Racal_RA6790_GM_Alignment_tuning_manual_2003.pdf

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1、 RACAL RA6790/GM ALIGNMENT AND TUNING MANUAL From M February 2003 Racal RA6790/GM Alignment however, the adjustments in some functions interact with other functions so chat care must be taken when any one function alone is aligned. The end-to-end checks are designed to make sure that a Receiver is o

2、perational after assembly of new or repaired circuit cards or modules. SECTION I. ASSEMBLED RECEIVER ALIGNMENT 3-2. GENERAL. The circuit card and module assemblies may be aligned and checked after they are installed in a working Receiver. The following paragraphs provide detailed step-by- step instr

3、uctions for 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 be set as described in each procedure. Refer to T.O. 31R2-2URR-251 for location of circ

4、uit cards and adjustments. a. Power Supply Assembly AlO. The power supply used in the Receiver does not contain any adjustments or controls other than the line voltage select card located in A10J1. If all voltages checked correctly as specified in Section XI of Chapter 2, it can be assumed that the

5、power supply is functioning properly. If the power supply has not been tested then the 3-1 voltage levels as spelled out in Chapter 2 should be checked before performing any alignment procedures. WARNING The filter capacitors used in the power supply will retain an electrical charge after power is r

6、emoved. The capacitors should be discharged slowly by shorting the terminals through a protected resistive device. Disconnect the ac line cord from A10J1. Remove the metal cover from the power supply and then reinsert line cord and turn Receiver power on. Using the digital multimeter, check the volt

7、ages appearing on connector Racal RA6790/GM Alignment 0 dBm Bandwidth: 100 kHz Scanwidth: 2 MHz/Div Input Attenuation: 10 dB Scan Time: 0 as Racal RA6790/GM Alignment SLOW changed at a 30 Hz rate, FAST at a 1 kHz rate. (6) Press the LOCK pushbutton then rotate the tuning knob and note that there is

8、no frequency change. (7) Press ENTER then press numeral keys 2 and 9 and note that frequency displayed is 29.000000 MHz. c. Frequency Calibration Resolution. This test requires the digital frequency counter listed in Table 1-2. (1) Disconnect PI of cable W4 from J2 and A3 and using the cable coupler

9、 connect the digital frequency counter to PI on cable W4. (2) Ensure that the frequency is 40 MHz j8 Hz. This ensures that the internal Racal RA6790/GM Alignment Power ON Gain Mode AGC-SHORT BW 3.0 kHz (or closest bandwidth available) Receiver Tuned Frequency 1.5 MHz Detection Mode CW (3) Set the RF

10、 signal generator for an output of 1.5 MHz, CW at a level of -10 dBm. Connect the 50 ohm adapter (load) with the RF millivoltmeter to IF OUTPUT connector J2. (4) Note the IF output level indicated on the RF mi Hi voltmeter. (5) Remove the 50 ohm adapter (load) from the IF output and observe that the

11、 indicated output voltage increases by 6 dB 1 dB. (6) (Connect the digital frequency counter to IF output jack J2 and measure the IF frequency. This should be 455.000 kHz. f. Fixed and Variable BFO Operation. This test requires the 50 ohm adapter and digital frequency counter listed in Table 1-2. Ra

12、cal RA6790/GM Alignment & Tuning Manual Page 16 of 20 (1) Set the Receiver controls as follows: Power ON Gain Mode AGC-SHORT Detection Mode CW BW 3 kHz (or closest bandwidth available) BFO ON (word BFO displayed in Mode LCD) (2) Disconnect W6P2 from J5 on the A4 module. (3) Using the 50 ohm adapter,

13、 connect the digital frequency counter to W6P2 to monitor the BFO frequency. (4) Using the Receiver front panel controls, select each BFO indication listed in BFO indicator column of Table 3-2 and verify the frequencies listed in BFO frequency column are obtained. (5) Select USB and LSB modes and ob

14、serve the BFO frequency is 455.000 kHz. (SSB/ISB Receivers fitted with 08409 and 08410 option filters only.) (6) Disconnect 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

15、-1.11 452.780 458.330 2.22 -2.22 451.670 459.440 3.33 -3.33 450.560 460.550 4.44 -4.44 449.450 461.660 5.55 -5.55 448.340 462.770 6.66 -6.66 447.120 462.880 7.77 -7.77 447.010 462.990 7.88 -7.88 7.99 -7.99 g. Audio Output Power. This test requires the digital frequency counter and the RF signal gene

