Albrecht Tectalk User manual

SERVICE MANUAL
2-WAYPORTABLE
HANDHELD PMR
RADIO
TECtalk
Jan. 2000

CONTENTS
1. GENERAL
1.1General
1.2Characteristics andfeatures
2. SPECIFICATION
2.1General Specification
2.2Electrical Specification
3. OPERATION
3.1Pushbuttons
3.2ICONS onLCD
3.3Key Functions
3.4SettingandOperation
4. ADJUSTMENT
4.1Frequency synthesizer
4.2Transmitter
4.3Transmitter test
4.4Receiver
4.5Receiver test
4.6Symptoms,check point& corrections
5. DESCRIPTION OF RADIO CIRCUIT
5.1Frequency Synthesizer
5.2Receiver
5.3Transmitter
6 CHANNELDATA
1. GENERAL
1.1 GENERAL
TECtalk is aminimum sizedtwo-wayportablehandheldradio.
The frequency range is446.00625 ~ 446.09375MHz, 8 UHF operatingchannels
accordingtoEuropeanPMR 446 internationalagreementareavailable.
1.2 CHARACTERISTICS AND FEATURES
a) All activedevices inthis radioaresemiconductors and highdensity IC.
b) Theradiois designedvery compact and theweight isapproximately140gincluding
battery.
c) The unit is equippedwithCPU HD404889 fromHITACHI.
d) Power supply is designedforbattery operation with4cells alkaline(1.5V AAA)
batteriesor
4cells rechargeableNiMH batteriesof thesamesize.

e) Theradiois shippedwithfixed (non-detachable) rubber duck antennaandbelt
clipand carryingstrip.It comeswithout batteries. Other equipment is optional.
2. SPECIFICATION
2.1 GENERALSPECIFICATIONS
a) Frequency Range: 446.00625 ~ 446.09375MHz
b) Output Impedance: 50Ωunbalanced
c) ModulationType: 8K0F3E
d) Communication Mode:semi-duplex
e) Channel Capacity :8channels
f) Channel spacing:12.5kHz
g) Power : 6.0V(alkaline), 4.8V (NiMH)
h) Battery Life:ALKALINE: at1000mAh>30hours (Tx5%, Rx5%, Stand-by90%)
i) OperatingTemperature: -20 degrees C to+60degrees C
j) Dimension: 95.5(H)x 50(W)x 26(D)mm
k) Weight: 132 g(withBattery)
2.2 ELECTRICALSPECIFICATION
a)TRANSMITTER
1) Outputpower : Max. 500mW
2) Frequency Stability : ±5ppm(-20 ~+60 )
3) ModulationMethod:FM
4) Oscillation Method: PLLSYNTHESIZER
5) Max. Frequency Deviation: <+/- 2.5kHz (withtone)
6) Cooling Method: air-cooling Method
7) Spurious Emission : < -36dBm /-30dBm
8) FMHum/Noise: > -40dB (1kHz 60% modulation,w/CCITT)
9) Distortion: < 5% (1kHz 60%modulation)
10) Tx AudioResponse: 6dB/OCT +/- 3dBPRE-EMPHASIS (300Hz~2.5kHz)
b) RECEIVER
1) ReceiveMethod: DoubleSuper Heterodyne
2) ReceiveSensitivity : < 0.28uV(20dB SINAD w/CCITT)
3) SquelchSensitivity :6to8dBat12dB SINAD
4) Bandwidth: > 3kHz(6dBATT point)
5) Selectivity: < -60dB(25kHz)
6) Local Frequency Stability :+/- 5 ppm( between –20degreesC and+60degreesC)
7) Spurious Response: > 40dB
8) Audiooutput:200mW(Internal8Ohms loadTHD 10%) Ext:100mW
9) Distortion: < 5% (1kHz 60%Modulation)
10) RXAudioResponse: 6dB/OCT +/- 3dBDE-EMPHASIS (300Hzto2.5kHz)
11) S/N Ratio:< 40dB (1kHz 60%modulationw/CCITT)

