JRC JRL-2000F User manual

HF LINEAR AMPLIFIER
Manual

Preface
This manual providesinformationrequiredfor maintenanceand troubleshootingproce-
dures of the
JRL-2000F. Referto the instructions manualfor operation.

Contents

1 .Specifications
Operatingfrequency
bands
:I .8 MHz band 1.a00 to 2.000
3.5
MHz band 3.500 to 4.000
7 MHz band 7.000 to 7.300
10
MHz band 10.100 to 10.150
14
MHz band 14.000 to 14.350
18
MHz band 18.068 to 18.168
21
MHz band 21.000 to 21.450
24
MHz band 24.890 to 24.990
28
MHz band 28.000 to 29.700
MHz
MHz
MHz
MHz
MHz
MHz
MHz
MHz
MHz
Ratedoutput power
:SSB 1 kW PEP* 100°' duty cycle; 24 hour.
CW 1 kW* 100% duty cycle, 24 hour.
FSKISSTV 1 kW 100% duty cycle, 114 hour.
Output impedance
:50 R unbalanced, VSWR 3.0 (1 6.7 to 150 Q)
Harmonics :-60 dB or less
Intermodulation
distortion(IMD)
:-35 dB or less below PEP (at 1kW output)
Input impedance :50R unbalanced
Excitingpower
:100W max.
Frequencyswitching
time
: Lessthan 0.1 sec.
Powersupply voltage : 85 to 264 V AC, single-phase
Powerconsumption
:2.5 kVA or less (at 1 kW output)
lnput powerfactor
:95% or more (at 1 kW output)
Temperature range
:-10°C to 40°C
Protectioncircuits :PA excesscurrent; PA overheat; PA abnormal load;
AC power supply excess voltage; power supply overheat;
PA failure; excessive antenna
VSWR; excitingpower
excess; and antenna matchinganomaly.
Dimensions
:430(W) X 300(h) X 402(D) mm
Weght
: Approx. 28Kg
* Note :Rated output on 200 to 240V AC. The rated output power on 100 to 120V AC is 750W PEP.
3

2. Circuit Description
2.1 Configuration and Outline
The cabinet of the JRL-2000Fconsists of a front panel, a top cover, a bottomcover, a
rear panel and a mainchassis.
.
The equipment of the cabinetconsists of the followingfive units:
The operation of each unitwill be described below. Refer to the ExternalView (page
30) for the general configuration and Print Circuit Board Layout (page 55) for the parts
layout of the unit, respectively.
Unit Name
Power amplifier
Power supply unit
Matchingcircuit
Antenna switch
Control
Switch panel
Display
2.2 NAH-232 Power Amplifier Unit
Installation Position
At the bottom of the main chassis onthe righted side
At the bottom of the main chassisonthe left-handside
Upper part of the main chassis
Upperpart of the rear panel
Upper part
of the main chassis
Front panel
This unit is attachedto the lower part of the main chassis onthe righthandside. It
amplifiesthe drive inputpower sent from the exciter upto the rated output power by
the wide-bandlinear power amplifiers.
This unit consists of two CAH-377power amplifiers attachedto each heat sink respec-
tively, a CCB-367
PA control circuit attachedto the upper side of the heatsink, a CFF-
361 power combiner circuit attached to the bottom side of the heat sink, and a cooling
fan.
2.2.1 CAH-377 Power Amplifier
CAH-377power amplifier consists of two identicalwide-band linear ampliferswhich
operate independentlyof each other on the printed circuit board. Eachwide-band
amplifier has 12RFpower MOSFETsand amplifies a 20
W PEP input powerto 250W
PEP.
The RF power MOSFETis new generation's power device which has excellent resis-
tance to thermal stress and reflected power, a high linearity and a low high-order
intermodulationdistortion(lMD), as compared with the conventional bipolar transistor.
As the two wide-band linear amplifiers havethe same circuit, the circuit operationwill
be describedfor the left part of the connection diagram on page
39.
The input power signal from J1 is sent to the input transformer TI,and divided into
two signals with 180" phasedifference.
4

