10
Calibrating the LDS-910 Plus:
The LDS-910 Plus Receiver can be calibrated to the transmitter with an offset value so it shows the shield
effectiveness on the screen. These procedures will outline testing in the ISM band of 902-928Mhz. This
procedure should be repeated every time the unit is used to ensure accurate readings. The calibration
procedure is shown below.
1. Attach the antenna to the receiver unit and then turn on the power.
2. On the receiver unit, press the MENU button until the FREQUENCY MENU is reached. Set the CENTER
FREQ to 915.000 and the FREQ SPAN to 002.000. This should set the START FREQ to 913.000 and the
STOP FREQ to 917.000. Press the RETURN button to return the spectrum analyzer screen.
3. Depending on your location there may be noise in this frequency band. Observe the graph to select a
frequency with the least amount of signal. For the purposes of this document the frequency of
910Mhz is selected. Record this frequency for use in Step 6 in setting the transmitter.
4. On the receiver, press the MENU button again until you reach the ATTENUATOR MENU. Set the INPUT
to ATT 30dB. This turns on the internal 30dB attenuator for calibration. Without turning on the
internal attenuator, the receiver can only read a maximum of -10dBm.
5. Attach the antenna to the transmitter unit and then turn on the power.
6. Press the MENU button the transmitter unit until you reach the FRQUENCY MENU. Set the CW FREQ
to the frequency selected in Step 3. 915.000 is selected for this document.
7. On the transmitter, press the MENU button again until you reach the POWER MENU. Ensure the CW
POWER is set at the max value of 2.4dBm. Press the RETURN Button to return to the SIGNAL
GENERATOR menu. Press the ENTER button to turn on the RF power and enable the transmitter.
8. Place the two units at the distance the test will be performed at (recommended 5-15ft). Ensure the
units are placed away from reflective metal surfaces and have no obstacles in between them. Ensure
the antennas on the two units are in parallel. Record the maximum value seen on the receiver unit.
The maximum value is shown underneath the frequency on the receiver graph. Record this value.
9. On the receiver unit, now press the menu button until you reach the ATTENUATOR MENU. Insert the
inverse of the value record in step 8 under the OFFSET DB setting. Now press the RETURN button and
the value maximum value shown should be very close to 0. If not, adjust the OFFSET DB setting.
10. Finally, press the MENU button on the receiver until you reach the ATTENUATOR MENU again. Change
the INPUT back to DIRECT. This will turn off the internal attenuator and allow for a greater dynamic
range while testing.
Please note, the value shown is not the actual received signal strength. It is the received signal
strength plus the offset that was entered. This is useful because the measurement screen shows the
shield effectiveness without doing any calculations. It is also critical that the internal 30db attenuator
is turned on for calibration and turned off during normal testing. With the attenuator enabled, the