12) IF : 1'st IF = 21.7MHz
2'ndIF = 450kHz
13)Local Frequency :
1st Local Frequency= fc - 21.7MHz
2ndLocalFrequency = 21.25MHz
3. OPERATION
3.1 PushButtons andControls

1) Battery Door
2) Monitor Button
3) DetachableBelt Clip
4) Push-To-Talk (PTT) Button
5) Antenna
6) External Mic / Speaker
7) Built-inSpeaker
8) LCD Panel
9) Built-inMicrophone
10) UpButton& VolumeControl
11) DownButton&VolumeControl
12) FunctionButton
13) PowerOn/Off & EnterButton
3.2 ICONS on LCD
1) RSSI(Receiving SignalStrength Indicator) or TX Bar Icon
Indicatesthereceivingsignalstrengthandblinksduring
transmission.
2) Monitor Indicator
Appears when themonitorbuttonis used.
3) CTCSS Indicator
Blinks whenthe correctCTCSStoneis entered.
4)Auto ChannelScan Indicator

Appears intheautoscan modeor whentheautoscan modeis
activated.
5) DualWatch ScanIndicator
Appears indual watchscanmodeor whenthe dual watchscanmode is
activated.
6) KeyLockIndicator
Blinks inautolockselectionmodeor whenthe key lock is
activated.
7) VOX Indicator
Blinks inVOX selectionmodeor appears whenVOX is activated.
8) BatteryLevelIndicator
Battery Level Meter indicatestheremainingbattery strength.
9) PowerSave Display
Blinks whenthe power saveis activated.
The rateatwhichthe iconblinksvarieswiththepower saving
ratio.
Fast indicatesalowerpower saving whileslow indicatesahigher
Power savingratio.
10)TxIndicator
Appears when asignal is beingtransmitted.
11) RxIndicator
Appears whenasignal isbeingreceived.

12) LargeSegment Display
Indicates the channelnumber inuseat thenormalmode.
When theFunctionButton ispressed, it displays the function menu
insequence:CH / SC / dW/ UO /Udt / ALo/ CAL/ ton
13) Small Segment Display
Displays theCTCSStoneoptionat thenormal mode.
CTCSS option isdisplayedinHz.
Displays theSUBMENU of eachMENU inthefunction mode.
(e.g.CH 1~69/ SC: up,dn/ dW: channel number/
UO: high,off,low/ Udt:5sec, 3sec, 2sec, 1sec/ALo:off, auto/
CALnumber:1-7/ton:no-Freq) 3.3KeyFunction
3.3 KeyFunctions
3.3.1ENTER BUTTON(#13)
1) Short Touch - PowerOn
Press this button(#13)briefly toturntheuniton.
A short confirmingmelodywill play.
2) Long Touch - PowerOff
Press this button(#13)for longer than1.5seconds toturntheunitoff.
Note:Press it toconfirm therequiredoption for respective functionsduring
function editmode.
3.3-2FUNCTIONBUTTON(#12)
1) Short Touch
Press this buttonbriefly toenterfunctionedit modeinstandby mode.
2) Long Touch
Press for longer than1.5seconds toactivatetheKEYLOCK inthe
standby mode.
Pleasenoteall buttonswill bedisabledexceptthe Monitor Button(#2)
andPTTButton (#4) will remainfully operational.
3.3.3UP BUTTON(#10)

