Military Auxiliary Radio System in the Vietnam War Era
Updated: Oct 12
For many U.S. service members in Southeast Asia, a call home did not begin with a telephone. It began with a radio operator, a crowded MARS station, a high-frequency signal crossing the Pacific, and a family waiting beside a landline somewhere in the United States.
During the 1960s and Vietnam War era, MARS stood for Military Affiliate Radio System (the name was changed from Military Amateur Radio System in 1952 and was retained until 2009 when it became Military Auxiliary Radio System).
Better known as MARS, became one of the most important morale links of the Vietnam War era. It gave troops a way to hear familiar voices when commercial overseas phone service was either unavailable, unreliable, or far too expensive for ordinary use.
MARS was sponsored by the Department of Defense and organized through three service branches:
Army MARS
Air Force MARS
Navy-Marine Corps MARS
The system joined military communications units overseas with licensed civilian amateur radio volunteers across the United States. These volunteers, often experienced ham operators, adapted their private stations to work on dedicated military high-frequency channels near the amateur bands. Together, they handled health-and-welfare traffic, personal messages, phone patches, and emergency communications.
The K0UO Rhombic Farm uses Rhombic and LPDA arrays like the big MARS stations did in the 1950s to the 1980s
Operators such as Steven Walz, known in amateur radio as K0UO and associated with the MARS call AAT6PS, represent the kind of technically skilled radio people who kept the system alive. MARS depended on people who could manage equipment, procedures, interference, poor propagation, and the emotions of a family call under wartime conditions.
MARS filled a communications gap during the Vietnam War
The Vietnam War pushed MARS to its highest operational tempo. Troops were stationed across South Vietnam, Thailand, and nearby support locations. Many were young, far from home for the first time, and separated from families by distance, time zones, and limited communications infrastructure.
Commercial telephone links from Southeast Asia to North America were not a normal option for most service members. Even where limited service existed, access and cost put it out of reach. Mail could take days or weeks. Tape-recorded letters were treasured, but they could not replace a live voice.
MARS helped fill that gap.
Major hubs operated at U.S. installations in South Vietnam, including places such as Tan Son Nhut Air Base, Cam Ranh Bay, Da Nang, and Long Binh. Other stations operated in Thailand and across the wider Pacific support network. Signals often moved through relay points in Okinawa, Guam, Hawaii, and the Philippines before reaching volunteer stations in the continental United States.
At the height of the war, MARS networks handled tens of thousands of personal connections each month. Not every contact was perfect. Some lasted only a few minutes. Some were noisy, delayed, or interrupted by fading signals. Still, for many families, those brief calls became unforgettable.
Barry Goldwater's K7UGA / AFA7UGA Station: Senator Barry Goldwater operated a famous MARS station in Arizona that processed over 200,000 phone patches for troops in Southeast Asia during the late 1960s and early 1970s. Historical photos of this station feature massive log-periodic antenna towers and custom operator consoles. Steven Walz spent the summer of 1970 at this station, which was in Barry Goldwater pool house at his AZ home.
The system joined military discipline with amateur radio skill
MARS worked because it combined two cultures that shared a respect for procedure.
Military communicators brought structure, call signs, schedules, message handling rules, and traffic discipline. Civilian amateur radio operators brought deep practical experience with receivers, transmitters, antennas, propagation, and improvised fixes.
The civilian side mattered greatly. MARS volunteers across the country used private equipment, often in basements, garages, spare rooms, or backyard radio shacks. They modified gear to operate outside normal amateur allocations on authorized military auxiliary frequencies. They also installed antennas, maintained logs, handled message forms, and worked odd hours to match overseas traffic schedules.
A typical stateside MARS volunteer needed:
A suitable HF transceiver capable of single-sideband operation
Antennas for long-distance communication
Authorization to operate on assigned MARS frequencies
A telephone line for phone patches
A phone patch interface to connect radio audio to the landline
Strong operating discipline and patience
That last point mattered as much as the hardware. Operators had to manage emotional conversations while also controlling a technical circuit that could collapse without warning.
