Between SINCGARS and JTRS: AN/PRC-150 and 152

Running short on space and time (and frankly the old OPSEC reflex said “hold on now”), during the discussion of current radio systems I gave short mention to some radios in the hands of troops in combat today which are to some degree providing the bridge between the past and future of combat networks.

If you have watched Restrepo, you noticed prominent use of a couple of radios from Harris Corporation.  These are part of the company’s Falcon family of tactical digital radios and are considered Commercial Off the Shelf (COTS) radios.  In short the COTS designation means, although the system conforms to military standards, the system was not directly developed through a military project office.  The AN/PRC-150 and AN/PRC-152 offer the capabilities of SINCGARS along with some Joint Tactical Radio System (JTRS) compatibility.  (I would also note other COTS sets such as the Harris AN/PRC-117 and the Thales AN/PRC-148 which deserve treatment in separate posts.)

These are software-defined radios (SDR) compatible with the “waveforms” used on the modern battlefield.  What are waveforms?  Well simply put, a waveform is the definition of the network transmission characteristics.   For SINCGARS, that is FM, frequency-hop, in the 30 to 88 Mhz band.  In addition to SINCGARS waveforms, the Harris radios also operate on SATCOM DAMA, HAVEQUICK, and the plan old FM and AM waveforms.   The Harris systems are also rated as JTRS compliant with wavers.  The radios also offer embedded GPS capability.

Harris AN/PRC-150

At first glance, the Harris AN/PRC-150 resembles a SINCGARS with the keypad shoved to the side.  The PRC-150 weighs only twelve pounds, with rechargeable battery.  Options include a vehicle mount, base stations, and high-profile antennas (for longer range).

Harris AN/PRC-152

The PRC-152 brings back memories of the venerable PRC-126.  It weighs about two-and-a-half pounds with battery.  In a small hand-held package, this radio offers all the security and compatibility of the larger set.

Harris AN/VRC-110

And one better!  Harris offers an adapter, fitting into the existing SINCGARS mount, to power a set of PRC-152s designated the AN/VRC-110.

Many upsides to consider.  Arguably the Harris radios can meet most tactical needs, save a few.  One physical device reconfigured as needed to meet the mission.  The PRC-152 is for all purposes an individual soldier radio.  Issued with rechargeable batteries as standard.

But there are downsides.  The radios do not offer significant improvement for data rates.  The figure I’ve seen quoted most often is 14.4 kb maximum, which makes sense for the FM waveform.   Use of the SINCGARS waveform perpetuates the chief complaint about that system – ease of operation.  Use of GPS timing sources and improved variable fill devices simplifies operations, but the same can be said for SIP and ASIP SINCGARS.

From a maintenance perspective COTS systems offer a mixed bag.  First off, the equipment is typically under some form of warranty or other support arrangement.  That’s convenient in most garrison situations.   I’m told that Harris has positioned support teams forward to provide in-theater support.  Further Harris has provided training material for technical support staff.  In my experience COTS support usually works fine, because the vendor has a vested interest in keeping the system operating.  However, I’m a bit “old school” preferring to have a radio-repairman in uniform to do any repairs.

One complaint I have heard about the radios seems almost superficial in retrospect.  When dismounting the PRC-152, the user loses connections to data systems, and in many scenarios will only retain SINCGARS waveform compatibility.  Personally, I’d call that a “Duh!” observation.  When a soldier dismounts, he has two hands on the “bullet launcher” and no hands left for fancy laptops, PDAs, or antennas the size of shrubs!

In trade fliers sent out last year, Harris noted over 100,000 PRC-152s were in service with the US military.   While the Army and Marines have  indicated SINCGARS will remain the near-term radio set, these two Harris radios offer tempting alternatives should the JTRS run into more troubles.

Past, Present and Future of Tactical Radios – Part 10

In the first post in this series, I mentioned some long-standing requirements surrounding tactical use of radio:

  • Compatibility – initially between combat arms, later services and today coalition and non-military agencies.
  • Weight and size – the constant here is how much a soldier can carry, or space allocated in the vehicle.
  • Range – ever important as radios replaced wire/telephones for command and control
  • Clear circuits – free from natural or man-made interference.
  • Security – free from enemy jamming and intercept.
  • Durability and ease of maintenance – to include repair parts supply.
  • Ease of use.

In terms of compatibility, long gone are the days of incompatible infantry and armor frequency bands.  By the Vietnam war, retransmission systems actually bridged the gap from foxhole to division command (and beyond!) for voice traffic.  DoD wide standardization on the VRC-12 series and later SINCGARS ensured joint compatibility.  In the current operating environment, NATO affiliated coalition partners usually use compatible equipment.  However, interaction with non-NATO or non-military agencies often requires commercial radios (or the old practice of sharing sets).

Improvements in technology have reduced radio weight, increased range, provided clearer channels, and improved hardware reliability.  Recall the SCR-300 backpack radio of World War II which weighed 38 pounds, along with a 12 pound battery, with a range of three miles.  By Vietnam the PRC-77 weighed 14 pounds and boasted a five-mile range.  The ASIP SINCGARS weighs nine pounds and ranges to about six miles in backpack mode.    Similarly voice quality improved over the same time with electronic suppression of background noise, squelch options, filters, and channel spacing.  Security also improved with technology.  Encrypted, frequency-hop transmissions have all but eliminated the need for the obfuscation techniques of the past.

