Eddystone 990R - Page 17

Aerial
*
The receiver is
designed
for use
with aerials
closely matched
to
750
and
a
suitable
BNC connector
is
supplied
to
mate
with the coaxial
aerial socket
at
the
rear
of
the
set*
Low-loss
semi-air-spaced
feeder
cable
should be
employed
especially
when
oper-
ating
at
frequencies
towards
the
upper
limit
of
the
frequency
coverage.
Selection of
the
best
aerial for
use
with
the receiver
will
depend
largely
on
the
application for
which
it is
to
be used
and
must
of
necessity
be
left to
the
user
since
many diverse
types are
available
for
use
in
the frequency
band
concerned.
Reference
should
be
made
to
one
of
the many
handbooks dealing specifically
with
VEF
antenna
design.
IF Input
and
Low-level
Output
(l)
.
BNC
termination.
Facilitates
connection of
external
converter
to
extend
coverage
of
the
built-in
timer
unit
(input
frequency
10.7
MHz). All control facilities
function
as
for normal
operation
with
the
exception of the
TUNING, RANGE
SWITCH
and
SYSTEM
SWITCH.
A small
toggle
switch at
the
rear
of the
set
allows the built-in
tuner
to
be
shut down
to
prevent
signal
and noise breakthrough when using the
receiver
in
this
manner
.
The
same
socket
can
also
be used to extract
a
low-level signal
at
10.
7
MHz
w
ith
greater
bandwidth
than is
available
at the main
IF Output
socket.
Bandwidth
is
of
the
order 1
MHz
at
the
higher
frequencies in
the tuning
range and it
may well be
found
advantageous to
drive the
associated
panoramic
display unit
from this
output
in
certain
applications.
Adequate
drive is
available
for this
purpose.
IF
Output
(
2
)
.
BNC
termination.
Provides
output
at
10.7
MHz for
use
with
panoramic
display
or
other
ancillary
units.
Output is of
the
order 50mV
and
bandwidth
is
determined
by
the
setting
of
the
panel
SELECTIVITY
SWITCH
(either
50
or 200
kHz).
Video
Output
.
BNC termination.
Suitable for
external
loads
of
the order 10000.
External
lead
lengths
should
be
kept
to
a
minimum
to
preserve
the high-frequency
response
which
extends to
100
kHz with
external loading
of
250pF. A
small
DC
potential
of the
order
5.5
V.
is
present
at
this
output.
External
Oscillator
Input
.
BNC
termination.
Permits
connection of
external
oscillator drive to the
Mixer Stage
for
high-
stability
working.
Basic
drive
frequency
range
required
is
37-7-250.7
MHz
but the
built-in
frequency
multiplier
allows
for
multiplication
by
factors of two
or
three, so
reducing
the upper
limit
to
less
than
85
MHz.
Drive
requirement
from
a
low-
impedance
source
is
of
the
order
5G0mV.
The normal
oscillator
tuning
circuits
remain
operative
and
discriminate
against
spurioiis
drive
signals in
this
mode of
operation.
External
Loudspeaker
.
Two
terminals
are
provided
for
connection
of
an
external
loudspeaker.
The
output
is
marked
"30"
and
suitable
speakers
are
available in the Eddystone
range.
Full
details
are
available on
request.
Telephones
.
The
telephone
output
is
suitable
for use
with
low-impedance
type
headsets.
Circuit
arrangements
provide
for
muting
of
the
external
loudspeaker
on
insertion
of
the
tele-
phone plug.
The
Internal
speaker
can
be cut
by
means
of
a
panel
switch.
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