A MARS call was personal, but the circuit was still radio. Everyone had to share the channel, identify properly, and follow the operator’s instructions.
Classic Equipment in 1950s–1970s MARS
Transceivers & Receivers: Collins S-Line gear (32S-3 transmitters and 75S-3 receivers), Collins KWM-2 / KWM-2A transceivers, Drake R-4B / T-4XB "Twins", and heavy rack-mounted Collins R-390A / URR military receivers.
Phone Patch & Station Control Units: Collins 312B-4 station consoles (incorporating directional wattmeters and phone patch hybrid transformers).
Linear Amplifiers: High-power tube amplifiers like the Henry 2K, Collins 30L-1, or 30S-1 linears.
Teletype Machinery: Teletype Model 28 and Model 15 machines used for transmitting written MARSGRAMS via radioteletype (RTTY) or CW (Morse code) when voice conditions faded
Phone patches made the radio sound like a telephone call
The best-known MARS service of the Vietnam era was the phone patch. A phone patch connected a high-frequency radio voice circuit to the U.S. landline telephone system.
The process looked simple to the family on the receiving end, but several steps had to line up.
A service member reported to an overseas MARS station and waited for a turn. The overseas operator established contact with a stateside MARS station on a scheduled frequency. Once the radio path was good enough, the stateside volunteer dialed the family’s phone number. In some cases, the volunteer placed a local call. In others, the call used long-distance or collect calling arrangements.
A patch device then linked the radio audio to the telephone line. The family spoke into a regular telephone. Their voices traveled through the handset, into the patch, across the HF circuit, and out through a speaker or headset overseas.
It was not a normal phone call.
HF radio was usually half-duplex, which meant only one side could speak at a time. If both sides talked at once, they covered each other. Operators trained families and service members to pause, speak clearly, and use words such as “over” to signal the other person’s turn.
A typical exchange might sound like this:
“Mom, this is Jim. I’m okay. Can you hear me? Over.”
That simple “over” was not theatrical. It made the call work.
Phone patches also had limits. Conversations were usually short because many people were waiting. Operators reminded callers not to discuss classified information, troop movements, casualties not yet released through official channels, or operational details. The purpose was morale and welfare, not military reporting.
MARSgrams carried written words when voice was not possible
Phone patches were powerful, but they were not the only service. MARS also handled written messages often known as MARSgrams.
A MARSgram worked like a short radiogram or telegram. The sender wrote a brief message, often limited in length so it could move efficiently through the network. Operators transmitted it by voice, teletype, or other available methods, depending on the station and era. On the receiving end, another operator copied the message and arranged delivery.
MARSgrams were useful when:
Voice schedules were overloaded
HF conditions were poor
A service member’s family did not have easy phone access
A routine welfare message needed to move without delay
Emergency family information had to reach a command
The content was usually plain and direct. A service member might send word that they were safe, had received a package, or were thinking of home during a holiday. Families used the same path to send greetings, birth news, illness notices, or other personal updates.
MARSgrams lacked the emotional immediacy of a voice call, but they had one advantage. A written message could survive a bad radio day. If fading, static, or interference made a phone patch impossible, trained operators could still pass short traffic with careful repeats and confirmations.
HF radio made the network possible and unpredictable
MARS depended heavily on high-frequency radio because HF signals can travel far beyond the horizon. Under the right conditions, a signal can refract through the ionosphere and return to Earth hundreds or thousands of miles away.
That ability made global communication possible without satellites. It also made every circuit subject to nature.
Operators had to work around:
Time of day
Solar activity
Seasonal propagation changes
Thunderstorm static
Frequency congestion
Equipment drift
Local electrical noise
Weak antennas or damaged lines
A clear path from Vietnam to the western United States in one hour might fade badly in the next. Sometimes a relay station in Guam, Hawaii, Okinawa, or the Philippines could make the difference. These intermediate stations helped move traffic when direct contact was weak or impossible.
Single-sideband voice, often called SSB, gave MARS operators a practical way to carry speech over long HF paths. SSB used transmitter power more efficiently than older amplitude modulation and became a standard voice mode for serious long-distance work.
