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DAS-3 Loran


DAS Loran receiver-indicator.
DAS Loran receiver-indicator.

Description.-The DAS series of radio navigation equipment are shipboard units for receiving and measuring the time difference of signals from a pair of Loran transmitting stations. The received pulses are displayed upon the time scale of the indicator, so that the time difference may be accurately measured. With the aid of Loran charts and tables, the location of the ship is established on a Loran line of position. The intersection of two lines of position determines the position of the ship. The DAS-1, DAS-3, and DAS-4 are nearly identical in external appearances. The 3 and 4 versions are a slight improvement on the DAS-1 in that they have better components and construction, and a more sensitive receiver. The DAS-4 is slightly easier to operate. After certain required field changes the model designations are changed. The DAS-la and DAS-1b are successive modifications of the DAS-1. The DAS-1, DAS-3, DAS-4 are not mechanically interchangeable with the DAS or DAS-2.

Number of operators.-One.

Power supply.-3l6 va, 105 to 130 volts at 50 to 60 cycles.

Tube complement.-4 type 6SJ7, 2 type 6AC7, 9 type 6H6, 11 type 6SN7-GT, 4 type 6SL7-GT, 1 type 884, 1 type 5CP1, 2 type 2X2, 1 type 5T4, 2 type 2A3, 1 type VRl05/30, 4 type 6SK7, I type 5Y3-GT, 1 type 6SA7.

Range.-500 to 750 nautical miles during the day and up to 1,400 nautical miles at night.

Antenna.-The antenna is a vertical wire between 35 and 125 feet in length. It is usually formed by stretching a No. 12 A. W. G. stranded silicon-bronze wire between two insulators.

Receiver.-The four channels of the receiver may be tuned anywhere between 1,700 and 2,000 kc. (in DAS-1b, DAS 3, and DAS-4) but are normally set at 1950, 1850, 1900, and 1750. The receiver will detect a signal of 12 microvolts in DAS-1, 6 microvolts in DAS-3, and 2 microvolts in DAS-4.

Indicator.-The indicator contains a group of circuits for the purpose of visually measuring the time difference between pulses. Both timing markers and received pulses are displayed on the screen of the cathode ray tube so that the reading may be made within one microsecond. Two basic sets of recurrence rates are provided (in DAS-la or later modification and in the DAS-3 and DAS-4)-L(25 per second) and H(33 1/3 per second).

Dimensions and weights

      Units            Navy Type No.| Width    | Depth    | Height  | Weight
                      |             | Inches   | Inches   | Inches  | Pounds
      DAS-1
Antenna loading coil  | CFE-47342   | 9 1/4    |   5      | 5 1/4   | 4
Line filter           | CD-53142    | 3 3/4    | 6 3/16   | 2 5/8   | 3
Receiver-indicator assembly.        |  23      | 21       | 16 9/16 | 137 
 (Consisting of the following:)
  Indicator           | CFE-55118*  | 15 11/16 | 23 11/16 | 12 1/4  | (90)
  Receiver            | CFE-46216*  | 5 3/16   | 21 1/4   | 7 11/16 | (22)
  Mounting base       | CFE-10225   | 23       | 21       | 4 3/4   | (25)   
Total weight                                                          144 1/4

      DAS-3
Antenna loading coil  | CFE-47342-A | 9 1/4    | 5        | 5 1/4   | 4
Line filter           | CD-53142    | 3 3/4    | 6 3/16   | 2 5/8   | 3
Receiver-indicator assembly.        | 23       | 25       | 16 9/16 | 135 1/2
(Consisting of the following:)
 Indicator            | CFE-55118-A | 15 11/16 | 23 11/16 | 12 1/4  | (87)
 Receiver             | CFE-46216-A | 5 3/16   | 21 1/4   | 7 11/16 | (23 1/2)
 Mounting base        | CFE-10225   | 23       | 21       | 4 3/4   | (25)   
Total weight                                                          142 3/4

     DAS-4
Antenna loading coil  | CG-47335    | 8 7/8    | 5 1/2    | 11 1/8  | 8
Line filter           | CD-53142    | 3 3/4    | 6 3/16   | 2 5/8   | 3 1/4
Receiver-indicator assembly.        | 23       | 25 5/16  | 16 13/16| 142 1/2
(Consisting of the following:)
 Indicator            | CFE-55175   | 15 11/16 | 24 1/6   | 12 9/16 | (100)
 Receiver             | CFE-46268   | 5 5/16   | 21 1/6   | 9       | (171 1/2)
 Mounting base        | CFE-10461   | 23       | 21       | 4 3/4   | (25)   
Total weight                                                          153 3/4

 * Suffix letters are added to the type number to indicate certain field changes.
Literature.-Instruction Book for DAS-4 (Ships 322). Instruction Book for DAS-1, DAS-3 (NavShips 900,752). Loran Handbook for Shipboard Operators (Ships 278).

REFERENCES:

The information enclosed here is excerpted from:
Catalogue of Naval Electronic Equipment-April 1946- NavShips 900,116.

 

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Version 2.00, 11 Sep 2006