Racal Instruments RA6790/GM, Technical Manual

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Page 300: ...RACAL RA6790 GM ALIGNMENT AND TUNING MANUAL From Maxhdrm2 comcast net February 2003...

Page 301: ...r aligning the Receiver assemblies The alignment procedures require that external power be connected to the Receiver the Receiver power switch turned on and that the mode bandwidth AGC and frequency b...

Page 302: ...nput Attenuation 20 dB Scan Time 20 Msec Div Log Ref Level 0 dBm 10 dB Log Video Filter 10 kHz Scan Mode Internal Scan Trigger Auto 5 Set the Marker to a frequency of 30 MHz 6 Observe trace and adjust...

Page 303: ...Tuning Manual Page 4 of 20 45 MHz RELATIVE LEVEL 20dB 0 5MHz 40 453MHz EACH GRATICULE 10 MHz Figure 3 2 Alignment Waveforms 45 MHz RELATIVE LEVEL 20dB EACH GRATICULE lOdB EACH GRATICULE 10 MHz Figure...

Page 304: ...requency to 40 455 MHz Adjust L3 for notch 8 Check filter passband level from 45 to 70 MHz Ensure that this level is greater than 9 dBm 9 Check relative level at 41 MHz compared to level at 45 MHz If...

Page 305: ...ent and reconnect PI of cable A2W1 to J5 d Second Mixer Circuit Card Assembly A3 The second mixer assembly A3 is located in the bottom portion of the Receiver The RF signal generator and RF millivoltm...

Page 306: ...10 dB Scan Width Div 20 kHz Scan Time 0 1 Second Log Ref 0 dB 10 dB Log Video Filter 100 Hz 3 Remove a filter and connect a link between the filter input and output sockets Select this filter positio...

Page 307: ...CW rotation Select each filter position via the MODE panel Observe the trace on the spectrum analyzer for each filter selected It may be necessary to adjust the IF gain control to avoid distortion of...

Page 308: ...ed the A5 assembly is installed in the top portion of the Receiver towards the rear The test equipment required to align the A5 module includes the spectrum analyzer AM FM signal generator digital mul...

Page 309: ...ined delay 1 2 kHz 600 600 1500 1500 Defined delay 1 2 kHz 600 600 1500 1500 Defined delay 3 24 kHz 1620 1620 2150 2150 Defined delay 6 8 kHz 3400 3400 6800 6800 Defined delay 16 0 kHz 8000 8000 16000...

Page 310: ...trum analyzer While observing the spectrum analyzer trace adjust LI and L2 to obtain the bandpass waveform shown for Step 12 of the L4 adjustment procedures in Paragraph e If a double peak is obtained...

Page 311: ...Circuit Card Assembly A8 This circuit card assembly is located in the bottom portion of the Receiver The test equipment required to align this assembly includes the 50 ohm adapter digital multimeter R...

Page 312: ...ver front panel BFO and digital frequency counter indications Digital frequency counter should track 455 000 Hz above the Receiver BFO indicated frequency Also observe the digital multimeter indicatio...

Page 313: ...ing lamps are on 5 Make sure that the FAULT indicator is off If this indicator is on refer to Receiver manual 31R2 2URR 251 for information on clearing the fault 6 Perform BITE check as outlined in Re...

Page 314: ...signal generator level to 10 dBm 70 millivolts and set IF GAIN control to maximum 7 Decrease the RF signal generator output to restore the 1 mW reference and note the RF signal generator level This s...

Page 315: ...sconnect digital frequency counter and reconnect W6P2 to J5 on the A4 module TABLE 3 2 BFO TEST RESULTS BFO INDICATOR BFO FREQUENCY 455 000 kHz 456 110 0 00 kHz 453 890 457 220 1 11 1 11 452 780 458 3...

Page 316: ...ms Measure distortion Distortion should be less than 2 5 Connect phone output from Receiver front panel to distortion analyzer and adjust phone output for 10 mW into 600 ohms Measure distortion Distor...

Page 317: ...TOR connector and connect it to L S OUT loudspeaker 6 Note that power meter reads at least 1 watt 7 Disconnect power meter from L S OUT and connect it to the PHONES jack on the front panel 8 Note that...

Page 318: ...0 dBm output level All modulation off 5 Set the spectrum analyzer as follows Frequency 8 kHz Bandwidth 10 Hz Sweepwidth 100 Hz div Scan Time 2 secs div Input Attenuator 10 dBm IF Attenuator 20 dB 6 Ad...

Page 319: ...ference Voltage 0 dB Bandwidth 100 Hz Phase Reference A Delay Mode CW Frequency Step 50 Hz Delay Function Absolute 7 Adjust the Receiver manual IF gain control for a 0 dB reading on the network analyz...