Motorola R2550 Service Manual

							(00 
- 
19)  and  the 
monitor  and generate 
frequen-
cies  associated  with 
each.
To  change  the preset 
memory  frequencies,
perform  the following 
steps:
a.  Preds 
the MEM  key 
to 
access  the special
Memory  scrsen.
b.  Move 
the cursor  to 
the  appropriate  digit of
the  monitor 
or generate 
frequency  value
displayed,  and  enter 
the desired  frequency
information.
c.  Press 
the 
return  key  to 
return to the  previ-
ous  screen.
40 
						

							Section 
4
APPLICATIONS
4-I  BASIC  FM 
TRANSMITTER  TESTING
This  section  of the 
manual  contains  information
on  typical  tsst 
setups  to perform 
some of 
the
more  common  radio 
tests 
using  the 
R-2550. Motorola 
takes no 
responsibility  for 
application
accuracy,  applicability,  or 
safety.  Always 
refer
to  your 
own transceivers  service manual 
for
recommended  test 
methods 
and specifications.
Mtc
AUDIO
IN
TRANSMITTER  UNDEB  TEST
Figure  4-1. 
Basic  FM 
Transmitter  Testing 
Setup
4l 
						

							4-l.l 
Basic FM  Transmitter  Testing 
Setup
Refer  to Figure  4-1. 
Connect  the R-2550  Ana-
lyzer  RF 
VO  port 
to the  RF 
output  of 
the  trans-
mitter  under test. Connect  the R-2550  Analyzer
MOD  OUT jack 
to the  mic 
audio  input 
of the
transmitter  under test.
CAUTION
For  transtnit  power 
output mea-
surements,  connect 
the 
transmit-
ter  under  test 
only  to  the  R-2550
Analyzer  RF I/O  port. 
Do not
connect  it to the  R-2550 
Analyzer
ANT  port. 
The ANT  port 
is used
with  an 
antenna 
for off-air
reception.
The  built-in  RF 
load  dissipates
up  to 50 
W 
for  three 
minutes 
and
up  to 125 
W 
for  one 
minute.  If 
a
high-power  transmitter 
is keyed
into  the R-2550  Analyzer 
for a
rtme  long  enough  to 
threaten
overheating  the power 
measuring
circuitry,  the systems  audible
alarm  sounds 
and the 
display
changes  to 
the  RF 
LOAD 
OVER
TEMPERATURE  w 
arning,  si gnal-
ing  the operator  to 
unkey  (refer
to  paragraph 
3-4). 4-1.2 
Transmit 
Power, Frequency,  and
Frequency  Deviation  Measurements
1.  With  the cursor  located 
within the RF
Control  zone (refer 
to paragruph 
3-2),
press  ttre MON 
softkey  to 
Place  the
R-2550  Analyzer  into 
its Monitor  mode
of  operation.
Monitor  Mode
Sofikey
Within  the RF 
Control  zone, set 
as fol-
lows:
2.
RF Conlrol:  MONITOR
Iii!:*r::i:   i:i;ili: 
l,ll:j
Freq:  816.5000 
MHz
Altenuatlon:  -20 
dB
Mon RF  ln:  RF l/O
Modulatlon  Type:  FM Transmitter 
(
Frequensy
J. Set  the  SQUELCH  control 
to 
threshold.
For  low-power  transmitters,  it 
may 
be
necessary  to use 
a lower 
attenuation  value
in  order  to 
unsquelch  the monitor  (refer
to  paragraph 
3-5.1). Too high 
of 
an  atten-
uation  setting  or 
too  tight 
a squelch  set-
ting  inhibits  the frequency 
error reading
(refer  to paragraph 
3-7.1.1). Accurate
measurements  require 
sufficient  signal
level  from 
the radio 
to fully  quiet 
the R-
2550  Analyzers  receiver. Use good 
qual-
ity  cable  of minimum  length to prevent
cableloss  which 
can be 
a significant
42 
						

