Exalt Communications, Inc.
r-series
Installation and Management Manual
5000007 (ETSI)
84
2007-02-12 (draft)
Connect the system as shown in Figure 34, using the combination of fixed and variable
attenuation between the radio’s RF ports. Connect the volt meter to either radio’s RSL test point
and associated reference ground connection.
In this test, it is desirable to use pre-tested RF cables, known to be good, and the insertion loss is
known at the operating frequency. If the cables are short (6'/2m 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:
1.
RF output power
2.
Radio receiver threshold
To measure transmitter output power, simply insert any value of attenuation between the radios
between 60 and 90dB. Ensure that both RF output power settings are at maximum. Use the volt
meter to measure RSL in both directions. The RSL measured value should match the appropriate
value according to the inserted attenuation, such as:
RSL = RF Output Power – cabling losses – total attenuation
Verify output power by adjusting output power using the Exalt GUI (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, for a setting of Mode1 and 8 MHz, if the threshold for your measurement is
-86dBm, the output power is +24dBm, so the system gain is 110dB. 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 the GUI, reduce radio output power in 1dB steps
until the receiving radio (the one whose output power not being adjusted) Link LED turns from
green to yellow. This indicates 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 1dB 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, repeat the process in the opposite direction by
adjusting RF output power of the radio at the opposite end. Return the first radio to its original
power setting before adjusting the second radio.
Perform threshold measurement tests for all combinations of bandwidth and mode (modulation)
being used–especially when troubleshooting. It should not be necessary to vary center frequency,