1) Short Touch
Inthestandby mode,pressthis button briefly tomovetothenext
higher mainvolumelevel.
Inthe function edit mode,press briefly toshiftfrom thecurrent
option ineachsubmenutothe nextoption inthesamesubmenu.
2) Long Touch
Pressingthis buttonfor morethan1.5secondswill allow you tonavigate
atamorerapidratethroughdifferent volumelevelinthe standby mode
or through different menus inthefunctionedit mode.
3.3.4DOWNBUTTON(#11)
1) Short Touch
Inthestandby mode,pressthis button briefly tomovetothe next
higher mainvolumelevel.
Inthe function edit mode,press briefly toshiftfrom thecurrent
option ineachsubmenutothe previousoptioninthe samesubmenu.
2) Long Touch
Pressingthis buttonfor morethan1.5secondswill allow you to
navigateatamorerapidratethrough different volumelevel inthe
standby mode or throughdifferentmenus inthe functionedit mode.
3.3.5PUSH-TO-TALK (PTT) BUTTON(#4)
Press it firmly andspeak intotheBuilt-inMicrophone (#9) totransmit.
The red TxLED Indicatorattheright side of theLCD Panel (#8) will
be on.
Releaseittoreverttostandbymode.Whenanincomingcall is received,
thegreenRx LED Indicator onthe leftsideof the LCD Panel (#10) will
be on.
Call ToneTransmission
Press thePTT Buttontwicequickly tocall anotherparty onthesame
channel. ThewordCALLandtheTx iconwill appear inthedisplay.
The userselectedcall ringer melody will play.
3.3.6MONITOR BUTTON(#2)
Press it tocheck activity onthecurrent channel beforeyoutry to
transmit.
Adjust the VolumeControl (#10, #11) if necessary.
When youpress theMonitorButton,theLCD Panel (#8) will be illuminated
withanambercolorback-lightand boththeTx andRx LED Indicators will
be on.
Ifyoupress theMonitor Buttonduringthe functioneditmode,youwill
returntostandby modedirectly.

3.3.7EXTERNALMIC/SPEAKER (#6)
This jack accepts anoptional headset/microphone for totally handsfree
operation.
Pleaserefer totheuser manual orAlbrecht catalogue.
SeealsosectionregardingVOX SELECTION MODE.
3.4 SettingandOperation
3.4.1BASIC CHANNEL SELECTION
Inordertocommunicatewithother PMR units,bothyouandthereceiving party
must beonthesamechannel. Tectalk has 8 channels (1-8) asindicated by
thelargedigits intheLCD DisplayPanel (#8).
Before,tryingtotransmit on theselectedchannel, you shouldpress the Monitor
Button(#2) tocheck theactivity onthat channel.
Ifsomeoneis alreadyontheselectedchannel, youshould try another
channel whichis notoccupied.
Tochangethe basicchannel,inthestandbymode,press the
Up Button (#10) briefly tomovetothenexthigher mainchannelnumber.
Press the Down Button (#11) briefly tomovetothe next lower mainchannel
number.
3.4.2CTCSS (Coded ToneControlled SquelchSystem)
SUB-CHANNEL SELECTIONMODE
This featureallowsyoutohavemoreprivacy onthemainchannelbyusingtonecodes
(internationalnumberingsystem00-38)withinamainchannel. This enablesyou to
communicatewithYourpartners on the samemainchannelwhen all partnerstationsuse
the samesubcode.This helpstoavoidcongestion onthe mainchanneland filters out
unwantednoise,static andother stations usingdifferent codes.
Thereare38CTCSS subchannels for eachmain channel.
TochangetheCTCSSsubchannel,
Press theFunctionButton(#12)until thewordcTcappears intheLCD Panel (#8).
Press the UpButton(#10)orthe DownButton (#11)tochoosethe desiredsubchannelto
use.Thecorrespondingsubcodefrequency will be displayedinthelower right corner.
Press theEnterButton(#13) toconfirm your selection.
NOTE:
Tocommunicatewith other PMR units, theymust beswitched to thesame
channel andCTCSSsubcode. Tocommunicate withother LPD units thatdo
nothavesubcodes, switchyour unit tothesamechannel withthesubcode
set toOFF.
3.4.3AUTO CHANNEL SCANMODE
This featureallows youtoscanforan activechannelandcommunicatewiththeparty
transmitting.