Ease of use is a different matter – perhaps a step forward and a step back.  Yes, radio operators are free from cumbersome tuning procedures found on the World War II sets.  Yet one can deride the SINCGARS radios for complex configuration and loading procedures, compared to the old PRC-77.  However, as explained earlier, part of the SINCGARS complexity was self-inflicted.  While the number of dedicated communications personnel dropped, the Army placed more demands upon those left operating the radios.  Secure radio nets, with the option to pass digital data, are not simple to establish and maintain.  Ultimately, the radio is only as good as its operator.  As with any system, particularly combat systems, training is paramount.  I would submit that training has ultimately enabled the success of the current tactical radios.

Going back to the beginning of this series, I mentioned Joint Tactical Radio System (JRTS) which figures prominently in future plans (and I might add for all services as the Army and Marines are no longer the only tactical radio net operators).  While the JRTS project is at an advanced stage, these are not ready to replace the SINCGARS in the inventory.

The chief feature to the JRTS, as defined currently, is the use of Software Defined Radio (SDR) components.  Again, briefly, this allows the radio to be configured specifically for mission requirements.  In a conventional scenario the JRTS might operate as a SINCGARS.  Then in a natural disaster scenario, it might operate in compliance with relief agency networks, on different frequency bands than military channels.  The need for an adaptable radio is paramount given the diverse mission scope facing the warfighter today.

Regardless of the scenario, the digital battlefield is here to stay.  Any new system must support greater and greater through-put for data.  During Desert Storm, dial-up connection speeds were more than enough.  As indicated a few days back, current operations depend on connections ten or twenty times that.   Any future radio should provide the basis for a robust, high-speed network that can be extended to the individual soldier where needed (WHERE NEEDED).  SINCGARS is barely capable of handling the necessary data rates, so this shortfall is felt in the existence of numerous parallel systems in the hands of the warfighter as things stand today.

The ability to “define” the radio to any number of operational parameters will place more demands on those establishing and maintaining the radio networks.  Beyond just training, the radios need to be “grunt proof,” for sure.  What model would I suggest?  Take a page from the cell phone industry.  How complex is your iPhone or Android?  Sort of depends on the individual of course, but the learning curve tends to flatten out once the basics are mastered.

Also mentioned the first post in this series, the JRTS program is at risk as leaders look for budget cuts.  DoD faces a big invoice if JRTS is going to replace the current suite of radios (even if, as currently slated, that replacement will not be a one-for-one swap-out and will also be phased over a decade).  The procurement model needs to change even if the radios don’t.  First off, with technology evolving faster than contract life-cycles, DoD should avoid decade long development programs.  This may lead to limited procurement lots, likely even commercial systems adapted to military standards.  That also sets up “best of breed” evaluations at frequent intervals.

Further, scope programs to specific functional requirements; meet those requirements; and field equipment based on those requirements.  Remember the rush fielding of PRC-25s to Vietnam?  That was, in my opinion, because the Army worked towards the “perfect” radio, which would have been the PRC-77, not fielding the 90% “good enough” solution until troops in the field were in a bind.  But at the same time, any accelerated program should not skip the testing and validation.  “Good enough” should really be good enough for troops to stake their lives on.

In closing, let me say that I predict the current combat radios, SINCGARS and other contemporaries, are actually the last of a vanishing breed.  While the Army plans to hang onto those radios at least through the first quarter of this century, our communications patterns are evolving away from voice-only systems.  The days of commanding through a hand-mike are limited.

Past, Present and Future of Tactical Radios – Part 9

In the last installment, I introduced the first generations of SINCGARS radios, but left off with mention of the System Improvement Program (SIP) and Advanced SIP (ASIP) generations.  If one considers the PRC-77 based on internal improvements to the PRC-25, then perhaps the SIP and ASIP are analogous evolutions from the original SINCGARS.

After Desert Storm, Army planners realized further battlefield digitization was inevitable.  Through the early 1990s Army Communications-Electronics Command (CECOM) began programs to introduce near and long-term solutions to meet the digital requirements.  At the time, the tactical Army relied heavily on an integrated data-voice network from the maneuver brigade up to the theater level.   Mobile Subscriber Equipment (MSE), at division and corps level used packet switching to pass, what was for its time, high-speed data.  These formed the backbone of the Army’s first Tactical Local Area Network (TACLAN).

The “must have” application for brigades and above in the post-Gulf War was imagery, particularly from the much ballyhooed Joint-STARS.   But planners also recognized the need for more than intelligence products at the foxhole level – particularly friendly forces information, general situational awareness, logistics reporting, and digital supplements to field orders.

The problem was the hardware between brigade and battalion.  Maneuver battalions typically possessed two AN/VRC-97 Mobile Subscriber Radio Telephone (MSRT) tied into the MSE network.  MSRTs were ungainly – sort of a cell phone the size of the old VRC-12 radio.  Battalions often paired MSRTs with an AN/UXC-7 Lightweight Digital Fax, which weighed 55 pounds (“lightweight.” I’m not making this up!).  Clearly not an option for the front line.

Also in limited service was the Enhanced Position Location and Reporting System (EPLRS), providing “friendly forces” tracking using a set of digital radios, both vehicle mounted and backpack.

EPLRS Radio Set

Although not a true combat net radio, but in scope of this discussion, EPLRS offered a 56 kilobyte-per-second (kb/s) network for data traffic (again, state-of-the-art at the time).  With a data cable, an operator with a laptop could send and receive data.  The EPLRS software application displayed friendly forces within the network.  On the down side, the radio didn’t support voice traffic; weighed as much as a SINCGARS; and introduced another radio to configure.  While useful, the EPLRS was about a generations ahead of its operators in my opinion, with a steep learning curve.

