By Zach Hagadone
Reader Staff
The last time Brenden Bobby took a week off from “Mad About Science,” we wrote about 1950s technology — including the invention of video tape. That entry turned out to be particularly interesting, not least because it prompted Reader reader Valerie Maxey to reach out and let us know that her father, Alex Maxey, was one of the core members of the team at tech company Ampex that was responsible for developing the first practical video tape recorder in 1956.
With Brenden out for another week, we figured we’d delve deeper into the technology behind video tape and, thanks to Valerie’s additional information, the race to develop it.
The technology started with sound recording on magnetized metal wires in the late-1800s. Though theorized as early as the 1870s, Danish inventor Valdemar Poulsen is credited with the first working magnetic recorder in 1898. Though crude, Poulsen’s innovation — which came to be called the telegraphone — already operated on the same basic principles that led to later recording and storage technologies.
Put as simply as possible, the first magnetic recorders relied on the ability to convert sound waves into electrical signals by passing through the air and causing vibrations inside a microphone. To record those signals, Poulsen’s invention used a metal wire that passed through a magnetic field created by a small electromagnetic array — otherwise known as a recording head. At the same time, the electrical signals are moved through the field, causing constant fluctuations that physically arrange magnetic particles or sections of metal on the wire into specific patterns reflecting the characteristics of the signal.
Once the wire has been altered by the magnetic field’s interaction with the electrical signals, it is effectively stored as a kind of magnetic fingerprint. Now magnetized and carrying the specific pattern created when it passed through the recording head, the wire is run through another field that picks up on the magnetic pattern fluctuations emanating from the wire. This is the playback head, which responds by creating various levels of electrical voltage (in other words, replicating the electrical signals that were created when the original sound waves interacted with the microphone at the beginning of the process).
When run through a speaker, those electrical signals again create vibrations that are amplified and come out the other end as sound waves that — hopefully — match the ones that were initially recorded. Essentially, sound becomes electricity, electricity becomes magnetism on the wire, and then the magnetism is turned back into electricity and finally into sound again.
That technology was proved by the turn of the 20th century, but with more usage came the need for more storage capacity. There was only so much physical space on a thin metal wire to retain magnetic patterns, so other, more robust storage media was needed. The first innovation came with a metal ribbon (greatly increasing the surface area on which magnetic patterns could be created). In 1935, German chemical firm I.G. Farben’s subsidiary BASF came up with a cellulose acetate-based tape that was lightweight, and easier to produce than metal strips and could be coated with iron oxide particles. BASF’s step forward resulted in the Magnetophone, but the breakthrough was hidden from the world by the Nazis until after World War II.
The story of the video tape usually starts with U.S. Army Signal Corps Major Jack Mullin, who discovered a Magnetophone in a Frankfurt radio station shortly after the war. An electrical engineer, he took two of the machines apart and mailed them to San Francisco in pieces, then reassembled them when he got home. The devices made a splash with radio engineers and Mullin ended up working as chief engineer for Bing Crosby Enterprises.
We already told part of that story, but magnetic recording made a huge leap from sound to video recording in the early 1950s — what “would be like the difference between a paper airplane and a moon rocket,” according to the 1994 article “The Race to Video,” by Stewart Wolpin, in American Heritage’s Invention & Technology magazine.
A number of players were involved, including BCE, RCA and Ampex — the latter which assembled a team including Charles Ginsburg, Ray Dolby (a.k.a. Dolby surround sound), Charles Anderson, Shelby Henderson, Fred Pfost and Alex Maxey — the latter a mechanical prodigy without a high school diploma whose contributions greatly improved the efficiency of scanning and the efficiency of tapes themselves.
Poulsen’s original wire recording principles remained mostly the same; winning the race for a viable video tape recording technology centered on expanding storage capacity, and that meant super-sizing every aspect of the process: from more powerful recording and playback heads to improved magnetic signal scanning (one of Maxey’s individual contributions) to finding a tape medium that was durable and spacious enough to run at the high speeds necessary to achieve the bandwidths required to hold both the light and sound waves of video.
While Crosby’s crew and RCA made more P.R. waves, Ampex was quietly — and effectively — making those advancements, resulting in the Ampex Mark IV, which debuted before hundreds of CBS bigwigs on April 14, 1956 in Chicago and represented the first example of a truly commercial-grade video tape recording.
Thanks to Valeria Maxey for sharing her dad’s story and, for more detail, read Wolpin’s fascinating article. Meanwhile, stay curious 7B.
