User's Manual

1 1 7 B 2 0 W a t t VHF High Band Transla t or Upconve rt er/ Am plifie r Tray
Circuit Descript ion
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The RF Signal is bandpass filt ered for the desired VHF Channel frequency and then am plified by U1
( - 2 dBm Visual -12 dBm Aural) before it is connect ed to t he RF Out put Jack ( J2) of the Board. The
VHF output is connect ed to J7 of (A16- A2) t he VHF Filt er/ Am plifier Board ( 1150- 1101) on which it
is filt ered again and j um pered from J6 to J1 on the board. The + 12 VDC needed for operation of
the Filt er/ Mixer Board and the Filter/ Am plifier Board are provided by ( A6) t he + 12V( 3A) / - 12V Power
Supply Board (1092-1206). The filt ered VHF is am plified to + 8 dBm and -2 dBm, R9 set s t he gain
of t he Filter/ Am plifier Board using a Pin- At t enuat or circuit , and connect ed t o J2 t he RF Out put of
the Board.
J2 is cabled t o J3 on the Mixer/ Am plifier Enclosure Assem bly. The RF is connect ed to Jack ( J1) on
( A17- A1) t he VHF High Band Driver Board (1174-1107). The Driver Board cont ains a dual t ransistor
st age Q1 that produces an output of + 26 dBm Visual + 16 dBm Aural. (A17- A1) The VHF High Band
Driver Board and ( A17- A2) t he VHF High Band Am plifier Board are m ount ed on ( A17) the Am plifier
Heatsink Assem bly (1174- 1111) . The out put of the Driver Board connects t o J1 of (A17- A2) the
VHF High Band Am plifier Board ( 1174- 1101) . The VHF High Band Am plifier Board cont ains a dual
Transist or St age that am plifies t he VHF Signal to + 44 dBm Visual and + 34 dBm Aural. R5 and R9 on
the board are Bias Adj ust m ents which set t he gain of t he Board. The VHF High Band Driver Board
and t he High Band VHF Am plifier Board receive their + 26 VDC Bias volt age from ( A3) t he + 26 VDC
Switching Power Supply. DS4 the front panel m ounted Am plifier St at us LED, t hat is m ount ed
across J3- 2 and J3- 3 of t he VHF High Band Am plifier Board, will light if the + 26 VDC is present to
the board. The + 26 VDC is connect ed to t he board through ( F1) the 8 Am p Fuse. The out put of
the VHF High Band Am plifier Board at J2 ( + 44 dBm Visual and + 34 dBm Aural) is connect ed to ( A18-
A1) a Low Pass Filter Board (1174-1102, 1174- 1103 or 1174- 1104 depending on frequency) which
cont ains a Low Pass Filter and a 2nd Harm onic Trap. The filt ered out put is cabled t o ( A18- A2 &
A3) t wo Trap Filt er Boards ( 1174- 1105 or 1174-1106 depending on frequency) each Board cont ains
two Trap Filter circuit s. The first Trap Filt er circuit , cont aining C6 and C8, is tuned t o - 4.5 MHz
while t he second Trap Filter, cont aining C2 and C4, is t uned to + 9 MHz. The out put of (A18-A3)
Trap Filter Board connect s t o Jack ( J1) of (A23) a High Band VHF Coupler Board ( 1141- 1002) . The
VHF Channel Frequency Output of t he Coupler at J2 is direct ed t o the rear of t he Tray, the RF
Out put Jack ( J4), ( + 43 dBm Visual and + 33 dBm Aural) .
A Forward Out put Power Sam ple at J3 and a Reflect ed Out put Power Sam ple at J4 are provided by
the VHF Coupler. The Forward Power Sam ple is sent t o ( A24) a Splitt er Assem bly which provides
two Forward Power Sam ple out puts that are connect ed to J1 and J2 on ( A26) t he Visual/ Aural
Met ering Board ( 1161- 1103) . The Visual + Aural Forward Sam ple at J1 enters t he board which is
tuned to provide an Aural Only Out put Sam ple at Jack J6 - Pin 1 t hat connect s t o the front panel
m et er for m onitoring. The Visual + Aural Forward Power Sam ple at J2 ent ers t he board which is
tuned to produce a Visual Only Out put Sam ple at Jack J7 - Pin 1 t hat connect s t o the front panel
m et er for m onitoring. The Reflect ed Sam ple from J4 of t he VHF Coupler connect s to J4 of the
Visual/ Aural Met ering Board and provides a Reflect ed Out put Sam ple at Jack J9 - Pin 1 t hat
connect s t o t he front panel m et er for m onitoring.
SYSTEM CONTROL AND OPERATI ON
The syst em cont rol for t he Translat or consists of (A7) the Transm it t er Control Board ( 1161-1109)
which provides cont rol of the Syst em Operat ion and the m onit oring of the St at us of the Tray and
the Syst em . The board provides or rem oves t he com m ands for operation of t he System .
Associat ed wit h the Transm it t er Control Board are front panel LEDs for m onitoring of Operat e
( DS5)/ St andby ( DS6) and Auto ( DS7)/ Manual ( DS8) St at us, Therm al I nt erlock ( DS3) , VSWR
Cutback ( DS2), I nput Signal Loss ( DS1) St atus and the Am plifier St at us (DS4) of t he High Band
VHF Am plifier Board. I f t he Reflect ed Power Level increases above t he set level of R44, t he board
will cut back t he out put Power Level. The board also cont ains (S1) a Receiver/ Modulator Switch
that m ust be swit ched t o
the proper position depending on if the Syst em is a Translat or and contains a Receiver Tray or is a
Transm it t er and cont ains a Modulat or Tray. I f the Receiver Tray is select ed, DS4 will be lit and if
the Modulat or Tray is select ed, DS5 will be lit .