3-17
Figure 3-14.—Vhf-uhf wattmeter.
In-Line Wattmeters
The AN/URM-120 in-line wattmeter, shown in figure 3-15, measures power applied to a 50-ohm
impedance load and the power reflected from that load. The internal directional coupler is oriented such
that it responds only to a wave traveling in one direction on the transmission line. The coupler can be
rotated to accommodate either incidental or reflected power. The rf is then rectified, filtered, and applied
to the meter, which is scaled in watts. The rf power of 50 to 1,000 watts can be measured between the
frequencies of 2 MHz to 30 MHz; and 10 to 500 watts, between the frequencies of 30 MHz to 1,000
MHz.
Figure 3-15.—Typical in-line wattmeter.
