COLLINS 207B-1

GENERAL DESCRIPTION

1. PURPOSE

The Collins 207B-1 transmitter, is a 35 kilowatt amplitude modulated or a 50 kilowatt CW transmitter designed for land-based operation in the frequency spectrum of 4 to 26 megacycles. Designed primarily for high speed telegraphic communication and broadcast, it is capable of high power AM transmission, telegraphic on-off or frequency-shift keying at speeds greater than 400 words per minute, and of amplifying the power output of a single side band transmitter to a peak envelope power of 30 kilowatts. The transmitter is designed for higher than average program modulation.

This equipment is the latest developmont in high-powered transmission. It incorporates many new and desirable features which improve the reliability of operation and simplify adjustment of the equipment. The most outstanding feature is the system of motor-driven, servo positioned, continuous frequency coverage resonant circuits with which the transmitter may be rapidly tuned to any frequency within its range by means of nine simple front panel tuning controls.

The 207B-1 is equipped with the Collins 40G RF crystal oscillator as the standard exciter. However, any one of several different standard rack and panel type exciters may be used. For instance, the Collins frequency-shift keyer may be used as an exciter in conjunction with a stabilized master oscillator and power supply.

There is no need for a transformer vault or other protective enclosure since all the components which mount external to the transmitter are enclosed in sheet metal housings, to which wiring is connected through grounded conduit or flexible metal tubing. The transmitter and all components are completely air-cooled.

2. BASIC PRINCIPLES OF OPERATION

Operation of the Collins 207B-1 is based upon the principle of generating a low energy radio frequency signal, multiplying the frequency of the signal and amplifying its power sufficiently to obtain the desired high-energy, radio frequency carrier. The carrier signal is then modulated, interrupted, or its frequency shifted in accordance with the intelligence to be transmitted. The resulting radio frequency energy is then radiated from a suitable antenna.

The low energy excitation signal may be derived from the ten channel crystal controlled oscillator which is included in the transmitter, or from any one of several different standard exciters. This low-energy signal is passed through a buffer amplifier stage and two frequency multiplier stages where the frequency or the signal is multiplied by 2, 4, 6, or 8. After frequency multiplication the signal power is amplified to 15 kilowatts in the intermediate power amplifier and further amplified to 50 kilowatts in the final power amplifier stage.

Intelligence is superimposed on the carrier wave by the modulator stage for amplitude modulated (AM) transmission. The modulation voltage is fed simultaneously to both the intermediate and the final power amplifier stages. For code (CW) transmission the intelligence may be superimposed on the carrier by on-off keying or frequency-shift keying. On-off keying is accomplished by interrupting the carrier in the low energy buffer and first multiplier stages. Frequency-shift keying is accomplished by passing the signal through a frequency-shift keyer prior to its entering the buffer amplifier. The keyer then shifts the frequency of the carrier a small amount in accordance with the keying signal.

The transmitter is equipped witn the best possible safety and overload devices which afford complete protection to operating personnel and protect the equipment from damage caused by overloads and other normal equipment faults.

3. GENERAL DESCRIPTION OF UNITS

a. INTRODUCTION. - The Collins 2O7B-1 transmitter is contained within five handsomely styled sheet metal cabinets which bolt together to form a single unit. In addition, there are six small sheet metal enclosures which house the two power transformers, the two control units, the modulation reactor, and the modulation transformer.

Several features, new and unique to equipment of this power class, have made this a compact yet easily serviced equipment. A single type medium power triode is used throughout the r-f power stages, a pair in the intermediate power amplifier and six in the final power amplifier. The anode voltage requirements of this tube are relatively low thereby allowing the use of intermediate voltage rectifier tubes and smaller than usual filter and power supply components. The tubes and tank circuit components are forced air-cooled, thereby eliminating the customary bulky water cooling systen.

The externally mounted transformers and reactors are dry type, air-cooled and fully enclosed in grounded sheet metal cases. Connecting leads are brought in through grounded conduit and connected internally thus eliminating the usual requirement for additional protective enclosures. The high current primary circuits are fed directly to the plate transformers through the external control units thereby eliminating the space and service problems presented by large high-current wiring and control components located within the main enclosure.

All resonant circuits are continuously variable, motor driven and servo positioned thus eliminating the usual comp1ication of switching or shorting and awkward mechanical drives. Servo positioning allows the controls to be grouped at a convenient and logical location while the resonant circuit is placed where it best suits the requirements of the circuit.