Toaccess the Auto ChannelScanmenu,pressthe Function Button(#12)until the auto
channel iconblinks andSCappears inthe LCD Panel (#8).
Press the UpButton (#10)ortheDownButton (#11)tochoosescanningupordownfrom
thecurrent channelnumber.
Press theEnter Button(#13) toconfirm your selection.
The unit will beginscanning foranactivemainchannel. Ifatransmissionis detected,the
Rx andRSSIiconswill appear intheLCD Panel (#8).
Toturnoff the autochannelscanfeatureinthestandby mode, simplypress theFunction
Button(#12)once.
3.4-4DUAL WATCHSCAN MODE
This feature allowsyoutomonitortwo differentchannelsatthesametime. If youpre-set
anypriority channel other thanthe current channelinuse,thepre-setchannelwill be
scannedevery 0.5second andsignals youwhenacall is received.
Toaccess theDualWatchScanmenu,
Press theFunctionButton(#12)until thedual watchiconblinks anddW
appears intheLCD Panel(#8).
Press theUpButton(#10)or theDownButton (#11) to select thedesired
channel number youwishtoclosely monitor.
Press theEnterButton(#13) toconfirm your selection.
Toturnoffthedual watchfeatureinthestandbymode, simplypressthe
FunctionButton (#12) once.
3.4-5VOX SELECTIONMODE
The VoiceActivatedTransmission(VOX) function allows your voicetoactivate
transmissionautomatically whentheCommunicator is usedwithanoptionalhandsfree
mic/headset, orevenwiththe built- inMicrophone.tton(#4)withoutusingthePTT button.
Toaccess theVOX Selectionmenu,
Press theFunctionButton(#12)until theVOXiconblinks andUO appears intheLCD
Panel (#8).
Press theUpButton (#10)ortheDownButton(#11)toselectfromhigh,loworoff.High or
low settingdeterminesVOX responsesensitivity.
Press theEnterButton(#13) toconfirm your selection.
ToturnofftheVOX feature,enter theVOX selection modeandthenselect Off.

3.4.6VOX RECOVERY TIME SELECTIONMODE
This allows theresponsecharacteristics ofthe VOX function tobe precisely adjusted to
suit individualneeds.
Toaccess theVOX Recovery TimeSelection menu,
presstheFunctionButton(#12)untilUdtappearsintheLCD Panel(#8)with theVOXicon
blinking.
Press the UpButton(#10)orthe DownButton(#11)toselect from5,3,2or1second
setting.This setting determines thedelaytimebetweentransmittingandreceiving.
Press theEnterButton(#13) toconfirm your selection.
Pleasenoteyoumayneedtotry differentVOXtimesettingstodeterminethebest valueto
suit your speakinghabit.
ToturnofftheVOX feature,enter theVOX selection modeandthenselect Off.
3.4.7AUTO KEYLOCK SELECTIONMODE
This featurepreventsaccidentalchannelchangeanddisturbancetothepreferredsettings
oftheCommunicator. AutoKeyLock temporarily disablestheUp,DownandEnter
Buttons.
Toaccess theAutoKeyLock Selectionmenu,
press theFunctionButton(#12)until theautolockiconblinksandALoappearsintheLCD
panel (#8).
Press theUpButton(#10)or DownButton (#11) toselect theAutooption.
Press theENTERkeytoconfirm your selection.
Ifyoudonotpress any keyfor morethan15secondsinthestandby mode,all respective
keys will automatically belocked.
Toturnthe autokeylock onoroff instandbymode,simplypressandholdtheFunction
Button(#12)for morethan1.5seconds.
Toquickly activatetheAutoKeyLock, holdtheFunctionButton (#12)formorethan1.5
seconds.
3.4.8CALL RINGER MELODYSELECTIONMODE
This featureprovides7user selectablecall ringermelodies toalert you of acallingparty.
Toselect yourfavoriteCall Ringer melody,
press theFunctionButton(#12)until thecall iconblinks andCALappears intheLCD
panel (#8).
Press theUpButton(#10)or DownButton(#11) topreview the7availablemelodies.
Press theENTERkeytoconfirm your selection.

