Download Wavetek 147 Specifications

Field Sweeping with the SDA-5000: Test Point Compensation
order to perform tests without cutting off service, it is necessary to use test
points. Test points are ports that tap off enough signal for monitoring, but
leave most of the signal in the system where it is needed. Typical test points
have 20-30dB of loss between the signal being measured and the port
output.
Additionally, it is sometimes necessary to inject or read signals in locations
other than the exact point of interest. If a signal is to be injected into a
reverse amplifier, there are usually some internal amplifier losses between
the test point and the actual amp input. It is also sometimes necessary to
use external pieces of hardware to combine or split signals from the field
meter before you connect to the system being tested.
Test point compensation accounts for these factors and allows the meter to
display true system levels, even though hardware between the system and
the meter may affect what the meter really sees. For example, if a forward
test point were 30dB lower than the coax line it tapped into, normal meter
readings would be 30dB below real system levels. Using test point
compensation, you can cancel out this effect. Though this simple example
would be easy to work out in your head, more complex configurations can be
far more challenging. Meter test point compensation can help insure that you
interpret meter results correctly, with accurate results.
4
Test Point Compensation Configuration
NOTE: Test point compensation configuration has been
significantly changed and improved over previous
implementations. The new graphical displays for forward
and reverse test point compensation provide an at-aglance, simplified schematic of the test point connections
you must make and where test point losses are generated.
This information is designed to help you better see
relationships among the various entries, and to help you
enter correct data for each test point loss location.
Test point compensation allows the SDA-5000 to show actual levels in the
cable network, even though some losses exist between the meter and the
network lines. The SDA-5000 allows for separate adjustment of both forward
and reverse test point losses. The following steps show you how to configure
the SDA-5000 for test point compensation.
1.
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1.To adjust and review these levels, press the and 7 stu keys to call
up the FWD COMPENSATION screen shown in Fig. 4-1. (You can
also use the NAVIGATOR interface’s TESTPOINT item to get to the
FWD COMPENSATION screen.)