37CUST.CAL CUSTOMER CALIBRATION CHECKS FOR THE PSA-37D ( F type ) AVCOM SPECTRUM ANALYZER edited 10-2-01 SRK This unit is a "12 volt" version of the PSA-37D. EQUIPMENT NEEDED... A tuneable RF Calibrated Signal Source with a 60dB by 10dB step attenuator. Adjustable 50 watt, 12V DC power supply, Ext. DC plug, (mate for DC jack). Note: View is from the front panel. Chassis is Ground Reference. PRELIMINARY SETTINGS and OBSERVATIONS..... STBY LED should be lit whenever unit is plugged in and in the OFF position. Verify the 2dB/10dB toggle SWITCH is in the 10dB/Division position. Turn the BAND SELECT MHz switch ( BAND ) to the 0-500MHz Band. Turn SPAN full clock-wise. INTENSITY postioned 12 o'clock. REF LEVEL to 0 dBm position. SWEEP RATE at pointer position, of 1 o'Clock. > LINE OPERATION... Toggle POWER SWITCH to the LINE position. Baseline trace should become visable on the CRT screen. Turn VERTICAL CONTROL to move the baseline around the -65dBm tic-marks. Turn the CENTER FREQUENCY TUNING CONTROL ( TUNING ), to position the ZERO SPIKE into the viewable area. Verify normal operation of the SWEEP RATE CONTROL ( SWEEP ). Fast sweep rate in clock-wise position and visa versa. About 30 Hz rate max. Verify normal operation of switches & LEDs, and of BATT CHG. > BATTERY CHARGING..... Turn unit OFF, POWER switch to STBY. Check Battery Charging circuit, at EXT input. DO NOT SHORT!!! Typically, when BATT CHG switch is turned on, charge LED comes ON. An increasing voltage should be seen, nominally 12 to 14 volts. Verify normal operation of BATT CHG switch, voltage appearing at jack. Internal Battery is a diode drop away from this point, rechargeable from EXT jack, while in the EXT position. Rising voltage rate matches internal battery condition. Characteristic charge; trickle current ramps voltage up to 10 volts, then (1/2 A) high current flows, until 15.7V equalize voltage is reached, then current stops until voltage drops to 13.6V final float level. The maximum charging current is limited to about 1/2 an Amp. NOTE - charge voltage at EXT DC input jack is disconnected when in INT. Recharge from LINE in EXT or INT position but INTernal is best. > Check INT/EXT Power source input & POWER SWITCH... Select EXTernal DC Power input with rear panel INT\EXT switch. Apply external variable DC power via EXT. DC jack (center pin positive). External variable voltage set at 12.0 VDC nominal. Toggle POWER SWITCH to the BATT position. Maximum allowable dropout voltage is 11.70 volts at the EXT DC input. DC Fuse should be AGC-4, 4 Amp or equivalent. Operation should be the same in BATT position as it was for LINE operation. Toggle unit back into STBY mode, DID UNIT GO OFF?, turn off EXT DC source. (Unit should have gone off when put into STBY ) Disconnect EXTernal supply. > INTERNAL BATTERY LOAD TEST..... Switch INT/EXT, to the INTernal position. (best position for charging) Toggle POWER SWITCH to the BATT position. Operation should be the same in BATT position as it was for LINE operation. > Check BATT MONitor BUTTON... press when unit is ON in BATT or LINE. Reading = 12.0 volts nominal. (momentary readout, seen on the LCD display) Turn-off point = 11.7 volts during BATT operation. Loss of regulation point. Reading may be > 14 volts when charger is on. > Check INTENSITY CONTROL, clock-wise rotation increases intensity, visa-versa > Check HORIZONTAL ( 13 division ) OVERSWEEP... Turn TUNING to set ZERO SPIKE, 6 & 1\2 divisions from both ends of trace. (Use HORIZ to move alternate trace ends into view.) Next turn HORIZ (not TUNING) to move ZERO SPIKE to center of graticule. > CENTER