CCA Commercial Communications Associates, Inc

CCA's Medium Wave & Short Wave AM Broadcast Transmitters

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 worldwide 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 sever worldwide 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 AM1,000D, AM5,000F, AM10,000F and AM15,000F are 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 minuet 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.

SPECIFICATIONS
Nominal Power Output: AM10,000F 10 KW
AM15,000F 15 KW
Frequency Range: 500 Khz-2 Mhz (2-22 Mhz)
Frequency Stability: +/-5 Hz
Carrier Shift (@ 100% Modulation): 2% Max. (<1% typical)
RF Output Impedance (specify): 50 ohms standard
Modulation Capability: 125%
AF Input Impedance: 600 ohms
AF Input Level (@ 100% Modulation): + 10 dB 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): -55dB
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.
PA Tube: (1) 4CX15,000A
Modulators: (2) 4CX5,000A
IPA (15 KW & HF Versions): (1) 4-400
Harmonic Attenuation (2nd): -90 dB
(3rd) -80 dB
Others -80 dB