CECOM concurrently worked towards the integration of SINCGARS with the MSE and EPLRS networks.  SINCGARS SIP introduced a network interface card (NIC) option.  This gave the radio an IP address (just like the computer you are reading this on) and connected to the TACLAN.  An external InterNetwork Card (INC) performed routing functions between SINCGARS, EPLRS, or MSE networks.  In operation, a SINCGARS on a vehicle mount used an INC to connect to either EPLRS or MSE.  That radio set became the “gateway” for other SINCGARS, even PRC-119s, and computer terminals (imagine a big, fat 1990s era laptop) connected by data cables.  Although the data rate remained at 19 kb/s.  In 1995, CECOM demonstrated this setup as part of “Force XXI,” with a team in the field at Fort Gordon passing an email through SINCGARS to a garrison terminal at Fort Monmouth.   And, no it was not a PowerPoint attachment!

SINCGARS SIP, designated RT-1523C or D, were externally similar to the second ICOM sets.  The SIP also introduced an interface to the standard Precision Lightweight GPS Receiver (PLGR) devices, and allowed the radio to pass its position to other stations in the network, thus making SINCGARS a “poor man’s” EPLRS.  Further, the GPS provided a handy time source to resolve continuing time drift issues.

Keeping with the ever evolving electronic technology, the next upgrade for SINCGARS featured a digital signal processor further reducing the physical size of the radio. Although I’ve never seen it stated in such terms, the ASIP in some regards answered a pressing need (once again) for squad level radios.  Ever since the introduction of frequency hopping radios, the old single channel PRC-126s’ days were numbered.


The radio, designated RT-1523E, weighed 9 pounds even with battery, handset, and antenna.  Even at half the width, the ASIP fits the older SINCGARS mounts.  Note the large side panel on the photo above, which is the compartment for a BA-5590 battery.


But the “time drift” issue remained.   The official solution involved a new fill device.  In the mid-1990s the Army began introduction of the AN/CYZ-10 ANCD (or “crazy ten”) device to replace the various fill devices (KYK-13 being the most familiar).

The "Crazy Ten" ANCD

The ANCD, with all those buttons and tiny display, carried all five variables (and more), including time, needed for SINCGARS operations.   I’ll be blunt in my assessment – the initial fielding was rushed without proper training and the devices were complex in operation.  The “crazy ten” worked, but I spent many a tense moment trying to figure out what button I’d skipped around COMSEC change over time.

In 2001, the US Army and Marines had the best system of combat net radios in the world, particularly considering the digital capability.  Trouble was, the system was designed around a conventional war to match up with conventional threats.  The asymmetrical wars in Afghanistan and Iraq brought requirements unseen by the original SINCGARS requirements.  The adversary lacked sophisticated jamming and intercept capabilities, rendering some of the radio’s features unnecessary.   Yet, the warfighter needed more support for data traffic than ever imagined.  In a war where routine patrols could become front page news within hours, rapid dissemination of information was paramount.

A senior communications officer once confided that OIF and OEF are “bring your own damned radio” wars.  With the distinction between conventional and special forces blurred, many new radio types arrived in line units. Many “limited procurement” radios found their way into the combat zone.  Commercial “fill in” (or COTS) products abounded.  In the remote areas, regular infantry squads used single channel satellite radios (practically unheard at that echelon before 2001).  Partly addressing the needs, the AN/PRC-117 multi-band radio appeared in significant numbers.

PRC-117 in TACSAT Mode

The PRC-117 offered capability to operate with SINCGARS FH nets and single channel satellite nets.  As seen in the photo above, the set is about the same size and weight of a PRC-119.  And somewhat a glimpse into the future, the PRC-117 is a “software-defined” radio.

In retrospect, while many (including me) have cursed SINCGARS for its complexity, the radios have proven adaptable and reliable.  Over the years, better training programs have resolved the complexity issues somewhat.  The system has served through a transition from “voice-centric” radio nets to a time of “data-centric” computer networks.  For what it is worth, the VRC-12 and PRC-77 family served as the primary US Army radios from 1965 until about 1992 – some 27 years.   SINCGARS took over that role starting 1990 and is still going strong at 20 years with no replacement in sight.  Current plans call for over 400,000 SINCGARS remaining in Army inventories out to 2028.

In the last post in this series, I will summarize 70 some odd years of combat radio development and offer my thoughts about what could and should be done for the future.

Past, Present and Future of Tactical Radios – Part 8

Before the Christmas break, I left off the discussion of tactical radios discussing different issues and requirements from the late 1970s and early 1980s.  The main reason I didn’t jump from the Vietnam era radios straight into the first digital radios was to give those issues and requirements their proper air, as they lead directly to the advantages and limitations of that radio system.

The Army started development of the replacement for VRC-12 and PRC-77 radios, now called Combat Net Radios (CNR), in 1974.   The technical requirements, as mentioned in the previous post, included enhanced communications security, support for digital traffic, and improved reliability.  The Army needed highly reliable communications to synchronize lean force structure in combined arms operations.   After a decade and a half of work, around 1988, the Army fielded the SINgle Channel Ground and Airborne Radio System, or SINCGARS for short, to front line units.

