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Bird Model 4391A Power Analyst
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signal coming from the element, whereas the Model 4391A
uses peak and negative peak detector circuits to measure
peak and minimum square root of power and combines them
using the equation:
With this technique, operation of CW mode is predictable
regardless of envelope shape (see Figure 4).
Reading
Reflected CW
Power
Operation of the reflected CW power mode is identical to
that for forward CW power described above with two
exceptions: the readings are taken from the element in the
socket marked “REFLECTED” and the range of the element
is assumed to be 1/10 the range indicated by the range
switches.
Reading SWR Two elements with a 10 to 1 power range ratio are required
for this mode. Press the SWR key momentarily. If average
forward power is between 10% and 120% of the scale and the
average reflected power is less than 120% of the reflected
element range, SWR will be displayed. If any of the above
conditions are not met, an error message will be displayed.
Two arrows pointing to the right — or “greater-than”
symbols — indicate over-range, while two left-pointing
arrows — or “less-than” symbols — indicate under-range or
too little power. Refer to Table 2.
CW POWER
Peak Power Minimum Power+
2
------------------------------------------------------------------------------------
⎝⎠
⎛⎞
2
=
Figure 7
Reflected
Power (CW)
Figure 8
Standing
Wave Ratio
(SWR)