Alignment Procedure; Frequency Characteristics Vs. Temperature - GE MASTR II Maintenance Manual

MODULATION LEVEL ADJUSTMENT
The MOD ADJUST (Rl27) was adjusted to the proper setting before shipment and should
not normally require readjustment . This setting permits approximately 75% modulation for
the average voice level. The audio peaks which would cause overmodulation are clipped by
the modulation limiter. The limiter, in c onjunction with the de-emphasis network, instan-
tane ously limits the slope of the audio wave to the modulator, thereby preventing over-
modulation while preserving intelligibility.
TEST EQUIPMENT
1. An audio oscillator (GE Model 4EX6Al0)
2, A frequency modulation monitor
3. An output meter or a VTVM
4. GE Test Set Models 4EX3All or 4EXBK12
PROCEDURE
1. Connect the audio osc illator and the meter across audio input terminals JlO
(Green-Hi) and Jll (Black-Lo) on GE Test Set, or across P902-6 (Mike High)
throug h a 0.5 microf arad (or larger) DC blocking capacitor, and P902-5
(Mike-Low) on the System Board.
2, Adjust the audio oscillator for 1-Volt RMS at 1000 Hz.
3. For transmitters without Channe l Guard, set MOD ADJUST Rl27 for a 4.5-kilo-
hertz swing with the deviation polarity which gives the highest reading as
indicated on the frequency modulation monitor .
4. For transmitters with Channel Guard, set Channel Guard MOD ADJUST Rl28 for
zero tone deviation. Next, with the 1-Volt signal at 1000 Hz applied, set
MOD ADJUST Rl27 for a 3.75 kHz deviation. Then remove the signal from the
audio oscillator and set Channe l Guard MOD ADJUST Rl28 for 0.75 kHz tone
deviation.
5. For multi-frequency transmitters , set the deviation as d e scribed in Steps 3
or 4 on the channel producing the largest amount of deviation.
PA POWER INPUT
For FCC purposes, the PA powe r input can be determined by measuring the PA supply
voltage and PA current, and using the following formula:
Pi
=
PA voltage x PA current
where :
Pi is the power input in Watts,
PA voltage is measured with Test S e t 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
the 1-Volt rang e ( 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 G in the Test 1 position,
and with the HIGH SENSITIVITY button pressed (10 amperes f ull scale).
Example:
Pi
=
12,6 Volts x 5.0 ~:> .mperes 63 Watts
I COM FREQUENCY ADJUSTMENT
First , chec k t he fr e quency to de termi ne if a ny adj u s tment i s required . The f re-
quenc y shou ld be set wi t h a f r equency meter or c ounter wi t h an abso lu t e accuracy tha t
is 5 to 10 t imes better t han t he t olerance t o be mainta ine d , and with t he ent ire rad i o
as near as pos sible to an ambient t emperature of 26 .5 °C (79 , 8 °F).
M ASTR II ICOMs s hould be rese t o nly whe n t he f requency shows deviations in excess
of t he f o llowing limits :
A.
B .
±0.5 PPM, when the r adio i s at 26.s •c (79.B °F).
±2 PPM at a ny other tempera ture wi thin the r ange of -5 °C to +55 °C
(+2 3 °F to +131 °F).
C . The spec ification limit ( ±2 PPM or ±5 PPM ) a t any tem perature wit hin
the ranges of -40°C to -5 °C ( -40° F to +23 °F) o r +Ss •c to +7 0 °C
(+13 l °F t o +l58 °F ) .
If an adj ustment i s r e quired, pry up t he c o ver on the top of t he ICOM t o expose
the trimmer , a nd us e one of the f ol lowing proc e dures :
If the radio is a t a n ambient tempera t ure o f 2 6 ,5 °C ( 79. 8 . F) , s et the osc i llator
for the correct operating fr e qu ency .
If the radio is not at an a mbi e n t temperature of 2 6 .s •c, set ting errors ca n b e
minimiz ed as f o llows :
A. To hold s et t ing err or to ±0, 6 PPM (whi~h is cons idered reas o nable for 5 PPM
ICOMS) :
l .
Maintain the radio at 26,5 °C (±5 °C) a nd set the oscillator t o
desired f r equency , or-
2. Main tain the radio a t 26. 5° C ( ±l0 °C) and o ffse t the oscilla t or, as a
func t i o n of actual temperature , by the amount s hown in Figure 9 .
B . To hold s et t ing er ror t o ±0.35 PPM (whi c h i s c o ns idered reasonable for
2 PPM I COM s ): Main t a in unit at 26 , 5 °C (±5 °C) and o ffs et t he oscillator ,
as a fu nction of actu al t empera t ure, b y t he a m ount s hown in Figure 9 .