U.S. Army photo.
AN/PRC-119 Backpack SINCGARS

SINCGARS consisted of a modular set of radios equipping ground units, paired with compatible aircraft radios.  These were not just “Army” sets, but also used by the Marines, Air Force, and Navy.  The aircraft sets are outside the scope of this study, but the chart below breaks down the major components of the SINCGARS ground variants.

The radio itself evolved through several generations, but the supporting components remained the same generally speaking.  The AS-3900 antenna sensed the radio transmit frequency and automatically adjusted resistance to match, eliminating the “clacking” matching units of the old VRC-12 series.  For command posts, the OE-254 antenna (three up and three down) did not require reconfiguration with frequency changes, as with the older RC-292.  The power amplifier boosted transmit power to allow a planning range of 40 km.  (Many units would report 50 km out in the desert.)  Without the amplifier, SINCGARS ranged about 10 km.

OE-254 Antenna

SINCGARS transmitted on the frequency range of 30 to 88 Mhz.  By reducing the channel separation to 25 Khz, SINCGARS doubled the number of available channels.   Radio operators keyed in the frequency from a numeric pad on the front of the radio.  Gone was the old dial; replaced by an LED digital display.  SINCGARS had space for six pre-set frequencies (and two additional spaces reserved for special functions described below).  The radio operated in single channel (SC) mode or frequency hop (FH) mode.

The backpack versions (PRC-119 or dismounted VRCs) weighed about 20 pounds when dressed out (comparable to a PRC-77 with KY-57).  The BA-5590 (same used on the KY-57 VINSON), gave about six to eight hours of life (if you were lucky).  Field experience lead me to plan for a 6 km range, instead of the 10 km range noted in the technical manuals.

At the heart of SINCGARS was a frequency hopping technology which addressed the long-standing jamming and intercept threat.  Simply put, in frequency hop mode the radio skip 100 times a second through the frequency range.  To work properly, the radio needed five keys, or variables.  First a crypto key for encryption.  Second a TranSec (TSK) that provided the hopping pattern.  Third a HopSet specifying the set of frequencies to use.  Fourth the NetID, a number between 000 and 999, identified the radio network.  And lastly a synchronization time.

The first four variables required the operator to perform a set of about two dozen steps, in sequence.  This was difficult to train, but once an operator got the hang of it, no more complex than setting head-space and timing on a M2 .50 cal.  But the synch time proved a troublesome in practice.  By default the radio reset to 00 seconds of 0 hour of 0 day.  Even when set, radios would drift off time.  New CNR practice revived the concept of a single net control station (NCS) or “master” set to the FH/M mode.  When that station broadcast, all radios on the hopset would re-synch time.

But this failed at several levels.  First, since 1940, the Army had brow-beat operators to reduce transmissions.   SINCGARS had a “time capture” mode that would pick up synchronization, plus or minus five seconds.  But this didn’t help where the day or hour was incorrectly set.  Lastly, doctrine called for the use of queue (CUE) and manual (MAN) frequencies allowing operators to “page” the net master.  But typically the NCS was the command radio which rarely had the time to drop out to respond.  In the field, users often resorted to the old practice of synchronizing wrist watches, then setting the radio’s time.

The first generation SINCGARS, using the RT-1439 radio commonly called non-ICOM (Internal Comsec), lacked the internal crypto circuits.  The only place I encountered these was Korea.  We used a special Y-cable to connect to external KY-57 crypto devices.


The second generation, or ICOM, used the RT-1523 radio and put the crypto circuits in the radio. Note the difference width difference between the ICOM (top) and the non-ICOM the photo below.


The early generation were great radios from the hardware perspective.  SINCGARS saw its combat debut in Desert Storm with 1st Cavalry Division, some Patriot batteries, and some USMC users – all told about 700 sets.  According to often cited statistics, SINCGARS achieved a mean time between failures rate of 7000 hours, compared to 200 to 300 for VRC-12 radios.  My personal experience strengthens this statistic.  In 18 months as a platoon leader in Korea, I never had a radio down for repair.  As a mechanized infantry SIGO, I had maybe ten SINGCARS turned in for repair in about 20 months – total.  (Yet on rotations to Kuwait, we’d have fifteen or more VRC-12 radios in the shop at any one give time.)

For digital data transmissions, SINGCARS supported up to 16,000 bps (bits per second). Sounds pale compared to our high-speed internet today, but in 1989, this was impressive.  But data transmission required clean, strong signals.  On good days, a practical transfer speed was 4800 bps over 20 km.  That would support TACFIRE and other early battlefield digital systems.  But demand would grow significantly by 1995.

The main complaint with these radios was, as alluded to above, the timing variable.  As a SIGO, I often rushed out to a “problem” only to resolve the issue by a time hack.   The problem, I feel, was not the hardware but the complexity of operation, training, and perception.  In 2nd Infantry Division, which received non-ICOM in 1989, from the division down the standard was “frequency hop, green” meaning fully secure.  With training, command emphasis, and real-world operations on the DMZ, the radios worked.  In CONUS, we were lazy, citing the need for compatibility with VRC-12 radios, and radio performance suffered.  However in two contingency deployments to Kuwait, we preferred to carry our own PRC-119s instead of using the PRC-77s issued in theater.

Bottom line – SINCGARS were too complex in operation, certainly not “grunt proof.”  Indeed, even the soldiers in the divisional signal battalion had problems learning the system!

