly accessible, but they could be used to offer completely unrelated niche services. The most famous of them was the Muzak background music service (typical elevator music).which in many ways reflected all the strengths and weaknesses of specialized radio services.
was initially distributed over power lines, but ended up using subcarriers during the 1960s and 1970s.
The audio signal for a subcarrier service used to arrive at the station’s FM transmitter site through an equalized telephone line. From there, it used to go through some sort of audio processing, and through the subcarrier generator at the station, and then through the exciter.
Stations that broadcast subcarriers had to have a FCC-certified SCA monitor and take periodic readings of the subcarrier frequency, injection level, and modulation.
At the reception area, an antenna was always installed on the roof, since FM subcarriers are even more sensitive to multipath degradation than stereo subcarriers. Installers used to carry in their trucks an assortment of high gain yagi antennasfrequency cut, gamma-matched 72 ohm 3 and 5 element.
Crossover antennas used to offer about 20 dB gain over broadband FM devices. In case of extreme reception problems, a stacking harness was available so that two or more antennas could be deployed.
Definitely, the quality of the subcarrier signals was inferior to that of traditional FM broadcasts, which contributed to Muzak’s elevator music reputation. And very soon, satellite radio (and later, webcasting) replaced many uses of subcarriers, as they were cheaper and allowed higher fidelity than an FM signal that was already split into frequencies.
So why was there a sudden increase in demand for subcarriers in the 1980s?
In 1983, the US Federal Communications Commission modified the rules regarding subcarriers, deregulating them and allowing their use without additional oversight. The decision expanded the subcarrier use cases to “any legitimate communications purpose, whether or not related to broadcasting“.
In the mid-1980s, subcarriers were being used well beyond their original use cases, especially in large markets.
Some common use cases were radio stations targeted at physicians (and paid by the pharmaceutical industry), stock market reports, and foreign-language radio signals targeted at specific ethnic communities.
But subcarrier radio broadcasts weren’t just about making money, they had value in areas you don’t even think about when listening to top 40 radio. That is why there is a radio device that can only pick up an FM station.
News reading subcarrier stations improved access to information
Now that you have a basic understanding of subcarrier radios, let me tell you about the radio we got. This radio only has one control accessible to the user, for volume. It can pick up the subcarrier signals of a single station, the 92.9 FMand not much else.
It’s described as “solid state” technology, but it’s not digital at all: when the radio is unplugged it kept playing for about ten seconds after losing power. And despite having a 1988 service date on the back, it’s likely much older, appearing to date from the 1960s.
The radio, produced for the company Radio Talking Book Network, was designed so that people with low or no vision could listen to the newspaper, in its entirety, in audio form. Developed by the public radio station KSJR-FM (later known as Minnesota Public Radio) and launched in 1969, the network was the world’s first example of a reading-by-radio service.
These services offer a selection of reading materials, usually newspapers, magazines and books.
The concept, while new to radio, was not entirely without precedent. The first ones were intended for the blind audience and were also based on one, in this case, vinyl records, decades before the format became popular for music.
Using a mix of staff and volunteer programmers, the Radio Talking Book Network gave listeners access to the newspaper in a format they could use. In a 1973 broadcast on student radio station KUOM, network host Larry Davenport talked about how the radio station had “one of the most select hearings in the state“.
The Radio Talking Book Network format was widely copied throughout the United States., especially by other public radio stations, and also in other countries. Although many of these services are now accessible online, radio devices such as the one we have discussed continue to be offered.
Microsoft tried to use FM subcarrier signals to turn normal devices into “smart” devices
You may remember the period in the 1990s when it was relentlessly touted as the next big thing, with services like PointCast launching the idea of the Internet as a method of getting tapes of constant information at all times.
As described in
“The company’s initial product was a screensaver displaying news and other information, broadcast live over the Internet”
Put like that, it doesn’t sound particularly innovative, and yet it was popular for a while.
PointCast was basically Twitter, but without the possibility of interacting with those information flows. Despite this seemingly modest business model, it was a bandwidth hog and was often banned from offices.
PointCast was one of the early failures of the dotcom boom.but the idea stuck, as streams of data continued to flood our eyes into the early 2000s. But, What to do with limited data sources?
During the 2003 Consumer Electronics Show, he offered a glimpse into the future of push technology. with nothing less than Bill Gates as protagonistthe company showed off a subscription network called DirectBand (also known as MSN Direct)which sent brief text updates via radio signals to devices such as clocks, coffee pots, alarm clocks, and magnets using a technology called SPOT (for Smart Personal Objects Technology).
Basically, Microsoft tried to invent the Internet of Things using 2003 technology plus FM subcarrier signals. And they actually got a lot closer than you might expect.
People in the audience laughed as Gates showed off a little magnet he had customized to receive Seattle traffic information, but what he meant was that these informational magnets could have a million specialized uses and be placed almost anywhere: briefcases, wallets, key chains, watch key chains.
It was a strange idea at the time, despite Bill Gates directly “predicting” the rise of the smartwatch just over a decade later. In fact, the Microsoft network helped bring some formative smartphones to life, most notably a Fossil model using the Dick Tracy brand.
The problem was that it was a one-way medium. Your friends could text you at will, but your Dick Tracy watch couldn’t respond.
Ultimately, it literally suffered from bad timing. Microsoft relied on one-way FM radio for data just at the time cellular broadband was taking off. Once that happened, few wanted a watch that could only receive very limited data through 12 channels of MSN Direct.
Microsoft’s network was generally forgotten by the public, though it did find some niche uses, particularly in the , where its ability to pull traffic notifications and weather forecasts came in handy. But the technology was not successful enough to sustain itself, and Microsoft ended the service in 2012.
As with the smart phones, Microsoft was an innovator in smartwatches, with some key advances demonstrating to the market just a few years after the company exited the market. The use of FM subcarrier technology was not perfect, but it was novel for its time and probably paved the way for future…
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