The upper front door of each of the five cabinets has a large glass window which affords a continuous view of all of the tubes contained within the bay. The upper front door, itself, provides access to all of the tubes within the bay as well as some of the adjustment controls not directly associated with tuning. These doors are hinged at the top and counterbalanced for ease of operation. They are further provided with dual interlocks, both positive electrical and automatic mechanical in nature, which remove all dangerous voltages and ground the circuits as soon as the door is opened. Status lights, illuminated meters and the main control switches are mounted in these upper doors. Identical interlocks are also provided on the large double rear doors. All interlocks for all the units are wired in series so that opening any door immediately removes the high voltage from the circuits in all of the bays. The cabinets each have a non-interlocked lower front door which provides access to the control relays and timers and several infrequently used controls. The lower door also contains a small drop door to provide a convenient means of access to the control panels of each of the bays, without having to open the lower doors.

b. LIST OF UNITS. - Collins 207B-1 transmitter may be broken down into the following major and minor units.

Intermediate Power Amplifier Unit (IPA Unit) which contains:
1. RF Oscillator 40G
2. Servo Amplifiers
3. Servo Power Supply
4. Patch Panel
5. Electronic Keyer
6. Control Panel
7. Buffer Amplifier, Frequency Multipliers and Driver Amplifier
8. Intermediate Power Amplifier
9. Coupling Network
10. Space and Switching for Additional Exciters
Power Amplifier Unit (PA Unit) which contains:
1. Servo Amplifiers
2. Servo Power Supply
3. Control Panel
4. Power Amplifier
5. Antenna Coupling Network
IPA Power Unit which contains:
1. Control Circuits
2. Low Voltage Supply
3. High Voltage Supply
4. Bias Voltage Supply
PA Power Unit which contains:
1. Control Circuits
2. High Voltage Supply
3. Bias Voltage Supply
Modulator Unit which contains:
1. Audio Amplifier and Driver
2. High Power Modulator
3. Modulator Bias and Audio Amplifier Power Supply
IPA Plate Power Control
PA Plate Power Control
IPA Plate Transformer
PA Plate Transformer
Modulation Transformer
Modulation Coupling Network

c. MAJOR AND MINOR UNITS DETAILS. - In more detail the major and minor units of the 207B-1 transmitter consist of the following:

IPA UNIT. - The IPA Unit is the second bay from the left. It contains on a special mounting space the unite described under paragraphs a, b, c, d and j below. This space is a pivoted, double width, 25" high standard equipment rack. Pivoting this rack provides easy access to the rear of all the units mounted thereon. The IPA Unit contains as permanent equipment the circuits and units described under paragraphs e, f, g, h, i and k.
1. RF OSCILLATOR 40G. - RF Oscillator 40G is a crystal controlled 10 channel oscillator. With proper crystals, the oscillator provides an output from 2-4.3 mc. Plate and filament voltages for this unit are derived from the main transmitter. It is mounted in the equipment rack of the IPA bay.
2. SERVO AMPLIFIERS. - There are six identical interchangeable, plug-in Servo Control Amplifiers mounted in a common enclosure on the equipment rack in the IPA bay. One of these units is associated with each of the six tuned servo-positioned circuits in the IPA Unit. Each contains a voltage amplifier, a relay control tube and a pair of motor control relays.
3. SERVO POWER SUPPLY. - The Servo Power Supply furnishes voltage to all of the Servo Ampifiers and drive motors located in the IPA Unit. It is mounted on the lower left side of the equipment rack immediately below the Servo Amplifier Unit.
4. PATCH PANEL. - The remaining unit in the equipment rack is the Patch Panel which contains eight jacks - one is the transmitter input jack and one is the crystal oscillator output jack. The other six are to be used as needed.
5. ELECTRONIC KEYER. - An Electronic Keyer is mounted on the right side of the Control Panel of the IPA Unit. It receives the keying impulses and accomplishes off-on keying of the transmitter proper. Provision has been made for keying of the transmitter by negative, positive, polar negative, or polar positive impulses for mark.
6. CONTROL PANEL. - The control panel carries the basic transmitter tuning and checking controls and is located behind the lower front door. Easy access to these controls is provided, however, by a small drop door located at the top center of the main lower door.
7. BUFFER AMPLIFIER, FREQUENCY MULTIPLIERS AND DRIVER AMPLIFIERS. - The buffer amplifier, frequency multipliers and driver unit are contained with a sub-assembly which is mounted to the left of the control panel. The unit is hinged so that it may be tilted forward for easy access to the interior. Inside are located a broadband buffer-amplifier, and two frequency multiplier stages. The driver tube is mounted on top of the assembly.
8. INTERMEDIATE POWER AMPLIFIER. - The Intermediate Power Amplifier is located on the top deck of the IPA Unit. It is a push-pull, cross neutralized, grounded cathode amplifier with both grid and plate circuits resonant and continuously variable from 4.0 to 26.0 mc. The resonant grid circuit, which also provides the plate tank for the driver stage, is contained within an air tight enclosure located behind the control panel. The power amplifier tube sockets are mounted on top of this enclosure. Cooling air for the IPA tubes is forced into this enclosure by the blower, located in the lower rear of the cabinet, and upward through the tube sockets to cool the tube radiators. The resonant plate tank circuit is located directly behind the Intermediate Power Amplifier tubes and is readily accessible through the large double rear doors.
  
