Icom IC-22S Instruction Manual page 3

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