For example: Ass um e the a mbient temperature of t he ra dio is 18,5° C ( 65.4° F). At
that tempe rature, the curve shows a correc tion fa c tor of 0.3 PPM. (At 25 MHz, 1 PPM
is 25 Hz . At 50 MHz, 1 PPM i s 50 Hz),
With a n ope rating f r e q uency of 50 MHz, se t t he osc i l lator f or a reading of 15 Hz
(0.3 x 50 Hz) hi g her t han t he l icensed opera t ing fre que n cy . I f a ne ga t ive corre c tion
factor is obtained ( at tempera tures above 26.5° C), set the osci l l ator for the indi-
cated PPM l ower than the l ice nse d operating f requency .
DEGREES FAHRENHEIT
61.8 65.4 69.0 7Z.6 76.6 7'-8 83.4 87.0 90.6 94.2 97.8
i+0.6
~+0.5
-+o.4
~ +0.3
a:
+0.2.
a: fO.I
UJ 0
~-0.1
z
-O.l
~ -0.3
CJ -0.4
UJ -05 a: .
LL. -0.6
[""-..
I'-.
I
I
I
"-'
i ~"---...
r-......
I
I
I
:
I
I
............
~'--..
T
t-....1
I I'-. r-......
I
16.5 18.5 20.5 22.5 24.5 26.5 28.5 30.5 32.5 34.5 36.5
I I I
-5• LIMIT REF. +~· LIMIT
DEGREES CENTIGRADE
RC-'%453
Figure 9 - Fr e q u enc y Charac t e ristics Vs. Tempera t ure
EXCITER
METERING---::::~
JACK
J103
MOD
ADJUST
R127
CHANNEL
GUARD
MOD
ADJUST
R128
N I A •
SYSTEM
BOARD
METERING
JACK
.:._ANTENNA
JACK
J906
TRANSMITTER ALIGNMENT
!!:QUI PMENT REQUl Rl':D
1. GE Tes t Set J. t o d e l 1 EX::S A11 o r Test Kit. 4 EXBKl 2 .
2 . A 50 - ohm wa t tmeter co nnected to ~n te n n a jack J 906,
3. A f r equency count e r.
PRELDUNARY CHECKS AND ADJUS 'J'~!£NTS
1.
P b ce ICO~s
o n
£xc1t er
Boa rd (cry10:t al.
fr e quency -= opo r~t i ng
fre que ncy .;. 3 ) .
2. For a larR"e Ch:1 1 1ge i n f requency or a bad l y llli s:l- al 1.gn cd t r a nsmitter , p r e - s e t t h e s l ugs i n T l Ol t hr o u g h T l 08 , and LlO l , Ll02 a nd
L l 03 to the bottom o ( t he co il f o rm.
r-------------------------------------·--------- ~OTE --------------------------------------~
The t u n i n g fl' Oqu e ncy Cor mu lti - freq u ency t r ansmi t t ers is de t e r mined by t he oper ating freq uenC}' a nd t h e f r o -
que nc y spr ead bo t woeen t r a nsmit ters . Re f c 1· to the t a b i ·e bel ow for ma )timum f req u enc y s pr ead,
3. For multi-f r e quency t r i'ln~ mitt ors wit h a ! r oq u c ncy spro n d l ess tha n t ha t s pec H ied i n co l u mn {l) , tune t he tr a nsm i tters to the
lowest f req u e n cy.
For freQ llc':!nq' spread exceeding t he limits speci f i od i n column ( 1) , tun c- t he t ran s mi tter uf5 i n g a c ent e r fr e quenc y t u nc u p ICOM.
Ex cept the max i mum t r e q u en c y spread ca n be exte nded to t he li llits :spoc1 ticd i n c o l umn (:· l ) with l dB d egra dation .
For t u n i ng LlOl , Ll02 , Ll03 . Alwa ys t u ne L l Ol , Ll02 , L l 03 o n t h e lowes t fre q uency.
~lu lt i - freq u cn cy Tra ns mi t ter T u n ing
MAXIl.IUM F REQUENCY SPREAD Tr<J~ n Sm itt ~z·
Freque nc y Range
( 1) without c e nter tu n i n g wi t h c ent e r t un i ng with c e nt e r tuni n g
25-30 Mllz
30-36 MHZ
36- 4 2 l!.Hz
42- 50 :dHZ
. 080 MHz
. 1 0 0 .Mifz
. l2 0 11 Hz
.140 MHZ
, 160
MH:z
. 2 00 l1IIz
. 240 M Hz
. 2 8 0 MHZ
( l dD dogra < Ja tion )
,320
~Hz
. 4 00 M HZ
. 470 M HZ
. 54 0 MHz
4 . Con nect t he r ed plug on t he GE Te s t Se t t o thG Sy s t o 111 Bo~rd merto ring j a c k , t~n d tho black p l ug to t h o Exciter m e t ering j~ck .
