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4)
Tune the source under test for maximum reading on the DETECTOR meter.
5)
If
the probe was inserted in (3) above, turn the INSERT PROBE control back
to its fully counter-clockwise position.
Then read the power of the source on the
WATTS meter.
2.6
REMOTE OPERATION
If the power meter has to be connected directly to the power source it may be
inconvenient to read or operate the instrument.
If
so,
it
may be better to use it
with the detector unit and load detached from the monitor unit.
To do this, pull out the INSERT PROBE knob to disengage the dog clutch,
depress the catch on the ternunating load and withdraw the load and detector assembly
as far as the interconnecting lead will allow.
Operation is the same as in Sect. 2. 5 except that probe insertion is controlled
directly by the slotted knob on the detector unit.
2.7 DETERMINATION OF MODULATION DEPTH
The depth of amplitude modulation of an r. f. signal having a sinusoidal envelope
can be determined as follows:
1)
Measure the output power of the source under test with the signal unmodulated.
Let this reading be Pc watts.
2)
Modulate the signal and again measure the output power.
Let this reading be
Pm watts.
3)
Calculate the modulation depth.
This can be evaluated since P c, P m, and the
%modulation, m, are related by
2502 (1a)
p
m
p
c
m2
(1
+
2)· ....................
(1)
9
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