							4.
factor 
in 
RF  power 
measurements  espe-
cially  at 
UHF  and above
With  the 
cursor  located 
within the 
RF
Control  zone, press 
the RF 
DISPLAY  soft-
key:
Key  the 
transmitter  and 
read 
the power
(Input  Level)  and 
frequency  error (Freq
Err).  Refer 
to your 
radios  service manual
to  determine  if 
power 
and frequency  are
within  specified  limits 
and determine  if
any  adjustments  are 
required 4-t.3 
Modulation  Measurements
1.  Key  up 
the  transmitter  with 
appropriate
PL  (or 
DPL)  enabled
NOTE:  Microphone  pickup 
of 
background
audio  noise in 
the  testing  area 
mtry
result  in 
deviation  tneasurernent  er
rors.  Consult  your 
transceiver  mnnual
for  the 
proper  procedure  to 
disable
the  microPhone  audio
When  monitoring  the 
PL (or 
DPL)  devia-
tion  as 
follows,  refer 
to your 
radios
service  manual 
to 
determine  if 
any  adjust-
ments  are required.
Introduce  a 
! 
kHz  audio  modulating
signal  from 
the MOD 
OUT connector
toiateO  on 
the  front  panel 
of the  R-2550
Analyzer  to 
your 
radio  Check  your 
ra-
dios  service  manual 
to 
determine  the
minimum  audio 
signal  level 
required  for
proper  MIC sensitivity  as 
well  as the
maximum  level 
required  to 
ensure  proper
IDC  (Instantaneous 
Deviation Control)
function.
5.
J.l1:1 
1;1.  iii: 
i::iiliri..\1
l*,.rir  i:jl.:{::  fi 
itt  :.iiir,; 
ii:i:{  DeV: 
75O Hz
ir:i?{:  i:t:. .: 
..ll 
ii::i  ir:i.lili 
1...i 
:ii.i;  :.li:N::
f211  :ril 
ili: 
i:rii;i]i.ri.
ii,,ti!  !:t:x:i  fi 
ii.i  :,:Jii.; 
].:ii-l;  !-!*r: 
iji:ii!:::
F1pqEn:  + 
47Hz  lnputlvl:705  dBm
43 
						

							The 
voltage  levels 
displayed  in 
the
iud.u  Cintrol 
zone are 
Peak  oPen,
*ii,  ,oltog  Source 
imPedance  of
ie  MOD  OUT 
Port is 
100  ohms
lum  the lkHz  signal  on 
and  set 
for
il**  level 
as 
detennined  in 
step  3
Verify  proper 
MIC sensitivity  by 
reading
;;;i;,i.n.  Refer 
to 
Your  radios 
ser-
irc,  **our  to 
determine  maximum  rated
;ffi  deviation  to 
dercrmine  if 
anY
odio**tno  are 
required 7. 
To 
measuro  the 
percen*gt:1  distortion
locate  the 
cursor  within 
the 
Display  Con-
t  ol  ,onr,  at 
the  fiieter:  field 
Press 
the
lr.rr  orsr  softkey  to 
measure  pefcentage
of  distordon
Refer  to 
the  displayed  digital-readoot-1nd
lt-gtuptt.  Refer 
to 
your 
radios 
:ervlce
Litirt  determine 
if 
any  adjustments
are  required.
8.
Set  ttre  l 
kHz  audio  modulating  signal 
for
maximum  level 
as 
dercrmined  in 
step  3
Repeat  stePs 4 
and  5
.(tt.!iii.- 
lilill:  (i(d! 
t. k
FixedlkHz:  040 
V 
-
i:i,friii,l  i.,:i:  i:r
i:i:ii:.}.  i3i 
ri 
fii:
!.)i!!t?:  /v{(! 
V I
r;od{tl  I 
il.!iiviiiiId{;iAlil:li
;rt,::rnai:  {iin 
V 
ri
f.Jd.:!l$r  l::ii 
i)iiiiri.rJi
lfuii  i:nr,::  ili{i..i:l:f  :$ilil 
D€v:.35 kHz
;r;1r1.  iir...  4) 
ii;  i::i:ir: 
l li 
:(ii;  iii:tl:!
44 
						

