Introduction | Details | Specifications |
Manuals
What is ModMinder?
ModMinder is
an innovative, highly accurate digital device for measuring,
displaying and analyzing peak FM deviation. It processes modulation
information digitally using an 80C88 microprocessor. Hundreds
of stations are already using ModMinder's new measuring and
reporting techniques to adjust processing with complete confidence,
to analyze competitive signals, and to verify compliance with
FCC regulations.
What does it do?
ModMinder can work with any wideband
demodulator, such as the one in your existing modulation
monitor, a high-quality FM tuner or MSI's internal RF demodulator
card. ModMinder provides a comprehensive, easy-to-use front
panel display of modulation information, as well as extensive
remote control and data transfer capabilities. Interface
to a conventional broadcast remote control is provided
by relay contacts and slowly varying DC signals. In addition,
completely new remote control, display, and analysis capabilities
are provided by ModMinder's RS232 interface to a remote
PC. Using a conventional 1200-bit-per-second modem over dial
phone lines, ALL of ModMinder's functions can be remoted
to any location - the studio, the home office, even across
the country. Using an MS-DOS computer, a modem and MSI's
software, modulation data can be displayed and analyzed
to provide important information about RMS modulation,
dynamic range, etc.
How does it work?
Conventional modulation monitors include
a Peak Flasher with a fixed response time of roughly 200
microseconds. ModMinder's response time is user-selectable.
As shipped from the factory, internal jumpers select between
the FCC-approved response time of 900 microseconds and
the old "industry standard" time of 200 microseconds.
In "FCC Mode" ModMinder ignores brief overshoots that contain
very little power. The more rapid response of ordinary
monitors means these brief excursions are counted as modulation-robbing
peaks. Because ModMinder ignores them, either the average
modulation can be raised or the amount of processing greatly
reduced. Often, doing some of each is most desirable. Typical
improvements in modulation will range from 1 to 4 dB depending
on the amount and type of processing employed.
How well does it work?
ModMinder is highly accurate. Typical
monitors have an accuracy of ±5.0% Their resolution is no better than an operator's ability to read a moving-point meter. But ModMinder delivers ±1.0%
accuracy and 0.5% digital resolution.
Is it legal?
In a word,
YES. In a Declaratory Ruling dated December 4, 1989, the
FCC's Chief Engineer wrote: "If
the equipment does indeed meet the pre-1983 technical requirements,
I expect it would produce valid readings of FM modulation.
Equipment meeting the pre-1983 requirements is satisfactory
for determining compliance with the current FCC modulation
requirements."
ModMinder complies with the one millisecond peak flasher
response time requirement of 47 CFR 73.332(d) (4)(I) and
(ii) - the "pre-1983 requirements" referred to above. Compliance
has been verified in independent testing by a licensed
P.E. Copies of his report and the complete FCC letter are
available from MSI.
Displays
Peak Modulation: The highest modulation
peak attained during the previous second is shown on a
3 digit numerical display, which is updated each second.
This unique display eliminates the constant "tweaking" with
the peak flasher control of a conventional monitor to find
what the real peak modulation is. It is invaluable in setting
up or verifying the performance of an air chain.
ONE MINUTE COUNT: The number
of overmodulation occurrences in the past 60 seconds is
displayed on a 2 digit numerical readout. This is a "rolling" minute:
Each overmodulation occurrence increments the counter.
When the occurrence is one minute old, the counter is decremented.
Thus the display shows only those over-modulation events
that have occurred in the past minute. If the preset limit
is exceeded, the display flashes.
OVERMOD: This red LED lights
for 0.25 second (jumper option for 2.0 seconds) each time
the preset over-modulation limit is exceeded. The minimum
duration peak is user selectable: In FCC mode, the shortest
peak that is reported as an overmodulation event is 900 microseconds.
In the PEAK WEIGHTING mode the shortest over-modulation peak
is 200 microseconds.
PEAK WEIGHTING: This
green LED indicates that the response time and standoff
time parameters are set to a user-selectable value (factory-adjusted
to the former "industry standard" of
200 microseconds) as opposed to the FCC-approved values
used in FCC Mode.
