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Check to make sure that the rear-panel
RF SOURCE SELECT
switch is in the
ANT
(antenna) position, and that the
MOD-
MONITOR INPUT
switch is set to
AIR
(off-air operation).
Tuning In
Find a strong, local station. Use the up/down
ADJUST
buttons
(13)
to tune the 531N to a good signal at your location. If you
cannot pick up your own signal easily, choose a station that
does come in well.
You may wish to set some of the station presets
(16)
to your
own and other local signals. Enter your first choice into
memory #1 by holding down the #1 memory button. In a cou-
ple of seconds the frequency readout
(12)
will ‘wink,’ signaling
that the choice is entered.
Re-tune the 531N to other stations and enter each into addi-
tional memory positions in the same manner. Once frequencies
are entered, give any button a momentary push to bring up the
stored frequency.
Signal Quality
Evaluation
Even with a 3-foot wire antenna, a strong local station should
light at least half the segments of the
SIGNAL LEVEL
display
(17)
. Be sure that the station you select has low multipath dis-
tortion as well; no more than a couple of the segments in the
MULTIPATH
bargraph
(18)
should be lighted. Try repositioning
the 3-foot wire to minimize multipath pickup. Neither the
LOW
SIGNAL
nor the
MULTIPATH
alarm indicators
(
26)
should light.
If either alarm condition is indicated, choose another station or
connect a roof-mounted antenna.
When the 531N is in actual Mod-Monitor service, the two signal-
quality warning indicators
(26)
must be off
if measurements are
to be trusted. This usually calls for a rooftop antenna with a
rotator for meaningful comparative measurements of other sta-
tions in your market.
Carrier
Modulation
Display
Neglecting the effects of a low signal or multipath distortion
condition, the
CARRIER MODULATION
display
(2)
shows peak
deviation as a percentage, with 100% equivalent to ±75kHz car-
rier deviation.
The default measurement mode for total modulation looks for
carrier deviations in both directions and gives the higher of the
positive or negative deviation peaks. The 531N is in the default
mode when
both
the
POS DEV
(3)
and
NEG DEV
(4)
indicators
are lighted. As previously discussed under
MEASUREMENT
PITFALLS AND LIMITATIONS
on Page 25, the
SELECT
button
(6)
lets you monitor positive and negative deviation independently.
Refer back to that discussion for how and when to use this fea-
ture.
Unless there is a reason for doing otherwise, the
CARRIER
MODULATION
display
(2)
should be kept in the default mode
(LEDs
(3)
and
(4)
both on) for the most exact confirmation of
the station’s maximum carrier deviation.
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