Nautel XR12 Troubleshooting Manual

Also see for XR12: Installation manual Operation and maintenance manual Preinstallation manual

Contents

XR12 Troubleshooting Manual Detailed Circuit DescriptionsPage 2-8 Issue 3.0 2009-07-28- E1 in INT position (pins 2 and 3 shorted)- E2 in INT position (pins 2 and 3 shorted)- E4 in EXT position (pins 1 and 2 shorted)The applied RF must be precisely the carrier frequency (fc ) and its peak-to-peak voltage (sine orsquare wave) must be between 5.0 V and 12.0 V.External 10 mhz sourceAn external 10 MHz can be used for synchronization (i.e., GPS lock). When an external 10 MHzsignal is to be used as the RF drive source, the shorting shunt posts must be configured as follows:- E1 in EXT position (pins 1 and 2 shorted)- E2 in EXT position (pins 1 and 2 shorted)- E4 in INT position (pins 2 and 3 shorted)The applied RF must be precisely 10.00 MHz and its peak-to-peak voltage (sine or square wave)must be between 2.2 V and 8.0 VInterphase PDM driver PWB (NAPM10B)See electrical schematic Figure SD-14.Carrier level controlThe carrier level control circuit consists of U6, U2A, U2D, U3B, U3D, and their associatedcomponents. U6 is a four-quadrant analog multiplier connected as a variable gain, wide-band, linearamplifier. The modulation reference (I1) input is multiplied by a factor determined by the level of thecarrier ref (I2) and B+ ref (I4) inputs to determine the gain and, in turn, the I3 output.When there is no unbalanced audio input at J1-15, U2D's output (TP6), which is the modulationreference, will be a nominal 1.4 V. When a pure audio sine wave is present at a level that will produce100% modulation, the output of U2D will be a sine wave varying from 0 V to 2.8 V. The resultingcurrent flow through R12 is U6's I1 input.