OF EXPANSION ..... Slowly turn the SPAN counter clock-wise, while adjusting the CF TUNE to keep the ZERO SPIKE on the CRT screen. SWEEP RATE at pointer position, of 1 o'Clock. Note the LCD reading is = to, or near 0 MHz! ( The ZERO SPIKE should be fine tuned for maximum ZERO SPAN amplitude.) Turn SPAN to full clock-wise position. LCD reading should be the same. Adjust HORIZ Pot, to move the ZERO SPIKE to the center of the graticule. > CHECK VARIABLE SPAN..... Center frequency reading shouldn't change much from full span to zero span. Note; Sweep Rate affects this reading, keep below marked point, best results. > Checking HORIZONTAL CALIBRATION of GRATICULE..... Turn BAND to the 3.7 to 4.2 GHz band. CF TUNE to about 3970 MHz. Turn SPAN to the CAL position. (Full span is clock-wise, CAL position.) Connect the RF source to the RF INPUT, and check for a > 500 MHz span. Check that a 3.7 and a 4.2 GHz signal are 8 divisions apart. Slight readjustment of TUNING may be needed, typically 3970 MHz CF or so. > DOWN CONVERTER FREQUENCY & TUNING END POINTS..... The end tuning values should be about 40MHz above 4200 or 4240MHz, and 40MHz below 3700, or 3660MHz, at the extreams of the TUNING range. Frequency readings of either 3.7 or 4.2 GHz at zero span or full span should be accurate and preceise, with SWEEP RATE, at nominal setting. > CHECKING UPCONVERTER ALIGNMENT.....( check all hardware for tightness.) Turn TUNING so the 3.7-4.2 GHz signals are centered on the graticule. ie; the 500 MHz full span is +\- four divisions from center line. NOTE: The ZERO CAL, a recessed pot just below BAND SELECT MHz switch will simultanously adjust the tuning of all bands, except the 3.7 to 4.2 GHz band. The lower bands are upconverted to allign with the 3.7 to 4.2 GHz. Turn BAND to the 1250-1750 MHz band, and inject a 1250 MHz signal. 1250 MHz should align with a 3.7 GHz spike. ( First division of graticule ) Turn to 950-1450 band, inject 950 MHz... 950 MHz should align with a 3.7 GHz spike. ( First division of graticule ) Turn to 500-1000 band, inject 500 MHz... 500 MHz should align with a 3.7 GHz spike. ( First division of graticule ) Turn to the 0-500 band, inject 500 MHz... 0 MHz should align with a 3.7 GHz spike. ( First division of graticule ) 500 MHz should align with a 4.2 GHz spike. ( next to last division ) > LNA POWER CIRCUIT CHECK..... Plug in a 18volt lamp load into the "BNC" connector. Set your DVM to the 20 volt scale and measure at the center pin of the "N". CAUTION... Do not allow meter lead to short circuit to the connector barrel. Throw LNA POWER SWITCH to the 12volt position, DVM reading is 12volts nominal. Toggle LNA SWITCH to the 18volt position, DVM = 18volts nominal. Observe the 18 volt load lamp and the LNA LED are operating as expected. Look for anything unusal in the CRT sweep display. Check for excessive voltage drop thru upconverter, while loaded, typically = 0.06 V drop. The "N" splitter/combiner, has virtually no loaded voltage drop. > CHECKING AMPLITUDES..... Turn REFERENCE LEVEL SWITCH (REF LEVEL) to 0dBm. Fairly slow SWEEP RATE. Apply a 98 MHz test signal generator, that has a 10dB/step attenuator. Turn SPAN to the CAL position. (Full span is clock-wise, CAL position.) Turn the TUNING to center the 98MHz signal, turn the SPAN toward ZERO. ( Use a SPAN about 1 MHz / division, near zero span.) Adjust VERTICAL CONTROL to set signal peak on a Graticule Line. Switch 98MHz signal attenuator one position at a time, ( a 10dB step). Verify GAIN is 10dB per vertical division, one division per attenuator step. With the VERT near 12 O'Clock and