Biggest "Portable" Radio
July 1945 Radio-Craft

July 1945 Radio-Craft

July 1945 Radio Craft Cover - RF Cafe[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 managerial services.

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, respectively.

Biggest "Portable" Radio

Biggest "Portable" Radio, July 1945 Radio-Craft - RF CafeThe "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