Palstar Commander VHF-1200 User manual

VHF-1200 / VHF-2000
6 M LINEAR AMPLIFIER
Owner’s Manual
PALSTAR, INC.
Command Technologies Division
9676 N. Looney Road
Piqua, Ohio 45356
U.S.A.
Customer Service and Sales Telephone: [phone]
International: 937-773-6255
Fax: [phone]
E-mail: [email protected]

2
Table of Contents
Introduction 3
S ecifications 4
Un acking Instructions 6
Installation Pre aration 6
HV Transformer Installation 7
Safety Warnings and Precautions 8
Connections 9
O erating Procedure 9
Ty ical O erating Conditions 11
Circuit Descri tion and Adjustments 12
Tuned In ut & T/R Relay Schematic 14
Control and Bias Board Schematic 15
Meter Board Schematic 16
High Voltage Power Su ly Schematic 17
VHF-1200 RF Deck Schematic 18
VHF-2000 RF Deck Schematic 19
Warranty, Service, and Returns 20

3
INTRODUCTION
The Commander VHF-1200 and VHF-2000 are Grounded Grid class AB2 linear ower
am lifiers that o erate on the Amateur 6 Meter band.
Over-drive and over-grid current rotection is rovided by an auto-reset circuit that laces
the am lifier in standby if a reset grid current limit is exceeded.
Genuine CPI/Eimac 3CPX800A7 external anode triodes, with forced air cooling and
modern circuitry, insure efficient and conservative o eration. The VHF-1200 uses one
tube, the VHF-2000 uses two.
6:1 Vernier reduction drives on all tuning controls allow smooth and easy tune-u .
A rear anel in ut tuning control allows a higher in ut circuit Q for excellent linearity
and a low in ut VSWR across the 6 Meter band.
An automatic delay circuit, for ro er cathode conditioning before RF drive can be a -
lied, extends tube life. A 50 ohm resistor in the late su ly ositive lead and a 200 ohm
resistor in the negative lead rotect the tube in the event of an arc.
The Commander VHF-1200 and VHF-2000 feature a full com liment of control and me-
tering functions for easy on-the-air o eration.
A dual rimary ower transformer allows 200/234 VAC o eration.

4
Specifications
Commander VHF-1200
6 M Linear Power Amplifier
• Modes: USB, LSB, RTTY, FM, & CW
• Power Requirements: 200/234VAC 50/60 Hz.
• RF Drive Power: 15-25 W Nominal; 35-40 Watts Max. For Full Out ut (1.2 kW PEP on
SSB)
• RF Output: 750 W maximum, FM or RTTY
• Input Impedance: 50 Ohm unbalanced; rear anel adjustable
• Output Impedance: 50 Ohm nominal
• Antenna Load: 2:1 VSWR maximum
• Harmonic Suppression: Better than -60 db down @ rated out ut
• Intermodulation Distortion: Better than -35 db down @ rated out ut
• Weight: 75 lbs (34 kg)
• Cabinet Size: 18” x 16” x 7.75” (45.7 cm x 40.6 cm x 19.7 cm)
• Tube Compliment: One 3CPX800A7 Ceramic Metal Triode
• Cooling: Forced air, ressurized chassis

5
Specifications
Commander VHF-2000
6 M Linear Power Amplifier
• Frequency Range: 50 to 54 MHz
• Modes: USB, LSB, RTTY, FM, & CW
• Power Requirements: 200/234VAC 50/60 Hz.
• RF Drive Power: 15-25 W nominal - 35-50 W Max. for full out ut (1.5 kW PEP on SSB )
• RF Output: 1500 W maximum, FM or RTTY
• Input Impedance: 50 Ohm unbalanced; rear anel adjustable
• Output Impedance: 50 Ohm nominal
• Antenna Load: 2:1 VSWR maximum
• Harmonic Suppression: Better than -60 db down @ rated out ut
• Intermodulation Distortion: Better than -35 db down @ rated out ut
• Weight: 75 lbs (34 kg)
• Cabinet Size: 18” x 16” x 7.75” (45.7 cm x 40.6 cm x 19.7 cm)
• Tube Compliment: Two 3CPX800A7 Ceramic Metal Triodes
• Cooling: Forced air, ressurized chassis

