Realistic PRO-2020 User manual

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PRO-2020
PLL SVNTHESIZED
VHF/UHF AM/FM RECEIVER
)Catalog Number:20-112
Manual provided by G.E.Taylor, scanned by L.P. Glaister VE71T
CUSTOM MANUFACTURED FOR RAD IO SHACK ~ A DIVISION OF TANDY CORPORATION

GENERAL OPERATION OUTLINE
Press IPROGRAM I.
Advan ces t o ne xt cha nne l,
kev-in the Ireq ue ncy and
press
[]EI]; repeat to
memorizedesir edfrequenc ies,
one by one.
Press !PRIORITYI ; il
SQUELCH is ON, starts pri-
oritv functi on.
1I SQUELCH is OFF, set
to th
eprio rit ychann el.

DISASSEMBLY DIAGRAM
Co
Step 1:
Step 2:
Step 3:
Step 4:
Removetwobracketscrews @andthebracket
W~ove four screws @) two from each side of the
Cabinet.
Removetwoscrews
@frombac kotcab ineto
Open
thecab inet. Use care not to damage leads of
speakerinstalledonthecab inet.

ALlGNMENT AND TEST POINT POSITIONS
j
~T10 7
@j~
@~ ,. I
TP-106
WJ0
T1rAö
g"
&1
2
L ~
@" '· I
@JT C-l05
~
~ I@ TC-l07
~ ~
~
T~O '
T ~02
@) TC-lrAö
~
~ ~
T! '
~
ALlGNMENT PREPARATION
Testequ ipmentrequired
1. Oscilloscope (0 - 500 kHz, 0 - 50 MHz )
2. AC VTVM
3. DC VTVM
4. FrequencyCounter (SOMHz)
5.8ohmdummyload
S. Slow Sweep Generator with variabie marker 110.7 MHz)
7. VHF Sweep Generator with variabie marker
(30 - 50 MHz, *6 8- 88 MHz, 108 -17 4 MHz)
8. UHF Sweep Generator with variabie marker
(41
0- 512 MHzl
9. FM SignaI Generator (30 - 50 MHz, *S8 - 88 MHz,
138 -1 74 MHz, 410 - 512 MHz)
10. AM Signal Generator (108 - 136 MHz)
NOTE1 :Use non-metsttic tuning tools.
The test eauloment and Receiver should be warmed up at least 10 minutes before proceeding with alignment.
Input signal from the Generator should be kept as low as possible and still obtain usabie output.
NOTE 2: A 9·volt betterv is required to hold the memory when AC is disconnected . Always be sure the unit is loaded with
afresh 9·volt betterv or the pre-programmed channels will be last rand will have to be re-proçremmed}.
.•OTE 3: For servicing VHF Mid band of European/A ustralian models, see Appendi x on pages 41and 42.

(
REFERENCE FREQUENCY osc ALlGNMENT
Step 1: Connect Frequency Counter to TPl and ground . Conneet the ground first to prevent IC-8 Iatch·up.
Step 2: Adjust TC-l sa tha t the frequency is 6 .40000 MHz ±10 Hz.
NOTEl: If 6.4 MHz faits to ascii/a te, it may due to /C ·8/atch·up .
Unp/ug the
power connector momen tary to rum power supp/v completety off.
IF SECTION ALlGNMENT
Step 1: Connect instrumentsas shownbe low.
Step 2: Adjust Tl05 for maximum output sa that the 455 kHz marker is in the center of the disc riminator curve and far
bestl inear
itya s shownabov e.
During Alignment, maintain Sweep Generator output at the lawest level possible to prevent averloading.
VCO ALlGNMENT
VHF LO BAND
Step 1: Cannect a DC VTVM to TP-l0 4 and graun d.
Step 2: ProgramCH1
,2and3asfalla ws:
CHl (30 MHz), CH2 (40 MHz), CH3 (50 MHz).
Step 3: Select Channel 3 (50 MHz) and adjust
TC-l0l far 9 .0Van the DC VTVM.
Step 4: Select Channel 1 (30 MHz) and adjust Tl03 far 1.0V o n the DC VTVM.
Step 5: Repeat steps 3 and 4 unt il na improvement is ob served. The DC VTVM shoul d show as below .
30 MHz Voltage at TP104 1.0V
40 MHz Voltage at TP104 3.4 ±0.3V
50 MHz Voltage at TP104 9.0V
VHF Hl BAND AND AIRCRAFT
Step 1: Connect a DC VTVM to TPl 04 and ground.
Step 2: Program CH1,
2,3,4 ,5and6asfollows .
CHl (108 MHz), CH2 (120 MHz), CH3 (136 MHz), CH4 (138 MHz), CH5 (160 MHz), CH6 (174 MHz).
Step 3: Select Channel 6 (174 MHz) and adjust TC102 for 8.0V on the DC VTVM.
Step 4: Select Channel 1 (108 MHz) and adjust L107 for 1.0V on the DC VTVM.
Step 5: Repeat step s 3 and 4 unt il no impr ovemen t is o bserved , The DC VTVM sha uld sho w as below .
108 MHz Voltage at Tp·l0 4 1.0V
120 MHz Volta ge at TP
·l04 2.1 ±0.3V
136 MHz Voltage at TP-l04 3.6 ±0.3V
138 MHz Voltage at TP
·l0 4 1.8 ± 0.3V
160 MHz Voltage at TP-l04 3.9 ±0.3V
174 MHz Voltage at TP
.l04 8.0V