The equipment was not casual consumer gear. Operators worked with receivers, transmitters, couplers, microphones, headsets, patch panels, frequency lists, and paper logs. Skill showed in small choices: changing frequency at the right time, rotating an antenna, reducing background noise, or asking both parties to slow down.
The human side of a three-minute call
The technical story matters, but MARS is remembered because of what happened in those short conversations.
A service member might wait in line after duty, step into a hot radio room, and hear a stateside operator say the connection was ready. A parent might answer a ringing phone and hear a stranger explain, “I have a MARS call from Vietnam.” Then a familiar voice would break through the static.
These calls carried ordinary words under extraordinary pressure.
People talked about school, weather, babies, cars, packages, pets, holidays, and home repairs. They avoided the subjects they could not discuss. They tried to sound calm. Sometimes the signal faded before anyone was ready. Sometimes the family cried after the line went dead.
The operators heard much of it. They were part technician, part traffic handler, and part quiet witness. Good operators kept control without intruding. They reminded callers to say “over,” watched the clock, adjusted audio levels, and protected the circuit for the next person waiting.
MARS did not remove the distance between Vietnam and home, but it narrowed it for a few minutes at a time.
The network had rules because the stakes were high
MARS traffic was morale traffic, but wartime communications needed discipline. Operators followed procedures for identification, traffic priority, frequency use, and message handling. Personal calls could not be allowed to interfere with official emergency communications.
Health-and-welfare traffic was common. Emergency traffic received more urgent treatment. If a family crisis needed to reach a service member, or a deployed person needed help contacting home, MARS could become more than a morale service.
The system also had to protect sensitive information. Families and troops were reminded not to discuss unit movements, locations beyond what was already public, operational plans, or casualty information outside approved channels. Even casual comments could reveal more than intended.
This balance made MARS unusual. It was personal but regulated. It used civilian volunteers but served military needs. It carried private emotions across public radio channels that others could potentially hear.
For that reason, operators enforced plain rules:
Keep messages brief
Speak clearly
Do not interrupt
Wait for the operator’s cue
Avoid sensitive military details
End the call when asked
These limits could feel frustrating, but they allowed the system to serve many people safely.
MARS after the Vietnam peak
The Vietnam era marked the high point of MARS as a mass personal communications bridge. As commercial international calling improved, satellite communications expanded, and later internet-based tools emerged, the role of MARS changed.
The system did not disappear. MARS continued to support military auxiliary communication, training, contingency operations, and emergency preparedness. Its emphasis shifted over time from routine morale phone patches toward backup communications and interoperability.
Still, the Vietnam War era remains central to the identity of MARS. It showed what a disciplined volunteer radio network could do at national scale. It also showed the value of civilian technical skill in support of service members and their families.
Today, it is easy to forget how hard a simple call once was. Mobile phones, video calls, email, and messaging apps have changed expectations. In the 1960s and 1970s, a voice crossing the Pacific by HF radio was not routine to the people receiving it. It was a gift.
Why the Vietnam-era MARS story still matters
The story of the Military Auxiliary Radio System in the Vietnam War Era is more than a technical footnote. It is a reminder that communication is part of morale, readiness, and family resilience.
MARS connected people through a mix of federal sponsorship, military procedure, amateur radio skill, and volunteer commitment. Its operators worked with imperfect tools under difficult conditions, yet they built a bridge that carried voices, reassurance, and urgent news across oceans.
The system’s success came from its human design. It did not rely on one perfect technology. It relied on trained people at both ends of the circuit who knew how to listen, wait, repair, repeat, and try again.
For the service member in Vietnam, the parent in Kansas, the spouse in California, or the volunteer operator tuning through static late at night, MARS made distance briefly bearable. That is why its Vietnam-era legacy still carries weight among radio operators, veterans, and families who remember the sound of a faraway voice saying, “I’m okay. Over.”
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MARS DOD 1970 File https://youtu.be/9o_PRKBF8Tw?si=O7Z5_Sp0L2Ye0EkX
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