Icom IC-22S User manual

Icom IC-22S
PLL Synthesized
2-Meter Transceiver
Instruction Manual
and Service Notes

Icom IC-22S PLL Synthesized 2-Meter Transceiver
Instruction Manual and Service Notes
2
SECTION I.
Specifications
GENERAL
Semiconductor Complement
Transistors 34
FET 7
IC 13
Diodes 33 to 128 depending on channels
Frequency Range (for specification) 146-148 MHz
Voltage 13.8 Volts DC (negative ground)
Current Required
TX 2.0 amps @ 10 Watts 0.9 Amps @ 1
Watt
RX 0.7 amps at maximum audio
0.4 amps squelched audio
Size 58 mm (H) x 156 mm (W) x 218 mm (D)
Weight 1.9 kilograms
Antenna Impedance 50 ohms
Number of Channels 23 channels selected from any of the
132 channels on 15 KHz spacing
Frequency Control Stabilized master oscillator PLL
programmed by diode matrix
TRANSMITTER
Power Out 10 watts or 1 watt (selectable)
Modulation Width 5 KHz
Microphone Impedance 500 ohms
Spurious Level Lower that –60 db below carrier
RECEIVER
Modulation Acceptance 16F3
Type Double Superhetrodyne
1st IF 10.7 MHz
2nd IF 455 KHz
Receiver Sensitivity 4 db below 1 uV or lower (0.4 micro)
1 uV S+N/N 30 db or better S+N/N
Spurious Response 60 db or more attenuation
Bandpass +/-7.5 KHz: -6 db
+/-15 KHz: -60 db
Squelch Sensitivity -8 db below 1 uV
Audio Output 1.5 watts or more into 8 ohms

Icom IC-22S PLL Synthesized 2-Meter Transceiver
Instruction Manual and Service Notes
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SECTION II.
Description
This transceiver is extremely rugged and completely solid state. State of the art devices
such as integrated circuits, field effect transistors, varactor and zener diodes are engineered
into a tight-knit, straightforward electronic design throughout both transmitter and receiver.
Reliability, low current demand, unexcelled performance, and ease of operation are the net
result.
The dual conversion receiver with its FE front end and high-Q helical cavity resonators
boasts low noise and sensitivity of 0.4 volts or less. Signal gain of 90 db or more is
accomplished from the second mixer back by virtue of a 6-stage IF amplifier. The need for
additional front end RF amplification is thus eliminated. Zener-regulated PLL controlled first
and crystal-controlled second local oscillators produce very good stability. Audio
reproduction is of an unusually high order of distortion free clarity.
The transmitter section will produce a minimum of 10 watts output. Again, a phase locked
loop is employed for initial frequency stability. Twenty-two (22) channels are provided for
operating convenience and versatility. High-Q stages provide minimum interstage spurious
response. A low pass filter is placed at the output to ensure undesirable frequency products
are not being transmitted. Final PA transistor protection circuit is incorporated in the final
circuitry. A new design heat radiator is employed to increase final reliability.
All circuitry is constructed on three printed circuit boards that are easily accessible for
servicing. The printed circuit boards are housed in a sturdy frame that is, in turn, housed in
a rigid metal case providing an extremely durable and rugged unit. Care has been taken to
filter and regulate internal DC voltages. A DC input filter is provided to eliminate alternator
or generator whine generated in the vehicle environment. Test points are brought up from
all major circuits to facilitate maintenance checks and troubleshooting should the need
arise.
Each unit comes with built-in speaker, a high quality dynamic microphone, mobile mounting
bracket, microphone clip, DC cabling and plug, external speaker plug, and operating
manual. A modern styled face plate, large S-meter, small size and low profile design
complete the unit’s styling. It is a welcome addition to a dashboard or fixed station.

