The Evolution In Broadcast Technology

Posted in Broadcast History.

[August 2025] Anyone who has entered the broadcast industry in the past ten years sees it in a totally different way compared with those who have worked in radio and TV for decades. Some common tools were not available as recently as 20 years ago – and if you named some common tools from past decades, younger folks may not even recognize them. Ron Schact takes us on a tour of the evolution of broadcast engineering.

Looking back at the last 100 years or so, at least from the beginnings of commercial broadcasting, the technical people and the equipment they operate have undergone some major changes.

Of course, this is not to say that broadcast engineers are different from others when it comes to job changes. Even farmers now have computerized planters, combines, and what have you with GPS, as well as so many other technical gee-gaws to produce a bigger harvest. On the other hand, in many ways, radio was really the beginning of electronic technology, usually the first electronic device in the home. Yes, lowly AM radio started it all, and the broadcast engineer has been there all along.

I would have to say that broadcast engineering goes through thirty-year changes, major changes which can be looked at in depth.

EARLY BROADCAST ENGINEERING

Let us start with a look at the first 30 years, 1920-1950s. (Yes, broadcasting was already 10 or more years old when the government started recognizing it, and most gear was “homebrew.” Each station looked a bit different, but they were all struggling just to get a signal on the air.)

The technology was simple: AM radio. Yes, AM was IT; nothing else was available.

Radio transmitters started off with modulated oscillators, no crystals, motor generator sets to provide DC Voltages, flat-top antennas, and vacuum tubes. De Forest moved us on to vacuum tubes and mercury vapor rectifiers. Major Armstrong invented the superheterodyne radio receiver, which remains today the standard radio reception circuit for AM. Crystal control (stations did rather “move around a bit” on the dial, vertical antennas, and higher fidelity were introduced.

This was the era when most developments were made to present and improve the quality of audio on AM. In those days, you had symphony orchestras playing concerts most evenings somewhere on the AM dial, and engineers did so much development to make it sound as good as possible.

If you want good information on AM fidelity, transmitters, modulators, and antennas, look for books written in this era, specifically the 1930s. Those guys knew how to make an AM station sound good and radiate a formidable signal.

REGULATION TAKES A NEW FORM

Up until 1934, the government was trying to catch up to broadcasting with regulations.

The Department of Commerce and the Federal Radio Commission made a series of rules, some of which broadcasters obeyed – and some they did not. Finally, in 1934, the Federal Communications Commission was established, specifically to bring order to the AM band through its Rules and Regulations.

The FCC saw to that with several monitoring stations around the country, including a super one in Grand Island, Nebraska. Their task was to make sure everyone complied with the Rules.

TUBE TIME DID NOT MEAN TELEVISION

There were no transistors to speak of until the mid to late 1950s, so at that time, vacuum tubes ruled the roost.

As I sit here writing this, I am listening to my All-American 5. For those of you who are not familiar with an All-American 5, it was a simple 5-tube superheterodyne AC/DC radio made by every company in the world. Most used identical circuits with some variations, but the typical All American 5 had a tube lineup as follows:

a 35Z5 or 35W4 rectifier,
a 50L6 or 50C5 for audio output,
a 12SQ7 or 12 AV6 served as the first audio detector,
a 12SK7 or 12BA6 IF amplifier, and
a 12SA7 or 12BE6 local oscillator/converter.

All of the tube filaments were in series, adding up to 121 Volts, so no resistors were necessary.

FM AND TV GET STARTED

The 1940’s also brought a few new items for the broadcast engineer to learn: FM and television.

The beginning of FM was very rocky as Major Armstrong demonstrated his frequency modulation system. Compared with AM, it was a significant improvement in sound fidelity. FM started in the 40 MHz (or Megacycles” (Mc) as they would say at the time) band but was then displaced to the 80 to 100 MHz area due to the efforts of RCA, which did not want competition for its AM stations and affiliates while they were pushing television.

Unfortunately, in those days, people were afraid to buy FM radios for fear it would move again. Besides that, most FM stations were just a simulcast of what was on AM. So, yeah, it sounded better, but who cared? The day’s popular music sounded good enough on AM. Besides that, cars did not have FM unless you owned a Cadillac.

1950 TO 1980

Now, let us move our focus to the next 30 years: 1950 through to 1980.

This is when television really started to blossom, and the radio engineers who had been dealing with antenna reactance, audio proofs, and ribbon microphones now had to deal with sync pulses, back porches, blanking, sweep, and other video things no one knew about.

FM also began a slow growth, and guys who were content with 8 kHz program lines now had to deal with 15 kHz audio, low distortion, pre-emphasis, and the other quirks of FM.