UHF BAND
Step 1: Connect a DC VTVM to TP-104 and ground .
Step 2: Program CH1,2and3 asfollows :
Chl (410 MHz), CH2 (430 MHz), CH3 (512 MHz!.
Step 3: Select Channel 3 (512 MHz) and adjust TC·106 for 9 .0Von the DC VTVM.
Step 4: Select Channel 1 (410 MHz) and adjust L111 for 1.OVon the DC VTVM.
Step 5: Repeat steps 3 and 4 unt il no improvement is observed. The DC VTVM should show as below.
410 MHz Voltage at
TP·l04 1.0V
430 MHz Voltage at TP·104 1.8± 0.3V
512 MHz Voltage at TP·104 9.0V
RF AMP ALlGNMENT
VHF LO BAND
Step 1:
Connectinstrumentsasshownbelow.
Step 2: Program 30 MHz (CH1). 40 MHz (CH2) and 50 MHz (CH31.
Step 3: Select Channel 2 140 MHz) and adjust nOl and Tl02 for maximum RF waveform . { .
Step 4: Check Channels 1 - 3 for the maximum RF waveform. A slight deviation (as shown below) is acceptab le.
/\\71\
I ,
VHF Hl AND AIRCRAFT
Step 1: Connect instruments as shown below .

Step 2: Program 108 MHz (CH1), 120 MHz (CH2). 136 MHz (CH3). 138 MHz (CH4l. 160 MHz (CH5) and 174 MHz
(CH61.
Step 3:
SelectChannell (108MHz) and adjust Ll04and Ll06for maximum RF waveform.
Step 4: Select Channel 5 (160 MHz) and adjust L103 and L105 for maximum RF waveform .
Step 5: Repeat steps 3 and 4 to obtain the max imum RF waveform f or each channel.
Step 6: Check Channels 1 - 6 for the
maximum RF waveform at each frequency marker. A slight dev iation (as shown
below) isacceptable.
UHF BAND
Step 1: Conneet instr ument s as shown below .
Step 2: Program 410 MH z (CH1). 430 MHz (CH2) and 512 MH z (CH31.
Step 3: Select Channel 2 (430 MHz) and adjust TC
·l03 . TC-l04 . and TC-t05 tor maximum RF waveform .
Step 4: Select Channel 3
(5t2 MHz) and adjust TC·tOl for maximu m RF waveform.
Step 5: Check Cannels 1 - 3 for the maximum RF waveform at each freq uency marker. A slight dev
iation (asshown
below is acceptable ,
430
FREQ(MHzi

OVERALL ALlGNMENT AND SENSITIVITY MEASUREMENT
Step 1: Con neet Signal Gene rator (SSG) to ANTenna jack and AC VTVM to EXT. SPKR Jack .
Step 2: Turn SOUELCH fully counterclockwise. Set for recept ion of the channels noted in the following chart.
SettheSSG tothe center ofeach band.
CH BAND FREO .
1 VHF LO (MlD) 40 MHz (78 MHz)
2VHF Hl
160MHz
3UHF 512MHz
4
AIRCRAFT 120MHz
Step 3: Set the Signal Generato r frequency to 512 MHz (channel 3). Readjust TC -l07 for maximum sensitivitv,
Step 4 : Set the Signal Generator frequency to 120 MHz (channeI41. Adjust Tl04, Tl06 and Tl07 for maximum
sensitivity.
Step 5: For each f
requenc y /channel, set Signa I Generator to each frequency (FM: 3 kHz deviation, AM: 60% rnodu -
lation) . Set VOLUME
control for 0 dB (0.775 V) reading on the VTVM.
Step 6: Turn off the
modulation and measure the (S +Nl/N ratio.
ZEROMATIC FUNCTION AND HOW Ta CHECK IT
I
*Z eromatic functions when OUTPUT 1 is in "H" level.
To
adjust el vo ltage, receive signal in Manual mode , and set T105 to get half sup ply voltage (IC101, 4 pin). It is con -
venienttousethe National WeatherServ iceSignalfortheadjua tment .
In the event
Zeromatic does not function right, refer to " REFERENCE FREQUENCY asc ALlGNMENT" and check
6.4 MHz, and adju
stT105aga in.

RESET TIMING (lC-1)
5V
OV~
5V I
I Ir--
OV~
I I
II
f.-;.-2
ms
----t
Figure1
NaTE :
Pin31 of IC·'
isthe RESETterminalwhich
functionsatLlevel. ItrevertstoH level
2msafterPin42VDD.
CPUCLOCK OSCILLATION WAVEFORM (JC-1)
4V \fW\/\fvi
I I
DV I I
1 I
~
2 .5~s
Figure2
IC-3 INPUT/OUTPUT WAVEFORM
NaTE :
This is the basic waveform of CPU (lC-1).
Ceramic
ResonatorIX -2)
generate
s400 kl-iz for about ZBus
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~1 :IL
ov I : :
~s :
I: :1
Figure3
NaTE:
Waveform at Pin No. 5 is CPU ncn
interruptsignal.Musthaveabovewaveform
ortheCPU program malfunctions .

IC-4 INPUT/OUTPUT TIME CHART (150 MHz displayed,inProgramMode)
c
5V
I"
ov
5V
14 OV
5V {
13 OV
5V
OV
5V
l"
ov
5V
10 ov
I 1 II
5V I1
lLJl
I
9ov 11 I
I I I
I 1
1-1
11
10.12 ms II
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INPUT 4