User's Manual

Operating voltage for IC15 is controlled as follows. During transmit, an active high signal from the logic

board, TX2 IN, CN6-6, turns on the top half of Q11 which turns on Q21 applying voltage to IC15. An

UNLOCK active high signal from the PLL circuit Q7-C controls the lower half of Q11. When the PLLNCO

is out of lock, the top half is prevented from turning on. This disables the transmitter.

The power output section of PM-1 operates directly from un-switched

battery voltage. Voltage is present

here even if the radio is switched OFF. DISCONNECT THE BATTERY CABLE WHEN SERVICING THIS

SECTION. All earlier amplifier stages operate from switched, controlled voltage which is under control of

the power-off timer switch IC13.

4.4 PLL CIRCUIT

The PLL function is performed by IC3. Reference Oscillator OSC1 sends a 12.0 MHz signal to IC3-1

where it is divided to a reference frequency of 5.0, 10, or 12.5 kHz by counters under control of data from

the logic board on pins 9, 10, and 11. A sample of the RF signal from the VCO from CN2-4 RF is applied

to IC3-8. This is divided by 64 in a pre-scaler and further divided to the same 5, 10 or 12.5 kHz reference,

also under control of data from the logic board. This data changes depending on the selected channel

and PTT line. The two references are compared by a phase detector to produce a phase difference

voltage on pin 5. Q5 and Q6 are charge pumps which are used in developing the phase difference

voltage. This passes through a loop filter composed of D9, D10 and associated components and

becomes the control voltage applied to the VCO at CN2-6 where it is used to vary the capacity of

varactors used in tuning the oscillator frequency. This control voltage is also buffered by IC4 and is used

as a tuning voltage for the receiver RF section. Switch IC5 speeds up the loop filter to allow rapid

frequency shifts in the scan mode.

If the VCO is out of lock, a logic low appears at pin 7. This is inverted by Q7 and is applied to Q11 to

disable the transmitter.

4.5 LOGIC UNIT

The radio operating firmware is programmed into the CPU, IC203, at time of manufacture. The Logic Unit

provides most of the control for the radio as indicated in the various sections discussed above, using

firmware stored in IC203 and data stored in memory IC201. Regulator IC205 provides 5 V to power the

board. IC204 resets the Microprocessor on “power up.” A manual reset may be done by shorting the two

points marked RESET. These are located near IC201.

IC202 is the DTMF encoder/decoder. FVR201 adjusts the tone output level to the audio processor IC8.

Tone input at CN6-16 TONE IN goes to the decoder IC202-2. This signal comes from the Audio

Processor IC8-48. A successful decode is sent to the CPU and to the main unit on CN6-4 to open the

Squelch Gate.

IC201 is a memory chip which stores data programmed into the radio. This includes frequencies, channel

names, CTCSS/DCS, ANI, encode/decode numbers and all timer data entered during initial

programming.

4.6 CONTROL UNIT

Please refer to the Radio Operation section for complete information on use of the various controls. The

Control Unit connects at CN4. This unit contains the channel/squelch switch, volume control, keypad

speaker, display, control switches for scan, monitor and shift and the microphone connector. The

channel/squelch switch sends pulses to the Logic Unit to select channels or adjust the squelch. This

switch is also used to select call numbers stored in memory.

Q401 supplies reduced voltage to the LCD backlight LED’s. Q404 changes the brightness of the

backlight under control of LED control signal from the logic board on CN4-11 LED.