User's Manual

8 3 6 A 2 k W UHF Tr a nslat or , I nt erna lly Diple x ed Det ailed Alignm e n t Pr oce dur e
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the Pow er Adj ust Gain Pot , locat ed on the Front Panel of the UHF Excit er Tray, t o obtain + 0.8 VDC
on the Front Panel Meter in the ALC Posit ion. On t he ALC Board ( 1265- 1305) , m ove t he Jum per
W3 on J6 t o the Manual Posit ion, between Pins 2 & 3, and adj ust R87 on the ALC Board for + 0.8
VDC on the Front Panel Met er in t he ALC Posit ion. Move t he Jum per W3 back t o Aut o, between
Pins 1 & 2, which is t he norm al operat ing posit ion. The det ected I F signal level at J19- 2 of the
ALC Board is connected t o t he Transm it t er Cont rol Board that dist ributes t he level to the Four UHF
Am plifier Trays where it is used as a reference for t he aut om at ic gain cont rol ( AGC) in each
Am plifier Tray.
( A6 , A7 , A8 & A9 ) UH F Am plifier Tr ays ( 1 2 9 4 - 1 1 1 2 Low Ba n d, 1 2 9 4 - 1 1 1 3 M id Ba nd, or
1 2 9 4 - 1 1 1 4 H igh Band)
Check t hat the out put power of the Translat or is 100 % , if it is not , adj ust the Power screw driver
Adj ust Pot locat ed on the front panel of the UHF Excit er Tray as needed t o achieve 100% .
When test ing one of the UHF Am plifier Trays t he ot her circuit breakers, locat ed on t he AC
Dist ribution Panel, should be t urned Off. The Am plifier 1 Circuit Breaker applies pow er t o the Top
left UHF Am plifier Tray, the Am plifier 2 Circuit Breaker applies power to t he bot t om left UHF
Am plifier Tray, t he Am plifier 3 Circuit Breaker applies power t o the bot t om left UHF Am plifier Tray
and the Am plifier 4 Circuit Breaker applies pow er t o t he bott om right UHF Am plifier Tray. The UHF
Am plifier Trays should be t urned on into a dum m y load of at least 600 Wat t s t o verify t hat t he
Tray is funct ioning. Preset t he AGC Swit ch on (A8) t he Am plifier Cont rol Board (1265-1414) t o t he
AGC On posit ion. The four UHF Am plifier Trays are set up in pairs, t he t op two A6 wit h A7 and t he
bot t om two A8 wit h A9. Swit ch On t he Am plifier 1 Circuit Breaker, locat ed on the AC Dist ribut ion
Panel. Swit ch t o Operat e the Translator Operat e/ St andby Switch, locat ed on the UHF Excit er, and
observe t he power supply m et ering posit ion on t he UHF Am plifier Tray. I t should read + 26.5 VDC
when t he Tray is swit ch On and the Translat or is in Operat e.
Switch t he Tray t o the % Out put Power Met er Posit ion and adj ust t he front panel Gain pot located
on that Am plifier Tray t o 100% on the Met er, then back off the Gain Pot to the reading as writt en
on the Test Dat a Sheet for your Translator. Repeat for t he Am plifier 2 Tray of the pair. Swit ch
the Translator to Standby and reconnect t he UHF Am plifier Trays t o t he ( A10) UHF Tee Assem bly.
Repeat the above procedure for Am plifier 3 and Am plifier 4. After t he setup of all four Am plifier
Trays, swit ch the Translat or to Operate and adj ust t he Phase Cont rols on each of the Am plifier
Trays to give m axim um Output Power on the Front Panel of the UHF Excit er. The Output Power
reading on the front panel of t he UHF Excit er should be 100% , if it is not , adj ust t he Power
screwdriver Adj ust Pot locat ed on the front panel of the UHF Excit er Tray as needed to achieve
the 100% Out put.
Switch t he I nput Test source t o select a NTSC 3.58 MHz Modulat ed St aircase or Ram p Test
waveform and set up the st at ion dem odulator and m onit oring equipm ent t o m onit or t he differential
gain and different ial phase of t he RF Out put signal.
I f a synchronous dem odulator having a quadrat ure video out put is available, it can be used wit h an
X- Y Oscilloscope to display incident al carrier phase m odulat ion (I CPM) . As shipped, the Excit er
was preset t o include linearit y ( gain vs. level) and incident al phase ( carrier phase vs. level)
predist ortion. The predistortion was adj ust ed t o approxim at ely com pensat e t he corresponding
non- linear dist ort ions of t he Am plifier which is driven to place t he Sync Level near sat urat ion.
Move the Jum per W1 on J4 on the ALC Board t o t he Enable Posit ion. Refer t o the Test Dat a Sheet
for your Translat or for t he final test readings on each Am plifier Tray. Adj ust t he Phase Pot locat ed
on each UHF Am plifier Tray t o obt ain m axim um % Visual Out put Power. Adj ust each of the Gain
Pots, on the UHF Am plifier Trays, equally, as needed to obt ain 100% Visual Out put Power on t he
Front Panel Met er of the UHF Excit er.