BAUER 701B

GENERAL DESCRIPTION

MODEL 701B 1000/500/250 Watt AM Transmitter

The Bauer 701B is a self-contained plate modulated AM transmitter capable of up to 1,100 Watts output in the 535 to 1620 KHz band.

Solid state devices are combined with only one tube type to provide a simple, highly dependable design. A high quality oil filled modulation transformer eliminates moisture deterioration and assures long lasting reliability. Another quality feature is the vacuum capacitor used for plate tuning which eliminates arcing and roller coil freezing, associated with conventional tuning methods. The 'Tally Light' system will reduce downtime and help preventive maintenance by identifying the point of overload. The 701B has a dummy load as standard equipment.

Frequency response of the 701B is excellent, distortion is low, and 125% positive peak modulation capability is there for those who wish to use it.

Simultaneous full meter display of all important functions can be monitored with doors of the 701B closed. Access to the front panel switches and subdidiary metering is through a non-interlocked hinged front door, which can be changed to open from either side. Rear access is provided through a full-size, hinged and interlocked door. All control circuitry is mounted on a swing-down front panel for easy accessibility. There is only one front panel tuning control. Remote control interface kits are optional for the user's choice of systems.

The entire transmitter is housed in a single steel cabinet which is mounted on a sturdy 12-gauge steel base.

Bauer 701B

SIMPLIFIED POWER CUTBACK
The 701B is supplied in the user's choice of two powers. A single switch controls final plate voltage, audio, and RF drive simultaneously. (See 'Ordering Information')

SOLID STATE POWER SUPPLIES
All power supplies use encapsulated silicon bridge rectifiers which provide low power drain, cooler operation, and reliable performance. A single low voltage transformer provides bias voltage for the modulator tubes, 25 volts for the RF drive section, 800 volts for the modulator screens, and 400 volts for the solid state audio driver.

An epoxy-sealed plate transformer provides high voltage for the modulator and final amplifier tubes.

SOLID STATE OSCILLATOR AND RF DRIVER
Adding an extra measure of transmitter stability, the 701B utilizes a solid state oscillator and RF driver. An ovenless crystal operating in the highly stable area four times carrier frequency is used. Two binary divider IC's operating in tandem count down the oscillator to the desired carrier frequency. A buffer transistor follows the divider, then an output transistor that is matched to the final grids through an "L" network.

Type 4-500A tetrodes have been used in the RF section of the transmitter, reducing the required stages and the power consumption. Tetrodes also eliminate the need for neutralization.

The parallel operated final tubes operate in conventional Class C at an average efficiency of 75%. The built-in dummy load is capable of full power operation continuously.

HIGH QUALITY MODULATOR
A simple two stage transistor amplifier provides ample audio drive for two 4-500A tetrode modulator tubes operating Class AB-1. A high quality modulation transformer, sealed in oil, provides exceptional sound and modulation capability.

Bauer 701B

OPTIONAL EQUIPMENT
(factory installed) RMK-1 Remote Control Kit, including control relay interface assembly and motor rheostat. CVT - Constant Voltage Transformer to maintain filament and low voltage supplies within ±1%, 60 Hz only.

ORDERING INFORMATION
The 701B is supplied complete with tubes, transistors and crystal, tuned and tested on frequency. Specify one maximum and one switchable lesser power level between 250 and 1,000 Watts. If no specification is made the transmitter will be furnished in 1,000/250 Watt switchable configuration.

POWER REQUIREMENT
The 701B operates from 208-240 volt, 50/60 Hz, single phase power supply.

Bauer 701B diagram

TECHNICAL SPECIFICATIONS
AF Input Impedance	600 ohms
AF Input Level	+10 dBm ±2 dBm (100% Modulation)
AF Response	50-10,000 Hz (95% Modulation) ±1.5 db (typical - ±1 db)
AF Distortion	50-10,000 Hz (95% Modulation) less than 3% (typical - 1.5%)
Noise	(below 100% Modulation) 1000 Watts - 55 db; 250 Watts - 52 db
Frequency Range	540-1600 KHz
Frequency Stability	±10 Hz 0-50°C
Output Impedance	50 Ohms unbalanced - others available on special order
Carrier Shift	3% or less (0-100% Modulation)
Dummy Antenna	50 Ohms - Capable full time operation 100% Program Modulation
Power Output	1000/500/250 Watts - Any combination of two power levels (capable 1100 Watts)
Power Supply	208-240 volts ±5%, 50/60 Hz, Single Phase
Power Consumption	(1000 Watts output - 90% PF Approximate: 0% Modulation 2950 Watts; 30% Modulation 3400 Watts; 100% Modulation 4150 Watts
Ambient Operating Temperature	To 113°F
Altitude Range	To 7500 - Higher Altitudes on special order
Size	75" High, 34" Wide, 25½" Deep
Weight	1000 lbs. NET
Specifications may change without notice

TUBE COMPLEMENT
RF stages		AF stages and modulator
Number	Type	Number	Type
2	4-500A	2	4-500A

THIS TYPE OF TRANSMITTER IS INSTALLED IN THE FOLLOWING COUNTRIES
	ITU	Country	ITU	Country
	BOL	BOLIVIA	CAN	CANADA
	GTM	GUATEMALA	MEX	MEXICO
	NZL	NEW ZEALAND	PRU	PERU
	VEN	VENEZUELA