AUDIO FAILURE: If program audio fails,
whether the failure is silence or a steady tone, this red
LED will light. Any total loss of dynamic range will trigger
this alarm following a user-selectable waiting period.
THRESHOLD SETTING: Under each numeric
display is a yellow LED. When either is on, the preset limit
for that display is shown. The UP and DN buttons raise or
lower the limits.
100% INDICATOR: Red
and Green LEDs located on the rear panel near the INPUT
LEVEL adjustment. Between 99.75% and 100.25% the green
LED is on. Above 100.25%, the red indicator is on. When
set using the Bessel null procedure, these indicators allow
calibrating ModMinder to ten times greater accuracy than
the FCC has ever required.
Controls
THRESHOLD SETTING: A multifunction control
that:
- Toggles each of the
displays between showing parameter values and preset limits.
When the preset limits are displayed, the yellow LED beneath
the display is on. Viewing the ONE MINUTE COUNT threshold
automatically clears the one minute counter.
- Allows
setting the preset limits for peak modulation and the
allowable number of overmodulation occurrences in a rolling
minute.
- Puts
the unit into an extensive self-diagnostic routine.
UP
and DN: Push-button recessed behind
the front panel. Used in conjunction with the THRESHOLD
SETTING, these buttons set the preset limits for overmodulation
and maximum counts per minute. In the diagnostic mode
they select various options.
INPUT LEVEL: A rear panel
20-turn trimmer that sets the input sensitivity of
the ModMinder. Used with the 100% INDICATOR to calibrate
the unit.
PEAK WEIGHTING (ON/OFF): An
internal jumper mounted on the main printed circuit
board selects the dynamic characteristics of the peak
detector and the one minute counter. With peak weighting
OFF, the parameters fall within the specifications
of the FCC's Dec. 4, 1989 Declaratory Ruling. With
this function switched ON, the dynamic parameters are
set by user-selectable components. As shipped from
the factory, these components provide a 200 microsecond
response time in line with former "industry standards".
Relay
Outputs
PEAK FLASH: Closes for
0.25 or 2.0 seconds (jumper-selectable) whenever the
modulation exceeds the preset limit: Follows the action
of the OVERMOD indicator.
ONE MINUTE OVERCOUNT: Closes
whenever the one minute count exceeds its preset limit.
Remains closed for as long as the count is above the
maximum. The ONE MINUTE COUNT display flashes when
this relay is closed.
AUDIO FAIL: Closes
if there is a program audio failure. Any absence of
dynamic range, whether silence or a steady tone, will
activate this relay and its associated indicator.
Analog
Outputs
LOCAL METER: A Fast DC
output for driving a conventional moving pointer
meter to provide a continuous indication of peak
modulation. Uses a unique, easy to read ballistic.
Any good quality zero to one milliamp meter may be
used, or a meter and panel may be purchased from
MSI.
ONE SECOND PEAK MODULATION: A
DC voltage proportional to the highest peak attained
in the previous second. The value is held for one
second until it is updated with the new one second
peak value.
ONE MINUTE ROLLING COUNT: A
DC voltage proportional to the ratio of the number
of occurrences of over-modulation to the preset counts
per minute limit.
Serial Data
An RS232 input and output allows
for complete remote operation of the ModMinder. The
output is a data stream carrying real-time modulation
information at 1200 bits per second - fast enough
to drive a moving pointer meter accurately. All other
front panel information is embedded in the data stream.
The RS232 input duplicates the front panel controls
of the ModMinder. It is not necessary to use this
input. The output can be used as a one way data stream.
Diagnostics
- LEVEL
1: Whenever the ModMinder is powered
up it automatically goes through a brief self-test
diagnostic routine. All LEDs and indicators are turned
on, all relays closed, and all analog outputs are taken
to full scale for two seconds. Then the reverse happens,
i.e. all of the listed items are turned off for two
seconds. Then normal operation begins.
- LEVEL
2: If the THRESHOLD SETTING button
is pressed during the self-test, ModMinder will enter Level
2 diagnostics. Specific relays and analog outputs can be
exercised in this mode.
- LEVEL 3: Pressing
the UP button while the unit is in Level 2 diagnostics
places the system in Level 3 diagnostics. In this mode,
any ASCII terminal connected to the RS232 port provides
full item-by-item diagnostic access.
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