Alignment Procedure - GE Mastr II Maintenance Manual

MODULATION LEVEL ADJUSTMENT
The MOD ADJUST (Rl27) wns adjusted to the proper setting before shipment and should
not normally require readjustment. This setting permits approximately 75% modulation for
the sverage voice level. The aduio peaks which would cause overmodulation are clipped by
the modulation limiter. The .limiter, in con.) unction with the de-emphasis network, instan-
taneously limits the slope of the audio wave to the modulator, thereby preventing overmod-
ulation while preserving intelligibility,
TEST EQUIPMENT
l. An audio oscillator (GE Model 4EX6Al0).
2. A frequency modulation monitor.
3. An output meter or a VTVM.
4, GE Test Set Model 4EX3All or 4EX8Kl2.
PROCEDURE
l. Set the station g:ain control Rl4 to it::; fully clockwise position.
2. Connect the audio oscillntor and the meter through a 0.5
11F
(or larger) DC block-
ing capacitor, across audio input terminals JlO (Green-Hi) and Jll (Black-Lo) on
GE Test Set, and connect the Red Test set plug to the system Red metering plug.
3. Set the audio generator frequency to l kHz,
A. In all station combinations except Local Control Intermittent Duty combina-
tions, set the audio generator output to 30 millivolts RMS,,
B. In Local Control Intermittent Duty station combinations, set the audio
generator output to 1,0 volt RMS.
4. For transmitters without Channel Guard, set MOD ADJUST Rl27 for a 4.5 kHz swing
with the deviation polarity which gives the highest reading as indicated on tbe
frequency modulation monitor.
5. For transmitters with Channel Guard set Channel Guard MOD ADJUST Rl05 for zero
tone deviation. Next, with the 30 millivolts signal at 1000Hz applied, set MOD
ADJUST Rl04 for :l. 75 kHz deviation. Then remove the signal from the audio oscil-
lator and set Channel Guard i\IOD ADJUST Rl28 for 0.75 kHz tone deviation.
6. For multi-frequency transmitters, set the deviation as described in Steps 4 or 5
on the channel producing the largest amount of deviation.
7. Remove the audio oscillator and key the mike. While talking in a normal voice
at a distance of four to six inches from the station microphone, adjust station
gain control Rl4 for a deviation of 3 kHz as measured on the deviation monitor.
PA POWER INPUT
For FCC purposes, the PA power input can be determined by measuring the PA supply
voltage and PA current, and using the following formula:
i'i PA vol Lage x PA current
where:
Pi is the power input in Watts,
PA voltage is measured with Test Set Model 4EX3All in Position G on the 15-Volt range
(read as 15 Volts full scale), and with the polarity switch in the (-) position. With
Test Set Model 4EX8Kl2, use the B+ position and tbe 1-Volt range (read as 15 Volts full
scale), with the HIGH SENSITIVITY button pressed and the polarity switch in the (-)
position.
PA current is measured with the Test Set in Position Gin the Test l position, and with
the HIGH SENSITIVITY button pressed (10 amperes full scale).
Example:
Pi= 12.6 Volts x 5.0 amperes 63 Watts.
I COM FREQUENCY ADJUSTMENT
First, check the frequency to deternine i f 11ny adjustment is required. The i're-
quency should be set with a frequency meter or counter with an absolute accuracy that
lS 5 to 10 times better thnn tho tolernnco to be maintained, nnd with the entire radio
as near as possible to an ambient temperature of 26.5°C (79.8"F).
MASTR II ICOMs should be reset only when the frequency shows devintions in excess
oi' the following limits:
A. ±0.5 PPM, when the radio is at 26.5"C (79.8"F).
B. ±2 PPM at any other temperature within the range of -5°C to +55"C
(+23"F to +l3l"F).
C. The !:>pecification limit (±2 PPM or ±5 PPM) at any temperature within
the rnng-cs of -40cC to -S"C (-40°F to +23"F) or -t-55''C to +70'-'C
(-t-131 "F to +l58"F).
