— 9 —
Carrier Strength and Alarm
(Menu Screen 2)
The
RF
bargraph on this
menu screen displays
the incoming signal lev-
el; an
RF
numerical value
given as well. This num-
ber is the incoming carrier level in dBµV. In the illustration,
the
51
represents a level 51dB above one microvolt, or
about 0.35 millivolts.
The
RF
display has no association with the dB scaling above
and below the LCD window. Those dB scales are used only
for audio level measurements in Menu Screen 6.
The lower LCD scale is labeled
LOSIG:
with a pair of tic
marks off to the right. Push the jog wheel and
LOSIG
will
change to a blinking
LO
,
followed by a number.
Turn the knob and the
leftmost tic mark can be
moved to any point be-
low the bargraph. This
LO
setting denotes an RF level that
the input must fall
below
to trigger a Low Signal alarm. The
alarm comes after a 5-second delay, just to ensure that the
level has indeed dropped.
During normal receiver operation, whenever the
RF
bar-
graph falls below the left tic mark,
LOW SIGNAL
will flash
on the LCD screen and the
L
terminal on the rear-panel con-
nector will be activated. Refer to Pages 5 and 14 for using
and programming this terminal.
Push the knob a second time and
HI
will flash. This lets
you to adjust the alarm reset level, the level that the RF car-
rier must return to for the Low Signal alarm to reset. This
setting should be just a bit below the normal carrier level,
that way you’ll know that the station is back on the air at
full power.
In setting the alarm trigger and reset points, take nighttime
pattern and power changes into consideration, as well as
allowances for typical signal fading as the station’s sky
wave kicks in at sundown, if you are monitoring at a signifi-
cant distance.
Background noise level at the receiver location is another
factor. Receiver AGC may bring up a distant co-channel
— 10 —
signal or random noise enough to hold-off the
LOW SIGNAL
alarm. Be sure to verify a proper alarm setting when the
station is legitimately off the air.
Once proper trigger and reset points have been determined
and set, remember to push the knob again to fix those
points in memory.
Mute on Low Signal
(Menu Screen 3)
This is actually a ‘squelch’ function that mutes the audio
outputs of the INOmini 674 during a Low Signal alarm con-
dition. As the receiver AGC can introduce a good amount of
gain in the absence of a valid carrier, RF noise can be
brought up to objectionable levels when the station goes off
the air. This function may be toggled between
On
and
Off
;
be sure to push the knob afterward to commit your choice
to memory.
The squelch/muting function has implication with respect
to the Audio Loss alarm. This is covered under the
The Au-
dio Loss Alarm
subheading, below.
Signal-to-Noise
(Menu Screen 4)
SN
gives a relative approximation of the signal-to-noise
quality of the tuned signal. This measurement takes vari-
ous signal quality factors into account, but is really valid
only when the carrier is unmodulated. Again a numerical
value is assigned to the
SN
readout, but it really only de-
notes the number of active bargraph segments.
No hard-and-fast rule can be derived from this display, ex-
cept for “more is better.” Remember: this measurement is
meaningless when the carrier is modulated by program au-
dio.
The Audio Loss Alarm
(Menu Screen 5)
Navigate to this Screen
and push the knob.
Audio Loss
will begin
blinking. Turn the knob
to dial-in a desired alarm
delay time; that is, the time in seconds between the onset of
‘dead air’ and a front-panel indication and rear-panel Audio
Loss tally. The delay may be programmed in one-second
increments between
1s
and
120s
(two minutes). Turn the
