TM-9-2350-273-BD M60 M48 Battle Damage Assessment and Repair Download
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TM 9-2350-276-BD COMMUNICATIONS SYSTEM Procedural Steps (Cont'd) o. To calibrate the FREQUENCY DIAL, rotate the FREQUENCY TUNING KNOB (27) while looking into the FREQUENCY DIAL VIEWING WINDOW (5) and select the frequency listed below that is the closest to the desired operating frequency. Band I: 22.050 MHZ 28.350 MHZ 34.650 MHZ Band H: 36.225 MHZ 40.950 MHZ 42.525 MHZ 45.675 MHZ 48.825 MHZ The frequencies are noted on the frequency dial with an extended graduation line capped by an arrowhead. P. Set the MODE SELECTOR SWITCH (3) to the receive only (right) position. q* Depress and hold the TONE CALL BUTTON (25). A tone should be heard in the earphones. Rotate the FREQUENCY TUNING KNOB (27) until a zero beat is obtained. While rotating the FREQUENCY TUNING KNOB (27) the tone should be heard to progress from a high pitch to a low pitch then to a high pitch again. The proper setting of the FREQUENCY TUNING KNOB (27) is the point at which the tone is at its lowest pitch or totally absent. Note the relative positions of the index line and the frequency graduation line through the FREQUENCY DIAL VIEWING WINDOW (5). If the index line is within 1/5 of a frequency graduation (5 KHZ), no adjustment of the index line is necessary. Proceed after releasing the TONE CALL BUTTON (25). If the index line is not within 1/5 of a graduation (5 KHZ) the following adjustments must be made: 1. Release the TONE CALL BUTTON (25). Using a screwdriver, remove the INDEX LINE ADJUSTMENT (4) plug. NOTE This adjustment is quite stiff. Care should be exercised to not change the frequency setting while adjusting the index line. 2. Insert the screwdriver into the hole disclosed and contact the index line adjustment. Rotate the adjustment right or left until the index line exactly corresponds to the selected frequency graduation line. 3. Replace the INDEX LINE ADJUSTMENT (4) plug. 4. Check the setting by repeating steps (q) and (r). When no adjustment is required, proceed to the next step. s. Return the MODE SELECTOR SWITCH (3) to the Simplex position (left). 11-36