Continuing from Part 4 – As this is a look at the evolution of radio systems at the very forward edge of the battlefield, I’ll cover the backpack radios in a bit more detail.
As mentioned in Part 4, the military began looking at practical ways to adapt transistors for combat radios – first issuing requirements in 1952. In 1957, the Army tested a series of transistor based backpack radios, then designated XC-1 through 3. These became the PRC-25, which the Army designated as “standard” in 1961. (Go here for pictures of the PRC-25’s “guts.” Also see more details on the PRC-25 Radios.) Yet initially the Army purchased only limited quantities and only for operational test programs. The PRC-25 was never meant to be issued in large numbers, as the Army sought to develop the “ultimate” or “perfect” radio instead of settling for a 90% solution (remember this, I’ll touch on it later!). But regardless, as the war in Vietnam began to draw on the Army’s resources, warfighters demanded the “new” radios.
Initially, advisers and units sent to Vietnam used the old PRC-10 radios (whose issues and limitations I’ve discussed earlier). By mid-1965, MACV commander General William Westmoreland requested two thousand PRC-25s for issue to troops entering theater. Many historians have aptly highlighted the inadequacies of the old radios as the catalyst for this request. However, recall a significant portion of those early build-up deployments were air-mobile formations. The addition of the helicopter to the battlespace revived the old radio frequency band issue. The architects of air-mobility at Fort Benning opted to put VRC-12 series radios in those early “Hueys” (typically AN/ARC-122 radio sets with two AN/VRC-46s installed). So the troopers of the 1st Air Cavalry Division needed PRC-25s to best coordinate with their rotary winged rides.
These radios made an immediate impression on the warfighters, enabling a shift in tactics. Unlike in previous wars where squad patrols might never travel farther than a thousand yards from the front lines for more than a night, fighting in Vietnam featured long-ranging, small-unit patrols. The squad and platoons needed reliable, long-ranging backpack radio sets. The PRC-25 fit the bill. In a 14-pound package, the “prick” (infantrymen are apt to simplify nomenclature with a label they might better identify with) offered a five kilometer range from its standard backpack antenna. The AT-892 “whip” or “tape” used layers of thin metal laid in a sandwich, held in place by rivets and bands. The composition allowed the antenna great flexibility without compromising the electronic profile.
And other options extended the radio set’s range. If the tactical situation permitted, radiomen could place larger profile antennas. In particular the RC-292 ground-wave antenna extended the range of the backpack set out to around eight kilometers, if not more.
The down side of the RC-292, aside from the ground footprint required, was antenna tuning. The elements, those metal “sticks” projecting out of the antenna head, required “cutting” lengths to match the desired frequency band. Lower frequencies required more elements than the higher frequencies. Such limited operational flexibility at times, requiring re-assembly of the antenna for a simple frequency change.
Another innovation that extended range in Vietnam was airborne retransmission. The 173rd Airborne Brigade used this early and often. I have not discussed retransmission (or retrans) in great detail, as it is more a communications “tactic” than direct change in the combat radios themselves. Often misunderstood, and thus misused, retrans allows the rebroadcast of one radio network onto another. Using the right equipment this might mean networks of the same or different frequency bands, wave forms, or even mediums. Putting the retrans station in a helicopter effectively extended the range of the backpack radio to anything within radio line of sight of the helicopter, often 100 miles or more depending on type of radio sets in the helicopter. Yes, retrans allowed senior level commanders to “reach down” to squads if needed. But this also allowed squads to “reach up” to resources for much needed support.
The PRC-25 was for all practical purposes “grunt-proof.” Communication failures in combat decreased. I can’t put it better than simply, the PRC-25 worked. Attrition of trained radio operators often forced infantrymen into RTO roles. With little to no training, the infantrymen did well. This success circulated through the Army manpower system, and lead to the introduction of radio operations training to all personnel. (A nice primer to Vietnam-era radio operation is found on the Vietnam Research website.)
Stories of the PRC-25 in action highlight the radio’s ease of use and reliability. The most often cited vignette involved 1st Battalion, 27th Infantry (Wolfhounds), 25th Infantry Division during Operation Attleboro in 1966. Pinned down, the battalion commander, Major Guy S. Melody had his operations sergeant, Sergeant First Class Ray Burdette, place an RC-292 against a tree. The PRC-25, augmented by a retrans, became the only means of contacting the surrounded battalion. Eventually Melody would direct eleven different companies in the fighting, coordinate fire support and close air support, and effectively defeat a substantial attack by the 9th NVA Division, all through that simple backpack radio link.
Perhaps an even better measure of the radio’s success, the Viet-Cong and North Vietnamese used captured examples in preference to radios supplied by Chinese and Russian sources. By the closing stages of the conflict, both sides used PRC-25 (or updated PRC-77) radios for tactical communications.
But as good as the PRC-25 was, the tactical communications system still faced some problems. First, the radio still used one vacuum tube in the RF output. Second, the PRC-25 lacked support for electronic encryption called a “secure mode” (recall the VRC-12 series radios introduced that capability). Third, the original battery used to supply power, the BA-386, was a short-life alkaline-cell type. Fourth, the PRC-25, a platoon radio, was often pushed down to the squads due to the failure of the Army to find a replacement “handie-talkie,” taxing the resources of the squad and that of maintenance support. Lastly, the PRC-25 (and VRC-12 series) still required a substantial maintenance/logistical support chain.
I will look at how the Army addressed those issues, as tactical communications evolved during and after the Vietnam War.