4. SERVICE ANDADJUSTMENT
4.1Frequencysynthesizer (PLL)
a) Opentheradio,disconnecttheantennaandconnect apower meter
Anda50Ohms dummy loadwiththeinternal antennaconnecting pointof
TECtalk.
b) Check the voltagebetweenTP& GND indigitalvolt meter.
c) Thenset thelow channel of TECtalk thelowest frequency.
d) AfterpressedPTT key of TECtalk , trim VC1for adjustingthe lowest
frequency ofTx channel to DC 1.5V inthevoltage ofTP1.
e) After releasing thePTTkey, Andthencheck ifthehighest frequency
ofRx channel is withinDC 1.0V inthevoltageofTP,
4.2 TRANSMITTER
a) Connect EUT & measureequipmentaccording toblock diagrambelow.
b) Connect DC 6.0V, voltagepreset toEUT.
c) Connect"power meter" & "dummy load(50Ohms)".
d) Adjust Txfrequency according totrimming trimmer VC2.
e) Connect AF oscillatortomic terminalforconform modulationdegree.
f)Adjust the frequency of AFoscillator to1kHz andadjust AF level
shouldbe100mV.
g) Checkingoscilloscope and modulation meter. max.
frequency deviationshouldbe in+/- 2.5kHz.
4.3 TRANSMITTER TEST
a) Output PowerTest
power(6.0V DC) shouldbe Max.500mWandin -50% range.
POWER SUPPLY
EUT POWER METER
MODULATION METER
AVVTVM
OSCILLOSCOPE
DUMMY LOAD
DISTORTION METER
AF OSCILLATOR
FREQUENCY COUNTER
SPECTRUM ANALYZER

b) Audio Response
ConnectAF oscillator toMic terminalandthenfirm theaudiolevel
that doesn't distortionthewaveofoscilloscopeinthe frequency range,
300Hz to3kHz. Check theaudiolevelfor 300Hz to3kHzbasedon frequency
standard,1kHz.
c) Modulation Degree Test
1) Connect AF oscillatortotheMIC terminal and thenadjust the level
to100mV
2) Measuretheoscilloscopewaveandhepointneedleof modulationmeter
after pressingPTT key.
3) Sweepgradually the frequencyof AF oscilloscope from 300Hzto3kHz.
4) At this time,thepoint needleof modulationmeter shouldbein
thelimit of+/- 2.5kHz.
d) Spectrum Test
1)terminate antenna outputwith50Ohmsanduseapower attenuatorof 20dB,toavoid
harmonics generatedbyanalyzer overload.be20dB more.
2) observethe spectrum withpressingPTTkey. The harmonics shouldbe
less than -36/-30dBm (with20dBexternalattenuatorthereading will be –56/-30dBm).
4.4 RECEIVER
a) Preparation
1) Adjust thepower supply toDC 6.0V
2) Adjust Voltage levelto0.7Vrms( at 8Ohmsspeakeroutput load)after poweron.
b) Connection method
SSG EUT
DISTORTION METER
AVVTVM
OSCILLOSCOPE
8OhmsLOAD
POWER SUPPLY
SINADMETER

c) Signalgenerator Adjustment for RX sensitivitytest
1) Adjust SSG tochannelfrequency.
2) Adjust modulation frequency, 1kHztomodulation degree,1.5kHz.
3) Afteradjustingthe frequency of SSG tochannelfrequency,setRF level
to -47dBm.
d) Checkandadjust Squelch sensitivity
1) Set thestandardchannel.
2)Insquelchmode,SQvolumeRV1mustbeturnedcounterclockwisetoopenthesquelch.
3) AfteradjustingSSG tochannelfrequency, theRF levelofSSGis set
sothataSINAD of 8∼6dB is obtained. Turnpotentiometer carefully sothat
Squelchjustopensat that point.
4.5 RECEIVER TEST
a) Rxsensitivitytest
SSG shouldbeadjustedto12dBofSINAD's point needle
Observewaveform of oscilloscope atsignalgenerator signal modulatedwith1kHz
audioand1.5kHz frequency deviation. The 12dB Sinadpointshouldbereachedwithan
RF levelof –110to -107Bm.This isagoodsensitivity.
b) Audio Distortion Test
1) SSG shouldbeadjustedlikeway of point a)andRF level set to -47dBm.
2) Adjust to0.7Vrms( at 8Ohms load)observingaudiowaveform.
3) Readtheneedleof distortionmeter (it shouldbelessthan5%distortion).
c) Squelch Test
After RFlevel of SSG shouldbeset tothelowest level, RFlevel should
be gradually increaseduntil speaker makesaudiosound.Atthispoint,
check RF level(Check iftheSINAD is 8∼6dB). Check thatsquelch will close when Levelis
reducedtominimum. Ifnot, readjust RV 1andcheck again.
4.6 Symtoms, Check point & Correction
a) Diagnosis method
1) Check eachswitchtowork well.
2) Check voltage ofbattery.
3) Problem whetherproblem comesfrom transmitter or receiver?
b) Troubleshooting
a)Transmitter
①Power key is onconditionbutdoesnot work.