If an adjustment is required, pry up the cover on the top of the ICOM to expoc;e
the trimmer, and use one of the following procedures:
If the radio is at an amblent temperature of 26.5°C (79.8°F') set the o:;,cillalur
:for the correct operating frequency.
If tbe radio is not at an ambient tempex·alure of 26.5"C setting errors cnn !Je
minimized as follows:
A. To hold ~etting, error to ±0.6 PPM (which is considered l'Caf>onable for 5 PPM
ICOMS):
l. Maintain tile :t'adio at 26.5°C (±S"C) and ~el I he osclllntor to
desired frequency, or-
2. Maint:;in the radio <1l 26.5'C (±l0°C) and offset the oscillator, as a
function of actual tempe:t'ature, hy the amo11nt "'!1nwu in Figure 9"
B. To hold setting error to ±0.35 PPM (which is considered reasonable for
2 P~! ICOMs): Maintain unit at 26.5"C (-t5°C) and offset the os~illator.
as a function of actual tempernture, by the amount slwwn in F'ig:ure 9.
For flxamplP.: A"'sume thf' amhient tomp('ratnro of the radio is l8.5°C (65.4°F). At
that temperature, the curve :.:haws a correction fa~tor of 0.3 PPM. (At 25 MHz, 1 PPM
lS 25Hz. At 50 tlliz, l PPM is 50 Hz).
With an opernting frequency of 50 MHz, set the oscillator for a reading of 15Hz
(0.3 x 50 Hz) higher than thP licensed operating frequency. If a negative correction
factor is obtained (at temperaturos above 26.5°C), set the os~illator for the indL~u­
ted PPM lower than the lict2nsed operating Jrequency.
DEGREES FAHRENHEIT
618 654 690 726 76.6 79.8 834 870 906 942 978
;:Et0.6r--~
a._ +05
a._
+04
0::: + 0.3
~
+02
0:::+01,
w '
of-
>-
-0 I
~
-02
w --03
::)
0 -0.4
w
-0 5
0:::
lL -06 L_
16 5 18 5
-1
i
T--,--T-~
I , .
I . .
-1--i--- - - -
- -+-
- - - - + - - - - ----<
------+--
1
! +
20 01 22 S 24 2
26
5
28 5
30 5
32
5
34
s
36
5
- 5" LIMIT C<EF
+5" LiMIT
DEGREES CENTIGRADE
F(-2453
Figure 9 -Frequency Characteristics Vs. Temperature
11\ifU-tPIII HP T -''N~>
CIJNli•'JIJOIJS DLJTY
;\LL CXCEPT I OU,L
r:0~JTROL SYSJCP.'
ROAI: lJ .\·IL T~RING JACI<
MOD
ADJUST
R127
CHANNEL
GUARD
MOD
ADJUST
R128
EXCITER
ASSEMBLY
CONTINUOUS DUTY
PA ANTENNA
JACK J243
INTERMITTENT DUTY
PA ANTENNA
-
..
JACK J201
PA
ASSEMBLY
PA
METERING
JACK
J205
TRANSMITTER ALIGNMENT
LBI-4732
EQUI P~'IENT REQUIRED
1. GE Tust Set \Iodel 4EX3All or Test Kit 4EX8Kl2.
2. A 50-ohm wattmeter cormectud to antenna jack J906.
3. A frequency counter.
PRELBIINARY CHECKS AND fiD.JUSniENTS
l. Place ICOM::; on Exciter Board (crystal frequency - operating frequency 7 3).
2. For a large change in frequency or a badly mis-aligned transmitter, pre-set tho slugs to TlOl through TlOS. and LlOl, Ll02 and LlO::l to the
boltom of the coil form.
NOTE
The tuning frequency for multi-frequency trnnsmitters is determined by the operating- frequency Dnd the
:frequency spread between l'reqllencies. Reier to the tnblo below for maximum frequency spread.
3. For multi-frequency transmitterf> with a fruquer:cy spread less than that specified in column (1), tune the tn1nsmitter? to the lowest
.frequency.
For frequency spread oxceodlng t!1e limits specified in column (1), tuno the transmitter 11sing a cent~r [J·eqtJency t11ne 11p ICOM. Except the
maximum frequency spread can be extended to tht> linits specified in ~olumn (3) with 1 dB deg-radation.
