1-6
888-2621-001
12/5/07
WARNING: Disconnect primary power prior to servicing.
Section I Operator Guide
Z3-48HD+
i. The Z3-48 System Controller FWD PWR meter should be reading near 20%.
Select the REJ PWR meter position on the Z3-48 system Controller and verify its
reading is near 0%. If this reading is more than 2-3%, this again may be the result
of either amplitude or phase mismatch between the two combiner inputs to the
4.77dB combiner. Adjust the power level 2-3% out of just transmitter C. If this
minimizes the reject power to near zero, continue on to the next step. If power
from each transmitter is back to the same or more than 10% reject power exists, a
phase mismatch may be adjusted by changing the physical length of W900 in the
drive circuit. Some experimentation will be required. Add or remove BNC elbow
adaptors or a very short length of cable (2-6 inches) to W900 at the transmitter C
Exciter Switch board output. Reject power may be the result of a different con-
nection from what was originally used at the Harris test facility. Usually, no
adjustment of amplitude of phase will be necessary.
j. Once reject power is down below 5% on both System Controllers, raise power in
all three transmitters to 100% watching that reject power does not exceed 10%. If
any reject power exists, repeat the above steps for adjustment of amplitude or
phase of all combiner inputs. Some fluctuation of power will be noticed due to
the type of detection used for an IBOC signal and its peaks.
k. Select the RFL PWR position on the transmitters and the System Controllers and
verify that they all read at or near 1.01VSWR.
l. Depress the LOW ON push-button switch on both System Controllers and verify
that all transmitter output levels drop to approximately 50% and that the System
Controllers also indicate near 50% in the FWD PWR positions.
1.3.1
RF Metering
Three metering functions are provided by each System Controller. They are: Forward
output power in percent of allowed forward power (FWD PWR); reflected power
displayed as load VSWR (RFL PWR); and combiner reject load power in percent of
normal (REJ PWR). Below are the approximate values of the normal average RF levels
for a Z3-48HD+ combined transmitter system calibrated at full output in the combined
mode. See Table 1-1.
Table 1-1 System Controller Average Power Metering
Indication
FWD PWR 100%
RFL PWR 1.00
REJ PWR 100%
Z3-48 System Controller
FM+HD
21kW
As Indicated
4.67kW
HD only
10.5kW
As Indicated
2.33kW
FM only
30kW
As Indicated
6.67kW
Содержание Z3-48HD+
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