AMERITRON QSK-5PC Instruction
Manual
AMERITRON QSK-5PC
T/R SWITCH PC BOARD
INTRODUCTION
The Ameritron QSK-5PC is a PIN diode QSK circuit board designed
for use in Ameritron's AL-80A, AL-80B, AL-82, AL-1500 and AL1200 amplifiers. Ameritron can not assist customers with the
installation of the QSK-5PC in any amplifier other than these
five units. The QSK-5PC is rated to carry the full power of
these amplifiers except on SSTV, RTTY and PACKET. On these high
duty cycle modes the QSK-5PC will handle a maximum of 1000 watts
with a 5 minute on and two minute off duty cycle.
Ameritron also offers a "stand-alone" PIN diode QSK adapter
called the QSK-5. The QSK-5 is an entirely self-supporting unit
with an internal power supply. The QSK-5 is the best choice for
applications where maximum convenience and flexibility is desired. The QSK-5 connects to the station equipment with standard
connectors to facilitate installation and removal.
QSK BOARD OPERATION
Keying Circuit Timing:
The timing of the transceiver keying circuit is critical with
any QSK switch. The transceiver MUST
of RF and QSK output lines. The transceiver QSK line must pull
low BEFORE RF appears on the output connector and release AFTER
the RF envelope reaches zero to operate with any QSK switch. A
few transceivers do not meet this requirement even though they
are advertised as QSK transceivers. There is no way to
completely correct this problem without modifying the
transceiver.
One indication of improper timing is the flashing or failure of
fuse lamps LP1 and LP2. These lamps protect the transceiver
from failure of the receive diodes. Any component failure that
causes the receive diodes to conduct during the time interval
the transmit diodes are conducting will connect the amplifier's
output directly to the input. This may result in an oscillation
have the proper sequencing
AMERITRON QSK-5PC Instruction
Manual
that can cause damage to the transceiver. NEVER REMOVE OR
DEFEAT THESE LAMPS. They will only fail if there is a timing
or component problem. If you remove the fuse lamps, the
transceiver may be damaged. If the lamps flash or fail, a simple
test can be made by sending a string of very slow dashes with a
keyer. Slowly raise the power on the transceiver until the
lamps begin to flash. If the lamps flash at the beginning or end
of each dash, the timing of the QSK line from the radio is at
fault. If the lamps light throughout the entire length of the
dash the QSK line should be unplugged and the RLY jack of the
amplifier should be grounded. If the lamps still light, then
the QSK switch has a circuit problem. If the lamps do not
light, the problem is in the radio or the connection to the
radio. Another indication of improper timing is the generation
of clicks or leading or trailing edge "chopping" of the signal.
This indicates hot switching is occurring. This is strictly a
timing problem.
Timing can be measured with a dual trace scope. The triggered
trace should be connected to the QSK output line of the transceiver(open collector lines will need a pull-up resistor connected to 12 volts) and the RF output monitored with the other
trace. RF must not appear until one millisecond after the QSK
line is low. The QSK output line of the transceiver must not
go high before the RF envelope drops to zero.
RECEIVE:
In RECEIVE the QSK board functions as follows: When terminal
D is high, R10 and R16 bias Q5 into conduction. This holds the
collector of Q5 below three volts. IC1A and B are biased at 50%
of the supply voltage with the inputs arranged so that IC1B is
on in this mode. IC1B turns Q4 on and this pulls the base of Q3
low removing the high voltage from the receive diodes(D2, 3, 4
and 11) and grounding the junction at L6. This allows 12 volts
to flow through the diode string from L5 and L7 to the common
cathode point at L6. This turns the receive diodes on. R17 and
C19 control the time delay of the receive diode turn on to
insure the transmit diodes have time to turn off before the
receive diodes are turned on.
IC1A will be off when terminal D is high and Q2 will not
conduct. This allows Q1 to be forward biased by R5 and pull L2
up to 400 volts. This voltage cuts off D1 first and then D10, 9,
8 and 7. This disconnects the input of the amplifier before
disconnecting the output.
AMERITRON QSK-5PC Instruction
Manual
TRANSMIT:
In TRANSMIT the circuit functions as follows: Point D is held
below 2 volts. This removes the forward bias on Q5 and allows
the collector to go high. IC1A turns on after a slight delay
caused by the charge time of R18 and C20. Q2 turns on and
discharges the transmit diode string through D5. Q1 is forced
off by the removal of base bias by Q2. The 12 volt supply then
flows from R27 through the diode string to Q2. This places the
transmit diodes in conduction by biasing them with
approximately 600 mA of forward current.