Even in advance of the first generation fielding, the program managers pursued better versions of the SINCGARS.  In addition to addressing the time synch and complexity issues, the Army wanted more data throughput.  Those radios, which began to arrive around 1996, were the System Improvement Program (SIP) SINCGARS.  I will discuss those, and the Advanced SIP (ASIP) radios, in the next post in this series.

Spotlight: Comms in RC South – Afghanistan

Recently Brigadier General (Promotable) Ben Hodges gave a presentation to the Northern Virginia Armed Forces Communications and Electronics (AFCEA) chapter.  General Hodges has recently returned from a tour as Deputy Commander of Regional Command (RC) South in Afghanistan.  He focused the keynote presentation on the communications and data links used to support the warfighter in RC South:

The presentation dovetails nicely with my discussion of Army tactical communications and developments from World War II to the present.  A brief but interesting look at the current state of communications in theater:

BG(P) Hodges Presentation on RC-South’s Communications (PDF)

[scribd id=45800186 key=key-19jgdkjo4cjre9pazlab mode=slideshow]

A few points I’d like to emphasize.

On the first slide after the cover, General Hodges presented a title with “C5ISR”.  The Army fights with acronyms.  This stands for Command, Control, Communications, Computers, Coalition, Intelligence, Surveillance, and Reconnaissance.   Yes, coalition in bold.  The school-house teaches there are 4 “c”s.  Warfighting experience in Iraq and Afghanistan has demonstrated the need for a 5th.  The communications and data infrastructure over which the war is fought is indeed a shared resource.  Tactical flexibility, which used to be expressed in kilometers-per-hour or maximum range, also must consider how fast it takes to get an instant message down to the subordinate headquarters, regardless of the uniform or flag.

Plenty of photos of troops operating in Afghan, including MCLIC and APOBS (there’s a topic for you XBrad!).  But note the media presence on slides 9 and 10.  The local media is a component of the battlespace in Afghanistan.  As we learned in Iraq, a bit of good press goes a long way.

Look over the photo of the Company TOC on slide 11.  Situational awareness presented via large screen TV.  Several computers with live data feeds.  And on the left, the old “Fox Mike” – FM radio set.   Sort of a mix of the latest and greatest with the communications equipment from my generation.  Photos on the following slides show more command posts.  The old map boards are still there, and still useful in lots of ways.  But notice number of computer screens, telephone systems, and (you have to look for them) the radio sets.

Side 18 presents a great example of how the modern battlefield is increasingly digitized as we fight an information-centric war.  Biometric data collection.  Twenty-five years ago, we could not even anticipate this need.  Today it is a requirement.

And to support all those computers in the CPs, hand-held biometrics collection points, along with all the other gadgets, the warfighter needs bandwidth on those communication links.  Look at slide 21.  Sort of reminds me of that hockey-stick global warming chart.  Eight month time span, the bandwidth expanded ten-fold.  And I bet if you doubled that today, the commanders on the ground would say it’s still not quite enough.

And what does that increased bandwidth look like on the ground?  Slide 23 – a FOB bristling with SATCOM, line of sight, and FM antennas.

The presentation is a good, but quick, look at the communications required to support operations in the battlespace today.  But trust me only brushing the surface….


Past, Present and Future of Tactical Radios – Part 7

Continuing from Part 6 – As related in the earlier post, some factors facing the post-Vietnam Army that influenced the development of tactical communications included:

  • Force structure changes
  • Need for a proper squad radio
  • Increased communications security requirements
  • Digitization of the battlefield
  • Need for even more reliable hardware

The force structure changes affected tactical communications in two regards.  First, communications staff within the line units diminished.   Radio operators (MOS 31C and later 25C) held slots down to the line companies.  After experience with easily operated AN/PRC-77s in Vietnam, these slots became bartering chips in a larger game of personnel allocations.  The Signal Corps needed personnel to man the new division/corps/theater multi-channel communications network.  As the Army moved from the H-series to J-series TOE, the combat arms gave up radio operators in order for promised coverage by mobile field phone service from the divisional signal battalion.  In the “new” army, radios would so simple to operate, everyone would be an RTO.

Reorganization also reduced the number of radio repairmen and logistic support.  By the time of the J-series TOE, line companies lost their radio repair specialists (MOS 31V), consolidating them within a 15-20 man battalion commo section.   Also with changes to the support system, the repair system authorized fewer radio module substitutions at the battalion level.  The army consolidated the specialized technicians and the bench stock of repair parts at the divisional and higher level.

To resolve the shortfall at the squad level, the USMC developed the AN/PRC-68, with initial fielding in the mid-1970s.  The radio operated between 30 and 79.95 Mhz, with a 50 khz channel separation, making it compatible with the platoon radios.  It offered a range of 3 to 5 km.  The initial model had some limitations due to the antenna matching.  Improvements lead to the PRC-68A and B models that resolved the antenna problems among other things.  The Army continued development into the AN/PRC-126, which expanded the upper range to 87.975 Mhz with a 25 khz channel separation.  The 126’s arrived in units from the mid-1980s on.  These true “handie-talkie” descendants weighed only three pounds, even with the rare KYV-2 secure module attached.

The PRC-68s and 126s were for the most part good hardware.  But from an operator’s standpoint, frequency changes on the PRC-126 in particular was time consuming – sort of like setting an alarm clock waiting for the right number to increment.  In bad lighting, the display could be hard to read.  And there were the batteries.  The BA-5588 was rather light, so nobody complained about carrying a few extra.  But when the power ran low, the radio gave off an annoying warning beep.  And the batteries always seemed short in supply.   Lastly, with the withdrawal of the communication specialists from the line, the quality of operator maintenance dropped off.  (Although I heard a lot of interesting “a dog ate the radio” stories because of this.)

