P-20
FM Exciters - Transmitters
MidStation
EX1000 MidStation - 1200W Broadband FM Stereo Exciter/Transmitter
Start Guide for use
TransmitterControl
TheTransmitterControlsectionofthe audioandpowersupplyboardhasseveralfunctions.One oftheseis
to sense the PLLLOCK detect signal from the RF module. If this module goes out of lock, then the radiate
control logic circuit provides a signal to the power supply to turn off the +Vcontrol supply to the RF power
module, causing the transmitter to stop radiating.Also, this section detects if the VSWR level is more than
permised, so the transmitter control turn the equipment in «FOLDBACK» this reduces the DC level to the
RF power module until a level that allows the equipment doesn’t stop to work. All of these parameters can
beviewthroughtheLCDDisplayonthefrontpanel.
MeteringandStatus
TheMeteringandStatuscircuitryontheAudio,PowerSupply,TemperatureandRFsectionsconditionsthe
various system parameter samples for accurate meter indications, and drives the status LEDs on the front
panel.
ServicePowerSupply(AC)
ThetoroidaltransformerconvertstheACvoltage(220Vstandardor110Vspecialversion)intotwoidentical
voltages of 22V, one of these will be regulated by a switching regulator (Buck) to supply the 4 Fans of the
equipment. The other one will supply all serviceable voltages, that are: +12V, -12V and +14V. All of these
are also regulated by switching regulators assuring great efficiency and consequential low internal
temperatures.
In the main PC board of the EX1000 MidStation, there are others DC regulators that supplies the voltages
requiredforitsoperation.Theoutputsare:+5V(mainprocessoranddisplays)+8VfortheVCO,PLLandRF
driverstransistors.
ZVSSMPSsystem
To supply the RF output stage and adjust its level, a ZVS Switched Mode Power Supply was developed.
TheACvoltagefrom220VisconvertedtoDCthroughadiodebridgeandfilteredbyacapacitorbank.Then,
the DC voltage is switched by ZVS mode and according the RF level set by the user this voltage can vary
from5Vto48V supplyingtheBLF578RFtransistors.Thisway,iftheuserneedstoadjusttheRFlevel,heis
adjusting the DC level at the LDMOS (all RF levels between 10 and 1000W may be adjusted, like for
example550W).
CARDS: ONLY THE FULL-VERSION COMES WITH THE CARDS INSTALLED FROM FACTORY, IF
THE USER HAS OPTED TO BUY THE EQUIPMENT AT ITS BASIC VERSION AND DECIDES TO BUY
THE CARDS LATER, THE INSTALLATION IS EXTREMELLY EASY (SEE DETAILS ON THE NEXT
PAGES)
AudioProcessorCard
The user can obtain cards for simple connection to the EX1000, the first card is an audio processor dual-
band, that processes independently low and high frequencies, always maintaining high the dynamics of
transmission. This processor can be enabled or disabled at the front panel.The audio processed is limited
anditwillnotproduceover-modulationinthetransmitter,inadditionthesoundqualitywillbeexceptional.
StereoGeneratorCard
TheStereoGeneratorCardconsistsinanAMDSB/SCstereogeneratorofexcellentaudioseparation.Also,
theuser canchooseifthetransmittionwillbeinstereoormono.Theparametersofthiscardcan beviewon
theLCDoftheequipment.
Digital15kHzLow-passFilter
The digital 15kHz filter card is suitable for who needs to transmit programming that the audio frequency
doesn’t pass of 15kHz. Is most important to place this card when is installed the stereo generator card,
becausethehighfrequenciesisnotimportanttotransmitinthiscase.
MidStation Series - EX1000
SRFMIDST-011208 REV.A
EX1000 MidStation - 1000W Broadband FM Stereo Exciter/Transmitter
