RCA ET-3619 AM / CW radio transmitter
Date: circa 1921
Inventory Number: RS0723
Classification: Radio Transmitter
Place of Origin:New York, New York
Dimensions:37 x 34 x 28 cm, 28 lb. (14 9/16 x 13 3/8 x 11 in., 12.7 kg)
Bibliography:Radio Enters the Home
Radio Enters the Home
DescriptionThis is an RCA / General Electric model ET-3619 AM / CW radio transmitter with four vacuum tubes (currently missing). The tubes would have been model UV-202, 5 watt Radioton tubes or similar. These served as oscillators. The AM [amplitude modulated wave] transmitted at 10 watts; the CW [continuous wave] at 20 watts.
The transmitter was built for operation on wireless telephone telegraphy (AM) or continuous wave telegraphy (CW). The method of signalling was controlled by the rotary switch on the left, which has two positions, marked "PHONE" and "CW."
The rotary switch on the right controls the wavelength by means of a variable condenser in series with the antenna circuit. It is labeled "ANTENNA CONDENSER."
Between the switches is the antenna ammeter made by the Radio Corporation. It is the hot-wire type, model UM-530, with a scale of 0-2.5 amps.
The rear of the instrument has a large oscillation transformer for use with the vacuum tubes, which generate the radio frequency oscillations. It consists of 25 turns of .060 inch x 3/8 inch copper strip that is nickel plated. It is mounted on a base, with 4 binding posts, to which are attached flexible conductors with clips. The clips are attached at selected tap points on the coil transformer. The clips have wing nuts. The metal parts are nickel plated.
Mounted under the coil are two motor generators needed for vacuum tube transmission. They are model UP-414 and UP-415 by RC / GE. Also under the coil is a large radio frequency choke, model UL-1655, wound with brown covered wire; two resistors with dark blue covering, and other circuitry items.
The instruments are mounted on a sturdy base (possibly of wood) and a panel made of "Bakelite-dilecto"--a standard insulating material for radio equipment.
It is self-contained, having everything needed for 20 watt transmission, except the power supply (a RCA Kenotron Rectifier Unit model ET-3620), and the following items which can be attached externally: a send-receive switch, a telegraph key, a microphone transmitter and its battery. For the Kenotron Rectifier Unit, see CHSI RS0722.
Signedplate on front panel: Radio Transmitter / MODEL ET-3619 / [RCA logo] / Radio Corporation / of America / LICENSED ONLY FOR / AMATEUR EXPERIMENTAL / AND ENTERTAINMENT USE / AND ONLY TO EXTENT INDICATED / IN ATTACHED NOTICE / N.P. 25080
on face of meter: AMPERES / [RC logo] [GE logo] / MODEL UM-530
on knobs: [GE logo]
Inscribedon affixed tag: Radio Transmitter / MODEL ET-3619 / GIVE MODEL WHEN ORDERING PARTS / TELEPHONE AND TELEGRAPH / OUTPUT 20 WATTS / PLATE INPUT 160 MILLIAMPERES 350 VOLTS / FILAMENT INPUT 9.4 AMPERES 7.5 VOLTS / PAT'D AUG. 28, '06 JAN. 15, 07 OCT. 6, '14 OCT. 17, '16 JULY 3, '17 / OCT. 23, '17 OCT. 22, '18 MAY 10, '21 JULY 12, '21 / LICENSED FOR AMATEUR EXPERIMENTAL / AND ENTERTAINMENT USE AND ONLY TO EXTENT / INDICATED IN ATTACHED NOTICE. / M'F'D' BY GENERAL ELECTRIC CO., U.S.A. / FOR Radio Corporation / of America
on affixed tag: Notice! / THIS DEVICE IS NOT LICENSED EXCEPT FOR / AMATEUR EXPERIMENTAL AND ENTERTAINMENT / RADIO USE, AS SET FORTH AND TO THE EXTENT / INDICATED IN THE CURRENT ISSUE OF THE CATA- / LOGUE OF RADIO CORPORATION OF AMERICA. NO / EXPRESS OR IMPLIED LICENSE IS GRANTED / /UNDER ANY PATENT OWNED BY THE RADIO / CORPORATION OF AMERICA, OR UNDER WHICH / IT IS LICENSED TO USE OR SELL THIS DEVICE AS / AN ELEMENT OF OR PART OF ANY COMBINATION OR / ORGANIZATION EXCEPT AS EXPRESSLY SET / FORTH IN SAID CATALOGUE./ NP-25086
Historical AttributesThis AM / CW radio transmitter was the type used by the first HAM radio operators and commercial broadcast radio stations. It was designed to work with the Kenotron rectifier power supply.
Primary SourcesRadio Corporation of America, Radio Enters the Home (New York: Radio Corporation of America, 1922), part 3, esp. pp. 86-98. The instrument is pictured on p. 98.
ProvenanceCruft Laboratory, Harvard University