16、rator listed in Table 1-2. (1) Disconnect distortion analyzer and connect digital frequency counter to AF LINE output. (2) Set Receiver controls as follows: Power ON Gain Mode AGC-SHORT BW 3 kHz (or closest BW available) Detection Mode CW Receiver Tuned Frequency 1.5 MHz BFO +1.00 kHz (3) Set the RF

17、 signal generator for an output of 1.5 MHz at 97 dBm, CW. (4) Tune the RF signal generator (or Receiver) to produce an AF output of 1.0 Racal RA6790/GM Alignment & Tuning Manual Page 17 of 20 kHz +50 Hz as indicated on the digital frequency counter. (5) Set the AF output level to 1 milliwatt using t

18、he LINE LEVEL control on the Receiver front panel and phone output. (6) Select Receiver bandwidth of 6.0 kHz (or closest bandwidth available) and AM detector mode. Amplitude modulate the input signal 30% at 1 kHz. (7) Observe that the AF output level is within 5 dB of the reference set in step 5 for

19、 both line output and phone output. (8) Slowly rotate the AF gain control through the control range. Observe that the phone output level varies smoothly over the full control range. h. Audio Distortion. This test requires the distortion analyzer and RF signal generator listed in Table 1-2. (1) Disco

20、nnect digital frequency counter and connect distortion analyzer with 600 ohm load to AF LINE output. (2) Set Receiver control as follows: Power ON Gain Mode Manual Gain Detection Mode CW BW 3 kHz (or closest bandwidth available) BFO -1.00 kHz Receiver Tuner Frequency 1.5 MHz (3) Set the RF signal ge

21、nerator for an output of 1.5 MHz at -47 dBm, CW. (4) Adjust manual gain control for 1 mW output into 600 ohms. 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 dis

22、tortion. Distortion should be less than 3%. i. Operation After Restoration of Power. (1) Carefully note the Receiver tuned frequency, BW and other displayed functions on Receiver front panel and de-energize the Receiver. (2) After 1/2 hour, energize the Receiver and ensure that the Receiver returns

23、to the display noted in step (1). j. Out of Band Intermodulation Distortion. This test requires the RF signal generator, AM/FM signal generator, step attenuator, signal combiner and RF millivoltmeter listed in Table 1-2. (1) Connect the RF signal generator and AM/FM signal generator to the two input

24、s of the signal combiner. Connect the output of the signal combiner to the input of the step attenuator and its output to the RF millivoltmeter through its RF probe. (2) Set the step attenuator to 5 dB then set the RF signal generator to 12.55 MHz, at a level of -10 dBm, CW. Set the AM/FM signal gen

25、erator to 13.05 MHz at a level of -10 dBm, CW. (3) Increase the step attenuator to 70 dB. Disconnect the RF millivoltmeter from the step attenuator and connect the RF millivoltmeter to J2 on the Receiver. (4) Connect the output of the step attenuator to Jl on the Receiver and tune the Racal RA6790/G

26、M Alignment & Tuning Manual Page 18 of 20 Receiver to 12.55 MHz. (5) Adjust the manual IF gain control on the Receiver for a -10 dBm reading on the RF millivoltmeter. (6) Tune the Receiver to 12.05 MHz and set step attenuator to 5 dB. Note that the RF millivoltmeter reads 65 dB below reading in step

27、 5. (7) Tune the Receiver to 13.05 MHz and note that RF millivoltmeter reads 65 dB below reading in step 5. k. Audio Output Power. This test requires the AM/FM signal generator, the junction box and the power meter listed in Table 1-2. (1) Connect the AM/FM signal generator to Jl on the rear panel a

28、nd set to 29.550 MHz at -97 dBm level and AM modulated at 30%. (2) Turn Receiver on and tune to 29.550 MHz. Set AGC to medium and select 6.8 kHz bandwidth. Rotate AF control on front panel to maximum clockwise position. (3) Connect the junction box to connector J3 on the Receiver rear panel and conn

29、ect the power meter to MONITOR connector on the junction box. (4) Note that power meter reads at least 1 milliwatt. (5) Disconnect power meter from MONITOR 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

30、connect it to the PHONES jack on the front panel. (8) Note that power meter indicates at least 10 milliwatts. (9) Rotate AF control through its complete range and note that phone output level varies smoothly. l. Noise Figure. This test requires the noise generator, 50 ohm adapter and RF millivoltmet

31、er listed in Table 1-2. (1) Connect the RF millivoltmeter with the 50 ohm adapter to connector J2 on Receiver rear panel. (2) Connect the noise generator to connector Jl on the Receiver rear panel. Turn the noise generator on and adjust for 15.5 MHz at a low level (3) Turn Receiver on, tune to 15.5

