Service manual

Service Manual SD170E Series

Page 19 of 44

Alignment

Transmitter Alignment

Connect the unit to a Service Monitor with the power meter set to the 10 W scale (or auto range).

Refer to figure 4.4 under commissioning section

TCXO

Set the channel selector to the mid-range frequency 460MHz (U2) and 155MHz (V2), adjust

TCXO1 for a reading accurate to within ±200Hz.

TX VCO

TX VCO is pre-tuned at the factory and no further adjustment is required

To verify the alignment of the TX VCO, check the VCO Control voltage.

Set the unit to the highest transmit frequency, 490MHz (U2), 174MHz (V2). Key the

transmitter and verify that the VCO control voltage is under 10.0 Volts. If necessary adjust

C208 of TX VCO to 10.0 Volts.

Set the unit to the lowest transmit frequency 440 MHz (U2), 146(V2) key the transmitter and

verify that the VCO voltage is above 1.8 Volts. If necessary adjust C208 to 1.8 Volts.

Note: use TP1 to measure the voltage.

Deviation

CTCSS and DCS Deviation and Balance Adjustment

Set the unit to a mid-frequency range and a CTCSS of 67Hz. Activate PTT and adjust RV402

(deviation adjustment) for desired CTCSS tone deviation.

Switch to a channel with the same frequency and CTCSS of 250.3Hz. Activate PTT and adjust

RV1 (balance adjustment) to desired CTCSS tone deviation, same as above step.

Switch between the 67Hz channel and the 250.3Hz channel and adjust RV1 until the deviation

is the same on both channels. It may be necessary to readjust RV402 to get the desired

deviation.

Audio balance and deviation adjustment

Set the unit to a mid-frequency and input the TX data with 400 Hz standard audio level

(100mV for data or 10mV for audio in). Increase the signal level to 20 dB from standard

level.

Monitor the demodulated signal from service monitor. Adjust RV1 to make the monitored

signal to be a balanced square wave.