							4-1.4 
Off-TheAir  Measurements
1.  Connect  the 
TEKA-24A  Pick-Up 
Antenna
to  the  R-2550  ANT 
Port OPerate 
the
transmitter  under 
test 
either  into 
its 
own
anrcnna  or 
into  a 
dummY  RF 
load
2.  With  ths 
cursor  located 
wittrin the 
FtF
Control  zone, 
press 
the MON 
softkey  to
place  the R-2550  Analyzer  into 
its 
Moni-
tor  mode  of 
oPeration 4. 
Check  transmitter  frequency and 
modula-
tion  as 
detailed  in 
paragraphs  4-12 
and
4-r.3.
NOTE:  This 
method  may 
be used  to 
verify
ftequencY  and 
modulation  of 
a re-
motely  located  tansnxitter  by 
reducing
the  attenuation  setting 
to 
fully  realize
the  sensitivity  of 
the  R-2550  Analyzer
  Off-The-Air  monitor 
function
3. Monitor 
Mode
FFcontrol:  lMolttlronl
Preset--  B/W: 
NB
FIeq:  816.500OMH2
Anenualion:  -20  dB
lvlon  RF 
ln:  ANT
Modulatlon  TYPe: 
FM
Set 
the SQUELCH  control 
to 
threshold
Within  the 
RF 
Control  zone, 
set 
as fol-
lows:
Transmitter Carliel
FrcquencY
-20  dB
Antenna  Poil
FM  Modulalion
45 
						

							IVER 
TESTING
ual  connins  information
,i  p.rrot* 
some of 
the
rts  using  the 
R-2550 The 
R-2550  Analyzer  DVM 
input 
is 
unbalanced
Gfi;;;;TY:l;ffi  fi?i::3ff :::#;
to  measure  balanc
receiver  audio 
outputs  or 
telephone  lines
Figure  4-2 
Basic  FM 
Receiver  Testing 
Setup
46 p.^gffio-t
RECEIVEB  UNDER 
TEST 
						

							-^-2.1 
Basic 
FM 
Receiver  Testing 
Setup
^tefer  to 
Figure  4-2 
Connect  the 
R-2550  Ana-
lyzer  RF 
VO  port  to 
the radio  antenna  connector
Connect  the 
radio  audio  output  to 
VERT/SINAD
port  of the  R-2550  AnalYzer
CAUTION
With  some  radios,  grounding  the 
speaker
leads  wiII 
damnge  the 
audio  circuitry
lJse  isolation  techniques  on 
these  radios Within 
the 
Audio  Control  zone 
set as
follows: Setto6oP/o ol
System  Deviallon
3.
l.  With  the 
cursor  located  within 
the 
RF
Control  zone (refer 
to paragraph 
3-2)
press  the GEN 
softkeY  to 
Place  the
if-ZSSO  Analyzer  into 
its 
Generator  mode With 
*re 
cursor  located 
within ttre 
Dis-
play  Control  zone, press 
the AC VOLTS
softkey  to 
display  the 
ac 
voltmeter:
Adjust  the radio 
for rated  power 
output
by  computing  voltage 
needed for 
rated
pt*.t  with load 
resistor/speaker  in 
use
anO  setting  the 
radio  volume  to 
produce
required  voltage-
4.
of  operation.
Generalor  Mode
Soltkey
a!
2.  Witttin
lows:
NOTE: the 
RF  Control  zons, 
set 
as fol-
5.
Radlo  Under
Te6t  FrequencY
For  setuP  and 
distortion  mea-
surements,  set 
outqut  level to 
at
least  i0 
dB  above  sensitivitY
threshold.  ( 
-80  dBm  re 
commende  d) {.1:::rl*l 
1,;:;.1:iiiir  illjriii.tii:.ii.::i;
RF  Conlrol:  GENERATE
6,ii?*i.r:.   Lrlid: 
itlli
Freq:  816.500o MHz
Output  Level:  -1 
12  dB
Mon  HF ln:  RF 
l/O
Modulation  TYPe:  FM
14ri:+rr ;:.{}.:Tii..-ift:{if 
:jii
f:r.r.1.i  Jt:  i!  i
n 
						