  An alternate provision is made for operating the intermediate and final power amplifier as linear amplifiers driven by a single side band suppressed carrier exciter such as the Western Electric D-156000 twin channel unit. The grid circuit of the intermediate power amplifier is arranged to be modified so that it presents a 200 ohm balanced load to the exciting single side band transmitter. Approximately 500 watts of peak exciting power are required.
9. COUPLING NETWORK - The coupling network occupies the top or the IPA Unit. It is a resonant circuit continuously variable across the entire frequency range and is suspended, as a unit, on rails or tracks from the top of the cabinet. Magnetic coupling from the plate tank coils to the inducctors of this coupling network is therefore varied by the positioning of the coupler on its rails.
10. SPACE AND SWITCHING FOR ADDITIONAL EXCITERS. - Space for auxiliary exciters is provided in the lower front of the IPA bay. A space of 19-1/4" is available on the right half of the panel and 10-1/2" is available on the left panel. Extra switching jacks are provided on the patch panel.
11. GENERAL - The upper front door of the IPA Unit has a large glass window to provide continuous visibility of the Intermediate Power Amplifiers. All meters directly associated with tuning or adjusting the r-f stages in the bay are mounted above the window. The filament, DC controls, and colored status lights are located below the window on the upper front door. A ventilating blower cooling the Intermediate Power Amplifier tubes is located on the floor of the unit. Dual interlocks for personnel protection are incorporated on all but the lower front door.
PA UNIT. - The PA Unit consists of the entire center bay. It contains the following units and circuits.
1. POWER AMPLIFIER. - The Power Amplifier is located on the top deck of the PA Unit. It consists of six forced air-cooled triode tubes operating in a push-pull grounded grid circuit. Three independent tubes, identical to those used in the Intermediate Power Amplifier, are mounted in a special common socket, and operated in parallel for each side of the push-pull circuit. No neutralization is necessary because of the inhererit isolation between the input and output circuits of the grounded grid amplifier. The cathode or input circuit of the Power Amplifiers is an extension of the output coupling circuit of the Intermediate Power Amplifier, and is therefore located in the IPA Unit.
  
  Special r-f chokes are inserted in the filament leads to prevent them from short circuiting the input circuit. These chokes and a variable input capacitor are located in the enclosure directly above the power amplifier tubes. This enclosure will be referred to as the cathode box or enclosure throughout this book. A pair of special grid contact and by-passing assemblies are fastened to the bottom surface of this cathode box.
  
