TM 11-6625-2837-14&P-7 TECHNICAL MANUAL OPERATOR'S ...

Section 4 TM 11-6625-2837-14&P-7
4-13A. OUTPUT ACCURACY (Cont’d)
PERFORMANCE TESTS
11. Set the wave analyzer controls as follows: frequency 11 kHz, resolution bandwidth 3 Hz, sweep mode off, dBv/LIN
- dBm 600:1 switch to dBv/LIN, amplitude reference level -40 dB, AFC switch unlock and scale 10 dB.
12. Connect the other equipment which follows the 4 MHz Low Pass Filter as shown in Figure 4-4A.
13. Tune the wave analyzer frequency control for the maximum meter reading. Adjust the input sensitivity and vernier
controls for a midscale meter reading. Press the AFC control for frequency lock.
14. Wait 30 seconds for the DVM reading to stabilize. Record the DVM reading. This is the reference level equivalent
to the last power meter reading ( +3 dBm).
15. Use the following formula to calculate the obsolute RF output level from the System Under Test:
dBm = dBm1 -A dB +2(V-Vreff
dBm is the RF output level
dBm1 is the actual RF level measured at the +3 dBm (O dBm OUTPUT RANGE setting) in Step 4.
A dB is the difference in 10 dB step attenuator setting.
V is the DVM reading for each individual OUTPUT RANGE.
Vref is the reference DVM reading.
NOTE
The wave analyzer recorder output sensitivity is 2dB/volt.
16. Set the RF Section OUTPUT RANGE switch to -10 dBm; set the 10 dB step attenuator to the 40 dB. Wait 30
seconds for the reading to stabilize. Record the DVM reading in the table following step 17. Calculate and record
the RF level in the table.
EXAMPLE:
dBm = dBm1 --(ΔdB) +2 (V1 -Vref)
dBm1 = 2.8 dBm
ΔdB = 10 dB
V1= 2.388 Vdc
Vref = 2.433 Vdc (from step 14)
dBm = 2.8 - (10) +2(2.388-2.433)
= 2.8 -10 +2(-0.045)
= -7.29 dBm
4-10