If you’re 18 and at a rave party, it’s not good to feel alone.
You definitely need help. If you’re 69 and at
home, it’s 0300, and you hear strange noises in your house,
it’s not a good feeling to be alone then either. The chances
are you really need help. And if you’re standing
before a divorce judge and your attorney has just quit your
case… without a doubt you need more help than you can
imagine. However, if its 1942
and you’re treading water at sea, alongside a downed
Mustang, the chances are that although you may feel
alone you are not alone. Given the examples just
stated, I would rather be treading water at sea, next to my
downed fighter plane, than in any of the other situations.
Why?
Because thanks to the U.S. Army Signal Corps I would likely
be
treading water along side of an SCR-578.
What’s an SCR-578,
you ask?
Well, if you can manage to get it and you
into that damned inflatable dinghy before that shark
sniffing at your boots decides to see what an Army Air Force
pilot tastes like, you’ll soon find out. What you’ll find
out is that you’re now sharing your lifeboat with your own
private Gibson Girl. And this little beauty may save your
life.
As Signaleers, most of us think in terms of our branch being
responsible for prosaic means of communication… methods and
systems meant to connect people in order to foster better
command and control of a battle space. But that’s not always
the case. Regular readers of this website know that the
Signal Corps gets involved in lots more than just producing
and operating combat radio systems. One of the more
interesting areas—one that has received surprisingly little
recognition—is the area that deals with survival radios. If
you’re in trouble and need to be able to reach out and touch
someone, the chances are that the radio or telephony device
you do it with had its start with the U.S. Army Signal
Corps, back in World War II.
When it comes to survival radios however, to be fair, the Germans seem to be the first to have figured
out that having spent a ton of money training a man for
combat, spending a little more to save him after he got into
trouble was a far better use of money than leaving him to
die and then retraining a replacement. And since back then,
when they were perambulating over how to solve this problem
of soldiers dying on the job by some means other than being
shot, most of the trouble that came along where lives could
be saved had to do with naval vessels being sunk at sea,
well… it made sense to find a way to help those who found
themselves floating around in the vicinity of a downed ship
call out to the world and say ‘come rescue me.’
It was this kind of thinking that caused the Germans in
World War II to develop a hand-cranked 500 kHz rescue radio
called the NS2. Nicknamed the "Notsender" for the letters in
its designation, it was little more than an emergency
transmitter that employed two crystal controlled vacuum
tubes. Of interest, the design of the unit used a radio case
that curved inward in the middle, so that a user seated in
an inflatable life boat could hold it securely above their
knees and between their legs, at which point they could then
crank the attached generator handle to produce the power
needed to cause the thing to transmit a May Day signal. In
the case of the German NS2, a very basic Morse code distress
signal was sent out when the handle was cranked.
The British found an NS2
floating around somewhere near a German
warship they sank, and being as inquisitive as ever picked it up and wondered what it was.
Thinking that is was nothing important they didn't bother to
tell anyone else about it but instead disassembled it to try and
figure out what possible purpose it served. Fortunately, a
little while later they found a second one and sent that
one off to the U.S. Army Signal Corps. The Signal Corps
immediately recognized it for what it was, and within a few
months had copied the idea and released the SCR-578, the
designation of which stood for not only the emergency
transmitter itself, but all of the accoutrements that went
along with it.
Issued mostly to the Signal Corps’ then controlled Army Air
Force, the SCR-578 was meant to be carried on every aircraft
that flew over-water, serving as an emergency transmitter in
the event of a crash landing. The reality turned out to be otherwise
however, as most combat fighter pilots tended to prefer to
leave the thing behind and instead use the
weight savings to carry additional rounds of ammunition
instead.
Here’s where we come to the Gibson Girl part. Operationally,
to assure that a downed pilot could use the device while
still kicking at sharks, the unit was shaped like the German
sibling it was copied from. It had an hourglass shape that
allowed it to be held between the legs while it was cranked.