C1, C2, C5, R1 and R2compose of a circuit which matches an inputimpedance.
TI1andT21 are transformers which insulatethe excitation signal from ground level.
Thetwo excitationsignals are consumed by R17to R20and R27 to R30which are the
gateterminating resistors of the RFpower MOSFET.
As a
RF hasthe insulatedgate, itcan be assumedthat only the equivalent input
capacitanceexists between gate and source.
The gate terminating resistorshunts this inputcapacitance.
The RFpower MOSFETTRI1to TRI
6 are connectedparallel.They are excited by
the signalvoltage at bothends of the gate terminating resistor and they amplifythe
output current in a half cycle. On the other hand, TR21 to TR26 amplifythe output
current inanother half cycle. These output currents of half-cyclesare fed to the pri-
mary winding of the output transformer T5 andthe current waveform of full-cycle is
composed. These output currents flow to the loadcircuit via output terminal
J4.
As a result,the upper part of the output voltage waveform isamplifiedby TRI1to
TR16,and the lowerpart by TR21 toTR26.
The SEPP circuit, incontrast to the transformer-coupledpush-pullcircuit, seldom
generatesa phasedifference when composingoutput waveforms. Therefore, a wave-
form with less distortion can be obtained.
Thetransformer
T3 provides a gate-biasvoltage to the RFpower MOSFETfor the
operation inclass
AB.
A DC biasvoltage of approx. 2.5 V is providedthrough T3 to each RFpower MOSFET
from CCB-367 PA control circuit. The resistors
R61 and R62,connectedbetweenthe
4
thirdwinding of T3 and the second winding of the inputtransformer TI, work as a
negativefeedback.
(Note):The chips with same charasteristicsare packagedto the RFpower MOSFET
2SK408 and 2SK409. However, the lead layoutdiffers.

2.2.2 CCB-367 PA Control
CCB-367PA control isattachedto the upper side of the power amplifier unitand is
equippedwith a bias voltage control circuit for the two power amplifiers, a coolingfan
control circuit, protectioncircuits and an input power splitter.
1)PowerAmplifier Bias Voltage Control Circuit -
As the RFpower MOSFETof CAH-377 power amplifier operates in class AB, the DC
bias voltage which determines the operating point current (idling current) is essential.
The gain of the power amplifier can bechanged bychanging the DC bias voltage.
The normal bias voltage is about 2.5V DC
. However,the bias voltage varies accord-
ingto the
KEY signal state or the temperature change of the heat sink to get the
optimum gain of the power amplifier.
IC4(1/4to 414) and IC5(1/4to 414) are DC amplifierswhich send out a bias voltage to
the RFpower MOSFETblock of each SEPP circuit. This bias voltage can be adjusted
with variable resistors RV11 to RV14and RV21 to RV24. The reference voltage for
this bias voltage is obtained from the developed voltage between the base and the
emitter of TRI and TR2. TRI and TR2 are attachedtothe side part of the heat sink of
CAH-377power amplifier. As the base-emitter is driven by a constant current,the
base-emittervoltage depends onthe temperature of the heat sink.
The base-emittervoltage is amplified by the DC amplifier IC3 (414) and sentto each
power amplifier block as a biasvoltage
.
As the RFpower MOSFET, employed inthe JRL-2000F, has a negativethermal
coefficient,the gain decreases when the temperature of the heat sink rises. To com-
pensatethis, TRI and TR2 check the temperature of the heat sink and operateto
keepthe gain constant, regardlessof the temperature change, by controllingthe bias
voltage.
The comparator IC3 (314) controls the bias voltage by referencingthe
KEY signal.
Fig.2 shows each waveform of the signal voltage.
KEY
& PTT signal @ from outside, passes the time-constant circuit composedof C1
and R2, and is switchedby the comparator. The comparator output @, sent out from
No.14 pinof lCl , passesthe time-constant circuit composedof R5, CD14 and C2, and
the
DC amplifier IC3 (414) and then isformed to a signal voltage waveform G.
The signal voltage waveform @ isapplied to the DC amplifiers IC3 (314) and IC (4/4),
and controls the bias voltage of each power amplifier block.The bias voltage @varies
accordingto the KEY & PTT signal.

OFF
H
OFF
@ KEY & PTT signal
L ON ON
@ No.14 pin of ICI (314)
5v
ov
2.5V
@ Biasvoltage of
each PA OV
Fig .2
2)APC (AutomaticPower Control) Circuit
The APC circuit prevents excessive output by controllingthe bias voltage of the power
amplifierwhen the outputof the linear amplifier exceedsthe ratedvalue.
The output power signal
Vf, detected bythe CFG-111 matchingcircuit, isfed to the
comparator IC1 (414) and comparedwith the referencevoltage adjusted by the vari-
able resistor RV3.
When the Vf signal exceedsthe ratedvalue, the comparator
is turnedon andthe
comparator output voltage controls IC3(314) and IC3 (414) (DCamplifier to control the
biasvoltage). As a result, the bias voltage drops andthe output power is controlledto
beconstant incase of excessive output.
When the comparator is on, the OVER DRIVEsignal is sent to the switchpanelvia
diode CDI, and lights upthe DRIVE LED
in red.
3)TemperatureDetector Circuit.
The base-emittervoltage of the temperature detector transistor TRI and TR2 attached
to eachof the two heatsinks is comparedby the comparator IC6 (114) and IC6(214),
and IC6 (314) and IC6 (4/4),respectively.
As TR1 and TR2 have a negative temperature coefficknt of about
-4.5 mV1"C (de-
gree centigrade)the base-emittervoltage drops when the temperature of the heat
sink rises.
Variable resistors RV1 and RV2set the referencevoltage of the comparators IC6 (214)
and IC6 (414) to the base-emitter voltage which corresponds to the temperature of 80
"C of the heat sink.
At this time, the referencevoltage of the comparators IC6 (114) and IC6 (314) is the
same as that which correspondsto the voltage when the temperatureof the heatsink
is
50 "C. Therefore, whenthe temperature of the heat sink exceeds 50 "C, the com-
parator IC6 (114) or IC6 (314) is turned on, and "High" levelvoltage is applied.

