Model
8754A
Pin
No.
I
13
15
16
23
24
3
Inputs/Outputs
J7
PROGRAMMING
PIN
FUNCTIONS
(Cont'd)
Function
J7
INPUTS
(Cont'd)
Electrical Length
or
Degrees/Sweep Select
1 = Electrical Length, 0-16 cm (Disabled when EXT
RF
is selected.)
o= Degrees/Sweep, 0-190 degrees/Sweep (Not disabled when EXT
RF
is
selected.)
Selects function'
of
A/R
LENGTH and
B/R
LENGTH controls. "Electrical Length"
introduces a phase shift proportional
to
RF
frequency which compensates length
differences between
A,
B,
and
R inputs. "Degrees/Sweep" introduces a phase shift
proportional
to
CRT X-axis (sweep). The phase
introduced
is
zero at
the
beginning
of
the
sweep, and increases linearly
to
the
selected value
at
the
end
of
the
sweep.
The equivalent length added
to
the
R
input
depends on
the
SWEEP WIDTH and
is
calculated
as
follows:
EI
\
t·
I
Le
.
th
( ) Phase added/sweep (degrees)
ec rIca ng m = _
Sweep Width (MHz) X 1.2
.,-----
Degrees/Sweep
may
be useful
to
equalize large differences in electrical length over
narrow sweep widths,
or
when EXT.
RF
is
selected.
Stop Sweep
1 =Continue Sweep
o= Stop Sweep
Allows external control
of
sweep.
Sweep Trigger (negative going edge trigger)
When this pin is grounded, a sweep will be triggered
if
the
front-panel SWEEP
TRIG
is
depressed,
and
the
retrace cycle
is
completed.
Tuning Marker
(Output
and
Input)
When ground is applied,
the
trace moves
up
1/4 major division
on
rectangular trace
or
has increased intensity
on
polar trace. In full sweep mode, this line
is
momen-
tarily internally grounded when
the
full sweep TUNING marker
is
displayed.
Relock and Trace Blanking
1 = Unblanked
When 0,
the
CRT trace is blanked. A transition
to
1 initiates a 1.5 ms sequence dur-
ing which
the
CRT is blanked and
the
receiver relocks. Minimum pulse width
is
20llsec.
Relock and Trace Blanking (Inverted Polarity from pin 24)
o= Unblanked (Normally
0)
When 1,
the
CRT trace is blanked. Transition
to
0 initiates a 1.5 ms sequence during
which
the
CRT
is
blanked and
the
receiver relocks. Minimum pulse width
is
20
J1sec.
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