July 1945 Radio-Craft
[Table of Contents]
Wax nostalgic about and learn from the history of early electronics.
See articles from Radio-Craft,
published 1929 - 1953. All copyrights are hereby acknowledged.
"Portable" is a matter of
perspective when it comes to large systems. Anything that can be put on wheels
and moved over land is technically portable, but the speed at which it can be
brought into operation once relocated is what really defines whether something
is portable or not. To be truly portable, all of the requisite support equipment
must travel with it; e.g., electric generators, fuel, water, food, personnel
facilities (if needed), etc. The
MPN−14 portable airport surveillance radar (ASR)
and precision approach radar (PAR) unit I worked on in the USAF truly qualified
since it was entirely self-contained and the necessary power generators were
supplied by a separate shop within the 5th Combat Communications Group to which
I belonged. Other shops provided creature comfort facilities, ground-based and
satellite radio communications, tactical air navigation (TACAN), security, and
A few times each year we had what were called "Healthy Strikes" where claxons
would sound in the barracks and at strategic locations around the base (Robins
AFB, Georgia), thereupon concerned members had one hour to gather deployment
gear and report to their respective shops. After a briefing, we proceeded to
disassemble and pack the radar trailers (equipment, utility, and rapcon), go to
the out-processing center to receive orders and have medical records and
passports checked, and finally pick up the trucks for towing the radar trailers.
Back at the shop, we hooked up the trailers, ticked off last-minute checklists,
and drove the trailers to the staging area in preparation for moving out. Our
destination was Herbert Smart Airfield, in Macon, where the entire 5CCG
established a compound and erected our equipment. After system check-out, a USAF
bizjet flew in to validate the ASR, PAR, and VHF and UHF radios. We slept in
tents for a week or so - unless it was super hot out, then we'd sleep in the air
conditioned radar trailers. There was a maximum time allotted for the time from
claxon to driving out the gate, and then from arriving at the field and being
operational, but I don't recall. It was something like 12 hours and 8 hours,
Biggest "Portable" Radio
The "world's biggest portable" fills
fourteen large trailers and requires two others for power supply and one for
hauling supplies. Short-and long-wave antennas identify their respective trailers.
Receiving station in Trailer 14 may be set up a distance from transmitters,
to which it can then be connected by short-wave links, as shown in Sketch 2.
Possibly the largest mobile radio station ever constructed was developed
by the Communications Division of the U.S. Signal Corps Headquarters for use
on the West Front in Europe. Completely installed in seventeen large trailers,
it has a power of no less than sixty kilowatts - which would be a very respectable
figure for a large permanent broadcast station.
The station was capable of transmitting 200,000 words daily across the Atlantic,
while sending radioteletypes and photographs at the same time. Simultaneously,
it was used as a broadcast station for entertainment of Allied troops within
an area of 25 to 30 miles.
Manufactured by the French under Signal Corps supervision, the station can
be packed up and moved, or set up and put into action, in little more than 24
hours. In spite of this "portability" it has all the ordinary facilities of
a fixed radio station of comparable power, and has its own power plant. It is
equipped with broadcast facilities, radio facsimile for transmission of photographs,
and the normal, message-handling radioteletype (RTTY) channels. It has equipment for
recording on wire, disc, and film.
High-power radio receiving and transmitting stations are usually
separated a considerable distance from each other to avoid mutual
interference between transmitted and received signals, and ordinarily are
connected by telephone lines. With this new mobile radio station, an
efficient innovation has been added. The inter-communications between units
is by means of special very-high-frequency radio, associated with suitable
voice-frequency carrier equipment to provide the required number of keying
controls and channels.
Once the radio station convoy has reached a set location, the complete unit
can be set up and operating in little more than 24 hours. It can be dismantled
and moved with equal facility. The antenna arrays are supported by 72-foot poles,
jointed in eight-foot lengths for convenient transport and erection. An efficient
team can erect these poles in 15 or 20 minutes.
All the equipment for the independent operation of the station is ingeniously
disposed in the trailers in the following manner: Trailers numbered 1, 2 and
3 each hold a 50-kilowatt diesel power unit and a 275-gallon fuel tank. A master
power switch is attached for converting from Diesel power to commercial power
when the latter is available.
Trailer 4 holds a low tension power supply and voltage regulator, with a
12,000-volt filter condenser. Trailer 5 contains a high-voltage (12,000-volt)
DC rectifier unit, 6 has a Western Electric two-kilowatt driver-condenser, very-high-frequency
transmitters and receivers, and associated carrier equipment.
Trailer 7 carries a 60-kilowatt power amplifier, which is fed from the transmitter
contained in trailer 6, while trailer 8 has an Army Forces Network transmitter,
an air blower for the high power air-cooled tubes of the station and a workshop.
The Signal Center is composed of five trailers - numbers nine to thirteen
inclusive. Trailer 9 holds supplies and two very-high-frequency transmitter
and receiver systems. Trailer 10 contains special carrier equipment. Trailers
11 and 12 have six high-speed teletype machines and associated facilities for
handling traffic. Trailer 13 has facsimile transceiver units, the broadcast
studio, and a control booth in which space has been set aside for the wire,
disc and film recorders. This trailer is also the home of the portable American
Forces Network studio.
The receiving station, consisting of one Western Electric receiver, very-high-frequency
transmitters and associated carrier equipment, is fitted into trailer 14. Trailers
15 and 16 each hold a 25-kilowatt gasoline power unit, while trailer 17 carries
the Army Pictorial Division hut.
The project was executed under Major General W. S. Rumbough, Lynchburg, Virginia,
Chief Signal Officer, Communications Zone, European Theater of Operations, and
the station is manned by a team composed of personnel selected for their technical
proficiency and operating skill. Administrative and guard personnel have been
provided to make the team completely independent and self-sustaining.
Posted January 15, 2021