Icom IC-22S PLL Synthesized 2-Meter Transceiver
Instruction Manual and Service Notes
4
SECTION III.
Installation
Unpacking
Carefully remove your transceiver from the packing carton and examine it for signs of
shipping damage. Should any shipping damage be apparent, notify the delivering carrier or
dealer immediately, stating the full extent of the damage. It is recommended you keep the
shipping cartons. In the event of storage, moving, or reshipment becomes necessary, they
come in handy. Accessory hardware, cables, etc. are packed with the transceiver. Make sure
you have not overlooked anything.
Location
Where you place the transceiver in your automobile is not critical and should be governed
by convenience and accessibility. Since the unit is so compact, many mobile possibilities
present themselves. In general, the mobile mounting bracket will provide you with some
guide as to placement. Anyplace where it can be mounted with metal screws, bolts, or pop
rivets will work. For fixed station use, a power supply should be designed to produce 3 amps
for the transceiver.
Power Requirements
The transceiver is supplied ready to operate from any regulated 13.5-volt DC, 2.5 amp
negative ground source. An automobile 12-volt, negative ground system is usually more
than adequate. Some not must be taken, however, of the condition of the vehicle’s electrical
system. Items such as low battery, worn generator/alternator, poor voltage regulator, etc.,
will impair operation of your transceiver as well as the vehicle. High noise generation or low
voltage delivery can be traced to these deficiencies. If an AC power supply other than the
matching supply is used with your transceiver, make certain it is adequately regulated for
both voltage and current. Low voltage while under load will not produce satisfactory results
from your transceiver. Receiver gain and transmitter output will be greatly impaired.
Caution against catastrophic failure of the power supply should be observed.
CAUTION: Excessive voltage (above 15 volts DC) will cause damage to your
transceiver. Be sure to check the source voltage before plugging in the
power cord.
Included with your transceiver is a DC power cable with plug attached. The red wire is
positive (+) and the black wire is negative (-). If your mobile installation permits, it is best
to connect these wires directly to the battery terminals. This arrangement eliminates
random noise and transient spikes sometimes found springing from automotive accessory
wiring. If such an arrangement is not possible, then any convenient B+ lead in the interior
of the vehicle and negative frame can be utilized. Your transceiver provides an internal DC
filter that will take out a large amount of the transient difficulties anyway. Remember that
the unit operates on a negative ground system only –it cannot be used in a positive ground
automobile.
After making your connections, simply insert the power plug into your transceiver. When
your transceiver is mated with its matching power supply, the power cable from the IC-3PA
is simply plugged into the same receptacle in the transceiver and the AC line cord into any
convenient wall receptacle.
Antenna
The most important single item that will influence the performance of any communication
system is the antenna. For that reason, a good, high quality, gain antenna of 50 ohms

Icom IC-22S PLL Synthesized 2-Meter Transceiver
Instruction Manual and Service Notes
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impedance is recommended for fixed or mobile operation. In VHF as well as HF, every watt
o ERP effective radiated power will make a difference. Therefore, 10 watts output into a 3
db gain antenna yields 20 watts effective radiated power, assuming a low VSWR, of course.
Therefore the few more dollars invested in a gain type antenna is well worth it.
When adjusting your antenna –mobile or fixed –by all means follow the manufacturer’s
instructions. There are some pitfalls to be aware of. For example, do not attempt to adjust
the antenna for lowest VSWR when using an SWR bridge not intended for VHF use. Some
instruments will give readings with as much as a 40% error. A Drake WV-4, Bird model 43,
or Sierra model 164B with VHF cartridges
The RF coaxial connector on the rear chassis mates with a standard PL-259 connector.
Some models may have metric thread. In any event, the RF connector will mate with almost
any PL-259 connector if care is taken to seat them properly.
Microphone
A high quality dynamic microphone is supplied with your transceiver. Merely plug it into the
proper receptacle on the front panel. Should you wish to use a different microphone, make
certain it is of the high impedance type; at least 500 ohms or better. Particular care should
be exercised in wiring also, as the internal electronic switching system is dependent upon it.
See the schematic for the proper hookup. Under no circumstances use a “gain preamp” type
microphone. The audio system in your transceiver is more than adequate and additional
pre-amplification is unnecessary. To use this class of microphone is to invite distortion.
Synthesizer Programming
Your transceiver does not need crystals to set the frequency. It has 22 channels selected by
the channel selector switch. In addition, the channel selected has three options of how the
Offset is handled: receive and transmit on the programmed frequency (SPX), receive 600
kHz higher than the programmed frequency (DPX A), and transmit 600 kHz above the pro-
grammed frequency (DPX B). The programming is done on the diode matrix board by
soldering computer grade diodes into the boards in the locations indicated on the diode
matrix diagram. Please refer to the chart on pages 22~24 for the locations.