At the same time, the concern for AM audio started to dwindle, especially when the transistor was developed. Transistor radios were everywhere. In the 1950s and through the 1960s, AM radio was the haven for Rock and Roll – and kids went through more 9-Volt batteries than food. “The loudest station wins” mentality took over, so it became a loud modulation (distortion) war on the AM dial with very little concern for audio quality. The goal was to make it audible, as loud as possible, and then increase it by 3 dB.

FROM ONE TO TWO CHANNELS

Meanwhile, with no one wanting to advertise on FM, the FM band began to adopt a format of beautiful music with no commercials. Then FM managed a big hit – stereo on FM.

Wow! Everyone had to buy a stereo receiver or a stereo console to hear the glorious sound. For radio engineers, though, It was not without headaches: balanced, phased 15 kHz lines to the transmitter, time syncing the L+R with the L-R subcarrier every Monday morning during the maintenance period. I remember the first stereo generator I installed – it was in 1962. It took up half of a 7-foot rack and had more 12AT7s in it than any local distributor had in stock!

During the 60s, we also got into some pretty serious radio automation – especially on the FM dial. The original systems used reel-to-reel decks and either carousels, the Shafer Spotter or the Gates 55 cart deck for spots – usually it was all relay-controlled with pin programming or stepper relays. Moving into the 1970’s, the automation systems were upgraded with the invention of DTL and TTL integrated circuits. The systems became basic computers. At this point, the radio engineer came into the digital world with on’s and off’s and only analog audio.

Starting in the mid-60s, the radio guys working on TV had some new technology to absorb: color. On top of all the racks of early TV gear, now we needed a color burst, differential phase, VTR banding, and transistorized broadcast equipment with those horrible printed circuit boards. UHF TV also got going, so now the engineers had to deal with Klystrons, super high-power, water-cooled tubes, and high-gain antennas.

TRANSMITTER AND STUDIO CHANGES

Starting with the lower-powered units, transmitters began being manufactured with transistors.

The old 4-400, 833A, and 892R tubes started to disappear, but so did, in some ways, transmitter reliability. Hit one of those older guys with a lightning bolt, and they shrug their shoulders. But, if a bunch of 2N3055s got hit with lightning, they are completely out to lunch.

Back in the studio, for the most part, we were still replacing styli in turntables and cleaning heads in cartridge machines. The TV guys were still dealing with VTR’s, image orthicons, vidicons, and some fairly simple, mostly mechanical, automation systems.

1970S – A DECADE OF NEW TECHNOLOGY

As solid state devices proliferated, the 1970s again brought changes, especially changes in technology.

Automation systems in both radio and television were basically real computers loaded with ICs that were memories, processors, and IO cards. More transmitters started using logic control with ICs, and the old oscilloscopes that used to look at modulation, response, and distortion were now into digital pulses.

AM transmitters underwent significant changes, transitioning from class C RF stages modulated by push-pull class B tubes to several hundred pounds of iron. A technology called PDM (Pulse Duration Modulation) or PWM (Pulse Width Modulation) was gaining popularity. FM transmitters are increasingly utilizing phase-locked loops, making precision crystals a thing of the past.

AM STEREO

One innovation that did not last was AM Stereo. In many ways, it was a flash in the pan, but a slow burner.

Leonard Kahn developed a system of independent sideband transmission in the 1950s, but the FCC ignored it. When the FCC opened the door in the 70’s, everyone jumped on the bandwagon with a system including Kahn.

Unfortunately, Kahn did not have the manufacturing facilities to make the ICs to decode his system. Motorola, which had no previous interest in AM radio, developed a system that was not as stable or clean as Kahn’s, but they could manufacture the ICs to decode it and give them away for companies to produce stereo receivers for the Motorola system alone. After some legal wrangling, Motorola mostly won out, but it was very short-lived. Stations on local channels found out that the Motorola system did not work at night when the skywave caused a negative effect, so stations slowly dropped it, and car radios stopped being made.

There are still a few AM Stereo operations going, but not many.

1980 TO 2010

Our next 30-year block to consider is 1980 through 2010.

There have been huge developments:

The CD: No longer are we playing analog vinyl; music now is coming out on CDs. The audio is digital. Some is really good and some is really poor, but no one is looking back.
Automation systems are now using microprocessors and are full-blown computers, still, for the most part, controlling mechanical playback devices, even if they are just CD players.
Audio and video programming is still analog
FM really gained ground over AM, although there are still a lot of AM stations doing very well. FM discovered that if they played the same music as the AM guys but with fewer commercials, it would attract an audience. Rapidly, FM radios were everywhere, so AM had no real advantage other than coverage.
AM also suffered especially in Japanese automobiles when they began using sharp crystal and ceramic filters in the radios, limiting the bandwidth to +/- 3kHz.
Television news gathering stepped up to live microwave trucks and video cassette cameras. Some stations flew their own helicopters for news gathering, equipped with FLIR gyro-stabilized lenses and microwave transmitters.
Automation took another leap as satellites became the thing. I believe the first radio format to be available on satellite was Country Coast to Coast. With that, the radio station could operate with minimal staff and produce a professional product. Great for the station’s bottom line, but bad for the public. No more localism, announcers are two thousand miles away and have no idea what is going on in your local area.
The national radio networks also started delivering their programs by satellite, Mutual being the first with analog, then the big three followed with digital. The Scientific Atlanta receivers with the little door to change crystals, or the Comtek, either of which took up half a rack. Now engineers are dealing with 4000 MHz digital audio, TI links from the AT&T microwave, and wasp nests in the feed horn. A whole gamut of new problems.
Much the same goes for television, just bigger dishes, more snow to move in the winter, and more programs to lose in the spring and fall from sun fades.
As things progressed, the engineers had to switch direction as now more and more of the plant was becoming digital with more RJ45s, and fewer XLRs and BNCs.