  Anode, grid, and filament connections are so arranged that the tubes can be inserted as plug-in units from the bottom of the anode or plate casting. Since this would be a rather awkward procedure by hand, a special platform arrangement which holds three tubes has been devised. This platform is raised or lowered by a hand-wheel operated elevator to plug-in or disconnect the tubes. Cooling air for the tubes is forcedd upward through these elevaators from the air chamber upon which they are mounted. A single large blower is located on the floor in the rear of the cabinet. The plate tank and output coupling circuits occupy the upper half of the rear portion of the cabinet. The plate tank circuit consists of two oppositely wound variable inductors and two variable vacuum capacitors all mounted with their axes vertical. These four variable elements are driven simultaneously with the proper speed ratio by a motor driven chain and sprocket arrangement located on the shelf below the tank circuit.
2. ANTENNA COUPLING NETWORK. - The output network consists of a similar pair of variable coils and a single variable vacuum capacitor arranged to be varied simultaneously by a tuning motor. The netwcrk is suspended, as a unit, on rails from the top of the cabinet and moved forward or backward to vary the coupling to the plate tank coils.
3. CONTROL PANEL. - The control panel carries the power amplifier, plate tuning, antenna tuning, loading and transmitter checking controls. It is located behind the lower front door of the bay. Easy access to the controls is provided, however, by a small drop door located at the top center of this main door.
4. SERVO AMPLIFIERS. - There are three identical interchangeable servo amplifiers mounted in an assembly rack in the center of the lower part of the PA Unit. The servo amplifiers, in conjunction with their tuning motors, serve to position the three tuned circuits in this bay, viz., PA PLATE TUNING, ANTENNA LOADING and ANTENNA TUNING.
5. SERVO POWERR SUPPLY. - The Servo Power Supply furnishes voltage to the three Servo Amplifiers located in the PA Unit. It is mounted at the bottom center of the assembly rack in the r-f bay.
6. GENERAL. - A large glass window in the upper front door of the PA Unit provides continuous visibility of the Power Amplifier tubes. Meters directly associated with tuning or adjusting the r-f stages in the bay are mounted above the window while the filament and DC voltage controls and the colored status lights are mounted below the window. On the floor of the bay, readily accessible through the rear doors, is the blower which provides the forced draft ventilation for the Power Amplifiers. All doors except the lower front have dual interlocks to afford adequate protection for the operating and maintenance personnel.
IPA POWER UNIT. - The IPA Power Unit consists of the left hand bay of the 207B-1 Transmitting Set. It contains the following units and circuits.
1. CONTROL CIRCUITS. - A vertical panel inside the lower front door of the IPA Power Unit mounts all of the control and overload relays and the timers which are associated with both the IPA Power Unit and the IPA Unit. The control circuits, of course, are also interlocked with those of the remaining two bays to afford complete and adequate operation and protection. The lower front door is not interlocked and may be opened at any time without exposing open or unprotected circuits. A small drop panel on this door provides convenient access to the controls most often used in connection with the IPA Power Unit and the IPA Unit.
2. LOW VOLTAGE SUPPLY. - 600 volts DC positive to ground for the operation of the frequency multiplier and buffer stages, the driver screen and RF oscillator 40G is provided by a common low voltage supply. Two xenon gas filled 3B28 rectifier tubes for this supply are grouped at the end of the rectifier shelf in the IPA Power Unit.
3. BIAS SUPPLY. - 400 volts DC negative to ground for biasing the frequency multipliers, driver, intermediate power amplifier, and off-on keyer is provided by a common supply located in the IPA Power Unit.
4. HIGH VOLTAGE SUPPLY. - The six 4B32 rectifier tubes mounted on the tube shelf are part of the plate voltage supply for the Intermediate Power Amplifiers. The high voltage transformer for this supply is mounted external to the unit. The filter components are located on the floor of the bay and are readily accessible through the large double rear doors.
5. GENERAL. - Access to and continuous visibility of the rectifier tubes is provided by the upper front door with its large window. Meters associated with the high voltage DC, the primary AC voltage and the Intermediate Power Amplifier filaments are located above the window. Status lights and controls are mounted below the window. A blower for circulating air in the power bay is mounted on the floor of the unit and is readily accessible througn the rear doors. No special cooling is required for the rectifiers since they contain the inert gas xenon and hence can operate efficiently and properly in spite of extremely wide temperature variations. All doors except the lower front are provided with dual interlocks for the protection of personnel.
PA POWER UNIT. - The right hand bay of the 207B-1 transmitter is designated as the PA Power Unit and contains the following units and circuits.
1. CONTROL. - A vertical panel behind the lower front door mounts the control and overload relays and the timers which are associated with both the PA Power Unit and the PA Unit. They are, as mentioned previously, interlocked with those of the other three bays. The lower front door is not interlocked and may be opened at any time without exposing open or unguarded circuits.
2. HIGH VOLTAGE SUPPLY. - Twelve xenon gas filled 4B32 rectifier tubes are associated with the high voltage supply which is used to furnish the plate voltage to the Power Amplifier stage. The tubes are mounted on the top deck of the PA Power Unit and are readily accessible through the upper front door. The high voltage filter components are mounted on the floor of the bay and are accessible through the rear doors. The high voltage supply transformer is mounted external to the PA Power Unit.
