70DRU-3 DIGITAL RECORDING UNIT (OPTIONAL)RECORD LEVEL ADJUSTMENTAT-300 EXTERNAL TUNER (OPTIONAL)FUSE LOCATION12 MAINTENANCEINTERNAL ADJUSTMENTSREFERENCE FREQUENCY CALIBRATIONNote:The transceiver is adjusted at the factory prior to shipping.Unless necessary, DO NOT perform this adjustment.1 Remove the top case (10 screws) from thetransceiver.2 Set the following on the transceiver:• Mode: CW• MONI control: Center• AF gain control: Center• Menu No. 24 (CW PITCH): 800 Hz• HI/SHIFT control: 800 Hz• LO/WIDTH control: 1000 Hz• RIT function: OFF• Break-in Function (VOX): OFF3 Tune in a standard frequency station such as WWVor WWVH at, for example, 10.000 or 15.000 MHz.Adjust the transceiver Tuning control so the Displayreads the exact frequency of the station. You shouldhear a beat tone of approximately 800 Hz.For 800 Hz:faf = (fdisplay/20.000 x ∆freference) + 800 Hzwhere ∆freference is the shift from the 20 MHzreference frequency4 Close your CW key and you will hear a transmitsidetone of approximately 800 Hz. This sidetoneproduces a double beat tone when it combines withthe received signal. Adjust the AF gain control andthe MONI control so you can hear the double beatclearly.For 800 Hz:fsidetone = 800 Hz x [(20 x 106 + ∆freference)/20 x 106]where ∆freference is the shift from the 20 MHzreference frequency5 Adjust the TC-800 trimmer to minimize the frequencydifference between the received 800 Hz tone andthe 800 Hz sidetone.Remove thetop case.TC-800Remove thebottom case.VR3Fuse forAT-300Remove thetop case.
