User's Manual

Exalt Communications, Inc.
EX-5r Installation & Management
5000007 60
2006-05-17
Connect the system as in figure B-1, using the combination of fixed and variable attenuation in
between the radio’s RF ports. Connect the voltmeter to either radio’s RSL test point and the
associated reference ground connection.
In this test, it is highly desirable to utilize RF cables that are pre-tested, known good and the
insertion loss is known at the operating frequency. If the cables are short (in the range of 6 feet or
less), you can estimate the loss, including connectors, to be less than 1dB each. The estimate of
cable loss is critical to the overall confidence of the measurements made in this test.
There are two critical specifications that can be tested in this configuration:
- RF output power
- Radio receiver threshold
To measure transmitter output power, simply insert any value of attenuation between the radios
between 60 and 90dB. Make sure that both of the radio’s RF output power settings are at
maximum. Using the voltmeter, measure RSL in both directions. The RSL measured value
should match the appropriate value in accordance to the inserted attenuation. Such as:
RSL = RF Output Power – cabling losses – total attenuation
You can further verify output power by adjusting output power using your computer (in
administration mode) and evaluate the corresponding change to the RSL measurement.
For threshold testing, the key is to insert a measured amount of loss that is close to, but not
exceeding the radio’s specified system gain. System gain is the difference between RF output
power and receiver threshold. At your selected modulation and bandwidth settings, determine the
specified threshold performance, and choose a value of attenuation (including cable losses) that
adds to roughly 5 to 15dB less than the system gain.
For example, if the threshold for your measurement is -88dBm and the output power is +24dBm,
so the System Gain is 112dB. Choose a value of total attenuation in the range of roughly 100-
105dB. Once this attenuation is inserted, verify RSL readings as in the first step, and then, using
your computer, reduce radio output power in 1dB steps until the receiving radio (the one whose
output power you are not adjusting) Link LED turns from green to yellow. This would indicate
that threshold has been reached. At this point, verify the equation for system gain using the new
output power level setting and verify that the threshold performance is meeting or exceeding the
published specification.
Due to the variation of measurements and accuracies involved in this test, you
may read a measurement that is 1 to as much as 2dB off of the expected value. It
should be of no concern unless the value is more than 3dB worse than expected.
Once threshold is verified in this direction, you may repeat the process in the opposite direction
by adjusting RF output power of the radio at the opposite end. You should return the first radio
to its original power setting before adjusting the second radio.