For tuning LlOl, LlO~, L103, alwnys tune LlOl, Ll02, LlO:~ on the lowest fl"uquency.
Multi-frequency Transmitter Tuning
,----
.
Trunsm1ttcr MAXIMUM FREQUENCY SPREAD
Frequency Range
(l) without center Luning
I
wi t11 center tuning ' wit 11 canter tuning
(l dB degradation)
25-30 MIIZ .080 :V!Hz
I
.160 Ill Hz .320 11Hz
I
:l0-36 MIIz
.100 MI!z
I
.200 MHZ
.400 MHz
36-42 }!Hz .120 Mil.-; .240 M!Iz .470 MHz
42-50 MHZ .140 MHz .2RO .MHz . 510 li!Hz
4. Connect t!Je red plu~ on the GE Test Set to the Systom Boord metering .Jack, and the black plug to the Exciter motoring jack. Set the
polarity to-:-, and set the rang-e to the Test 1 position (1-Volt position for 4EX8Kl2) for all ucl,justments. NOTE: Witl1 the Test Set
connec1 ed J·o lhe PA metering ,jack, the voltr.ge reading at position "}'"with the HIGH SE~SITIYITY button pressed may !Je couverted to
driver collector current [)y reading t!1e current as 10 amperes full scale. The voltage readinp; at position ''G" witll the HIGH SENSI-
TIVITY bulton pressed may he converted to PA ccllector current by reading the: current as 10 ampere;:, full scale.
5. All adjustments ;u·u madu with the transmitter keyed. Unkey tile Lransmittor between steps to avoid unnecessary heating.
STBP \!ETEH POSITION TUNING CONTROL ' METER READING ! PROCEDURE
'
I
l.
o~'
'-"
I
LlOl
I
Max.imum Tune LlOl for maximum muter reading.
S\
MOD-l
2.
l~lv'-l
B Ll02 & Ll03 ~laximum Tunu Ll02 and then Ll03 for the nwximum meter readinJ.
>-----
~· 0V~
c
I
3. TlOl & T 102 See Procedure
j
\ • MULT-1
I 4.
r-s·
Ol,i
D ':S!<-}
.,.
TlOJ, T 102. See Procodux'e
~ \ JULT-2 TlOl & Tl04
1
F
l'r c ~-
Tl05, Tl04, Soe Procedure
~~{
\'!ULT-:J
Tl06
&
Tl07
~----
f - ' -- .
6.
""\~
G
~-;~ lC;]·_,_
TlOtl. Tl07 ~Iaximum
~\)~J
AMPL-1 & Tl06
c
1' 5 6
--~---+-·-
~----~-
?\ ;; - - - · - --·-·-·-. '-- - --
I 1.
Cl<l::l , .lilaximum
I
-11
AMPL-1
/7\
DRIVE
~ I
(on PA)
R216
L__
Tune TlOI for
'
dip in meter re:1ding. and then tune Tl02 for maximum
meter reading:.
Tune Tl03 for maximum motor reading and •·o-<Jdju!Oi Tl 02 ocd T101 for
maximum meter reading. Then tunc Tl04 I.' or
'
dip
"'
meter readinp;.
Tune TlO::~ for maximum met or rending and ro-adj ust Tl01 for maximum
meter reading. Then tunu Tl06 for
'
dip in met or reading and Tl07
for maximum meter reading.
-·~-~~~--- '
- -
T "me T108 for maximum meter reading, and then ro-adju::;t T!07 and
Tl06 for maximum meier reading.
Move the black motering plu~ tn the PO\\·Ur Amplifier metering jack
and tune Cl4J and Cl56 for maximum motor reading.
Set Power Adjust potentiometer R216 00 tlw PA board ['or tllo desired
po·wer output (from 1 5 to 50 Watts).
ALIGNMENT PROCEDURE
25--50 MHz, 50-WATT STATION TRANSMITTER
INTERMITTENT
&
CONTINUOUS DUTY
Issue 2 9