ⓐBatterycouldcompletelybedischarged.
ⓑBatterycell wronginserted?
ⓒContact problembetweenBattery and Radio?
②Fail totransmit
ⓐRunoutofbattery or chargeproblem.
ⓑFault of PTTkey
ⓒFault of Q4,Q5.
③Transmitter works butfrequency is unmatched
ⓐdefectivefrequency synthesizer.
ⓑdefectiveX-tal (X2).
④Noaudiomodulation (TxpowerandTx frequency arenormal)
ⓐProblemofmicrophoneor mic connector.
ⓑIC U7problem.
⑤Tx is set whenswitchis on.
ⓐTx switchproblem
2) RECEIVER
①Rx doesnot work
ⓐSpeaker lineopen problemor connector problem.
ⓑReceiver power circuit problem.
ⓒAudioamplifier BasebandIC U4problem.
②Only noisesound
ⓐU12problem.
ⓑVCO problem.
③Rx sensitivity isweak
ⓐAntennamountingproblem.
ⓑFront-Endcircuitproblem.
ⓒLocaloscillationfrequency deviation.

ⓓSF1SAWfilterfail.
ⓔVCO problem.
④Squelchdoesnotwork
ⓐU12problem.
ⓑControl logic problem.
5. DESCRIPTION OFRADIO CIRCUIT
5.1Frequencysynthesizer
Frequency synthesizer consists ofVCO, PLLIC(built inPRESCALER) and
loop filter.
a) VCO
VCO is composedofONE VCO. Oscillationcircuittakes colpittscircuit using
variableDiode.And VCO iscomposed ofD1,Q8,Q9,C81,C75,VC1,L1,C74,C76.
VCO control voltagethroughloop filteradjusts frequencyand microphone
signalthrough modulationterminal generates FMmodulation.
b) PLL IC
PLLIC is adjustableIC toproducethe desired frequencywhichVCO
provides throughloop filter.It hasinternal counterusing21.25MHz
reference frequencytogenerate6.25kHz as referenceSignal. VCO frequency
from prescaledinput is divided signal andcompared withreference
signalphaseinphasecomparator. Built-inchargerpumpchanges voltage
(until twosignalsareinphase)andchargedvoltagesupplies VCO
throughloop filter toproducethedesired frequency.
Frequency dataassociatedwithchannel goesto PLLIC by CPU
throughCLOCK,DATA. PLLIC enablesby strobelineof CPU.
c) Loop Filter
Loop filter is composedofR48,R49,C84,C85and forms pulses frompin14
IntotoDC andeliminates harmoniccomponents inpulses.
It helpsVCO oscillateclearly as DC voltageis supplied intoVaricap.
5.2 RECEIVER
This is composedof Dual Conversion Super Heterodyne.First IF is
21.7MHz. Local oscillatorfrequency islower in1'st IF thanRx
frequency. It is calledlow sideinjection. SecondIF is 450kHz.2nd
localoscillatorfrequencycomes to21.25MHz.

