Eddystone 990R - Operation

Certain
precautions
must
be
observed
when
using
the internal muting
facility.
Tun-
ing
adjustments
for
example
should
not
be
carried
out without
recourse to
the
built-in
tuning meter,
(greatest
accuracy
being achieved
with this in the
"EM"
position).
Accu-
rate tuning
ensures
that
the signal
is
correctly
centred in
the IP
passband
and
so
offers maxi mum
protection
against
loss of
signal
due to possible
drift
either
at
the
receiver
or
transmitter.
Use
of the
"WIDE" selectivity
position will prove
advantageous
in
this
direction
if
adjacent
channel
interference
presents no
problems.
Care must
be
taken
not
to
change
to an
alternative aerial
without first
checking
that
the initial
setting
of
the
MUTING GAIN
CONTROL
still provides
satisfactory
results.
Likewise,
the
settings
of
the
RP
and
IP GAINS
should not
be
disturbed
when
using
"MANUAL"
control,
since
any
change
in gain
in
this portion
of
the
receiver
will
directly
affect
the
level
of
noise
throughout
the set.
The
AP
GAIN
and
LINE
LEVEL
controls
however,
can
be
adjusted as
required
with
no effect
on
muting
performance.
It
may
be
found
best
therefore
to
operate
with
AGC in use, even though there
is no
real
need
to do
so.
This
obviates
any
possibility
of
inadvertent
adjustment
of
the
manual
controls
causing
loss
of
signal
since
these are of
course inoperative
with
the MANUAL/
AGC
SWITCH
at
"AGC".
Any large
change
in
operating
frequency
should
be
accompanied
by re-adjustment
of
the
MUTING
GAIN
CONTROL
to
ensure
reliable
operation of
the
muting
circuit.
A
compromise
setting
can
usually
be
found such
that
the receiver can be
tuned
over the
greater
part
of any
one
range
with
satisfactory
un-rauting
on
signals
of
5RP
upwards.
Care
should
be
exercised
to
tune
slowly,
making
full use of
the
"WIDE"
selectivity
pos-
ition
as
a
further
aid
to
ease
of
station
selection. Variation
in noise
level
from
range
to
range
is
such
that
different
settings of
the
MUTING GAIN CONTROL
will
be
required
on
adjacent
ranges.
This
should
present
little problem
since
it
is
doubtful
whether
the
muting
facility
would
be
required
in
this
mode
of operation, its
greatest
value
being in
spot-frequency
working.
Receivers
fitted
with
non-standard
filters
in the
"NARROW"
position
may suffer
some
degradation
in
muting
performance.
Operation
will
be
normal in the
"WIDE"
position.
Crystal
Controlled
Working
.
1
.
Calculate
the
frequency
of
the
crystal(s)
required
by following
the
basic rules
out-
lined
below.
Crystals
should
be
Style
"D" (international Style
"AA")
3rd
or
5th
overtone
(series
resonance)
.
(a)
Crystal
frequencies
must fall
in
the
range
37*7-88.0
MHz
to suit the
circuit
constants in
the
crystal
oscillator
circuit.
(b)
The
oscillator
injection
frequency
must fall
10.7
MHz
higher than the
required
signal
frequency.
Operation
with the
oscillator
"low"
is
not
possible.
(c)
Fundamental
or
harmonic
operation
(multiplication by
factors of 2
or
3)
is pos-
sible
without
any
change
in
internal
circuit
configuration.
(d)
Signal
frequencies
in
the
band
27.0-77*3
MHz
can be controlled by
fundamental
frequency
crystals.
Crystal
frequency
is
calculated
by
applying the formulas
-
xtal
f .
+10.7
MHz
.
sag
(e)
Signal
frequencies
in
the band
64.7-165.3
MHz
can be controlled
by fundamental
crystals
operating
at
half
the
required
injection frequency.
Frequencies
in
the
band
102.4-240.0
MHz can
be
controlled
by fundamental
crystals
operating
at
one
third
the
required
injection
frequency.
Calculate
as
follows
s-
xtal
f .
+
10.7
sl£
MHz
f
. +10.7
xtal
3
-
22
-