Motorola SABER I User Manual page 39

2.
VCO
and Reference Motlulation Alignment
When adjusting deviation, two separate adiustments are required
-
one
for VCO modulation
and
the other for REFERENCE
modulation.
When
aligning VCO and Reference Modulation,
you
can measure the deviation during the
alignment
process or in "real time."
You
do
not
have
lo
reprogram
the
radio
to
measure
the change. However, you will have to reprogram
the radio
to
make these
charpes permanent.
Do
NOT turn off the radio while aligning this
parameter. The procedure given below will
go
through both
ol these adjustments.
(a).
Follow
the'Setup Procedure in Section Vl-A,
Fig. 8.
(b)
Connect
the RF BNC oonnector
to
a
50 ohm load and to a service monitor so that you
can measure deviation.
(c)
Select
the VCO Modulation lunction on the ALIGN CHANNEL menu using the
ENTER
key.
(<l)
Using
the
UP
anow key,
set the
VCO Modulation value to
$1F.
(e) Seba the
REFERENCE Modulation lunction on
the ALIGN CHANNEL menu by using
rhe ENTER key.
(f)
Using
the
UP
arrow key, set
the REFERENCE Modulation value to
$0F.
@)
Now select
the VCO Modulation lunction
on the
ALIGN CHANNEL menu.
(h)
Apply
a 1 kHz, 25
mVrms tone to
the
external
microphone port on the test set. Measure
this levet at
the AC/DC metering iacks on the Portable Test
Set.
Measure deviation
by
keying up the radio.
(i)
De-key
the radio and adjust the
VCO modulation value (decrease the value
if
the
measured deviation
is
higher than
the required value) by using the
DOWN key to
decrement
value.
The valid range
for this parameter is from $00 to $1F with a delault
value of $1C.
0
Re-key
the radio and
measure
the deviataon. Repeat the procedure (this step and the
step above this) until
the required deviation is reached.
(k)
Apply
a 0.355 Vrms, 1 kHz tone to the
auxiliary
transmit port on the radio (the female
BNC
connector). The signal level should be measured with the audio generator
connected
to the radio.
To do
this you will
have to use a T-connector
so
that you
can
simultaneously apply the
signalto the
radio
as
well as applying it
to
the AC meter.
(D
Seba lhe
REFERENCE Modulation lunction on the ALIGN CHANNEL menu by
using
the ENTER key. By selecting this lunction,
the radio
service software enables the
auxiliary port
ol the radio after being keyed.
NOTE
Relerence modulation cannot be aligned on channels that have MDC signalling
enabled. On completion o,
the MDC signalling, the radio disables the auxiliary port.
(m)
Key
the radio, and measure this deviation and note it as DEV
t.
De-key
the
radio
(n)
Remove the 1 kHz
lone and apply a 0.355Vrms, 20 Hz tone
to
the auxiliary port.
(o)
Key
the radio, and measure this deviation and note it as DEV
2.
De-key
the radio.
32
Servicing the Radio