Kenwood NXR-800 Service Manual

Also see for NEXEDGE NXR-800: Brochure Instruction manual Instruction manual Instruction manual Instruction manual

Contents

NXR-800154-2. 1st-Mixer circuitThe unwanted out-of-band RF components produced byQ1 are attenuated by the BPF. Only the desired signal istransmitted to the A1 Double Balanced Mixer (DBM). Here,the desired signal is mixed with the first hetero signal.49.95MHz is produced as the 1st Intermediate Frequency(IF1).BPFL134,135A1Mixer IF149.95MHz1st local400.05~430.05MHzFig. 17 1st-Mixer circuit4-3. 1st-IF circuitsThe IF1 signal produced by the 1st-Mixer circuit is trans-mitted through either one of two 1st-IF circuits with differ-ent bandwidth. The signal passes through the WIDE bandconsisting of D9, XF1, Q19, XF3, Q28 and D13 only in Ana-log_Wide mode. Meanwhile, the signal passes through theNARROW band consisting of D10, XF2, Q20, XF4, Q29, andD14 only in Analog_Narrow, NXDN_Narrow or NXDN_Very-Narrow mode.XF1 and XF2 is 2 pole and XF3 and XF4 are 4 pole Mono-lithic Crystal Filters (MCF). They are BPF for removing spu-rious noise occurring close to the desired signal. The DCswitch consists of Q31, Q32, Q26 and Q25, switches theWIDE and NARROW bands of the 1st-IF circuits.D9SWD13SWQ25SWQ32SWQ31SWQ26SWL46,52XF1L74,90XF3Q19 Q28Analog Wide8WR8WRD10SWD14SWL47,53XF2L75,91XF4Q20 Q29Analog NarrowNXDN NarrowNXDN Very-Narrow8NR8NR+8VIF_SW4-4. Demodulator circuitsThe desired signal that passed through the 1st-IF circuitspasses through the distributor consisting of LC parts and isfed to the IF system IC_IC12, IC13. The signal in Analog_Wide or Analog_Narrow mode is mixed with the secondlocal oscillator hetero signal by the mixer in IC12. 450kHz isproduced as the 2nd Intermediate Frequency (IF2).It passes through D15, CF2, D16, D19, CF5 and D20 pathif the modulation mode is Analog_Wide. It passes throughD15, CF3, D16 and D19, CF7 and D20 path if the modulationmode is Analog_Narrow. The base band signal FM-detectedby the quadrature detection circuit consisting of L128, Q57,and Q58 and is amplified to a signal level of approximately100mVrms by IC20 and is then transmitted to the controlunit (X53-413) from CN42 (pin12).The signal in NXDN_Narrow or NXDN_Very-Narrow modeis mixed with the second local oscillator hetero signal by themixer in IC13. 450kHz is produced as the 2nd IntermediateFrequency (IF2). Here, irrespective of modulation modes,it passes through the CF4 and CF6 path. It is transmittedas the base band signal via IC14 to the CN43 control unit,X53-414.CF2, CF3, CF4, CF5, CF6 and CF7 are hexode CeramicFilters. They are BPF for removing spurious noise occurringclose to the desired signal.Fig. 18 1st-IF circuitsCIRCUIT DESCRIPTION