32、MHz, select 6.8 kHz bandwidth, CW, BFO +1 kHz and maximum IF gain. (4) Note reading on RF millivoltmeter, then increase noise generator output level until RF millivoltmeter reading increases by 3 dB. (5) Noise figure shall be no greater than 12 dB. m. RF Input Impedance. This test requires the RF si

33、gnal generator and vector impedance meter listed in Table 1-2. (1) Connect the RF signal generator output to the RF input of the vector impedance meter. (2) Connect the vector impedance meter probe to Jl connector on Receiver rear Racal RA6790/GM Alignment & Tuning Manual Page 19 of 20 panel. (3) Tu

34、ne the Receiver to 5.0 MHz. Adjust RF signal generator to 5.0 MHz with a +3 dBm output level. (4) Set vector impedance meter frequency range to 4.5-14 MHz and magnitude range to 100. (5) Note reading on vector impedance meter. Reading shall be between 45 and 55 ohms and in phase (0 degrees). (6) Rep

35、eat steps 3, 4 and 5 for both 15 and 25 MHz. (7) Vector impedance meter shall be between 45 and 55 ohms and in phase at both 15 and 25 MHz. n. Phase Jitter. This test requires the RF signal generator, signal filter assembly and spectrum analyzer listed in Table 1-2. (1) Connect the RF signal generat

36、or output to the input of the signal filter assembly. Connect the output of the signal filter assembly to Jl on Receiver rear panel. (2) Connect spectrum analyzer with 600 ohm load to J2 on Receiver rear panel. (3) Tune the Receiver to 1.400000 MHz, select 6.8 kHz bandwidth, manual AGC, CW mode and

37、tune BFO to +8.00 kHz. (4) Adjust the RF signal generator for 1.400000 MHz at -40 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) Adjust the sp

38、ectrum analyzer for a symmetrical response about the center frequency and adjust the Receiver IF gain control for peak response at 0 dB. (7) Observe trace and note noise levels are down at least 21 dB at +100 Hz and at least 27 dB down at +200 Hz. (8) Set the spectrum analyzer sweepwidth to 1 kHz/di

39、v and bandwidth to 30 Hz. (9) Adjust the spectrum analyzer for a symmetrical response about the center frequency and adjust the Receiver IF gain control for peak response at 0 dB. (10) Observe trace and note noise levels are down at least 42 dB at jl kHz and 51 dB down at 2 kHz. o. Filter Delay Char

40、acteristics. This test requires the 50 ohm adapter and network analyzer listed in Table 1-2. (1) Connect the network analyzer channel B output to connector A4J1 on circuit card A4 with the cable to circuit card A3 disconnected. (2) Connect the input of Channel B of the network analyzer to J2 on Rece

41、iver rear panel through the 50 ohm adapter. (3) Be sure filters are installed in the filter slot as shown in Table 3-3. Racal RA6790/GM Alignment & Tuning Manual Page 20 of 20 (4) On the Receiver select LSB and manual AGC. TABLE 3-3. SPECIAL FILTERS DELAY TEST PARAMETERS FILTER NUMBER FILTER SLOT RE

42、FERENCE FREQUENCY START FREQUENCY STOP FREQUENCY DELAY MICROSECONDS 4 FL1 455825 455600 457850 1000 5 FL2 454175 454400 452150 1000 6 FL3 455000 454800 455200 2000 7 FL4 455000 454400 455600 900 8 FL5 455000 453450 456550 1250 9 FL6 455000 451600 458400 1000 10 FL7 455000 447000 463000 1000 (5) Set

43、the automatic synthesizer (part of network analyzer) as follows: Frequency 455825 Hz Frequency Step 5 Hz Steps 10 Time/Step 100 millisecs Amplitude -10 dBm (6) Set the network analyzer controls as follows: Amplitude Function B-A Max Reference Voltage 0 dB Bandwidth 100 Hz Phase Reference A Delay Mod

44、e CW Frequency Step 50 Hz Delay Function Absolute (7) Adjust the Receiver manual IF gain control for a 0 dB reading on the network analyzer. (8) Measure delay at 455825 Hz by pressing START CONT pushbutton on the automatic synthesizer. (9) On the automatic synthesizer, switch delay function to relat

45、ive and enter the OFFSET by pressing the appropriate pushbutton. Stop the sweep. The required reference has now been established at +825 Hz. (10) Set the network analyzer and automatic synthesizer controls to measure the differential delay over the frequency range of 455600 to 457850 Hz in the CW or sweep mode as convenient. Compare the delay reading with the requirement set forth in Table 3-3. (11) Repeat steps 4 through 10 for filter numbers 4 through 10. Always select the filter to be tested and use the start and stop frequency shown in Table 3-3.