Marconi Instruments 2955 - Page 2

GENERAL
INFORMATION
AND
DATA
Counters
Due
to
there
being r.vo
frequency
counters,
simultaneous
AF and PP
frequency
readings can
be
displayed. Ranges
and resolutions
are
respectively 10 Hz to
20
kHz at
0.1
KzTand
1.5 to
1000 MKz
at
1 or
10
Hz.
Either
an
internal
or
an
external
frequency
standard
may be used.
Signal
generator
Tne signal
generator can be
amplitude,
frequency,, or
phase
modu-
lated, internally
or
externaHy,
the
internal
modulating
signal
being
obtained
from
the
.AH
generator. Amplitude
modulation
is
variable
up
to
70% for
carrier
frequencies
from
0.4
to 400
MHz. FM
deviation can
be
set
from
0 to
25 kHz,
and
4>M
deviation
from 0 to 10
radians.
Transmitter and
receiver
measurements
can be
made
from a
common
N-type
connector.
The
generator BNC
socket
is
automatically
protected
against
reverse
power
overloads.
ft
Modulation
meter
Automatic
frequency
tuning
and
levelling
of
the
modulation
monitor
provide accurate
measurements of
AM,
and
<I>M.
Because
of
the
independent
tuning,
modulation
measurements
are easily made on
duplex
systems.
The
modulation
may be
observed on
an
oscilloscope
and its
symmetry“checked
from
the
peak
and
trough
values
displayed
on a
dual
bar chart. The
demodulated
output
is
available
at a
rear
panel
socket.
Provision is
made
for audible
monitoring using
the
built-in
loudspeaker
or
by
an
external
loudspeaker
or
headphones.
RF
power
meter
The
absorption RF
power meter
will
measure
up
to
75
W
continuously
or
up
to 150
W
for
short
periods,
ever a
frequency
range
of
1.5
to
1000
MEiz.
Power
levels
may
be observ'ed on
an autoranging
bar chart
in
addition
to
the
digital
readout.
The
connection of
the throug.hUne
power
meter
(available
as
an
optional
accessory)
e.xtends the capability
of
the instrument by
enabling
measurements
or
forward
power,
reverse
power
and
VSWR
to be made.
AF generator
Tne AF
generator
provides a
range
of
frequencies
from
20
Hz
to 20
kfe
plus
a fixed 1 kHz
output used for
distortion
measurements
and
2
tone
test.
Its
audio
output is
available
at a
front pa.nei socket
and it also
provides
the
internal
AM.
FM
and
for the
signal
generator. A
combined
600
Q. balanced
to
unbalanced
converter
and
20 dB
attenuator
is
available as an
optional
accessory.
AF voltmeter Operating in
the range 20 Hz
to
20 kHz.
the
true
RMS
audio
frequency
voltmeter
has
pro%isions
for
measuring AF or
AF
plus
the
DC
component.
Band
-pass
and low-pass filters may be
selected.
Level may be
obser%'ed
on
an
autoranged
bar
chart.
Distortion
meter
Tie AF
distortion
and signal
to
noise
ratio
meter
and
the
associated
SINAD
meter
operate
at a
frequency
of 1 kHz
supplied
by
the AF
generator,^
The
bar
chart
displays
are
autoranged
at 10% and
30%
for
distortion
and
signal
to
noise,
dB
and 50
dB^ for SINAD.
^The CCITT
and
C-message
filters
(available
as
opriona'
accessories)
enable
psophometricaiiy
weighted
measuremients
to
be
made.
Tones
decoder and
encoder For
testing
selective
calling
tone
encoding
and
decoding
equipment,
the instrument is
capable
of
receiving
and
generating
four
defined
tone
frequency
standards
plus
a
user-defined
standard.
Sub-auaible
tones
can
also
be
generated.
Provision
is
made
to
receive
a sequence of
up
to
12
and
send
a
sequence
or
up
to 1 1
out
of 15
allocated
tone
frequencies. For
transmitter
testing,
each
received
tone
is
compared
with
the
standard
frequency
allocations held
in
memory
and,
if
within
limits,
its
tone
number and
%
frequency
error is
displayed.
For
receiver
testing,
the
tones
may
be
generated in single
step,
tone
burst
or continuous
cycle.
1-2
46881-622N
Aug.
88
(Am.
5)