Army Air Corps combat pilots of the time being what they were… men… it was
given the nickname the Gibson Girl… whether for its hour
glass shape or the part about where it was held between the
pilots legs and cranked, we don’t know. Either way, the name
stuck.
To make sure the signal generated was transmitted as far as
possible the unit was supplied with a metal framed box kite
that was stored in a folded position but was unfolded for
use. Once unfolded it was launched into the sky via a
balloon, which in turn was inflated by means of a small
hydrogen generator. The wire that linked the box kite and
balloon to the unit served as the antenna. As in the earlier
German version, power was provided by hand cranking.
The transmitter component of the SCR-578 was designated as
the BC-778. Its frequency was 500 kHz, and it put out 4.8
watts. At that power level it had a range of about 200 miles
(300 km). Unlike the German version which robotically sent
out the signal as the crank was turned, the BC-778 made
provisions for keying that could be either
automatic (sending a standard SOS signal) or manual. At the
time of its development and manufacture crystals were still
a scarce item for the Signal Corps, and so, the SCR-578, not
being high on the list of priority items to receive
crystals, used tuning circuits.
Despite these limitations the SCR-578 saw long and reliable
use, eventually finding its way into every branch of the
U.S. military, and after the war into civilian use. It was
not until much later that the Signal Corps released a
post-World War II version that was called the AN/CRT-3. Only
slightly modified from the original SCR-578, the AN/CRT-3
added a frequency in the 8 MHz range (to reduce the size of
the quarter-wave antenna needed). It was designed for use by
military personnel and civilians, in both ships and
aircraft. A well designed and accepted piece of survival
gear, the AN/CRT-3 saw usage up until the early 1970s.
The reader can readily understand that the SCR-578 and
AN/CRT-3 were transmission devices. That is, they sent a
signal out saying ‘come help me.’ But whether there was
someone out there listening for this signal or not was not
known. To complete the circle and make sure there were
people tuned in to the distress frequencies the Signal Corps
worked on developing a radio location device that could be
mounted inside of an airplane specifically outfitted to
perform the function of search and rescue.
This concept, when turned into reality,
caused the development late in World War II of
line-of-sight VHF radios. Centered around a much shorter
wavelength, VHF allowed the use of simple dipole or whip
antennas. The U.S. unit developed to serve this purpose
appeared post WW II and was known as the AN/URC-4. It
operated on the aircraft emergency frequencies of 121.5 and
243 MHz, which in turn involved wavelengths of 2.5 and 1.2
meters. At these wavelengths antenna lengths were ideally
suited to the types of search and rescue aircraft then being
used.[1]
As time moved on and the Vietnam era came to pass the Signal
Corps did its best to stay on top of the task of keeping the
survival radio systems it developed up to date, in terms of
the latest in technology. Unfortunately post Vietnam budget
issues constrained new radio development. The result was
that while better designs could have been produced and
brought to market post Vietnam they were set aside as part of the normal
knee jerk reaction Uncle Sam has after a war is over... the
one where Congress, acting in his name, cuts the budget for
everyone and everything with the word military attached to
it to the bone. In this case the effect
was that better survival radio technological designs and
circuitry sat on the drawing boards and failed to make it into
the form of a finished product.
Yet while circuit improvements may have stood still during
the early 70s, time itself was not standing still... nor
were events. In 1972 Congressmen
Thomas
Hale Boggs, Sr. and Nick
Begich, flying on a light plane in Alaska, crashed and
could not be found. Suddenly, Congress stood up and took
notice of what the U.S. military, in the guise of the Signal Corps, had been
saying for a number of years…
that better survival radio technology was available, including designs for
emergency beacons that self activated when a plane crashed.
Just like that the law was changed, the budget was
increased, and from that point
forward our always responsive Federal Government began
requiring that all aircraft carry an Emergency Locator
Transmitter (ELT) that automatically activated in the event
of a crash.
Initially, in order to get devices into the field quickly,
the frequency used was left at 121.5 MHz (the standard
emergency beacon frequency) so that existing
equipment/transmitters could be used. As time wore on though
newer devices began to reach the field, using 406.025 MHz.