Icom IC-22S PLL Synthesized 2-Meter Transceiver
Instruction Manual and Service Notes
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The matrix board may be removed by taking out the hold-down screw at the end of the
board and pulling gently straight up on the other end to disconnect the matrix from the
connector. The numbers 1 through 22 indicate the channel number to be programmed and
the numbers D-0 through D-7 indicate the position in which the diode is to be placed
corresponding to the insert positions on the Frequency versus Matrix Chart. Insert the diode
into the line for the desired channel with the cathode pointing UP. The cathode lead is bent
down to go through the board to connect to the other side. After the diodes have been
inserted for the channel, turn the board over carefully so as to not have the diodes fall out
and solder each of the leads with a small tip, low wattage soldering iron. Clip end diode lead
off as close to the board as possible. Replace the board on its connector and replace the
screw in the end.
An external speaker jack and plug is supplied with your unit in the event another speaker is
desirable. The external speaker impedance should be 8 ohms. The use of the external
speaker jack will disable the internal speaker. An 8 ohm headset can be utilized as well.
(See Fig. 2B)
CAUTION: DO NOT USE A SOLDERING IRON OF MORE THAN 40 WATFS ON THE MATRIX

Icom IC-22S PLL Synthesized 2-Meter Transceiver
Instruction Manual and Service Notes
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SECTION IV.
Control Functions
High-Off-Low Switch
Opens or closes the 12 VDC source voltage to the transceiver. “In High” position, output
power is 10 watts. “In Low” position, output power is 1 watt.
DPXA —SPX —DPXB
This determines whether the transceiver transmits or receives on the program frequency, or
+600KHz above the program frequency.
Volume Control
Controls audio output level of the receiver.
Squelch Control
Controls the squelch threshold point of the receiver.
Microphone Jack
Accepts 4 prong mike plug supplied on microphone.
S/RF Meter
Reads S signal strength in receive mode and relative RF output in transmit mode. The meter
face is illuminated with a white lamp when the transceiver is switched on.
Channel Selector
Selects one of 22 channels.
C.O.S. lamp
Also shows out of lock in transmit.
Transmit Indicator
Antenna Connector
Accepts standard PL-259 coaxial connector. Note that some transceivers may come with a
metric threaded connector. Most PL-259 connectors will mate satisfactorily if care is taken
to seat them properly. If you have difficulty, try a different make of PL-259.
External Speaker Jack
This jack mates with the plug supplied for external 8-ohm speaker or headset use. The use
of this jack mutes the internal speaker.
Power Cord
Mates with DC cord plug or power cord of IC-3P AC power supply.
Identification Plate
States model, serial number.
Accessory Socket
Center Meter, etc., can be connected with a 9 Pin plug.

Icom IC-22S PLL Synthesized 2-Meter Transceiver
Instruction Manual and Service Notes
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SECTION V.
Operation
Initial Preparations
Connect the microphone to the microphone jack.
Connect the antenna to the antenna coax connector. Make sure the coax line is of the correct
impedance (50 ohms) and is neither shorted nor open.
Make sure the function switch is in the off position, then connect the power supply cord to the
power supply jack. The red lead should be connected to the positive side of the power source and
the black lead to the negative side. In the event that these leads are improperly connected, the
transceiver will not function. No damage will be, however, incurred since protection is provided in
the P.A. for this purpose.
Turn the volume and squelch controls to the maximum counter-clockwise position.
Operation
When the function switch is set to either the high or low position the set is switched on and the
channel indicator window and meter will be illuminated.
Switch the channel selector to the desired channel.
Choose the proper DPX offset setting, or SPX for simplex operation.
Reception
Adjust the volume control to a comfortable listening level of noise, if no signal is present.
Carefully adjust the squelch control clockwise until the noise just disappears. This is the proper
squelch threshold setting and must be done when no signal is present. Your transceiver will now
remain silent until an in-coming signal is received which opens the squelch. If the squelch is
unstable due to the reception of weak or stations, adjust the squelch control further until the
proper threshold is obtained.
The S meter indicates the signal strength of the incoming stations and is calibrated in S units. and
db over S9. The light illuminating the meter acts also as lock indicator for the PCC.
Transmitting
Push the PTT (push to talk) button on the microphone and the transceiver will transmit. At the
same time the TX indicator will be illuminated red and the meter will provide an indication of
relative power output of the transmitter. The pointer will be on or near the red mark on the meter
scale when on high power and just a little over 1 on low power. Hold the microphone about three
inches from your mouth and speak in a normal voice. The microphone is of the dynamic type and
provides good pickup for all levels of voice.
To receive again, just release the PTT button. This will also switch off the light.

