Specifications
reverse biased and turned “off”. With the
series
gate “off”, the signal
path through the 5-NB is broken and
reception
is blanked for the
dura-
tion of the interferring noise pulse.
The 5-NB is turned on by the
acces-
sory switch in the SPR-4 which removes the ground from Pin 1 of P-5 and
allows Q3 in the 5-NB to oscillate permitting signals to mix in the 5-NB
balanced
mixer and eventually operates the
series
gate.
6.2.5 SERVICE DATA
A voltage char-t,
s
chematic ,
and a circuit board layout , Figure 10 are
provided for servicing the 5-NB.
6.2.6 ALIGNMENT
The 5-NB requires no alignment at the time of installation. However,
should alignment ever become necessary, the following
procedure
should
be used.
Connect
a
VTVM
at 15 volts full
scale
between the
chassis
and R46 of
the 5 -NB (see Figure 10
)
.
Tune
the SPR-4 to 2 1.9 MHz while using a
signal generator as a signal source.
With the
5-NB
turned off, ad just
C-21, C-26, and C-28 for maximum
S-meter
reading. It
may
be
neces-
sary to touch up the adjustment of C-21 for the best AM passband as
in-
dicated by the
S-meter.
With the accessory switch in NB position, and
the signal source turned off, adjust R-19 for maximum
positive
voltage
on R-46. With the’signal source turned on, adjust C-7 and C-18 for
minimum voltage on R-46.
Tune
the SPR-4 to 2 1.5 MHz while using the
2 1.5 MHz
crystal.
With the signal generator turned off, adjust the
spacing between C12 and C49 for maximum voltage on R-46. With the
signal generator turned on, and still on 21.9 MHz, adjust R-38 so
that
the
S-meter
has the same reading with the 5-NB installed as it
does
with
the jumper
cable
installed.
6.3
MODEL RY-4 RADIO TELETYPE ADAPTOR
6.3.1 GENERAL DESCRIPTION
The RY-4 Radio teletype Adaptor allows the 50 kHz
BF0
in the SPR-4 to
be remotely switched so that standard shift RTTY
tones
may
be centered
in the passband of the 50 kHz I .F.
filter.
The switching is performed by
an
external
circuit which must short the RTTY
jack
to ground.
When the mode switch is in the CW position and the RTTY
jack
grounded,
the
BF0
frequency
will
be switched to 48.590 kHz so that standard 2125
and 2295 Hz
tones
may
be received.
When the mode switch is in the LSB position and the RTTY
jack
grounded,
the
BF0
frequency will be shifted to 49.350 kHz so that standard 2 125
and 2975 Hz
tones
may
be received.
-26-
-