Bird Technologies 3140 Display - Manual (Page 21)

Calibration
11
Active Calibration
The active method will recalibrate the TPM completely. This proce-
dure will void the calibration and accuracy specifications for the unit.
The accuracy will be based on the accuracy of the reference power
meter used for this procedure. In addition to the equipment needed for
the active calibration, a Bird 6A340-ADJ Potentiometer Adjustment
Tool to adjust the potentiometers on the TPM is also needed.
Set the transmitter’s RF output to a desired power level using the ref-
erence meter on the test port and the test port calibration data. Then,
using a Bird 6A340-ADJ Potentiometer Adjustment Tool, turn the
potentiometers until the desired voltage output is reached. Extra data
points can be taken at different power levels to confirm the linearity
and generate a lookup table to drive the rest of the power levels.
The benefit of this calibration method is that the customer can set the
output voltage they want to drive their external meter. With the other
calibration methods, the customer simply uses TPM output voltages
as set at the factory.
1. Install the TPM to the transmission line. Refer to “Installing the
TPM” on page 4.
2. Remove the load from the Fwd testport.
3. Connect the calibration standard to the Fwd testport.
4. Apply RF power.
5. Record the transmitter frequency displayed and find the listing
closest to it on the TPM’s calibration data card.
Note:
Make note of the calibration factor.
6. Enter the calibration factor into the calibration standard’s offset
function.
7. Break the seal over the Fwd Cal hole.
8. Adjust the potentiometer manually until the voltage is such that
the calibration standard reads fullscale power = 4.00V.
Example: If the power is exactly 50% of fullscale, adjust the
potentiometer to get V=2.00V.
9. Repeat steps 1 to 9 for Reflected calibration.
Note:
Calibrating the reflected port is often optional.
Check with the FCC or other ruling body to determine if it is
necessary or not.