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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Power posit ion. At this 20% Reference Power reading, t he VSWR LED m ounted on the front panel
of the Excit er should be illum inat ed. I f not adjust R22 on t he Transm it t er Cont rol Board unt il t he
VSWR LED j ust turns On. Turn t he Power Adjust pot slightly CCW and t he LED should go out , turn
the pot CW until the LED j ust turns On. The Reflected Out put Power is now calibrat ed. Swit ch
the Translator to Standby. Re- t erm inate t he Translat or. Swit ch t he Translator to Operat e and
adj ust the front panel power pot for 100% Visual Power reading.
I F Phase Correct or Adj u st m ent
As shipped, t he Excit er was preset to include linearit y ( gain vs. level) and phase ( 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 Trays and should need no additional adj ust m ent.
Locat e ( A9) the I F Phase Correct or Board ( 1227- 1250) m ount ed in the UHF Excit er. The Am plit ude
Correct ion portion of the Board is not utilized in t his configurat ion, therefore t he Jum per W3 on J10
should be in t he Disable Posit ion, t o + 6.8 VDC, and R35 & R31 should be full CCW. R68 is t he
Range Adj ust m ent and should be set in the Middle. The Phase Correct ion Enable/ Disable Jum per
W2 on J9 should be in t he Enable Posit ion, t o Ground. Swit ch t he I nput Video Test source t o
select a NTSC 3.58 MHz Modulat ed Staircase or Ram p Test waveform and set up t he st at ion
dem odulat or and m onitoring equipm ent t o m onit or t he Different ial Phase or I nterm od Product s of
the RF Out put signal. There are t hree corrector st ages, locat ed on the I F Phase Correct or Board,
each wit h a Magnitude and a Threshold Adj ust m ent which are adj ust ed as needed t o correct for
any Different ial Phase or I nterm od problem s. Adj ust R3 Threshold, for t he cut in point of the
correct ion and R7 Magnit ude, for t he am ount of the correct ion as needed.
The jum per W1 on J8 is set t o give t he desired polarit y of the correct ion shaped by t he Threshold
R11 and Magnit ude R15 adj ust m ents. Aft er sett ing the polarit y, adj ust R11 Threshold, for the cut
in point of t he correct ion and R15 Magnit ude, for the am ount of the correct ion as needed. Finally,
adj ust R19 Threshold, for the cut in point of the correct ion and R23 Magnit ude, for the am ount of
the correct ion as needed. Not e : Adj ust ing these pot s changes all Visual param et ers and should be
used cautiously.
( A1 0 & A1 1 ) UHF H igh Pow er Tees
The inputs to the ( A10) UHF Tee are t he out puts of t he ( A6 & A7) UHF Am plifier Trays and the
inputs t o t he (A11) UHF Tee are t he outputs of the (A8 & A9) UHF Am plifier Trays. The inputs to
the UHF Tees are 50 ohm im pedances t o m at ch t he out put im pedance of t he UHF Am plifier Trays.
The two inputs t o each of the UHF Tees are com bined and then sent t hrough a piece of
transm ission line 1/ 4 of a wavelength long to transform t he out put im pedance of the Tees to 50
ohm s. The out put s of the ( A10 & A11) UHF Tee are t hen sent t o ( A12) a Hybrid Com biner which
com bines t he t wo inputs. The out put of t he Hybrid is connect ed to (A13) a Bandpass Filt er.
The Ba n dpass Filt er a n d ( Opt ional) Tra p Filt er a r e fact ory sw ept a nd sh ould not be t u ne d
w it hou t t he proper equipm e n t . D o not at t e m pt t o t une t he filt e r s w it hout a sw e ep
ge nera t or and preferably a net w ork ana lyzer. I f you t hink t uning is n e e ded consu lt Axce r a
Field Suppor t D epart m ent before be ginning.
( A1 3 ) Ba ndpass Filt e r
The input t o this filt er is out put of the Hybrid Com biner t hat is t he com bined output of the UHF
Am plifier Trays. The filter is m ade of alum inum waveguide and has five resonant cavit ies. The
filt er has five bolt s for t uning adj ust m ents, t hree locat ed in the m iddle on left and t wo on the right,
and four or six rods, depending upon the channel, for coupling adjust m ent s bet ween the sect ions,
located on t he front of t he Bandpass Filt er. The Bandpass Filt er also ut ilizes t wo int egral t raps at