Page 601 radio acoustic ranging 6443 



6443. Radio Power 



The minimum radio power that can be expected to give satisfactory signals at all 

 R.A.R. distances is about 3 watts. This amount of power is adequate during daylight, 

 except during periods of excessive interference. It may be inadequate for satisfactory 

 R.A.R. operation at night, because, in some regions, atmospheric interference increases 

 and the sky-wave signals are weaker during part of the period between sunset and 

 sunrise. 



The radio-frequency power output of the sono-radio buoys used by the Coast and 

 Geodetic Survey is from 3 to 26 watts. Most of the shore-station installations have a 

 radio-frequency power of from 10 to 100 watts. 



65. SONO-RADIO BUOYS 



651. Vincent Sono-Radio Buoy 



The Vincent sono-radio buoy, used principally on the West Coast, utilizes electric 

 equipment originally designed for use at R.A.R. shore stations. This equipment was 

 adapted for use in sono-radio buoys by only mmor alterations to the circuits and by 

 substituting types of tubes requiring less filament power. 



This sono-radio buoy has performed reliably for periods of more than 3 months, 

 during which time neither servicing nor adjustments were necessary. Where the acoustic 

 conditions of the water, the configuration of the bottom, and radio propagation are 

 favorable, reliable operation can be expected from the sono-radio buoy at distances as 

 great as 100 nautical miles or more. 



The audio amplifier and radio-frequency equipment are all housed in a 12- by 7- by 

 7-inch metal box, which has a hinged top and a removable subchassis. This box and 

 the necessary batteries for operation of the electric equipment are all secured inside 

 the buoy drum — the batteries in the bottom — by means of a wood framework. Cables, 

 connecting the equipment in the drum to the antenna and the hydrophone circuits, 

 pass through stuffing boxes in the cover of the drum. The buoy structure is described 

 in 2842. 



The circuit diagram of this instrument is shown in figure 133. Either a Vincent 

 hydrophone (6563) or a Dorsey hydrophone (6561) is used with this sono-radio buoy. 

 The other electric equipment — the audio amplifier, the keying circuit, and the radio- 

 frequency equipment — is described in 6511, 6512, and 6513. 



6511. Audio Amplifier 



The audio amplifier is composed of two transformer-coupled tubes. A hydrophone unit with an 

 impedance of 900 ohms is usually used, requiring an impedance-matching transformer to match this 

 unit to the grid of the first amplifier tube. The two tubes of the amplifier are pentodes, type 1,45, 

 with a 1.4- volt filament. The first tube is coupled to the second by means of a transformer designed 

 to operate from a tube of high plate impedance. This is a 1:2 transformer with a primary inductance 

 of 600 henries. The second tube supplies the energy to operate the keying circuit, being coupled to it 

 by means of a transformer identical to that used with the first tube. This amplifier is broadly resonant 

 at low frequencies, the necessary tuning being obtained by paralleling condensers across the primaries 

 of the coupling transformers. The gain is about 90 decibels, which is sufficient to give a reasonable 

 margin of sensitivity. 



Decoupling circuits are used in the B and C battery supply leads to prevent regenerative effects. 

 The amplifier gain is controlled by a variable potentiometer across part of the C battery, varying the 

 amount of voltage to the grid of the first amplifier tube. A metering jack is provided by which the 

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