Although non-tactical according to the book, many units turned to commercial equipment for “hand held” radio needs.  Two examples, that I became well acquainted with, were the AN/PRC-127 and Motorola Saber radios.   Both types featured rechargeable batteries and were easy to use.  But the radios operated on non-tactical frequencies and were not designed to be kicked about.  Although many infantry units attempted to use these radios on exercises, the type was best suited for garrison work.  However, these radios were examples of early wide-scale use of commercial-off-the-shelf (COTS) radios.

Turning to the communications security issues, the Army replaced the old NESTOR systems with KY-57 VINSON encryption devices starting in the early 1980s.


The KY-57 weighed five pounds, perhaps six with a BA-5590 battery for power.  Dispensing with the unpopular pins and paper of the NESTOR system, the operator loaded an electronic crypto variable into KY-57 with either a KYK-13 or KYK-15 fill device (which were filled with a temperamental KOI-18 tape reader).

KYK-13 on display at the National Cryptologic ...

Putting a KY-57 into operation required specific steps, executed in sequence.  But the sequence was easily learned (arguably easier than field stripping an M-60 machine gun!).   Kits allowed the KY-57 to secure the VRC-12 series and PRC-77 radios.  The backpack kit’s cables stood up well (in my experience at least).  On armored vehicles, because no space was allocated when the tanks and APCs were designed, the kits required cables to be jammed into cramped spaces.  And vehicle mounts required a “J-Box” stacked under the radio set.  J-box replacement required repairmen to disassemble the entire mount.  Both the KY-57 and the fill devices used a hold up battery (HUB), designated BA-5372, about half the size of a standard AA battery.  The HUB lasted about a month under normal conditions.

Generally the KY-57 was a “grunt proof” device.  About the only serious complaint was the handling of the crypto variable.  Variables could be corrupted or mis-matched.  Over-the-air rekeying was an option, but was rarely practiced.

The KY-57 addressed the threat of enemy intercept, but left the radios vulnerable to jamming and direction finding.  In the early 1970s the Army did identify the solution as frequency hopping (a concept invented by actress Hedy Lamarr, by the way!)  But the state of technology at that time could not deliver a radio using frequency hopping.  But the requirement became the prime feature for the next generation radios entering advanced development in the 1980s.

The Army also demanded the next series of radios support digital data exchanges.  The internet was barely more than a backbone network, yet the Army had already begun fielding the TACFIRE system controlling field artillery fires.  Also the air defenders used a Target Alert Data Display System (TADDS) to provide information from search radars to gunners.  While the VRC-12 series could support data transmissions, the data-rate was relatively slow.  Any new radios had to support fast (for the time) baud rates.

Arriving concurrently with, and largely enabling, this digital revolution, semiconductors, integrated circuit (IC) components, and micr0-chips became common place in the mid-1970s.  Pocket calculators became affordable, and the home computer was not far around the corner.  Just as the transistor overcame the limitations of the vacuum tube, the micro-chip supplanted the transistor.  The military was quick to identify the advantages of the new electronic components.  Not only could more circuitry be packed into a smaller package, but the components had a longer mean time between failures.

Through the 1980s, the Army focused on a new radio system using the new semiconductor technology to address security, digital data, and durability requirements.  This path lead to the subject of my next post – the SINCGARS radio series.

Past, Present and Future of Tactical Radios – Part 6

In part 5, I closed noting some shortfalls of the otherwise very remarkable AN/PRC-25 and the contemporary tactical radio sets:

  • Use of vacuum tube in the RF output component
  • Lacking support for electronic encryption
  • BA-386 power and life limitations
  • PRC-25 Used at squad levels where not intended by doctrine
  • Maintenance/logistic support chain

The first two issues were not new to the Army.  The intent (in my opinion) was to develop the follow on AN/PRC-77 as the “perfect” radio to address these issues.   But requirements from Vietnam hit before that radio was ready.  Externally indistinguishable from the PRC-25, the PRC-77 featured a new RF output component, removing the last vacuum tube.    The PRC-77 added circuitry to allow use  of cryptographic devices then being fielded in 1968.

AN/PRC-25 or 77 - can't tell from here!

The cryptographic devices issued to line units were the KY-38 NESTOR (more pictures here).  The KY-38 was as large as the PRC-77 and weighed nearly the same – effectively doubling the RTO’s load.

KY-38 - from Jerry Proc's website

An obvious question is why impose this device upon the warfighter in the first place?  Simple answer – because he asked for it.  Cold War planners assumed Soviet forces would use electronic intelligence gathering to harvest valuable information from combat radio networks.  The existing communications security practice, dating back to World War II, involved changing frequencies and call signs at intervals, code words, challenge-authentication tables, shackle codes, and other verbal tricks.  But these were mere obfuscation of information.  And such obfuscation consumed valuable time on both ends of the conversation.   The Army wanted a “green box” solution to provide end-to-end encryption of the signal.  In collaboration with the National Security Agency, the Army fielded the KY-8 for vehicle mounts, the KY-28 for aircraft, and aforementioned KY-38 for backpack use.