This frequency allowed the devices to be picked up by the Cospas-Sarsat international
satellite system. Cospas-Sarsat was a satellite-based search
and rescue (SAR) distress alert detection and information
distribution system that was created by the U.S., partly
in response to congressional mandates following the deaths of
congressmen Boggs and Begich. Operationally, the system was
jointly established by Canada, France, the United States,
and the former Soviet Union. It’s first functional use was
in 1979.
Based primarily on U.S. Signal Corps lab designs, the
benefit of the 406 MHz beacon was that it allowed each
transmitter to have a unique digital ID code. Anyone
acquiring a device for use in their aircraft was required to
register the code on the device, along with their contact
details, with the Cospas-Sarsat authorities. In this way,
even without anyone notifying the Cospas-Sarsat authorities
that a plane was missing, when a signal was detected the digital ID code allowed Cospas-Sarsat to reach out to the people who registered the
code and ask if everything was OK. Later, as time
allowed for the introduction of even more sophisticated
emergency beacon designs, newer models were introduced that
could transmit location specific information derived from an
internal GPS or GLONASS receiver.[2]
So successful was the Cospas-Sarsat system that over the
years many countries joined the project, either as 'providers'
of ground segments or as 'user states.' To date some 26
countries are providers of ground segments, while 11
countries are classified as user states. Today, Cospas-Sarsat, a concept that originated with the U.S. Army
Signal Corps, is based in Montréal, Québec, Canada, eh.[3]
Maritime emergency beacon transmitters on the other hand
have shifted from their early reliance on rescue radios that
operated at the 500 kHz distress frequency to the Cospas-Sarsat system too. In fact the 500 kHz frequency is
no longer officially monitored, although many ham radio
operators around the world still keep a radio tuned to the
frequency. To supplement the maritime environment’s unusual
requirements for more than one means of transmitting
emergency signals, radar transponders (which obviously
respond to and transmit signals able to be seen by radar
systems on other ships, versus radio systems) have been
added to naval kits, as have
hand-held marine VHF radios. The picture at right shows
the SART Radar Transponder.[4]
In terms of where the U.S. Military is in regards to
survival radios, military organizations now issue pilots and
other combat personnel individual survival radios. Unlike
the one-size fits all approach of the past, these radio
systems have become increasingly sophisticated, with
built-in Distance Measuring Equipment (DME), Global
Positioning Satellite receivers and satellite
communication. Looking back over all of the various survival
radio sets/systems that the U. S. military has used and the
Signal Corps has promulgated, one finds the following:
World War II
AN/CRC-7 - World War II era set, 140.58 MHz
AN/PRC-17
AN/PRC-32 - Navy rescue sets, 243 MHz
AN/PRC-49
AN/PRC-63 - Smallest set built
AN/URC-64 - (Air Force), 4 frequency rescue
sets. Four crystal controlled channels (225-285 MHz)
AN/URC-68 - (Army), 4 frequency rescue sets
Vietnam War and Later Eras
AN/PRC-90 - Vietnam War era airman rescue
set. The AN/PRC-90-1 and AN/PRC-90-2 are improved,
repairable versions. They operate on 121.5, 243 and
282.8 MHz AM. The PRC-90 also included a beacon mode, and a
tone generator to allow the sending of Morse Code.
AN/PRC-103 - (Air Force) Rescue Swimmer
Radio.
AN/PRC-112 - Offered synthesized radio in
the VHF and UHF aircraft bands. A PRC-112 and a hand held
GPS were used by Capt. Scott
O'Grady when he was rescued after being shot down
over Bosnia. The AN/PRC-112B, initially known as the Hook
112, is a PRC-112 modified to include a GPS receiver,
allowing encrypted position information to be sent. The unit
also has a Cospas-Sarsat beacon. The latest model PRC-112G,
built by General Dynamics can communicate with
satellites. Over 31,000 radios in the PRC-112 family have
been produced.
AN/PRC-125 (Navy) Rescue Swimmer Radio.
