CCA AM 15,000 F

GENERAL DESCRIPTION


15 kW Medium Wave & Short Wave AM Broadcast Transmitter AM 15,000 F

photo CCA AM 15,000 F * High Efficiency Power Amplifier Circuitry

* Easy-to-Service and Understand Circuitry

* Rugged Construction with High Quality Components

* Conventional, Heavy-Duty Power Supplies

* Designed for FCC, DCC, and CCIR Requirements

* Conventional, Dependable, High Level Plate Modulation

* Power Line Phase Drop-out Protection

* Step-Start Operation

CCA AM TRANSMITTERS
For over twenty five years, CCA transmitters have had the best TIME-PROVEN record for reliability. "Battleship" type construction, using high quality, conservatively rated components, is one reason CCA transmitters perform better and longer than others. Design is simple and easy to understand. Plate modulation is known for its dependability and world-wide familiarity. It also has a very pleasing sound and does not have the problems associated with other newer and higher voltage techniques.

Conventional relays are still the most reliable way to control power equipment in the typical transmitter environment. Vacuum tubes (valves) are still more cost effective for operating in severe world-wide conditions. With a conventional, conservatively rated power supply, relay control and dependable plate modulation, CCA AM Transmitters are more immune to the hazards of the broadcast environment.

GENERAL DESCRIPTION
The CCA AM 15,000 F is part of a family of medium wave and HF transmitters designed for use in all regions of the world. These reliable transmitters use solid state devices up to the RF power and modulator stages. The entire transmitter is contained in two cabinets. Extra bypassing and special HF techniques are used in the HF version.

EXCITER
A standard, crystal oscillator is used at its fundamental frequency or digitally divided down to the required carrier frequency, which ever is more appropriate. A programmable, frequency synthesized oscillator is optional.

DRIVER
The driver is solid state, except in the 15 kW and HF version where the extra drive of a buffer stage is needed.

POWER AMPLIFIER
The power amplifier uses the 4CX15000A, operating as a plate modulated class C amplifier. The 4CX5000A is used in the 5 kW version. Rugged silver plated inductors and vacuum capacitors are used in a Pi-L output network.

AUDIO PREAMPLIFIER/DRIVER
A solid-state module contains the audio preamplifier-modulator section, which amplifies the nominal +10 dBm input signal to the level required by the AM differential amplifier.

This high fidelity, solid-state module uses transistors in complimentary-symmetry. By careful attention to the reduction of cross-over distortion, a high fidelity signal is available for the modulator tubes.

MODULATORS
The modulator power amplifier stage consists of two tetrode tubes (type 4CX5000A) connected in push-pull and operated in Class AB1 mode. A front panel control permits adjustment of filament voltage. Modulator cathode currents are metered. Individual grid bias adjustment controls are provided.

POWER SUPPLIES
The main power supply uses a three phase rectifier circuit. Rugged silicon rectifiers are used throughout.

CONTROL/OVERLOAD/RECYCLING SYSTEM
A relay control system incorporates full overload protection and automatic three overload recycling with visual indicators which display the status of all critical circuits. In the event of intermittent or short term overloads, the circuit in which the malfunction occurred is immediately identifiable. The recycling system will automatically return the transmitter to service in the event of a momentary interruption of primary power or an overload condition. For overloads occurring three times within a one minute time interval, the recycling system will turn the transmitter off, with a visual indication of the circuit in which the overload occurred. The circuit then must be reset manually. The control circuit provides an automatic "step start" sequence to turn the transmitter on. 'After-cooling' is included as a standard feature.

REMOTE CONTROL
Terminations allow interfacing with all standard wire or STL remote control systems. These include start/stop and power output control and telemetering of PA plate voltage and current and RF output. Terminals are provided for monitoring equipment.

TECHNICAL SPECIFICATIONS
Nominal Power Output 15 kW
Frequency Range 500 kHz - 2 MHz (2 - 22 MHz)
Frequency stability ±5 Hz
Carrier Shift (@ 100% Modulation) 2% Max. (less than 1% typical)
RF Output Impedance (specify) 50 ohms standard
Modulation Capability 125%
AF Input Impedance 600 ohms
AF Input Level (@ 100% Modulation) +10 dBm Max. (+2 dBm)
AF Response 50-7500 Hz +1 dB
50-10,000 Hz +1.5 dB
AF Distortion 50-10,000 Hz 3% Max.
Noise (below 100% Modulation) -55 dB
Line Voltage (specify) 208/240/380 V
Line Frequency (specify) 50/60 Hz
Phase 3 (closed Delta)
Net Dimensions 76" W x 71" H x 34" D
Gross Weight Approx. 3,000 lbs.
Harmonic Attenuation (2nd)
(3rd)
Others		 -90 dB
-80 dB
-80 dB
Specifications may change without notice

TUBE COMPLEMENT
RF stages AF stages and modulator
Number Type Number Type
1 4CX15,000A 2 4CX5000A
1 4-400A



THIS TYPE OF TRANSMITTER IS INSTALLED IN THE FOLLOWING COUNTRIES

ITU Country
ITU Country