The receive diodes are disabled when Q5's collector voltage
charges C19 quickly through D13. This turns IC1B off which turns
Q4 off. This allows R6 to pull the base of Q3 high and the
voltage at the emitter of Q3 rapidly turns the center junction
of the receive diodes off by applying 380 volts of positive bias
to L6.
Voltage divider R8 and R12 allows IC1C to compare the status of
the receive diode bias to the voltage obtained through R11
from the transmit diode string. If the transmit diode string
is off and the receive diode string is on, the output of IC1C
will be low and Q6 and Q7 will be off. When the transmit diode
string is on and the receive diode string is off Q6 and Q7 are
biased into conduction.
Q7 can be used to switch the bias in an amplifier. The source
(terminal J) must be within 3 volts of ground and the drain
(terminal I) must be below 25 volts positive. The FET will
safely carry two amperes of current.
Q6 can be used to pull up to 100 mA of current to ground
(terminal K). The open circuit voltage must be below 25 volts
and positive polarity.
AMPLIFIER CONNECTIONS
The QSK-5PC installation requires modifications of the wiring to
the phono jacks on the amplifiers. The following is a list of
the new functions of the amplifier rear panel jacks:
12 V:
This jack is used to supply 12 volts for external accessories.
This jack can also be used for a "hand-shake" that confirms the
diodes have changed states. Optional instructions will connect
this jack to the open collector output of Q6 for the "hand-
AMERITRON QSK-5PC Instruction
Manual
shake." This jack will then pull low in the transmit mode. The
maximum rating of this connection is 25 volts open circuit and
100 mA of current when low.
RLY:
CAUTION!! This jack must always be directly connected to the
transceivers QSK output line. NEVER attempt to operate the
amplifier without this jack properly connected. Do not connect
any devices between this jack and the transceiver.
This jack provides the connection from the Key 2 terminal (D) of
the circuit board. This jack has 5 volts open circuit and supplies a maximum of 1 mA of current. This jack must be pulled
low (below 2 volts) at least 1 mS before RF is applied to the
amplifier. The jack must not be returned to an open circuit
condition before RF is removed from the amplifier. Failure to
comply with these restrictions will damage the amplifier or the
QSK board.
The QSK board will inhibit the receive signals for one mS after
this jack returns to an open or "high" condition.
RF IN:
This SO-239 connector should be connected to the RF out
connector of the transceiver.
RF OUT:
The antenna will connect to this SO-239. The antenna SWR must
be low if the QSK-5PC is operated at full ratings. To calculate
the safe power capability of the QSK-5PC use the following
formulas:
2800 divided by the SWR for SSB and high peak-to-average power
modes.
2250 divided by SWR for CW and high average-to-peak power modes.
1000 divided by SWR for RTTY and other high duty-cycle, high
average power modes.
NEVER EXCEED 2000 WATTS ON CW, 2500 WATTS ON SSB OR 1000 WATTS
ON RTTY.
The following are some typical SWR values and power ratings:
AMERITRON QSK-5PC Instruction
Manual
SWR SSB CW RTTY
1:1 2500 W 2000 W 1000 W
1.5:1 1875 W 1500 W 667 W
2.0:1 1400 W 1124 W 500 W
3.0:1 950 W 750 W 333 W
Parts supplied: (1) QSK-5PC board
(1) QSK-5PC plate with mounting spacers (6)
(8) #6 INT lock washer
(2) #6 flat washer
(2) male/female spacer 1-3/4"
(8) male/female spacer 7/8"
(6) 6-32 5/16" screw
(6) 6-32 1/4" nut
(5) ferrite bead
10-1/4" RG-58 18" orange wire
16-3/4" RG-178 17-1/2" red/white wire
21" blue wire 7" red teflon wire
15" yellow wire 6" teflon sleeve
CAUTION: ALWAYS DISCONNECT THE AMPLIFIER FROM THE POWER MAINS
AND WAIT FOR THE FILTER CAPACITORS TO DISCHARGE BEFORE REMOVING
THE COVER.
Refer to fig. 4 for identification of the correct soldering
post on the QSK-5PC during installation.
QSK-5PC INSTALLATION FOR THE AL80A/82/1200/1500
1. Remove the Amplifier's power cord from the outlet. Check
the high voltage on the amplifiers internal meter. AFTER THE
HIGH VOLTAGE HAS REACHED ZERO you may safely disconnect all the
station wiring and cables from the rear panel jacks. Place the
amplifier in a well lit area with adequate work space.
2. Remove the cover of the amplifier and connect a 2 watt or
larger resistor with a value between 10 and 100 ohms to the
chassis. Connect the other end of this resistor to the tube's
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