RADIO ACOUSTIC RANGING—ADAMS 227 
leave their stations in bad weather or be exposed to damage by storm. 
Ship stations are no longer used by the Coast and Geodetic Survey. 
Sono-radio buoys.—Soon after ship stations had been used success- 
fully, the idea was conceived of using a buoy in which was housed a 
fully automatic unit for receiving the sound impulse and transmitting 
the radio signal—hence the name sono-radio buoy. 
Two types of structures have been used for sono-radio buoys: One 
type in which a steel drum is held in a wooden framework, and the 
other a specially designed all-metal type. The latter requires more 
special fittings and parts than the former, but both are about equally 
successful. These buoys are constructed on the ship by the ship’s 
personnel, using readily available materials. 
From its long experience with the use of buoys as water signals, the 
Coast and Geodetic Survey has evolved a more or less standard type 
of wooden structure which has been used in the construction of sono- 
radio buoys. Such a buoy consists of a 50-gallon steel drum with a 
counterweight to hold it upright and a superstructure extending about 
16 feet above the water, the batteries, the radio transmitter, and the 
necessary electric circuits being placed in the drum. A vertical an- 
tenna is supported on the superstructure and the hydrophone is sus- 
pended from the counterweight at a depth of about 7 fathoms. 
The electric apparatus in the sono-radio buoy was designed espe- 
cially for automatic use in R. A. R. The principal parts of the equip- 
ment are the audio amplifier, the keying circuit, the radio trans- 
mitter, and the hydrophone. All parts must be especially constructed 
and are generally made by the radio technicians on the survey ship. 
The apparatus used in all sono-radio buoys is very similar, although 
minor differences have been incorporated depending on the conditions 
encountered. Sono-radio buoys can be used from 1 to 3 months with- 
out attention. 
The frequency of the sound of a bomb explosion is below 800 cycles. 
The electric apparatus is designed to receive and amplify sounds in 
this frequency range. The amplifier must be stable and any time lag 
in it must be small and relatively constant. The purpose of the keying 
circuit is to cause the radio transmitter to operate automatically when 
the bomb signal actuates the hydrophone. It is designed so that un- 
wanted sounds of comparatively low intensity will not operate the 
radio transmitter, but that when the sound of a bomb is received the 
transmitter operates instantly at nearly full power. 
Extra circuits are sometimes incorporated in sono-radio buoys for 
the purpose of shortening the transmitted radio signal. When radio 
returns are being received from several sono-radio buoys, it is obvious 
that an early, return which is prolonged unduly may blanket subse- 
quent returns coming immediately afterward from other sono-radio 