to turn on the transistor TR3 andthe cooling fan starts to rotate.
Whenthe temperature of the heat sink exceeds
80 "C, the comparator IC6 (214) or
IC6(4/4)turns on.
At this time a Low level PA HEAT alarm signalis sent to the CDJ-1143 control circuit
via diode CD7.
When the PA HEATalarm is issued,the JRL-2000F displays "A3".
4)PA UNBLAlarm Detector Circuit
The CFF-361 power combiner is equipped with a sensor R7which detects unbalanced
power when the power is combined.
This sensor detects the unbalancedpower and when the terminal voltage
of the sen-
sor increases,the comparator IC1 (214) turns on, and the PA BL alarm signal is gener-
ated.
When the
PAL alarm is issued, the JRL-2000F displays "A4".
5)PA LOADAlarm Detector Circuit.
The CFF-361power combiner is equipped with a circuit which detects Vf and Vr of
the PA outputterminal.
Vf and Vr are comparedby the comparator IC2(214).
When the VSWR value exceeds 3.0 at the PA output terminal because of a poor
matching situationwith the matchingcircuit, the ratio VrIVf exceeds 0.5 andthe com-
parator IC2 (214) changes from Low level to Highlevel.
This comparator output signaltriggers the flip-flop circuit composed of IC2(314) and
IC2(414),and turns over the output voltage to issuethe PA LOAD alarm signal.
When the PA LOADalarm is issued,the JRL-2000F displays "A9".
IC2(114) and the peripheraldevices compose of a circuit which resets the flip-flop.
6)PA OFF Circuit
When one of the three alarm signals of the PA control becomes Low level, or when
PA OFFsignal which forcedly turns off the power amplifier becomes Low level be-
cause of the operationof the other protection circuit, a Low level signal is sent tothe
inputterminal of the comparator IC1 (414) via CD4 or CD6 diode OR circuit andthe
output of lCl (1/4) turns from Low levelto High level.
;
This signal is appliedto the DC amplifier which controls the bias voltage of the power
amplifiers IC3 (314) and IC3 (4/4), and the bias voltage of the power amplifiers is set to
-9v.
If the bias voltage becomes -9V, the RFpower MOSFET of the power amplifier is cut
off andthe output power becomes 0
W, regardlessof the existence of the excitation
power.

7)Power Splitter Circuit
The excitationpower suppliedto J201 terminalfrom the exciter is appliedto the RF
transformer TI via-2dB attenuator circuit.
.
TIis an impedance convert transformer (50ohms : 12.5 ohms).
The excitationpower is distributedto each terminal P21 to P24.
2.2.3 CFF-361 Power Combiner
The CFF-361power combiner is attachedto the bottom of the power amplifier unit.
This circuit generates a 1
kW PEP bycombining the output power from the power
amplifier of the four SEPP circuits.
These power amplifier output currents are combined bythe
RF transformers TI and
T2, andfinally combinedbyT3.
As the output impedanceof
T3 is 12.5 ohms, the step-up transformer T4 is converted
to 50 ohms.
Resistors R1, R2 and R3 absorbthe unbalancedpower generated at both ends of
each combiningtransformer.
R3 is equipped with a sensor R7which detectstemperature.
When a large unbalancingpower is generatedamongthesefour power amplifier, R3
produces heatto increasethe resistanceof R7 and the
PA BL alarm circuit is acti-
vated.
The circuit, consistingof a current transformer T5, diodes CD1 and CDI, capacitors
C1 to C4 and resistors R51 to R54, detects Vf and Vr of the power combiner output
terminal.
Vf and Vr issuethe PA LOAD alarm when the VSWR of the power combiner output
terminal is 3.0 or more.RelayK4 isturned on when the
PA switch is on, andthe corn-
binedpower is sent to the matchingcircuit throughthis relay
.
2.3 NBL-169 Power Supply Unit
The NBL-169power supply unit is a regulatedswitching power supply whose power
output of
DC 80 V is generated using AC 100V to 240 V. Becausethe pulse-shaped
currentflows to capacitors ina smothing circuit ina power supply unit with a capaci-
tor-input type smothing circuit,the power factor of
AC input is, in general, about 0.5 to
0.6.
The JRL-2000Fhas employeda powerfactor corrector circuit inthe former stage of
the switching regulatorcircuit to obtain a powerfactor of approx.1.
The CBB-13powerfactor corrector is attachedto one side of the heatsink which is in
the center of the unit, and the CBG-68main PS unit is attachedto the other side. The
unit also incorporatesa switchingpower supply unit which generates a DC
+I2 V (4A)
power supply for the control circuit.