FM30 SeriesTechnicalManualPage 10
Connect the FM30 tothe mainsorDC supplyand wait forthe PLL toLOCK(the
front panelLEDindicateslock when green). Using the rearpanelpoweradjust
control(PWR. ADJ.)set the powertothat required.
6.3FORWARD POWERALARM
Thissetting definesthe point at whichthe front panelP. FWD. light changestored
and alsothe point at whichaforwardpowerfault isindicated at the Control/Monitor
socket (fortelemetryand/oroperation of an automaticchange oversystem). Adjust
the output powertothe fault levelrequired. Thismust always be less than the
normaloutput powerlevelbyenough toprevent spurioustriggering, 1dBisan
appropriatemargin(80%of the correct full power). Adjust the PFWDOK(RV4)
controlon the FMTXDISboardsuchthat the front panelP. FWD. light just turnsred
fromgreen. Finallyset the output powerback tothe normaloutput level.
6.4MODULATORINPUTLEVEL
ForFM30/Mand FM30/Ssee the adjustment section of thismanualcovering LimX.
The FM30 isnormallysupplied withthe modulatorinput levelset sothat an input
levelof +8dBuoverthe range 5Hzto100kHz(without pre-emphasis)givesa
deviation of 75kHz. If adifferent levelisrequired then it will be necessarytoreset
the ‘MODLEVEL’control(VR2)on the PLL7 modulatorboard. Toset it properlya
deviation meterwill be required. Thisshouldbe connected tothe front panelO/P
monitorsocket. If adeviation meterisnot availablethen the front panelmeter
shouldbe used, though thiswill not be asaccurate. Applya400Hzsine waveat
the levelrequired formaximumdeviation (normally75kHz). Adjust VR2controlto
givethe required deviation. The front panelmeteriscalibrated at the factoryat the
centreof the operating frequency band. Therewill be averysmall calibration error
at eitherend of the band.
6.5VSWRCUT-BACK LEVEL
Thisisthe minimumRFoutput powerthat the FM30 will provide withabadly
matched load suchasadefectiveaerial. It shouldneverbe set above7.5Wto
protect the poweramplifierunit. Assupplied it will be set to4.5W. Toset adifferent
value turnthe FM30 output powerdowntominimum, connect apowermetertothe
output and disconnect the dummyload oraerial. RemovejumperLK1on the
FMTXDISPCB. Turnthe output powerup until the desired reflected powercut-back
levelisobtained. ReplaceLK1and adjust the CUTBACKcontrol(RV2)suchthat
the front panelP. REFLEDjust changesfromREDtoGREEN. Turnthe output
powerup tofull and if necessaryslightlyadjust the CUTBACKcontroltoreducethe
cut-back leveltothe value required. Finallyreset the forwardpowertothe required
level.
