SECTION SIX
TUNING PROCEEDURE
HIGH LEVEL AM MODE
PRESET THE FOLLOWING CONTROLS
MODULATOR DECK
1 BIAS ADJUST FULLY COUNTER-CLOCKWISE
2 FILAMENT OFF
6 PLATE OFF
8 BIAS ADJUST FULLY COUNTER-CLOCKWISE
9 CW/PHONE PLACE TO PHONE POSITION
CONTROL PANEL
16 RF GRID BIAS FULLY COUNTER-CLOCKWISE
17 KEYING PTT
18 SCREEN BIAS HIGH
19 4-1000A FIL. OFF
MAIN POWER PANEL
37 PLATE VOLTAGE ADJUST-FULLY COUNTER-CLOCKWISE
38 CB2 (MODULATOR)-OFF
39 CB1 (MAIN POWER)-OFF
4-1000A RF DECK
27 SSB/AM AM
31 MOD MON FULLY COUNTER-CLOCKWISE
AFTER THE ABOVE PROCEEDURE HAS BEEN COMPLETED, REFER TO THE BAND TUNING CHART
FOR THE FOLLOWING:
28 INPUT BAND SLECECTOR SWITCH: PLACE ON DESIRED BAND
29 OUTPUT BAND SELECTOR SWITCH (L3): PLACE ON DESIRED BAND
26 OUTPUT –L SELECTOR SWITCH (L1b): PLACE ON 160M ONLY IF (L3) IS ALSO ON 160M
ALL OTHER BANDS PLACE (L1b) ON 80/20M
22 PLATE TUNE: REFER TO TUNING CHART
23 LOAD TUNE: REFER TO TUNING CHART
24 INDUCTANCE TUNE: REFER TO TUNING CHART
NOTE* The tuning chart settings were set for a plate load resistance of 3300 ohms and an output load resistance of 50 ohms. The actual operating plate load may vary quite a bit depending on Variac setting (Plate Voltage Adjust) and plate current. Plate load resistance of 8000 ohms may not be uncommon. Using this chart will bring you into the “ballpark”, so to speak. So use the chart as a preliminary set point and “fine tune” from there.
ONCE THE ABOVE STEPS ARE COMPLETE, YOU WILL BE READY TO
ENERGIZE THE TRANSMITTER
ENERGIZING THE TRANSMITTER
BEFOR YOU CONTINUE, IT IS ASSUMED THAT YOU HAVE A SUITABLE LOAD OR DUMMY LOAD CONNECTED TO THE TRANSMITTER’S ANTENNA CONNECTOR, A PTT SWITCH IS CONNECTED TO THE PTT KEY JACK <49> AND A SUITABLE EXCITER TUNED TO THE CORRECT OPERATING FREQUENCY IS CONNECTED TO EITHER THE “TRANSMITTER IN” OR “EXCITER IN” JACKS. IT IS ALSO ASSUMED THAT THE EXCITER WILL BE KEYED BY THE “KEY EXCITER” <51> OUTPUT JACK. A LOW-Z MICROPHONE SHOULD BE PLUGGED INTO THE MIC-IN XLR PLUG LOCATED ON THE BACK OF THE MODULATION DECK AND THE MIC/LINE SWITCH PLACED IN THE MIC POSITION.
STEP 1 ENERGIZE THE MAIN POWER CIRCUIT BREAKER <39>(CB1) LOCATED ON THE LOWER RIGHT HAND SIDE OF THE TRANSMITTER POWER PANEL. YOU SHOULD HEAR THE RF DECK BLOWER TURN ON AND THE GREEN INDICATOR LAMP <36>SHOULD BE LIT.
STEP 2 ENERGIZE THE MODULATOR POWER CIRCUIT BREAKER <38>(CB1) LOCATED ON THE LOWER RIGHT HAND SIDE OF THE TRANSMITTER POWER PANEL. THE BLUE INDICATOR LAMP <34> SHOULD BE LIT.
STEP 3 PLACE THE 4-1000A FILAMENT SWITCH <19> FROM “OFF” TO “ON”. THE 4-1000A SHOULD LIGHT.
STEP 4 PLACE THE MODULATOR FILAMENT SWITCH <2> FROM “OFF” TO “ON”. THE 304TL’s SHOULD LIGHT. AFTER A SHORT TIME DELAY, THE “READY” INDICATOR <3> SHOULD LIGHT.
STEP 5 ENERGIZE THE RF DECK PLATE BY PUSHING THE “PLATE-ON” <20> BUTTON ON THE CONTROL PANEL. THE ORANGE “PLATE VOLTAGE” LAMP <35> SHOULD LIGHT AND VOLTAGE SHOULD BE INDICATED ON THE “PLATE VOLTAGE” <13> METER. THE VOLTAGE SHOULD BE AROUND 2400 VOLTS.
STEP 6 INCREASE THE PLATE VOLTAGE VARIAC <37> TO THE DESIRED PLATE VOLTAGE.
STEP 7 PLACE “PLATE” SWITCH <6> ON MODULATOR TO “ON”. “PLATE ON” LAMP <5> SHOULD LIGHT.
STEP 8 PRESS THE “PUSH-BIAS ADJUST” <4> AND SLOWLY TURN THE “BIAS ADJUST” KNOB <1> IN THE CLOCKWISE DIRECTION AND ADJUST BIAS UNTIL A READING OF ABOUT 140mA IS INDICATED ON MODULATION PLATE CURRENT METER <7>, THEN RELIESE THE “PUSH-BIAS ADJUST” BUTTON.
STEP 9 TURN THE EXCITER OUTPUT POWER TO A VERY LOW LEVEL AND PRESS THE PTT KEY. WARNING: THE TRANSMITTER IS NOW KEYED UP!