If all this was not enough technology to adapt to, along came the 1990s.

COMPUTERS TAKE OVER THE STUDIO

Hmmm, the big question was: since we can store audio digitally on CDs, why can’t we store it right on a hard drive in a computer?

Well, at that time, a 4 GB hard drive still cost about $4000 (in 1983, 60 MB might cost $60k!), so the audio was compressed to within an inch of its life in order to store a full playlist on a couple of SCSI drives. I remember the first time I heard “Don’t Fear the Reaper” off of a hard drive. It was such a mangled mess that it was almost impossible to know which song it was. The fidelity of hard drive systems slowly got better as compression algorithms came about and hard drive prices came way down.

Personally, I still do not think digital audio is as good as analog, but my ears are too old to know better.

COMPRESSING TV PROGRAMS AND FREQUENCIES

The same sort of things happened with television.

Digital storage of programming grew, on tape using cartridges and digital reel-to-reel.
The UHF TV band ended at channel 69 instead of 82.

And the changes accelerated:

Cell phones popped up. Now, radio remotes no longer needed an ordered line or a Marti system; you could just plug a real mike into your bag phone and go out and do a remote.
TV stations started buying satellite uplink trucks to do broadcasts from a distance and locations previously unavailable by microwave radio, and ultimately, these channels became digital.
Something called “the Internet” popped up, and everyone was buying a home computer to get on the World Wide Web. Audio and video could be sent over the Internet instantly as long as it was digitally encoded.

www.nautel.com

The mid-1990s was the start of what you might call the digital overthrow.

Two systems of digital television were proposed. The fight between them continued until one became the victor, again, not the one I was in favor of.
The FCC had to figure out how to switch all of the stations to digital while keeping the analog going until enough digital sets were manufactured. They assigned every station a new channel, and after lots of moving, digital television became a reality.
Solid-state image receptors have made cameras so small that the video quality from a cell phone camera puts the old tube television cameras to shame. And the cameras the news people use all have digital storage.
Following on with progress brought us digital radio, both AM and FM. Now, many stations were all digital from the program source right out to the antenna. The FM stations and the AM stations can do both simultaneously, but digital AM never really took off as a supplement to its analog signal, as coverage issues and the sideband splatter and skywave issues made it pretty useless at night. Although an FM could do analog and digital at the same time, it was much harder for AM. Dropping the analog signal, Hubbard Broadcasting pioneered all-digital AM broadcasts, although attracting and keeping listeners was easy.

A NEW WORLD AHEAD

Now we engineers live in a fully digital world of IT.

Yes, there is still some analog, but we generate the programming digitally, we process it digitally, we send it to the transmitter digitally, and in television and many radio stations, it is transmitted digitally. Even the television microwave trucks have been replaced by bundling cell phone carriers to achieve enough bandwidth to pass quality video and audio.

Looking ahead, we will have a new digital form of television transmission coming around – it promises to be more robust, with more channels. Will we see AM radio or FM radio go all digital? The problem is, as someone once said, “everything that is wired will become wireless and everything that is wireless will become wired.”

Changes are continuing to happen fast. Consider:

Who still has a landline telephone?
How many people watch over-the-air television as opposed to Internet TV?
How many people listen to over-the-air radio? Local radio and television still can survive if they maintain their localism and connect with their audience, and not just become outlets for networks or juke boxes.

As the engineers, the guys (and gals) that keep the signal pumping out, it is just another day in Paradise; as long as the RF is squirting out of the antenna, people are happy.

There are some days, though, when I wish I could format C: on my brain to forget some of the old stuff and make room for the new. I am happy when I dig into my old H.H. Scott stereo amplifier, slip off the plate supply with the VOM, and a giant spark flies. Nothing is damaged, and I get the whiff of ozone.

Ahh … the smell of real electronics!

– – –

Ron Schacht (K3FUT) has been a radio engineer for over 60 years, during which he has built some 100 stations, including a dozen with directional antennas.

You can connect with Ron at:screamingeagle@wctatel.net.