Set t he polarit y t o ... , a n d s et t ho ra ng o to tho Tes t 1 posit i o n (1- Volt p os i tion for 4EXSX:l2 ) f or all ad j us t ments .
NO'TE : ' 1 \ ' i t h t he Tes t Set con ne cted to t h e PA motori ng j a c k , t nco vo lt: a~tco r ea di n g O) t pos ition " F " wlt h the HIGH SENSITI VITY
b u t t on pres sed ma y b e c o n v e rto d to dri ver c o l l ect or current by r eadi n ~ t h e curr en t as 10 a mpere s fu l l s e al(! . T he v olt age
r e adi ng a t position " G" wi th t he HI GH SENSITI VITY b u tton p r esse d mt~ y be c o nvert ed to PA c ollec'tor c:u r r e n t by t•cad i ng t hG
c urr e nt as 10 ~lrJpo •· es f ull ~ca l o.
5. A l J adjus tments fire 1n ade with the t ra nsmitt er k e yed. Un key t be trans mitte r betwee n steps. to a v oid u n n e c e ssa r y hea t i ng.
STEP
1 .
2 .
- -
3 .
4.
5.
6 .
7 .
"·
~IE1' E R POSI TJON
A
W OD - 1
c
MULT-1
D
Mt.:l:r-2
F
)IULT - 3
G
AMPL - 1
D
A)tPL- 1
DR.IVE
( o n PA )
TU~l NG CONTROL
L l Ol
Ll 02 & Ll 03
1'101 &. T l 02
T l 03 ; '1'102
I
T l Ol & 'tl04
T10 5 , 1'104 ,
T l 06 & T107
Tl OS , '1'107
& T 10 6
Cl43 1
Cl56
R2 16
Jt. ' !ETER READI NV
Jda x i m\\fll
I
Jt. l ax i mum
See Procedure
Sec ProcedurE.
See Proce d u r e
M:axi111Urn
M a x i mum
PROCEDURE
Tune L lOl f or max i mu111 me ter r ea d i n g .
Tu n o L l 0 2 and t hen L L03 for t h e maxi mu m mete r r eading .
Tu ne T l 01 for a d i p i n me t e r r e ad i ng, a nd t h.e n t una T102
for
maximulll me t e r
r e a ding .
Tu n e T lO:i fo r maxi mum me te'r r't::-ading and r c - adj us:t T l 0 2 a nd
T l 0 1 for maxi mum ma ter rea d i ng. T hen tune Tl04 fnr a d i p
in met e r re a di ng.
Tu nc T 105 f or fll.oJXi muM l1\ct er r eading ;a nd r e-adjus t T l04 for
ma Jti mum meter r e a ding . The n t u n e T l 06 f o r a d i p in me t e r
•·ea d i n g a nd T l 0 7 for lrttlXirnum me t er readin~ .
1' u n o Tl0 8 for ma xi mu m met e r r o adi n li!; , and the n r e - adj us t
T l 07 a nd TLD6 .C o r ma x i mum meter r e adi ng .
~lov e the bla c k mQteri ng p lu g t o th.e Power Am pl11 1 o r me t er-
i ng j ack and t u ne C143 a nd Cl 56 f o r ma x imum met&r ro ad i n g.
With the ba t tery v oltage <t"t 1 3 . 5 Volts o r t he PA c o l lector
v o ltage ::a t 13. 1 Vo l ts , s ot Pow e r Ad j ust pote n t i o mot o r R2 16
o n the PA boa r d for t h e d e::; ire d p o wer o u t put (fro m 15 to
5 0 W att s ) .
I f the batter y voltage i ~ not 1\ t 13.6 Volt s o r t t]e colle ~ tor
voltage at 13 . 1 Volts a nd fu l l ra t e d o u t put i s d esi red ( SO
Watts a t 13 . 6 Vo lts), set R2l6 f o r t he outpu t power accor d-
i ng t o t be b attery voltag e o r co llect or v o lt a g e shown i n
F i g u r e 10 .
~-------------- NOTE ----------------~
l
The PA c ollector vo lt age i s me asur e d as
I
___ d_ e s _c_r_ 1 b_ e_d_ 1 _ n __ t _ h c __ PA __ PO __ WE _ R __ IN _ :P _VT __ s_ e_ c t _ i_o_ n_. ___J
LBI-4896
ALIGNMENT PROCEDURE
25--50 M Hz, 50-WATT TRANSM I TTER
9 12 13
VOLTAG E
I I 14 1 5 1 6 I ss ue l
F i gu r e 10 - Pow er Ou t pu t Set t i n g Ch a r t