The SCR

Nov 10, 2023

Worldwide, militaries have always sought improved communication. Late in the 18th century, the French began sending messages via a national network of optical telegraph stations. Wired telegraphy proved valuable during the U.S. Civil War. Radio communication saw its first big military deployment during the Russo-Japanese War in 1904, with steady improvements during World War I, between the wars, and into World War II.

The SCR-536 was not quite up to the rigors of the battlefield. During an amphibious landing, one soldier reported, “it leaked water—and salt water ruined the sliding switch contacts.”Photo: U.S. Army/PhotoQuest/Getty Images

But the ordinary foot soldier didn’t get his own radio until the introduction of the SCR-536 Handie-Talkie in 1942. Built by Galvin Manufacturing (which later became Motorola), the SCR-536 weighed just 2.3 kilograms and was “designed for operation under battle conditions,” according to its technical manual. At the time, there was no other radio like it, and eventually 130,000 units were manufactured for the Allies during the war.

The handheld radio set first saw action in the Allied invasion of North Africa in November 1942. An ad for the radio featured a soldier’s endorsement: “Just like having a house telephone at your fingertips. We’re never alone. We feel safer, stronger, because we’re always in touch with our command post!”

Real-life experience with the radio was a little different. Some years ago, I acquired a 536 and a technical manual. I also got in touch with a retired Army officer, George H. Goldstone, who told me about using the 536 in the field, starting with Operation Torch, an amphibious landing in North Africa in November 1942.

In a December 1990 letter, Goldstone explained that the 536 was “intended as a radio for infantry company commanders to talk to battalion headquarters—and in that usage, it was inadequate from day one…. Ultimately it was used within infantry companies to communicate down to platoon leaders—a very short-range task.” According to the 536’s manual, it could operate over distances of 1 mile on land and 3 miles over salt water. But there were caveats: Hills, foliage, atmospheric conditions, and ground moisture could shrink the distance, as could the battery’s age and internal dirt and moisture.

Even at the shorter range, Goldstone wrote, “It had no end of problems.” During Operation Torch, he said, “it leaked water—and salt water ruined the sliding switch contacts. Then it required a special battery—and the entire supply of batteries for General Patton’s Western Task Force was on one ship, which the Germans torpedoed off Casablanca harbor. Fortunately for us, I had squirrelled away several boxes of batteries on every jeep in my Radio Section…. We had a supply of batteries for a while!”

Further complicating the radio’s use was its single frequency, which could not be changed on the fly. “This had to be done in our division radio shop, where we had a test rig set up,” Goldstone explained. “It could not be done at regimental or battalion level.”

Soldiers could be hard on the 536, he added. “One set came into our shop…with all the tubes dead. Some infantryman had used it to pound in tent pegs!”

After studying the manual—the TM11-235 War Department Technical Manual, to be specific—and the 536 unit I’d acquired, I gained a little more insight into how the radio worked and why it struggled to perform in the field.

The 536 used five “miniature” vacuum tubes that had been developed for civilian portable radios. To transmit, it used four of the tubes. To receive, it used all five. The unit contained two batteries: a 1.5-volt filament battery and a tall and narrow plate battery that supplied 103.5 volts. The designers of the Handie-Talkie were severely limited by the high power requirements of the unit’s vacuum tubes. The radio could operate for less than 24 hours on a set of batteries.

The 536 was simple to use. According to the manual, it was turned on by extending the antenna. “When thus connected to its internal dry-battery power supply, the radio set functions as a receiver. Pressing the press-to-talk switch converts the receiver circuit to a transmitter circuit.”

The radio could operate in any one of 50 channels between 3.5 and 6.0 megahertz. But changing channels required coils and crystals to be replaced in a maintenance facility—in Goldstone’s case, the division’s radio shop. There was no volume control.

The SCR-536’s technical manual included detailed suggestions on how to camouflage the radio and how to destroy it.Photo: Richard Brewster

The 536’s use of low-frequency AM transmission, not far above the broadcast band, required an enormous antenna. The unit’s 40-inch (102 centimeter) whip antenna was woefully inadequate at those frequencies. Worse, the long antenna became a target for enemy sharpshooters because it had to be held in a vertical position for best transmission.

Given the radio’s prominent antenna, I was puzzled at the manual’s lengthy discussion of how to camouflage the unit. “Knowledge of how to camouflage the radio set is as important as knowing how to operate it,” the manual explained. “A poorly concealed radio set will draw enemy fire, regardless of how well the operator may be hidden or covered.” Although various methods of camouflage are suggested, the manual states that “the most satisfactory way…is to insert in an issue drab sock.”

The Handie-Talkie saw wide use, but by 1943, the Allied Forces had a superior radio: the Galvin-designed SCR-300 Walkie-Talkie. It allowed the operator to select up to 41 frequency channels, versus the 536’s single channel. It also used VHF and FM, which meant less interference and reduced noise. And it had a much greater range—up to 8 miles (13 km).

Introduced in 1943, the SCR-300 was larger than the SCR-536, but it had 41 selectable channels, reduced noise and interference, and a range of up to 13 kilometers.Photo: Universal Images Group/Getty Images

But there were drawbacks. The SCR-300 was carried in a backpack and weighed a hefty 35 pounds (16 kg), about seven times as much as the handheld 536, and its batteries did not last more than 40 hours. Despite its size and weight, the SCR-300’s technical manual indicates that it was “primarily intended as a walkie-talkie for foot combat troops.”

But it would be a stretch to call the 300 a replacement for the 536.

The Axis powers apparently never had the equivalent of the SCR-536. But the Germans did field a radio set much like the SCR-300 that used rechargeable batteries, while the Japanese had one that relied on a hand-cranked generator.

After World War II, Galvin went back to producing civilian radios under the Motorola brand, and the company went on to become a major producer of vehicular radios for police and fire departments. These radios were technically quite similar to the SCR-300. The main improvements over the years were the eventual replacement of vacuum tubes with solid-state devices and the use of higher frequencies. These shifts allowed for the handheld two-way radios that are so common today, even as toys.

In 1983, Motorola introduced the DynaTAC 8000X, a walkie-talkie that for a time was the ultimate in personal communications. In its first incarnation, the 8000X was an analog unit. The system later became digital.

Today, the need for walkie-talkies like the 8000X has shrunk dramatically with the ubiquity of cellphones. Ironically, the range of a typical cellphone is no greater than that of the 536—the large number of geographically dispersed cell towers is what allows your cellphone to work. And, of course, battery life remains an issue.

An abridged version of this article appears in the October 2020 print issue as “Built for Battle.”

Part of a continuing serieslooking at photographs of historical artifacts that embrace the boundless potential of technology.

Richard Brewster, a retired nuclear power engineer, served until recently as project engineer on the hospital ship Global Mercy, operated by Mercy Ships. He previously wrote for IEEE Spectrum about re-creating the first flip-flop.