Jeep with Radio Set SCR-499

A version developed for glider transport is this Jeep, equipped with the SCR-499 radio set. Shown inside a what looks like a C-47 Skytrain on the left and on the right in a CG-4A Waco glider and deployed in the field. This combination was developed for quick deployment in the field. A complete setup would require too much time and a set like this was almost immediately available after landing. Notable in this pictures is, that it seems that both headlights were removed from the frontpanel. As far as is known, a normal 4x4 Jeep and Bantam trailer were used to convert these into the version shown above.

The Truck 1/4-Ton 4x4 and the Trailer 1/4-Ton 2wh

To reduce weight for transporting this combination in a plane, the manual states that a few items had to be removed from the truck. The rear bumperettes, horn, spare wheel and tire, rear seat and seat frame, rear view mirror, lifting handles, and windshield. To facillitate the placement of some of the equipment like the Radio Receiver BC-342, the right hand seat and seat frame had to be removed. Also the holder for 5-gallon gasoline drum, located on left rear of vehicle, had to be replaced and attached to the right rear of the vehicle.

The Signal Corps Technical Information Letter No. 34 from September 1944 states the following about this configuration: "A long-range radio set which could be transported by air in either a Cargo Glider CG-4A or Cargo Plane C-47, and which would be mobile and capable of operation immediately upon landing, was requested by the Air-borne Center, Camp Mackall, North Carolina. CW operation only was required, and operation while in motion was not necessary. Standard Radio Set SCR-499-( ), which includes the components of Radio Set SCR-399-( ), packed for air transport, is issued to the air-borne signal company for long range use but considerable time is required to move this equipment from a cargo glider or cargo plane and set it up to form an operating radio station. For this reason, it was desired to find a suitable means for mounting the principal components of Radio Set SCR-499-( ) as a mobile operating assembly, which could be easily moved, at least for a short distance. To meet this requirement, various arrangements were considered. An installation in a jeep and trailer appeared to be the most satisfactory, and Installation Kit MC-549, which includes equipment necessary for installing the components of SCR-499-( ) required for CW operation in a Jeep (Truck, 1/4-Ton, 4x4) and Jeep Trailer (Trailer, 1/4-ton, Cargo) to provide an operative assembly, was developed. As shown in the photographs, Radio Transmitter BC-610-( ), with necessary coils and tuning units, Antenna Tuning Unit BC-939-( ), Radio Receiver BC-342-( ), and necessary accessories are installed in the body of the jeep. One Power Unit PE-75-( ), a part of the installation kit, is installed on the front bumper of the jeep and a 5-gallon gasoline drum is mounted on the rear. An additional Power Unit PE-75-( ), extra gasoline drums, Antenna Assembly RC-293, spare tuning units, coil units, mast sections, and other spare parts, tool and test equipment, etc., are installed in the jeep trailer. Supplementary instructions for operation of Radio Set SCR-499-( ) in the jeep, not covered by Technical Manual 11-281 are provided as part of the installation kit. As seen from the above, complete equipment to provide CW operation is included in the jeep itself. One glider or cargo plane is required for transporting necessary personnel and the jeep with equipment installed therein, and an additional plane or glider for the trailer. The springs of the jeep must be depressed to permit loading of the jeep on the standard ramps of Cargo Plane C-47; chains for depressing the springs are included as part of the installation kit. As mentioned a power unit is provided on the bumper of the jeep but the load on the jeep may be reduced and satisfactory operation had by removing the unit from the bumper and using the power unit in the trailer. Mounting provisions permit installation of either power unit in either position. For increasing the range of the subject equipment, Antenna Assembly RC-293 is provided. This antenna includes two telescopic aluminum masts, 25 feet in height when extended; 250 feet of Wire W-148; guys, stakes, etc. It is used as an end fed % wave antenna. Instructions for use of this antenna are included in the supplementary operating instructions."

Below are the drawings taken from the TM 9-2715 C1 Manual from 1945, that describes in detail how the radio set SCR-499 should be installed in the Jeep (Truck 1/4-Ton 4x4) and the trailer (Bantam 1/4-Ton 2-wh). I mighty interesting version of this little Truck. The first three drawings show a clear overview of the installation from the top-, rear- and the left side of the vehicle. A complete set of drawings that show all alterations an additions needed wil be provided at the end of this article.

Below I describe the components of the radio set SCR-499 and how it was combined and I show what these parts are meant for. I do not yet have all details, but I want to gather more information on the subjects at hand. If someone has more info that I can and may use, please let me know via the contact form.

The Power Unit PE-75 was mounted on the front bumper. As can be clearly seen in the picture above and the detail drawings. Below are a few drawings and a picture of the unit itself. Here the skid base on wich the unit is placed is not modified. This skid base had to be shortened to fit on the front bumber. Also as can be clearly seen in the above shown picture, the Power Unit was altered to fit on the Jeep. In fact the Tool and spares box was removed. I take a little guess that this box was placed in the trailer. Also another Power Unit PE-75 was mounted in the trailer, evident in the picture and drawings.

The Antenna Tuning Unit BC-939-() is designed to match the impedance of the trammitter p-a (power-amplifier) stage to that of the antenna when a whip or long-wire antenna is used. The antenna tuning unit connects to the transmitter by a coaxial cable. A meter on the front panel of the antenna tuning unit measures r-f current; maximum current indicates optimum impedance match between the transmitter and the antenna. This unit was placed directly behind the driver

The Radio Receiver BC-342-() This radio receiver was of the superheterodyne type intended for general field usage. It was built ruggedly and was suitable for vehicular, portable, or fixed operation. The receiver was highly sensitive and selective and was designed for the reception of either continuous-wave (c-w) or amplitude-modulated (a-m) voice or tone signals. It was mounted on the right side of the vehicle beside the driver's position as can be seen on the drawings.

The Radio Transmitter BC-610-() was primarily designed for vehicular, portable, or fixed operation. This picture on the right shows the Transmitter with the Antenna Tuning Unit BC-939-(). Although this Transmitter was normally mounted in the 1½-ton Truck K-51 or in the Shelter HO-17, in this combination it was mounted in the 1/4-Ton 4x4 Truck.

ADV Azimut from France had a nice set of the complete Field Radio Set SCR-499. Some of the parts can be used for a nice model of the US airborne Jeep. But unfortunately this set is no longer available. Here a 3D printer can come in handy. Or if you are lucky eBay has a set somewhere.