							6. 
With  the cursor  located 
within 
the Dis-
play  Control  zone (at 
Display:),  press 
the
EXT  SCOPE 
softkey.
Set  scope  vertical 
and horizontal 
detlec-
tion  to 
observe  sine  wave  from 
receiver
audio.
Dlsplay:  EXTERML  SCOPE
l..it]:ii..  i:i.ii:t  ii$:.dii. 
ll{r$i.ri..jf} 
i.:i.i
l{rt:  i.ltf:i:
i:1.,
4-2.2  Receiver  Distortion 
Measurement
1.  With  the cursor  located 
within the Dis-
play  Control  zone, press 
the EXT  DlsT
softkey  to 
measure  percentage 
of distor-
tion.  enemat
Dlgorfon
Refer  to 
the  displayed  digital 
readout  and
bar  graph. 
Refer to your 
radios  service manual 
to determine  if 
any  adjustments
are  required.
4-2.3  SINAD  Measurement
1.  With  the  cursor  located within the Dis-
play  Control  zone, press 
ttre SINAD 
soft-
Refer to  the displayed  digital readout 
and
bar  graph.
Within  the RF 
Control  zone,  adjust  the
selected  RF level 
until the SINAD  read-
ing  on the 
SINAD  meter 
averages  12 dB
(instantaneous  reading will vary 
several
dB).
fit:f(it:lr|i: riiiiiii:.:ltll;il:j
Fii?$xli:  iil,lfri: lill
fr*!:ii  {jili.l.;{:iiii 
lrlil,r
Output  Level:  -1 
15  dB
ilir..ii  iii: lr,: 
fi:: iii::
l.,j:-.iiri;*ii+rittj.i{..  i;f.i
7.
ii{.iiit::;:rl:.,{i.;
2.
3.
2. key.
Irt
{.:r rr 
i:ri  :i 
i.-;.}:.;  r.ri 
: .} 
f . 
i..i  f 
j 
$::l
48 
						

							4. 
Note  RF 
output  level 
required 
for  SINAD
reading  of 12 
dB  (-115 
dBm tYPical
dependent  on 
manufacturers  specifica-
tions).
NOTE:  RF 
output  level 
can be referenced  to
mV,  uV, dBu,  or 
dBm.  Selection  of
units  is available  within 
the Display
Control  zone (OutPut 
Level:).
4-2.4  Modulation  Acceptance Bandwidth
1.  Set  the 
volume  control of 
the  radio 
to
lTTo  of its 
rated  audio  output  level.
2.  Set  the RF output  level 
6 dB  (doubles 
the
voltage,  i.e. 
0.35  uV 
increased  6dB 
= 0.7
uV)  above  the 
RF 
output  level 
required  in
paragraph  4-],) 
to 
achieve  the 
SINAD
reading  of 
12 dB. Read 
the  deviation  level 
required  in 
step
3.  A 
typical  modulation  acceptance band-
width  of a 
5  kHz  receiver 
is 
7 to 
8 kHz.
Refer  to your 
radios  service  manual 
to
determine  if 
any  adjustments  are 
required.
4-2.5  Receiver 
Sensitivity  Testing
(20  dB 
Quieting)
1.  With  the cursor  located 
within the RF
Control  zone, press 
the MON  softkey  to
remove  input 
signal  from 
the radio.
4.
Increass  the deviation  level 
until the
SINAD  meter 
display  returns 
to 12 
dB.
lncrease  as
required Monilor 
Mode
Soltkey
With  the 
cursor  located 
within the Dis-
play  Control  zone, press 
the AG VOLTS
softkey  to 
display  the  ac voltmeter:
Fi::ilr:t:h 
t 
i!:  iii!ll,:ifilf  i 
i:r
l:ii:rgir1:  !:it#:i,i[:l
fr4r:i:  li!{j.:i(ii!{iiiiiii:
Output  Level:  -109 
dB
Iir,ii  iii: 1.:  liir 
ln :
lrlt:rilr  i liiiir:rl  : l 
ii  {:.  ii 
l: lncrease 
6 
dB
3. 2.i1,l{ialj:r.i!ii: 
i).i:1::1:{ri.;.
Fixed  lkHz:  7 kHz  x
ilitJi:  ii.aiii 
ii.i:i: )
i.:i{triil::::.1:i.iiii;:li,r.itAij[:i.!
EkHz-
i:  .:]::r 
rl. :/.  1.
i-]tiftfri:;:.11lj4$Liit;.f..4i.ri:ii
$1:::.tt  r:iili/|iil
i::  l: 
i:r.  ri 
i...;.1:.;  ;)!:
49