baseline between the -65 dBm tic-marks... Verify absolute amplitudes (read at peak not height) for each REFERENCE LEVEL. A -40dBm input signal = a -40dBm signal read on screen graticule. Check REFERENCE LEVEL SWITCH, verify 2 division changes between each LEVEL. NOTE: maximum sensitivity is at -40 dBm REF LEVEL, baseline typically jumps up one division, to about the -50 dBm line, that is -90 dBm. Also note that VERT position is critical for proper amplitude readings, and only set in the 0 REF LEVEL position. > FLATNESS SWEEP... Turn SPAN to full CW (CAL) POSITION. (Typical CRT display shows ZERO SPIKE about 1 and 1/2 Div. left of center.) With VERT POSITION at 12 o'clock, baseline should be between the tic-marks. Sweep entire RF range for flatness. Slow SWEEP, and TUNING near 270MHz, use the sweep generator, 1 MHz steps, from 1 to 1750 MHz. All aligned? Each BAND should start and stop in the same places on the CRT screen. Vary input RF Signal Source from 0 to 500MHz, at some viewable amplitude. (Allow for Sweep and Deflection losses.)(Relitive change +or- 2dB overall.) (If questionable then check signal amplitude with TUNING and SPAN.) Stop tuning input RF generator at 500Mhz, should be at last graticule div. Switch BAND SELECT up one, signal should now be at the first graticule div. Continue tuning input RF generator, observe flatness across band. Stop at 1000MHz, signal should be at last division (not the screen edge). BAND SELECT up one, signal should be about 1 and 3/4's in from left. (950=1st div) Again sweep band for flatness and absolute amplitude. Retune RF generator to 1250MHz, signal should be just right of center screen. BAND SELECT up one, signal should be at the first graticule division. Sweep for flatness and amplitude across this band also. (1250-1750 MHz) The 1250 band is typically a little lower than the others. Turn BAND SELECT again, to 3700-4200 band. Input a 3.7 to 4.2 GHz signal sweep into the "N" connector input. Amplitudes should agree with RF generator's output meter. Check for unusual amplitude differences between the upconverter and higher frequency, combiner inputs! Be aware of losses thru setup cables. All signals displayed have an image about 12 & 52 MHz below themselves, that should be at least -20dB down. > CHECK VERTICAL CONTROL KNOB... Without any signal displayed on screen, adjust VERT OFFSET, ( at 0dB REF). Adjust VERTICAL CONTROL to move baseline to the -65dBm region, between the tic-marks, typically at 12 o'clock, if not...loosen set screw... Adjust (VERT) VERT. CONTROL KNOB's error, to obtain the 12 O'Clock position, while the baseline is between the tic-marks. Tighten the set screw ! > 2 dB/DIVISION SWITCH..... Test signal at -60 dBm, the VERT turned clock-wise, to move signal into view, baseline must be viewable with VERT CONTROL. Verify a 5 division change, for every 10dB signal step at RF INPUT. SPAN set to keep signal skirts at outside edges of graticule down 5 div. Adjust VERT CONTROL to keep signals in the viewable area. Check other input levels and relative ( 2dB per div.) 5 division, 10dB steps. Note: there is some compression that occurs near baseline and at 0 dBm in. Return 2dB/10dB SWITCH to the 10dB / Division, position. > ADA-10A OUTPUT CONNECTOR TEST... With scope, check for; ground, 11.0 volts, blanking pulses, and vertical sig. Verify blanking period = 6mS, MAX rate about 35mS, variable with SWEEP RATE. Vertical signal output equals about 1 volt / division on screen. Also baseline noise equals 1 volt dc, at 0 dB REF without any signal present. COMPLEATION..... Check all hardware for tightness.