Further experience in Vietnam underscored the threat.  In December 1969, a unit in 1st Infantry Division uncovered an enemy radio intercept team using captured US equipment alongside Chinese and commercial radios.  Journals found in the stash included operational information ranging from the time/location of air strikes to unit statuses, all gleaned from the radio nets.  The nature of the logs indicated this was not a singular occurrence.  The communists learned the obfuscation techniques and, using today’s term, hacked the American radio nets.

The NESTOR series suffered from several drawbacks:

  • KY-38 at roughly the size and weight of the PRC-77 doubled the RTO’s load.
  • Special X-Mode cable between the radio and KY-38 supplied in limited quantities.
  • Battery powered KY-38 increased battery consumption rates.
  • Complex process to load the crypto variables.
  • Device Overheating and reliability issues.
  • Need to wait a second or two when starting transmission for the encryption to synch before speaking.  (A precious combat second…)

Clearly this was not the solution to address the radio-intercept threat.  In the field, units used the devices sparingly, and as result still faced the threat of enemy intercept.  Once again, the equipment lagged behind the requirement.

Regarding batteries, the issue of a magnesium-cell BA-4386 partially addressed the battery life problem.  The BA-4386 lasted longer than the older alkaline types.  But patrols still needed substantial quantities of these “bricks” – displacing rations, water, and ammunition in the packs.  With PRC-25/77s pushed down to squad levels, the operational tempo of war, and the introduction of the comsec equipment, battery supply barely kept up with demand.

The Army issued PRC-25/77s down to the squads in place of failed radios designed for that echelon.  The AN/PRC-34/36 set, developed concurrently with the VRC-12 series and PRC-25, failed to meet performance goals as a PRC-6 “handie-talkie” replacement.    The Army then developed the AN/PRT-4 and PRR-9 combination.  With a PRT-4 hand-carried transmitter and a PRR-9 helmet mounted receiver, the overall system was cumbersome.  Tested in Vietnam, the PRT-4/9 lacked range and difficult to operate.  A Navy derivative, the AN/PRC-88, combining both units into a single box, also failed.  Frustrations with these projects eventually lead the Marines to develop their own radio which eventually became the AN/PRC-68 (leading to the AN/PRC-126).  But that product was not in the field until well after Vietnam.

Regarding maintenance support and logistics the issue was hardware reliability rates.  Now I would not dispute the “it worked” perception for the infantryman on the line.  And certainly the PRC-25/77, as the VRC-12 too, were much more reliable than previous Army radios.  But, in order to sustain the warfighter in Vietnam, the Army maintained huge quantities of repair parts and replacement (float) radios.  Radio users and repairmen also adapted to meet the problems.  When shipment of individual repair modules resulted in damaged parts, further straining the system, the logisticians introduced air-cushioned “jiffy bags.”  When supplies of whip antennas in theater ran out, modification kits allowed the use of PRC-10 whips on PRC-25s.  Handsets were so sensitive to moisture that most operators resorted to encasing them in plastic bags.

The PRC-25/77 and VRC-12s, for all their solid state reliability, continued to tax the maintenance and supply systems.  To sustain a goal of 100% readiness of combat radios in the line units, the theater maintained as much as one-third more devices (some sources say even more) as ready replacements.  Large numbers of personnel deployed to theater to simply repair and reissue radio systems.

Consider those support requirements in context of the times.  The Army fought Vietnam, until the last phases, with a draftee army and with a “sky’s the limit” budget.   After Vietnam, the Army had to reorganize as a leaner, but still lethal, force.  This translated to, among dozens of other things at the warfighter level, the need for radios requiring less specialized maintenance and fewer supporting personnel.

In front of this “draw down” cycle, the perception leaving Vietnam was that technology had evolved to the point that even the “knuckle-draggers” could operate the radios.  From about 1972 on, all soldiers received basic radio operations training, not just those assigned as communications operators.  This presented a significant opportunity to trim down an infantry division, as in the TOEs up to 10% of the personnel were communications staff.

In the Army’s “dark age” from 1975 to 1982, the calls for a smaller force structure, better communications security, a squad radio solution, and more reliable hardware – all drove the Army to look for new radios after Vietnam.   Further another factor, not mentioned until now, was the emerging digitization of the battlefield.  After 1973, the digital facet to modern combat could not be ignored.  I will turn to the Army’s next major radio development, relating how SINCGARS arrived on the scene.

Past, Present and Future of Tactical Radios – Part 5

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.

AN/PRC-25 - Left, base mount. Right, backpack

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.

RC-292 Antenna

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.)

PRC-25 in Operation, note whip antenna and the old M-1 series Carbine!

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.

The Past, Present, and Future of Tactical Radios – Part 4

Continuing from Part 3 –  In the last segment I was perhaps a little brief with the overview of post-Korean War vintage radio sets and explanation of the different working FM format bands.  Semi-officially, the 1950s era radio sets were known as the GRC-3 series, after the primary armored vehicle radio set.  Rather than another 1000 words, perhaps a diagram for reference:

US Army Radio Sets 1950s - click to embiggen

The diagram references the four (arguably just three with an overlap) bands, the base radios used on each band, and the radio sets issued.  Base radio designations for receiver-transmitters (RT) and auxiliary receivers (R).  For a more detailed component listing, please refer to Green Radio’s excellent technical breakdown.

Let me stress three points about the different bands.  First, the “platoon” band was for the most part an overlap of the “infantry” band.  Second, the reason for these separate bands goes back to the technology.  The radios of the day still used crystals with limited range.  To reduce the operator’s workload (and part inventory), the Signal Corps opted to “build in” crystals with specific frequency ranges.  Which leads to the third point, these specific frequency ranges assumed that radio traffic could be segmented by combat branch to some degree.