6
UNPACKING
Carefully remove your VHF-1200/VHF-2000 Am lifier from its shi ing carton making
sure there is no damage evident from shi ing. If there is any damage, notify the delivering
shi er immediately, fully describing the damage.
The HV ower transformer was shi ed se arately, as its weight would damage the cabinet
in transit.
The 3CPX800A7 tube(s) are acked inside the cabinet in the area where the transformer
will be installed.
Do not destroy the acking material since it may be reusable later, should you require fac-
tory service or need to trans ort the Am lifier for any other reason.
TRANSFORMER INSTALLATION
See the illustrated rocedure on age 7 to com lete installation.
TUBE INSTALLATION
Carefully remove the 3CPX800A7 tube(s) from the shi ing carton. This carton was located
in the area where the transformer was installed. Place the tubes in the tube socket with the
ro er in alignment. If you have maintained the ro er in alignment, the tubes should go into
their sockets easily. If you have to use undue force to insert the tubes, you may have the wrong
in alignment or one or more of the ins may be bent. If necessary, carefully straighten ins
with needle nose liers and reinstall. Install the anode stra s on the tube ca s as shown and re-
lace the to and bottom covers. The unit is now ready for o eration.
200/234 VAC Operation
The Commander VHF-1200 and VHF 2000 come factory wired for 234 VAC o eration. For
best o eration, you should use a dedicated 234 VAC main ca able of su lying 20 Am s of
eak AC current.
Commander Am lifiers manufactured for ex ort are wired for 234 VAC or 200 VAC de-
ending on the final destination.

7
Gri the transformer by the windings, as shown.
There is not enough room for your hands inside the
cabinet if you hold it by the base.
Carefully lower the transformer into the am lifier. Be
careful not to bum the backs of the meters and be
sure the connector lug is out of the way and will not
be tra ed under the transformer.
Position the transformer over the mounting holes in
the cabinet and insert the rovided carriage bolts in
from the to , through the transformer mounting tabs
and chassis slots. Next, slightly lift the chassis and
lace a flat washer and KEPS nut on the bottom side
of each bolt and tighten.
Plug the connector on the transformer into the one on
the wiring harness. It is keyed so that it cannot be
lugged in backwards. Make sure that the connector
halves are ressed together until the lock tabs sna in
lace.
This is the final osition of the transformer and the
connector lug.

CAUTION:
• DO NOT attem t any ty e of service or re air on this am lifier without first removing the
AC ower and allowing AT LEAST 60 MINUTES FOR THE HIGH VOLTAGE CAPACI-
TORS TO BLEED OFF !
• DO NOT o erate this am lifier with the to or bottom covers removed. DO NOT o erate
this am lifier with the internal RF tube com artment covers removed. Never lace any ob-
jects into the to ventilation holes. CONTACT WITH VOLTAGES IN THE CABINET
CAN BE FATAL ! EXPOSURE TO UNSHIELDED RF AT THESE POWER LEVELS
IS HAZARDOUS TO YOUR HEALTH !
• Never attem t o eration without first connecting an a ro riate antenna (2:1 VSWR Max)
or a 50 ohm dummy load with sufficient rating or SERIOUS DAMAGE TO THE AMPLI-
FIER MAY RESULT.
• Never o erate the am lifier with more drive than required to roduce the rated out ut for
the o erating mode used.
• Do not lace the VHF-1200 OR VHF-2000 in re eater o eration. These am lifiers are not
designed for unattended service.Never o erate any am lifier using an extension cord.
• Never cover the to of the am lifier cabinet with books, a ers or other equi ment as
OVERHEATING MAY RESULT.
FOR ASSISTANCE CONTACT THE MANUFACURER:
Tele hone: 800-773-7931
International: 937-773-6255
E-mail: info@ alstar.com
!! WARNING !!
CONTACT WITH VOLTAGES IN THIS AMPLIFIER CAN BE
!!! FATAL!!!

