Continuing from Part 2 – Like much in the U.S. Army, tactical communications evolved little in the years following World War II. Many of the same radios continued service into the Korean War. New developments, including long-range multi-channel and radio-teletype, supported division and higher level communications networks, and thus fall outside the scope of this discussion.
In the closing stages of the Korean War, the AN/PRC-6 replaced the SCR-536 hand held radio in infantry platoons. The PRC-6 introduced FM signal format to the squads and operated between 47 and 55.4 Mhz, with range remained limited to about a mile in good conditions. Also introduced during the Korea War, three new backpack radios differed only with regard to frequency range. The AN/PRC-8 covered 20 to 27.9 Mhz, the AN/PRC-9 worked on 27 to 38.9 Mhz, and the AN/PRC-10 operated from 38 to 54.9Mhz. The AN/PRC-10, of course, being the preferred company radio to allow compatibility with the hand held radios. One advantage over the World War II sets, the new backpack radios tipped the scales at around 22 pounds (verses 38 for the old SCR-300). The PRC-8/9/10 ranged just under five miles.
Parallel to these portable radios, the Army deployed a series of vehicle (armor and soft skinned) radios using the RT-66 receiver-transmitter as a building block. Like the infantry backpack series, the series offered different radios operating on different bands. The AN/VRC-8, -13, and -16 used the 20 to 27.9 Mhz band. The AN/VRC-9, -14, and -17 used the 27 to 38.9 Mhz band. And the AN/VRC-10, -15, and -18 operated on 38 to 54.9 Mhz. These different designations indicated variations with power supplies or other options. These vehicle mounted radios had a maximum planning range of 10 miles. All of these types, both vehicle and portable, continued the use of crystals and vacuum tubes, with all corresponding disadvantages. Tuner technology limited the frequency range each radio could operate over (and forcing the use of three different frequency bands). But recall, this was the height of technology at the time.
While the divided frequency bands sounds odd to a modern reader, this fit within the Army’s communication doctrine of the time. By the “book” infantry regiments operated with a command net and an operational net. Organic support formations, such as the mortars and anti-tank platoons had their own designated radio nets. Line battalions maintained an internal command net. Likewise companies operated on their designated command nets. By doctrine, the commander could direct the signal officer to create optional networks to support additional reconnaissance or security attachments, medical support traffic, or for liaison with adjacent units. (FM 7-24, Communication in the Infantry Division, dated 1944 describes these radio nets in more detail) Add to the spectrum of course the fire control networks transmitting back to the fire direction centers.
The number of radio nets, while manageable, required some mechanism to segregate traffic. The three frequency bands, noted in the radio particulars, happened to allow specific equipment to operate on specific frequency ranges for specific roles. I am told, but cannot find it referenced in the manuals, that planners allocated the 38 to 54.9 Mhz band for networks company and below.
That worked well in the “square” or “triangular” army formations used through the Korean War. But in the mid-1950s the Army began reorganizing around a monstrosity known as the Pentomic Division. Under that concept, each of the five “battlegroups” within the division contained five maneuver companies along with a number of combat support and service support elements. To manage this multi-headed formation, a battlegroup CP used a command net, an admin net, and a dedicated liaison net. Add to this nets for the engineer platoon, medical platoon, and supply platoon. The combat support company had nets allocated for the radar platoon, recon platoon, assault weapon platoon, and heavy mortar platoon. In short, a proliferation of radio networks, each requiring radio sets and dedicated radio operators. Communications personnel represented 9% of the battlegroup’s personnel strength!
The technology did not support such a cumbersome command structure. Command net became crowded, often at the commander’s discretion. Recall this was the time when the Army fielded the Davy Crockett tactical nuke. Odds are, the battlegroup commander would prefer to have that section on a tight leash, and not using some radio set on an incompatible frequency.
Doctrine reflected the complexity of the maneuver organization. The “new” divisional signal manual (again numbered FM 7-24) issued in 1961 exceeded it’s World War II predecessor by over 100 pages. Setting aside the inadequacies of the battlegroup from a command and control perspective, the communication requirements called for a simplified hardware solution – a single radio set series that used the whole military VHF frequency band.
On the positive side, the Signal Corps continued to refine its Signal Operating Instructions. While still complicated, standardization reduced some of the training issues. Printed SOIs included army-wide standard challenge-authentication and encryption tables. Still verbal encryption of sensitive traffic slowed delivery of the message.
As the U.S. entered the space race, the tactical warfighter faced many of the same problems noted in 1945:
- Radio range limited to 5 miles (portable) to 10 miles (vehicle mounted)
- Reliance on easily damaged vacuum tubes.
- Dependence on heavy batteries for hand and pack radios.
- Difficulty bringing the radios into operation – again selecting crystals, tuning, and calibrating.
- Vulnerability to jamming, either from enemy action or natural causes.
- Vulnerability to intercept, only partly mitigated by the SOI.
- Poor voice quality.
- Crowded command networks.
But as a plus, the backpack radio dropped in weight and, in spite of the use of three separate bands, the infantry-armor team spoke on compatible FM radios. More improvements were in the queue. I will look next at the “solid-state” VRC-12 family and the Vietnam-era radio experience.