3. BIAS SUPPLY. - Four 3B28 rectifier tubes are used as the rectifier of a high current low voltage (1.5A at 400V) bias supply for the power amplifiers. All of the components for this supply are located within this cabinet.
4. GENERAL. - The rectifier tubes are in constant view through the large glass window in the upper front door of the bay. Meters and controls for the unit are mounted above and below the window respestively. A blower to provide proper circulation of the air is mounted on the floor of the PA Power Unit and is accessible through the rear doors. Again no special cooling is required for the xenon tubes. Dual interlocks, both automatic mechanical and positive electrical in nature, are incorporated on all but the lower front door to provide adequate protection for personnel.
MODULATOR UNIT. - The Modulator Unit consists of the entire bay second from the right in the 207B-1 transmitter. It contains the following units and circuits.
1. AUDIO AMPLIFIER AND DRIVER. - The audio amplifier and driver stages are located on the rear wall and floor of the top deck of the Modulator Unit, respectively. The audio stage uses a twin triode, type 12AX7, operated as a balanced push-pull voltage amplifier. The audio stage is followed by two type 4-250A tubes operated as a push-pull voltage amplifier to provide the rather high (800 - 1100V peak) audio swing for the modulator grids. The driver tubes are mounted on the floor of the top deck through which cooling air is forced from the blower compartment. All three tubes are readily accessible through the upper front door.
2. HIGH POWER MODULATOR. - The high power modulator stage utilizes six type 8C25 triodes in a push-pull parallel circuit adjusted for class B1 operation. Three of the tubes form the left modulator and are located on the left side of the top deck of the Modulator Unit. The other three tubes form the right modulator and are mounted on the right side of the top deck. Cooling air is forced upward through the tube sockets and cooling fins from the blower compartment below. All tubes are readily accessible through the upper front door.
3. MODULATOR BIAS AND AUDIO AMPLIFIER POWER SUPPLY. - The 3 kilovolt supply uses two xenon-filled type 4B32 rectifier tubes. This supply furnishes 270 volts of plate voltage for the audio stage, approximately 1700 volts for the driver plate and from 670 to 1100 volts for the modulator bias voltage. The rectifier tubes are mounted in the rectifier compartment of the Modulator Unit and are readily accessible through the rear doors.
IPA PLATE POWER CONTROL. - The IPA Plate Power Control includes the primary line input terminals for the 230 volt power to all parts of the transmitter except the final amplifier high voltage power supply plate transformer primary. The following components are included: a fused 3 phase circuit to the transmitter for filaments, blowers, etc.; a combination overload protecting breaker and start-stop contactor; a delta-wye switch for the intermediate power amplifier plate transformer primary; and a set of series line resistors for tune-up purposes with a shorting contactor for normal operation. These components are housed in a heavy guage sheet metal box with a large front access door. This box is stamped with a wide variety of knock-out discs for conduit connection of the wiring. It is provided with four large mounting holes in its rear corners so that it may be wall mounted and connected directly to the primary line bus by means of rigid conduit.
PA PLATE POWER CONTROL. - The PA Plate Power Control consists of the primary line combination overload protecting breaker and start-stop contactor mounted in a heavy guage sheet metal enclosure. This enclosure is identical to the one which houses the IPA plate power control except that it does not have the ventilated resistor cage mounted on top. It is designed to be mounted on the wall near the main plate transformer with rigid conduit type wiring.
IPA PLATE TRANSFORMER. - The IPA Plate Transformer is a separate unit to be mounted on the floor separate from the cabinets. It is a three phase, dry type, air-cooled unit enclosed in a ventilated sheet metal case. It supplies the high voltage for the Intermediate Power Amplifier plate voltage supply.
PA PLATE TRANSFORMER. - The PA Plate Transformer is a separate unit to be mounted on the floor isolated from the cabinets. It is the main plate transformer of the power amplifier high voltage supply. This transformer is a three phase dry type air-cooled unit enclosed in a ventilated grounded metal case. It contains a fixed transformer and a motor operated variable transformer which raises or lowers the output voltage at the will of the operator. The voltage may be varied under load, from 40% below to 10% above nominal.
REDUCED POWER OPERATION. - The two left hand units of this equipment may be operated as the equivalent of a 205D-1 15 kw CW transmitter completely independent of the 50 kw power amplifier and its supply. A control circuit isolation switch, mounted on the relay panel of the PA Power Unit isolates the 50 kw control circuits and allows the intermediate amplifier supply to be operated alone. The intermediate power amplifier output circuit must be disconnected from the power amplifier input and connected to the transmission line to the antenna to complete the power cut back. This power cut back may be used as an emergency CW measure or for interim CW operation on circuits which do not require the full transmitter power.
MODULATION TRANSFORMER. - The Modulation Transformer is a separate unit to be mounted away from the main cabinets. Electrically this unit is a conventional modulation transformer. It is the air-cooled dry type and has a grounded sheet metal case with no exposed terminals
MODULATION COUPLING NETWORK. - The Modulation Coupling Network is also to be mounted external to the main enclosures. It is housed in a grounded well ventilated sheet metal case and has no exposed terminals.

