Precision Directional Coupler - Harris ZX2500 Technical Manual

ZX Series
STEP 1
STEP 2
STEP 3
STEP 4
STEP 5
5.4.2.1

Precision Directional Coupler

The ZX series transmitter features a precision directional coupler at the output of each
amplifier chassis and the final combiner output (where applicable).
quality average power meter, this coupler may be used to calibrate the transmitter
meters. A small label indicating the calibrated coupling factor at the test frequency is
affixed during final factory test. If the final operating frequency is known at the time of
final test, this coupling value will be for that frequency. If the final operating frequency
is not known, the coupling will be listed for a nominal test frequency, such as 98 MHz.
To convert the coupling value at the test frequency to a new frequency, the following
formula can be used:
C (dB) = C
1 0
Where:
C = coupling factor in dB at the new frequency
1
C = coupling factor in dB at original test frequency
0
f = the new frequency in megahertz
1
12/20/11
WARNING: Disconnect primary power prior to servicing.
Obtain calibrated reading of transmitter forward power from external
precision measurement source.
Determine operating mode via front panel STATUS LEDs (FM,
FM+HD, or HD).
If amplifier chassis reading is to be calibrated, perform these steps
a.Select forward power reading on amplifier front panel meter via meter
select pushbutton.
b.
Open amplifier front door and locate forward power calibration
potentiometer for current operating mode (METER CAL - FM, FMHD,
or HD) at upper left of controller board on reverse side of front door.
c.Adjust relevant potentiometer until desired reading is obtained on
meter.
d.Close amplifier front door.
If system meter reading is to be calibrated, calibrate reading for current
mode via front panel trimmer potentiometer on system metering
assembly face to immediate left of meters.
Procedure complete.
(dB)+ .0866*(f (MHz)-f
1
Section 5 Maintenance and Alignments
(MHz))
0
888-2595-001
When used with a
5-17