CESL                                                                                          SECRET                                                                                                              August 1943

404A                                    RADAR P LOTTING BOARDS.

                                            AUTHORIZATION: 1st Ind., from OCSigO, 19 Aug. 49, file SPSRB 418.44
                                            Plotting Boards, on basic letter from Army Air Forces to OCSigO, 23 July 48.

                                            DESCRIPTION: A study to determine the feasibility of using plastic material
                                            with satin finish similar to ground glass for use on GCI plotting boards as
                                            plotting surfaces.

                                            MILITARY CHARACTERISTICS: Inclosure with letter of authorization (see above).


                                            1. General.

a. The Chief Signal Officer has directed that a study be
made of the development of Radar plotting boards. A recent ‘
study of requirements for plotting boards for aircraft warning
equipment revealed that three types of boards are required:    (1) 10″ x 10″ Pack plotting Board for Radio Set AN/TPS-2.

    (2) 20″ x 20″ Lightweight plotting Board for Radio Sets
    SCR-602-A, SCR-602-T6, AN/TPS-1, AN/TPS-3.

    (3) 40″ x 40″ Long Range plotting Board for Radio Sets
    SCR-270, 271, 615, AN/CPS-1, 1200 mc Search and
    3000 mc Height Finding.

b. Hereafter, boards which are used for early warning
Radar sets and for reporting from a GCI station, will be
known as “Plotting Boards,” and tables which are used with
GCI stations and have built-in interception vector calculators,
will be known as “Navigation Tables.” The Craig Navigation
Table, previously referred to as the Craig plotting Board,
falls in this latter classification.

c. Investigation will be initiated into the matter of a
plastic material with a satin finish similar to ground glass
for use on GCI plotting boards as plotting surfaces. The
Plexiglass plotting surfaces used in the present boards, must
be marked with China pencil. Experiments with lead pencil
marking on ground glass surfaces show that a higher percentage
of intercepts may be completed with this method than with the
smooth surface of the plexiglass board.

d. It is believed that breakage of ground glass covers
in the field would be excessive since the cover of 30″ x 30″
is only 1/8″ thick. With this in mind, it appears that the
solution will be in a plastic material.


CESL                                                                                                      SECRET                                                                                                August 1943

410                                     RADAR FOR SEARCHLIGHT AND AA FIRE CONTROL.

1-410                                  IMPROVEMENTS TO EXISTING EQUIPMENT.

AUTHORIZATION: 1st Ind. from OCSigO to SCGSA dated 12 June 43, file SPSRD 400.12
R&D Prog.DESCRIPTION: This project covers the improvement and refinement of equipment
classified as “Radar for Searchlight and AA Fire Control.”

RADIO SET SCR-268, SCR-268-A, SCR-268-B and SCR-268-C.

DESCRIPTION: A mobile 206-mc aircraft detector and tracker. Determines azimuth,
elevation, slant range, and altitude. Contains provisions for data transmission
to a searchlight or gun director. Range 40,000 yards.

MILITARY CHARACTERISTICS: Recommended by SCTC Meeting No. 162, 9 Aug. 37.


                                        1. 205-Cycle Keying Adaptor.

a. Field tests are continuing on prototype models for
reduction of the keying repetition rate of Radio Set SCR-268
to 205 cycles. At the present time these tests are limited
to a single Radio Set SCR-268. As soon as manufactured models
are available, tests will be conducted on-several Radio Sets
SCR-268’s keyed from a central source.

                                        2. Skip-Keying.

a. The preparation of manufacturers’ drawings and field
instructions for the 1/3 skip keying unit is continuing.

                                        3. Data Corrector.

a. The Sperry Gyroscope data corrector for Radio Set
SCR-268 has been turned over to the Engineering Branch for
further testing.b. Sperry Data Error Corrector–Altitude Data Corrector
(SCR-268) has been received at this Laboratory and is undergoing

                                        4. Automatic Data Transmission (Datamat) – SCR-268.

a. Further investigations are under consideration to
determine whether slant range and altitude can also be transmitted
on the same telephone line simultaneously with azimuth

                                        5. Combined Remote Range Converter and Remote Data Plotter

a. Shop construction of the Combined Remote Range
Converter and Data Plotter is proceeding satisfactorily, and
operational tests are planned about the first of October 1943.


1-410                                               (Contd.)

                                                            G. Data Printer.

a. A representative of this Laboratory visited the RCA at
Camden, N. J., to observe and inspect a data printer for use
with Radio Set SCR-268. A satisfactory demonstration of the
performance of the unit was made. It is expected that the unit
will be shipped to this Laboratory for test in the near future.

                                          7. Mechanical Lobe Switcher.

a. Tests have been completed by Bell Telephone Laboratories
on the advisability of using a mechanical lobe switcher for
Radio Set SCR-268 metal antennas. These tests indicate that
it would not be advantageous at this time to modify the existing
antenna structure by the addition of a lobe switcher.

                                          8. Metal Antenna.

a. The new antenna presently supplied with Radio Set
SCR-268-( ), enables the set to provide accurate altitude data
at angles of elevation as low as 8°. The metal antenna is
used because of the extremely low angles of elevation normally
used in early warning work, and difficulties encountered in
effecting the extensive mechanical alterations necessary to
provide altitude and horizontal range data as a field modification.
At very low elevation angles, horizontal range is
almost equal o the slant range, and data on the latter is
available at the range converter. All range units furnished
with the Radio Sets SCR-516-C and SCR-516-E were converted to
and calibrated for 1367 cps operation and are designated
BC-436-C.b. A model adaptor plate and shelf has been constructed
and drawings are now in preparation for the procurement of
adjustable counterweight conversion kits for metal antennas.

c. A series of patterns has been obtained on the British
SLC Yagi Antenna with a view of adapting that type of antenna
for a lightweight antenna system for Radio Sets SCR-268-( ).
Theoretical calculations are in progress to determine what
resultant antenna pattern could be obtained from a combination
of such antennas.

                                            9. Lighter Wei ght Radio Set SCR-268-T8.

a. An illustrated booklet showing Radio Set SCR-268 as
modified by the proposed transmitter kit has been submitted for
approval. This modification will reduce the number of vehicles
from five to two.b. Work is continuing on the repackaging of the complete
Radio Set SCR-268-C to a Radio Set SCR-268-T8. A performance
test on the main power unit of Radio Set SCR-268-T8 is in


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