TECHNICAL SPECIFICATIONS
Total Cubical Contents	687 cubic feet (not crated)
Total Weight	16,800 pounds (not crated)
Frequency range	4000 to 26000 kilocycles
Frequency Multiplier Range	4 to 26 megacycles
First Frequency Multiplier	4 to 13 megacycles
Second Frequency Multiplier	4 to 26 megacycles
Type of Frequency Control	Crystal or Stabilized Oscillator
Type of Emission	a. A-3 (Amplitude modulated) b. A-1 (Carrier ON-OFF) c. Frequency Shift
Keying Speed	Up to 400 wpm both off-on and frequency shift emission.
Keying input Circuit Impedance	25,000 ohms - one line grounded
Nominal Carrier Output for Each Type of Emission	a. 35 kw for AM emission into a fixed 600 ohm load with a maximum SWR of 2 to 1 b. 50 kilowatts for A-1 emission, into a fixed 600 ohm load with a maximum SWR of 2 to 1 c. 50 kilowatts for frequency shift emission into a fixed 600 ohm load with maximum SWR of 2 to 1
Power Factor of Equipment	a. Starting: 82.5% (High Voltage Off) b. Standby: 80.5% (Key Open) c. Normal Operation: 96%
Power Source Requirements	a. Voltage: 207 to 253 volts; designed for a center voltage of 230 b. Frequency: 60 cps ±5% or 50 cps ± cps c. Number of Phases: 3 Phase d. Input Power: AM Unmodulated: 86 kw 100% modulated: 130 kw CW Key Down: 92 kw CW Key Up: 15.6 kw CW High Voltage Off: 11.2 kw e. Regulation Tolerance: 5% voltage variation from no load to 130 kw f. Protective Devices: Power Source fused or otherwise protected for 600 amp (max.) current to a 140 KVA load; must limit short-circuit current to 10,000 amps
Crystal	Type AN/CR-27/U with fundamental frequency between 2.0 and 4.2 mc required (Not Supplied by Contractor)
Modulation Method	High level Class B-1
Modulation Capability	100 percent
Audio Input Level for 100% Modulation	+10 ±2 dbm into 150/600 ohm input impedance
Audio Frequency Response	Equal to or better than ±2 db between 150 and 7500 cycles per second and ±4 db from 50 to 10,000 cycles
Audio Frequency Harmonic Distortion	Less than 5% RMS for fundamental frequencies 50 to 7500 cycles per second for values of modulation 0 to 90%
Carrier Frequency Stability	5 cycles per megacycle
Carrier Noise Level	AM - 50 db below 100% modulation over band of 70 to 7500 cycles CW - Less than 3% equivalent amplitude or phase modulation
Carrier Shift	5% maximum at 90% modulation
Ambient Temperature Range for Satifactory Operation	0 to 50°C (32°F to 122°F)
Elevation Above Sea Level for Satisfactory Operation	6000 feet maximum
Specifications may change without notice

TUBE COMPLEMENT
RF stages		AF stages and modulator		Rectifiers
Number	Type	Number	Type	Number	Type
8	3X2500A3	2	4-250A	8	3B28
1	4-400A	6	8C25	18	4B32
1	6AK5	1	12AX7
10	6X4	2	4B32
2	6AG7
2	807
10	12AU7
9	12AX7
2	VR90

THIS TYPE OF TRANSMITTER IS INSTALLED IN THE FOLLOWING COUNTRIES
	ITU	Country	ITU	Country
	D	GERMANY	GRC	GREECE
	J	JAPAN	MRC	MOROCCO
	PHL	PHILIPPINES	CLN	SRI LANKA