However, this certainly did not mean that only infantry units operated on 38 to 55 Mhz, or armored units were restricted to 20 to 27.9 Mhz.  Instead, the Signal Corps’ intent was to issue equipment based on the need to operate on certain communications networks.  For instance, armor units often used the AN/GRC-3 which included an RT-70/GRC radio offering access to the infantry frequencies allocated to platoon and squads.  Clearly this required a lot of radios, operated by a lot of radio operators (recall, 9% of the battlegroup strength allocated for communications personnel – wire and radio).  And one can imagine a number of scenarios where these different bands on different radio sets might offer an impediment to information flow.  While certainly better than the setup used during World War II, the GRC-3 series was still cumbersome in operation (not to mention a nightmare for the property book officer with no less than 24 component lists!).

By the early 1960s the next major leap in radio technology arrived to solve some of these ills – the first solid state semi-conductors.  Transistors first became practical in the late 1940s.  By 1954 the first transistor based receivers became the “hot” item on the American commercial market (There was no DARPA at that time, remember).   Within a few years, the Army began testing transistor-based radios with an aim to replace the GRC-3 series.  This project lead to the AN/VRC-12 series and the AN/PRC-25/77 family of radios.

Now we often think of things that go boom when referring to “classic” military equipment.  Yes, M-4 Sherman tanks, M-113 APCs, P-51 Mustangs, F-4 Phantoms, and I’ll throw in the Iowa-class battleships as examples of long serving, battle-tested “classics.”  Well I’d submit the VRC-12 family (including those PRC radios) are also “classics,” although without the boom.  How good were these radios?  Well after entering service in the early 1960s, the sets hung around in the inventory until just recently.

An Army training video from the 1960s expresses the virtues of the system rather well:


For those who can’t watch this captivating 27 minute clip :-), I’ll touch on some high points:

  • Radio set configurations based upon two types of receiver-transmitters (RT-246 and RT-524) and one receiver (R-442).  Outside scope of video were the PRC-25/77 and associated vehicle mountings.
  • Frequency range from 30 to 76 Mhz, divided into lower (30 to 52 Mhz) and upper (53 to 76 Mhz).  Not discussed in the video, this because of the need for two separate tuners, still a technology limitation, but with miniaturized circuits, easily overcome.
  • The VRC-12 series effectively dumped the “armor” band and part of the “artillery” band, but expanded into the cleaner high range frequencies.
  • The VRC-12 offered 920 channels, over 350 channels cumulative between the radios of the GRC-3 series.
  • Dispensing with the separate bands, if the operating frequency was known – say by browsing the Signal Operating Instructions(SOI)- any radio operator could tune into any net the mission required.  In theory from corps commander down to the individual squads.
  • Weight of vehicle mounted radios reduced to 100 pounds, with space needed down to 1.2 cubic feet.
  • Power out increased to 40 watts maximum, with range now reaching to 30 miles.
  • Simplified maintenance due to completely modularized construction.  Components supported “go or no-go” testing (a really big advantage).  However, note that while the new radios featured 100 transistors, the system still relied upon eight vacuum tubes.
  • Support for facsimile transmissions.  Yes, very seldom used, but foreshadowing the use of data systems of today.
  • Improved noise reduction with new squelch techniques.  However support for legacy squelch formats lead to operational issues later.
  • Tuning of the VRC-12 was simple – just turn the knob.
  • Briefly discussed, the VRC-12 series required “cutting” or matching of the antenna.  This required operation of a mechanical switch underneath the antenna matching unit, either automatically via a cable from the radio or manually by the operator, to the corresponding resistance level.

The early prototypes of these radios came out in the late 1950s.  Although production started around 1961, few were issued prior to 1964-5.  For reference, this chart details the components of the VRC-12 and PRC-25/77 family.

VRC-12 and PRC-25/77 Family - click to embiggen

With the introduction of these “solid state” radios, the Army had solved some of the issues facing communications at the tactical level.  However some issues remained unaddressed.  I’ll go into this in more detail later, but the PRC-25 evolved, with the addition of new features, into the PRC-77, thus the different designations.

  • Range extended out to 30 miles (vehicle mounted) or 5 miles (backpack)
  • Use of solid state, modular components, with minimal vacuum tubes.
  • Backpack radio weight reduced to 14 pounds and vehicle radio to 100 pounds.
  • Pack radios continued to use heavy, short duration, batteries.
  • Technical aspect of operation reduced to frequency, power, and squelch selections (and a few other options) using front panel knobs.
  • Still vulnerable to jamming, but new squelch feature greatly reduced natural interference.
  • Interception still a threat, and only mitigated by use of SOI based challenge-authentication and manual encoding.
  • Improving voice quality.
  • Increased number of channels, along with single frequency band, reduced command net congestion to some degree.

Across the board improvements came with the VRC-12 series.  The type saw a long service life in the US Army, from Vietnam to beyond the Gulf War.  And the type remains in use around the world.  In my next installment, I will look at that service, particularly the backpack radios.  Along the way I’ll consider wartime experience and evolving tactical doctrine, and point out what issues prompted the Army to start looking toward digital radios.

The Past, Present and Future of Tactical Radios – Part 3

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.

AN/PRC-6 U.S. military handi-talkie radio from...
AN/PRC-6 - Wikipedia

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.