Continuing from Part 1 – Although radio saw use before World War I, it was not until World War II that technology allowed the use of truly tactical radio systems that could move with the warfighter. Going into the war, the U.S. Army employed radios using two distinctly different signal format technologies – amplitude-modulation and frequency-modulation. And there were no AM-FM switches.
Infantry platoons and squads carried the SCR-536 – what we war movie watchers immediately identify as a “walkie-talkie” but was in wartime jargon a “handie-talkie.” The hand held radio operated between 3.5 and 6 Mhz, transmitting in the AM format. Using only a 1.5 volt battery, range was at best maybe a mile. But sufficient for squad and platoon use.
At the company level (and at times platoon headquarters) was the SCR-300, the authentic “walkie-talkie.” The SCR-300 was the first mass-produced FM backpack radio transmitting on 40 to 48 Mhz to a three mile range. Again, sufficient range for a company command net, but not enough power to attract unwanted (artillery) attention. SCR-300s and other radios at the battalion level linked in the companies, but the preferred method of communication was by the wire on the field phone. At the battalion level, the SCR-694 was available, transmitting in the AM format across the 3.8 to 6.5 Mhz band with a range between 15 and 30 miles (the later using Morse code).
Up until 1944 most tanks carried SCR-508 series radios. These operated on a 20 to 27.9 Mhz band transmitting in the FM format out to ranges up to ten miles. Another radio series, the SCR-509/510, operating on the same format and band served the artillery fire control networks. While “dis-mountable” these were too heavy for pack use and required a heavy brick-like battery (sound familiar?).
Doesn’t take a military genius to notice that all these radios offered disconnected networks. And the radios mentioned here do not take into account networks used to coordinate artillery fires or air support. Those radio nets used specialized equipment on different bands.
As often happens in American military history the solution to the problem came forward from the field. Armor and infantry teams began swapping radios as a standard practice. To facilitate lower level communications, and looking back at a post made a few days back, field phones appeared on the fenders of tanks wired into the intercom systems. The Army officially responded, essentially legitimizing the field modifications, with standardized kits to add phones to the tanks and with the AN/VRC-3 radio. The VRC-3 offered the same radio unit as used in the SCR-300, but with power adapter and mount for use on tanks or armored vehicles. These kits arrived in Europe towards the end of 1944, and later in the Pacific.
The problems with these early radios sound familiar, even 60 years later.
- The SCR-300 “walkie-talkie” weighed 38 pounds with battery. Not good for the “fighting” radio man.
- Limited range as mentioned above.
- Maintenance. These systems used crystals and vacuum tubes. Mishandling damaged the tubes. While quite sturdy for their time, these radios required a lot of care, particularly in high humidity environments.
- Battery. Battery life for the SCR-300 was about 12 hours for the “light” BA-80, and 20 for the “heavy” BA-70. The BA-70 weighed about 12 pounds.
- (Un)ease of use. Radio transmitters of this age required selection of crystals, proper tuning, and calibration. The technical manual of the SCR-300 detailed this multi-step process. Or better still watch this video demonstrating an SCR-508 in operation.
- As the radios operated on very narrow band ranges, they were susceptible to interference from many sources – in particular enemy transmitters. Jamming and intercept were common problems.
- Distorted voice over the radio. Partly a function of interference, but mostly just the nature of modulated and demodulated audio.
Yet even for those issues, the SCR-300, -508, -510, -536, and VRC-3 radios served well. At the time the United States was the world’s finest and largest producer of radio equipment. The US Army lavishly used FM radios, which were in short supply with other armies. Large quantities of repair parts and batteries feed the warfighter’s need. The massive mobilization of manpower afforded the luxury of targeted training for radio operators. The Army evolved a series of counter operations involving code words, challenge-authentications, and alternate frequency shifts to counter enemy jamming and intercept. And to mitigate voice distortion, the Army adopted the practice of phonetic spellings (although the key-words used were different than today’s NATO standards, i.e. “item” instead of “india”.)
Keep in mind that doctrinally, the Signal Corps entered the war considering the pigeon a viable means of communication (yes FM 11-80, the Signal Pigeon Company, is a good read if you have time). The preferred means of battlefield communications, according to the folks from Fort Monmouth, was either wire or courier. For wire operations, the Signal Corps devised wire-laying equipment that could easily move with the battalion trains. Where possible, a plow system allowed laying of buried wire at five miles an hour. In short, the signal troops could get a field phone right up to the very edge of the battlefield.
Such reliance on wire as a primary communications medium – with radio as the necessary secondary to support active operations – at the tactical level was fine for the pace of operations through most of World War II. Even in Korea, particularly in the later static phases, telephone met most of the Army’s needs.
But as planners turned to what they felt would be the inevitable war in Europe against the Soviets, they foresaw a wide-ranging, mobile form of warfare against an enemy who would target command and control facilities. The commander could not depend on a telephone-wire based communication network in such a combat environment. Further, experience in lower-intensity conflicts demonstrated the need for improved tactical radios. These LIC operations tended to be small unit, perhaps battalion and below, with infantry units occupying much larger battlespace than on a conventional field. These requirement shifts prompted changes to tactical communication doctrine and towards a new family of radio systems.
That is the subject of my next post – the early Cold War radios.