Atec Tektronix-DMA120-DMA121 - Manual (Page 4)

page 4
Adaptive Equalizer Display
Mode: This display indicates
linear impairments such as
poor frequency response and
reflections. Tap values show
how hard the equalizer is
working to compensate for
impairments. The display
includes a bar graph which
compares the values of the
different taps against a DVB
template. Bars approaching
or exceeding the template
value indicate that there is
noticeable system impair-
ment detected at the test
point.
New Measurement Technology
That’s Easy-to-Use
Using the DMA120 Series is
easy. Most measurement
functions are no more than
two menus deep. Navigation
through menus is straight for-
ward and there’s a MENU key
on the front panel that
instantly gets the user to the
instrument’s Main Menu
screen. Universal set up
parameters are part of a Set
Up screen. Measurement spe-
cific set up parameters are
part of the individual mea-
surement screens.
Digital transmission is new to
most cable TV system techni-
cians and so are measure-
ments to verify performance.
Technicians may not under-
stand exactly how these mea-
surements function or how to
interpret measurement
results. However, measure-
ments are still required to
continue system installation
and maintenance activities.
The DMA120 Series helps
technicians to continue work-
ing by providing measure-
ment pass/fail indicators. The
system engineer or chief tech-
nician can determine the
measurement-result thresh-
old values. This enables the
technician to continue work-
ing if measurements are pass-
ing or follow an Engineering
directive if failures are
encountered. Pass/fail indica-
tors are available for: MER,
RF Signal Level, Adjacent
Channel Level, Channel
Power-to-Noise, Severely
Errored Seconds (BER mode).
Status indicators also help
clarify measurement condi-
tions: the DMA120 Series
notes if it’s locking to the
incoming QAM signal and
also if it’s locking to the R-S
decoder output. The actual
received symbol rate is also
reported. Operating Convenience
The DMA120 Series uses a
moisture– and dust-proof
keypad. It uses a high-resolu-
tion LCD display with back-
light. Contrast controls are
conveniently located on the
front panel.
The DMA120 Series includes
many capabilities designed to
simplify the job of digital
plant installation and mainte-
nance. Ancillary enhance-
ments include:
• Print screen: Any measure-
ment or display mode
screen can be directly
printed via RS-232 inter-
face
• Up to 30 constellations or
100 other measurement
results can be stored in
internal memory with real-
time clock/date stamp,
measurement site name,
operator name, and ambi-
ent temperature
• User-changeable input
adapter (type F or BNC
– optional accessory)
• PC Card (PCMCIA) input
for 2 and 20 Megabyte
memory cards to store
additional measurement
results and/or system chan-
nel tables
• User-changeable, NiMH
battery to extend the oper-
ating day; battery capacity
indicator; user-selectable
automatic power down
Figure 5. Constellation Box Evaluate mode.