9
CONNECTING YOUR AMPLIFIER
Locate your Commander VHF-1200/2000 so that no equi ment is directly above it, as air
ex elled from the tube exhaust on to can become quite hot. Allow at least 3 inches clearance
on either side between the unit and other objects or equi ment.
Connect the RF OUTPUT of your transceiver to the RF IN connector on the rear of the
VHF-1200/2000 with 50 ohm coax.
Using RG8 or better coax, connect the RF OUT connector on the VHF-1200/2000 to a good
quality thruline Wattmeter, and connect the Wattmeter Out ut to the antenna, antenna tuner or
dummy load.
Connect the RELAY hono jack on the rear of the VHF-1200/2000 to the Normally O en
(NO) terminal of the RELAY jack on your transceiver. Read the manual that came with your
transceiver to find the ro er external connections. On some transceivers, this is not rovided,
and an alternate circuit will be required. Always use shielded cable for these connections. The
RELAY jack on the VHF-1200/2000 has ositive 12 VDC o en circuit on the center in and
requires the sinking of 55 mA of current when ulled to ground.
Connect the ALC hono jack to the ALC connection on your transceiver using a shielded
cable. Consult your transceiver manual for ro er ALC connection details.
Connect a ground lead (as short as ossible) from a good earth ground to the GROUND
ost on the rear anel.
The 12 VDC jack on the rear anel is an accessory for owering low current 12 VDC de-
vices (less than 100 mA.). Do not connect an external voltage source to the jack.
OPERATING PROCEDURE
After reading this manual and com leting the Installation / Pre aration Instructions, osition
the Commander VHF-1200/2000 front controls as follows:
ON / OFF OFF
OPERATE / STANDBY STANDBY
METER SWITCH V (PLATE VOLTAGE)
LOAD 50 - MIDDLE OF RANGE
TUNE MINIMUM CAPACITANCE (POINTER TO LEFT)
After resetting these controls, switch the ON/OFF switch to the ON osition. At this time
you will hear the blower running and see an indication of Plate Voltage on the meter, (a rox-
imately 2650 VDC)
The 3CPX800A7 used in this am lifier require a warm-u eriod before RF drive may be
a lied, to revent damage to the tube. A 2 minute warm-u is rovided by a solid state timer
circuit. At the end of the warm-u eriod, the green POWER LED on the front anel illumi-
nates and the unit is ready for o eration. Switch the meter switch to the I ( late current) osi-
tion.

10
Switch the OPERATE / STANDBY switch to OPERATE and key the exciter with ZERO
RF drive a lied. The red transmit light should come on, along with an indication of late
idling current on the meter (a rox. 100-160 mA VHF-2000; 80-100 mA VHF-1200). A ly a
low level of RF drive (5 W or less) and adjust the LOAD and then the TUNE control for maxi-
mum out ut as indicated on an external Wattmeter. COMPLETE THESE ADJUSTMENTS AS
QUICKLY AS POSSIBLE TO AVOID STRESSING THE TUBE(S).
Again key the exciter and while increasing the RF drive, adjust the LOAD control counter-
clockwise to obtain a eak in out ut ower while kee ing the grid current below 60mA. Read-
just the TUNE control clockwise for maximum out ut. Re eat this rocedure until the desired
out ut is obtained. When increasing ower out ut, the TUNE ca acitance will increase (clock-
wise on the dial) and the LOAD ca acitance will decrease (counterclockwise on the dial) When
ro erly tuned, the grid current will be eaked at the TUNE setting and turning the LOAD
counter-clockwise will decrease grid current and ower out ut. If the grid current rises, kee
turning LOAD counter-clockwise until it decreases. Do not exceed 600 mA (VHF-1200) or
1000 mA (VHF-2000) of late current on key down (see ty ical o erating conditions chart on
next age). If you exceed 70 mA (VHF-1200) or 100 mA (VHF-2000) of grid current the am-
lifier will dro out to Standby. To reset it, you will have to un-key the transmitter and reduce
RF drive.
With the meter switch in the I osition and while monitoring grid current, the Commander
VHF-1200/2000 is ready for on the air o eration. Normal SSB o eration is indicated by late
and grid current meter readings on voice eaks of a roximately 1/3 to 1/2 of the CW key down
value. For FM or other high duty cycle modes, limit out ut to 600 watts (VHF-1200) or 1000
watts (VHF-2000) maximum.
If your lanned o eration is on SSB, you should adjust the load control slightly counter-
clockwise, reducing the out ut slightly by about 30 to 50 watts. This adjustment is necessary to
insure that the am lifier has sufficient headroom to handle the late current eaks caused by the
com lex voice atterns during SSB o eration. Nominal and grid current readings during SSB
o eration will be about 30 to 40% of the key down CW readings.
CAUTION: THE TUNE AND LOAD AIR VARIABLE CAPACITORS
MAY ARC IF MAXIMUM DRIVE IS APPLIED BEFORE THE AMPLIFIER
IS PROPERLY TUNED. ALWAYS FOLLOW THE DESCRIBED TUNE UP
PROCEDURE TO AVOID CAPACITOR ARCING. ARCING MAY ALSO
OCCUR IF YOU ATTEMPT TO TUNE INTO AN ANTENNA WITH A
VSWR GREATER THAN 2:1.
If you should need any further assistance tuning this am lifier, feel free to call us at 1-800-
773-7931 and our staff will be ha y to hel you. If you are outside the United States we are
available at 937-773-6255