Icom IC-22S PLL Synthesized 2-Meter Transceiver
Instruction Manual and Service Notes
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SECTION VI
Theory of Operation
TRANSMITTER
Microphone, pre-amplifier circuit
The pre-amplifier circuit is composed of Q30, Q29, in an NPN, PNP direct-coupled 2-stage amplifier
configuration. The low noise transistors used and application of a large amount of feedback in the
1st stage gives a high signal-to-noise ratio and high stability.
Since DC voltage is supplied through Rl39 to the microphone connector, the ICSM2 (electrolytic
condenser microphone) can be used also. C 166, R140, C65 constituting a which filter suppress
high frequency regeneration and C 163 provided between base and emitter of the 1st stage
transistor prevents oscillation due to regeneration.
Pre-amplifier output is through R132 to the microphone circuit.
IDC circuit (Instantaneous Deviation Control)
Passing of signals through narrow band filter stage can result in distortion if the signal is over-
modulated and consequent degrading of following channels. To give improved limiting
characteristics Q28, Q27, Q26, are connected in a 3-stage direct-coupled configuration that results
in less distortion and protects succeeding stages from the effects of excessive input.
Since feedback is supplied to the 3-stage DC circuit and the input impedance is low, the frequency
characteristic of the differentiation by R130 and C159 is improved. R124 through which the
feedback circuit connects to ground serves for adjusting the operating point of Q26 and insuring
symmetry of clipped waveforms. Dl 8 and D19 are temperature compensating elements for the 3-
stage DC. circuit.
The limiter output is close to square waves in form, and since it includes harmonics an active filter
is provided to eliminate anything over 3 kHz. To prevent the frequency deviation from becoming
too large as temperature increases, compensation is made by thermistor R13, after which
adjustment is made by R12 to narrow the frequency deviation range.
Frequency modulation, 10.7 MHz Oscillator
Because of the quartz crystal characteristics in the frequency modulator Q24, a non-Controlled VXO
configuration, the circuit is tolerant of temperature variations, and there is less drift. Output signals
from the IDC circuit are supplied to the anode of varicap diode D17. To improve the temperature
characteristics, temperature compensation is effected by thermistor Rl06 connected to the cathode
of D17. The signal is set to 10.7 MHz by L4 connected to the cathode of D17.
Transmission Mixer
1C3 includes a constant current circuit and differential amplifier. 1C9 provides balanced output
from the 10.7 MHz oscillator and drives the two inputs of the differential amplifier. Local oscillator
output enters via the constant current input and differential amplifier output is filtered by L36,
opposite phase components of the 10.7 MHz output and local oscillator cancel, and so signals
obtained at the secondary side of L36 are LO+/ 10.7 MHz. The required LO+ 10.7 MHz signals are
obtained from the Band Pass Filter following L36.

Icom IC-22S PLL Synthesized 2-Meter Transceiver
Instruction Manual and Service Notes
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Interstage Amplifier
BPF output is amplified up to about 2 mW in the Q22 stage that is a MOSEFT with good linearity.
Low Level Amplifier
Interstage amplifier output is amplified to about 100 mW by stage Q19, which also functions as an
ALC circuit.
Driver stage
Low level output is amplified to approximately 1.6 W by Q18.
ALC Circuit
Spurious signals, which might occur when voltage is reduced or when the degree of excitation is
low, are prevented by a small amount of forward bias applied by bias circuit D14.
Part of this output is brought up to excitation level in the threshold type voltage-doubling rectifying
circuit constituted by D19, D29. When AI..C is not applied, the self-bias of Q5 causes Q16 to
conduct. When ALC is applied, both 015 and Q16 are close to cut-off, collector voltage of Q19 falls,
and the excitation level is lowered.
ALC is effective for both high power and low modes. For high power, the threshold level is
controlled by R73, and for low power, the threshold is set by R149.
Power Amplification
Output is amplified by Q7 to give an output of 10 watts, including low pass filter losses. Since
power handled in this stage is particularly high, use is make of an aluminum die-cast radiator
which is in direct contact with the rear chassis and serves to keep the transistor temperature low in
order to insure reliability. A padding mica trimmer which has an excellent temperature
characteristic and causes little induction loss is also employed.
Low pass filter and SWR detector
Power amplifier output includes harmonic components and in passing through 2 Chebyshev section
and one standard section in order to get to the ANT terminal, harmonic components are attenuated
by about 70 dB. Cut-off frequency of this low-pass filter is set to about 180MHz, and so there is
very little loss in the 146-148 MHz band.
SWR
D10, D11 constitute an SWR detector. The closer it is to the ANT terminal the better the detector
functions, but because of diode rectification, harmonics are produced. An excellent compromise is
therefore made by inserting the detector between the low-pass filters. Standing waves that pass
through the SWR detector are rectified by D11 and supplied to the RF meter. Indication of the RF
meter for proper high power output is set to 4/5 of full-scale by R156.
APC circuit
Reflected waves are rectified by D10 and then amplified by Q20, 021 up to the level set by 89. By
raising Q22 source voltage, excitation level is lowered, and damage to the power amplifier
transistor due to mismatch is prevented.