STEP 10 SLOWLY ROCK THE “INPUT TUNING” KNOB <29> BACK AND FOURTH UNTIL SOME PLATE CURRENT IS SEEN ON THE PLATE CURRENT METER <12>. ADJUST FOR PEAK READING. INPUT TUNING IS NOW COMPLETE.
STEP 11 FINE TUNE ADJUST THE “PLATE TUNE” <22>, “INDUCTANCE” <24>, AND THE “LOAD TUNE” <23> CONTROLS FOR A DIP IN PLATE CURRENT AND MAXIMUM OUTPUT POWER, AS YOU WOULD WITH ANY OTHER RF POWER AMPLIFIER.
STEP 12 NEXT GRADUALY INCREASE THE EXCITER OUTPUT DRIVE UNTIL THE GRID CURRENT METER <10> READS ABOUT 25mA. *CAUTION* DO NOT EXCEED 30mA OF GRID CURRENT! DAMAGE TO THE 4-1000A COULD OCCUR. SCREEN CURRENT SHOULD BE ABOUT 100mA. RE-TUNE OR “FINE TUNE” THE TRANSMITTER PLATE, INDUCTANCE AND LOAD CONTROLS AS NEEDED.
STEP 13 SPEAK INTO THE MICROPHONE AT A NORMAL LEVEL AND ADJUST THE “AUDIO GAIN” <8> CONTROL TO ACHIEVE 100% MODULATION ON YOUR MODULATION MONITOR OR SCOPE ON PEAKS. *WARNING* DO NOT EXCEED 310mA ON THE MODULATION CURRENT METER OR SERIOUS DISTORTION, FLAT-TOPPING AND ARCING WILL OCCUR! IF ARCING OCCURS WELL BELOW 100% MODULATION, RF AMPLIFIER TO MODULATOR IMPEDANCE MISMATCH IS PROBABLY OCCURRING. RAISING THE RF PLATE VOLTAGE, WHICH ALSO INCREASES THE OUTPUT POWER MAY HELP, BUT BE AWARE THAT YOU WILL NEED TO TOUCH UP THE TUNING. IF ARCING DURING MODULATION STILL OCURRS, CHECK TO SEE IF THE SSB/AM SELECTOR SWITCH WAS INADVERTENTLY LEFT IN THE SSB POSITION.
OPERATING THE GLOBEMASTER IN LOW LEVEL AM MODE
(USING THE GLOBEMASTER’S RF DECK AS A STAND-ALONE
LINEAR AMPLIFIER)
FOLLOW ALL THE ABOVE STEPS EXCEPT: (WE WILL ASSUME THE GLOBMASTER WAS JUST
OPERATED IN THE HIGH-LEVEL AM MODE FOR THE FOLLOWING STEPS)
STEP 1 TRANSMITTER IS UN-KEYED
STEP 2 ON THE CONTROL PANEL, PUSH THE “PLATE-OFF” PUSH BUTTON <21> PLATE VOLTAGE SHOULD DROP TO ZERO.
STEP 3 PLACE THE “PLATE” SWITCH <6> ON THE MODULATOR FROM “ON” TO “OFF” POSITION.
STEP 4 PLACE THE “FILAMENT” <1> SWITCH ON THE MODULATOR FROM “ON” TO “OFF” POSITION.
STEP 5 PLACE THE MODULATION POWER CIRCUIT BREAKER <38> LOCATED ON THE LOWER RIGHT SIDE OF THE TRANSMITTER FROM “ON” to “OFF”.
STEP 6 PLACE THE “CW/PHONE” SWITCH <9> FROM THE “PHONE” POSITION TO THE “CW” POSITION. THIS BYPASSES THE MODULATION TRANSFORMER.
STEP 7 ON THE RF DECK, PLACE THE “AM/SSB” SWITCH FROM THE “AM” TO THE “SSB” POSITION. THIS SHORTS OUT THE 4-1000A SCREEN CHOKE.
STEP 8 FOLLOW THE STEPS AS OUTLINED IN THE ABOVE “ENERGIZING THE TRANSMITTER” SECTION FOR TUNING UP AND OPERATING THE AMPLIFIER.
OPERATING THE GLOBEMASTER IN SSB MODE (USING THE
GLOBEMASTER’S RF DECK AS A STAND-ALONE LINEAR
AMPLIFIER)
FOLLOW ALL THE STEPS AS OUTLINED IN THE “OPERATING THE GLOBEMASTER IN THE
LOW-LEVEL AM MODE” AS OUTLINED ABOVE, INCLUDING TUNE UP AND OPERATION, AS
THERE IS NO CARRIER IN THE SSB MODE UNTIL AUDIO IS PRESENT.
STEP 1 AFTER TUNE-UP, SWITCH THE EXCITER FROM THE AM MODE TO THE SSB MODE.
STEP 2 KEY THE TRANSMITTER (PTT) AND, WITH NO MODULATION PRESENT, ADJUST THE 4-1000A’s GRID BIAS CONTROL <16> (LOCATED ON THE CONTROL PANEL) UNTIL APPROXIMATLY 100mA OF PLATE CURRENT IS INDICATED ON THE PLATE METER. THE AMPLIFIER WILL NOW PERFORM AS A CLASS AB2 LINEAR AMPLIFIER. YOU SHOULD RECEIVE EXCELLENT SIGNAL REPORTS! WATCH YOUR EXCITER DRIVE! BE CAREFULL NOT TO EXCEED THE MAXIMUM 25mA GRID and 100mA SCREEN CURRENT LEVELS ON PEAKS!
GLOBEMASTER TUNING CHART