510 BELL SYSTEM TECHNICAL JOURNAL 



used in increasing the transmission band width to a value much 

 greater than that of the antenna is explained. The power require- 

 ments of a single sideband installation are outlined and a description 

 of the six-phase rectifier, used as a source of high potential direct 

 current is given, together with a brief theoretical treatment of its 

 operation. Circuit diagrams, photographs, and a number of char- 

 acteristic curves are discussed. 



Production of Single Sideband for Transatlantic Radio Telephony.^ 

 R. A. Heising. This paper describes in detail the equipment and 

 circuit used in the production of the single sideband for transatlantic 

 radio telephony in the experiments at Rocky Point. The set con- 

 sists of two oscillators, two sets of modulators, two filters, and a 

 three-stage amplifier. The oscillators and modulators operate at 

 power levels similar to those in high-frequency communication on 

 land wires. The three-stage amplifier amplifies the sideband pro- 

 duced by these mo<lulators to about a 500-watt level for delivery to 

 the water-cooled tube amplifiers. 



The first oscillator operates at about 33, TOO cycles. Tin- iiioclul.aor 

 is balanced to eliminate the carrier; and the first filter selects the 

 lower sideband. In these transatlantic experiments the second oscil- 

 lator operated at 89,200 c\-cles, but might operate an>'where between 

 74,000 and 102,000 c\cles. The second modulator, which is also 

 balanced, is supplied with a carrier by the second oscillator and with 

 modulating currents by the first modulator and first filter. Tlu' 

 second filter is built to transmit between 41,000 and 71,000 cycles, so 

 that by varying the second oscillator, the resulting sideband, which 

 is the lower sideband produced in the second modulating process, 

 may be placed anywhere between these two figures. Transmission 

 curves for the filters are given as well as some aniplitude-frcciuency 

 performance curves of the set. 



A Null-Reading Astatic Magnetometer of Novel Design.' Rich.\rd 

 M. BozoRTH. This instrument is designed for measuring the mag- 

 netic properties of very small amounts of material in the form of 

 fine wires, thin tapes, or as thin deposits (electrolytic, evaporateil, 

 sputtered) supported on non-magnetic forms. The specimen, 4 cm. 

 long, is mounted parallel to the line joining the two needles, so that 

 its poles produce the maximum torque on the suspended needle sys- 

 tem, the position of which is read by mirror and scale. The effect 

 of the magnetizing cf)il on the needles is annulled once for all b\' the 

 suitably placing of an ,iu\ili,ir\ coil, and the magnetic efTecl of the 



• Proc. of I. R. E.. Vol. 13. page 201, 1925. 

 ' J. O. S. .\. and R. S. 1. 10, 591-8 (May, 1925). 