AN/PRC-149 Rescue Radio, replaced the
PRC-90, PRC-112 and PRC-125 for non-combat use. It included
both a GPS and Cospas-Sarsat beacon, and operated on
121.5 MHz, 243.0 MHz, 282.8 MHz, and 406.025 MHz. Built by Tadiran,
the PRC-149 used standard D cell batteries, unlike other
units that took special batteries.
AN/PRQ-7 Combat Survivor/Evader Locator
(CSEL). This unit combines selective availability GPS, UHF
line of sight and UHF satellite communications along with a
Sarsat beacon. It can send predefined messages digitally
along with the user's location. As of 2008, the PRQ-7 cost
$7,000 each, “batteries not included.” A
rechargeable lithium-ion battery pack cost $1,600, while a
non-rechargeable lithium-manganese dioxide unit cost
$,1520. As of October 2011 Boeing had delivered 50,000 PRQ-7s.
AN/URC-4 - 121.5 and 243 MHz.
AN/URC-11 - (243 MHz), "A" versions
replaced one audio tube with transistors.
AN/URC-10 - The RT-10 are sub-miniaturized,
completely transistorized UHF radio sets. They consist of a
crystal-controlled receiver-transmitter, a 16-v dry cell
battery, and a power cable assembly. The unit operates on
one channel in the 240-260 MHz band (usually 243 MHz). RT-60
and RT-60B1 are two frequency versions of the RT-10.
·
AN/URC-14 - (121.5 MHz)
With all of these systems out there, how can anyone feel all
alone? If you’re that guy we started off talking about who
was 69 years old and at home alone when his house was broken
into at 0300, it’s now clear that all you needed to
protect yourself was a good
AN/PRQ-7 beside your bed.
And if you are that guy standing before
a divorce court judge as your attorney resigns from your
case, then what you need is a AN/URC-68 rescue set. Why?
Because it will give you access to 4 different frequencies,
and in your case letting as many people as possible know
that you need help is the only thing that is going to save
you at this stage of your life.
And as for you claiming to be the 18 year old at the rave
party, forget about it. We all know
you are far too old to be him. And besides, what any 18 year
old needs to
survive he already has: a
cell phone and a Twitter account.
Footnotes
[1] On the Allies side, the VHF devices available for use
during WWII included the British Walter, a small single
vacuum tube oscillator design that operating at 177 MHz (1.7
meter wavelength). The Germans, pioneers in the use of VHF,
used the Jäger (NS-4), a two-tube master oscillator power
amplifier design that operated at 58.5 and 42 MHz. Both the
British and the German versions were small enough to be
carried in the life rafts that were found on single-seater
fighter aircraft.
- To return to your place in the text click here:
[2] GLONASS (Russian: ГЛОНАСС), acronym for Globalnayanavigatsionnaya sputnikovaya sistema or
Global Navigation Satellite System; a space-based satellite
navigation system operated by the Russian Aerospace Defence
Forces.
- To return to your place in the text click here:
[3] Ground Segments: Algeria, Argentina, Australia, Brazil,
Chile, People's Republic of China, Greece, India, Indonesia,
Italy, Japan, Republic of Korea, New Zealand, Nigeria,
Norway, Pakistan, Peru, Saudi Arabia, Singapore, South
Africa, Spain, Thailand, Turkey, United Arab Emirates,
United Kingdom, Vietnam and two organizations, Chunghwa
Telecom of Chinese Taipei and the Hong Kong Marine
Department. User States: Cyprus, Denmark, Finland, Germany,
Madagascar, Netherlands, Poland, Serbia, Sweden,
Switzerland, Tunisia - To return to your place in the text click here:
[4] A Search and Rescue Transponder (SART) is a
self-contained, waterproof radar transponder intended for
emergency use at sea. The radar-SART is used to locate a
survival craft or distressed vessel by creating a series of
dots on a rescuing ship's radar display. A SART will only
respond to a 9 GHz X-band (3 cm wavelength) radar. It will
not be seen on S-band (10 cm) or other radar. - To return to your place in the text click here:
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