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Fig* 2 Schematic of the ALTEC 460A Transistor Compressor Amplifier, While designed for telephone repeater service, the circuit is ideally suited for amateur transmitter applications, Output level varies less than 20 db for an input range in excess of 50 db.

Output noise level is —TO dbm. As designed, the unit draws 25 ma from a 52 volt source. However, the majority of this power is dissipated in the R11 dropping resistor. The actual power requirement is approximately 25 ma at 10 volts. Heavy negative feedback is utilized to reduce distortion and stabilize the gain of the amplifier. Gain is constant within 0-3 (11) for a 25% variation of supply voltage and within 0.2 db for an ambient temperature increase from 75° F# to 110° F. While the circuit is usable, as is, for many amateur applications^ more gain may be required for others. For these applications, gain may be increased to more than 50 db by opening the C4-R9 feedback loop. While this will make the gain of the amplifier more susceptible to temperature and supply voltage variations, no great difficulty should be encountered in fixed installations.

Radio Amateur Audio Compressor Schematic

Fig. 3 Performance curve of the ALTEC 460A Compressor Amplifier. White designed for automatic equalization of telephone circuit levels, it is ideol for amateur speech applications.

Fig. 3 Performance curve of the ALTEC 460A Compressor Amplifier. White designed for automatic equalization of telephone circuit levels, it is ideol for amateur speech applications.

The ALTEC 460A Transistor Compressor Amplifier is designed for use in communications systems, where it is desirable to maintain a relatively constant output level for a wide range of input levels. Since the problem is similar to that encountered in amateur transmitter speech systems, the circuitry of this unit, shown in Fig, should be of amateur interest. As in the line amplifiers, input and output impedances are 600 ohms. Below compression, the gain of the amplifier is approximately 35 db. Compression characteristics of this amplifier are shown in Fig. 3.

The last of the ALTEC units to be described is the type 461A Transistor Power Amplifier, rhis compact little unit is housed in the same style package as the other units and will deliver 2 watts output into an 8 ohm speaker, Fhe amplifier is designed for use in a speaker type, telephone terminating set but the circuit should be valuable in amateur audio work. Fig. 4 gives the schematic diagram of this little amplifier, input impedance is the standard 600 ohms which makes it compatible with the other units described.

While the writer is certainly not recommend-

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