a) Rx/TxConversion Circuit
Rx signal goestoRx/Tx conversioncircuitthroughFIXED antenna
connector, low pass filter(L5,L6,L7,C42,C43,C46,C47) and
receiver resonancecircuit composedofL8,C1.Whentransmitting,
voltagethrough R25,L12,D6supplies,D7ofreceiveinput is short and
Tx is oncondition.WhenPIN diodeis off incondition of Rx, L8
andC1resonateserially andmakeimpedancematchingat receiver
bandpass filter.(SF1).
b) Front End
Front-Endhas Q1toprovideahighsensitivity and low noise feature.
It employs SAWfilteras bandpass filtertoeliminateimage frequency
frequency andtoproduceenoughpass bandbyQ1inputandoutput.
c) Mixer
Mixer has one baseBFQ 67W(Q2) tofeaturehigh low noisequality.
It has RF signal throughL7,L8, SF1,SF2andQ1RF signalfromLocal
oscillator mixed.
It develops1'st IF ,21.7MHz. 1st IF goesto1stIF amplifier Q3(KTC4080)
basethroughX-talfilter XF1.
IF of mixing signals isselectedandenters the X-talfilter.
Outputimpedanceof mixer is directmatchedwithinput impedance
ofX-talfilter.
Matching offilter satisfies pass bandwidthoffilter, ripple
eliminationwithinthepass band,andattenuation characteristic ofstop
band.X-talfilter iscomposed oftwopolemonolithic X-talfilter,
with8kHzof IF bandwidth. R11is usedas impedancematchingwith1'st IF
AmpQ3.
d) IFAMP and Detection
1'st IF AMP Q3supplies IF(U12) mixer inputpin16throughoutput
resistor R13andC21 toneedgainininsertionloss ofX-talfilter
andlast stagecircuit. Multi-useIF IC makesupofmixer IF AMP.
pin12'ndlocalfrequency enter topin1.
It supplies mixerofinternal IC. Mixer outputofIC throughpin3passes
450kHz ceramic filter,supplies 2'ndIF amplifier andlimits.
After2'ndIF AMP hasaprocess ofenough gainand AMrejection,
it comestoquadraturedetection. Demodulatedaudiosignal byT1(QuadCoil)
is amplifiedandcomesout topin9.
Detectedaudiosignal through R22, VR1andinput inaudioampIC U4throughC22.
e) SquelchCircuit
Noisecomponentof detectedoutputs hasamplification

Squelchthresholdiscontrolledby Resistor R18,C31,R15
f) AudioAmplifier
Demodulatedaudiosignalenters topin2ofU4.After abovesignal is amplified
inU4theaudiooutputfor thespeaker is reached atpin5(throughC220).
5.3 Transmitter
When Tx starts withpressingPTTswitch, VCO output amplifiesthrough
Q4,Q5transmitsbyantennathroughlowpass filter.
Tx RF signalproduced from Tx VCO is amplified by DRIVER Q5through C53
andenteredQ4POWER TR input terminal withfinal amplification.
Afterthis stage, the signal is emittedatantennathrough50 Ohms matching
circuit tolowpass filter(L7,L6,L5,C42,C43,C44,C46,C47) toeliminate
harmonics.
5.3.1 AudioModulationandAudioAmplification
Audiosignal producedbyexternalor internalmicrophone isamplified and limitted
by IC U7. Theoutputsignalenters toVCO throughlowpassfilterand
U2. Max. Frequencymodulationdeviationis adjustedbyVR1
Audiomodulationandaudioamplificationhaspreemphasis characteristicof 6dB/OCT
by U7(NJM324V).
11. CHANNELDATA
CH Frequency (MHz) CH LocalOscillator (MHz)
1 446.00625 1 424.30625
2 446.01875 2 424.31875
3 446.03215 3 424.33215
4 446.04375 4 424.34375
5 446.05625 5 424.35625
6 446.06875 6 424.36875
7 446.08125 7 424.38125
8 446.09375 8 424.39375

© CopyrightAlbrecht Electronic GmbH & JcomLtd, Jan.2000
AlbrechtElectronic GmbH
Dovenkamp11
22952Lütjensee
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