HP 416A - Page 63

£. F or the ca li bration pro ce dur e., it is n eces s ar y th at the rati o m e ter
r ec eive v oltages of the s ame arnp H tude at b () th i nputs. Therefore
t he attenuator sho ul d be se t to offer th e s ame a moun t of l oss th at
the amplifie r is rated to yie ld in gain .
g. C onnect the amplifie r-output det ec tor to the M ode l 4 1 6A RE -
FLE C TED /P RO BE input . With the a mpli f ie r in operation, the re
now wi ll be two vo lt ag e s of approx i m a te l y the same amplitude at
the Mode l 416A i nputs, a vo lt age fro m th e detector monitoring
the amplifier input and a voltage from the detecto r monitor i ng
the amplifier output .
h. Set the signa l gen er ator rf fre quen cy to the design center fre-
quency of the am plifier.
i. Adjust the Mode l 4 1 6A S ET TO FULL SC ALE control to obtain a
100% reading on th e PER CE NT REFLE C TIO N (REFLECTO METER}
scale . This procedure ca li b rate s the rat i o meter.
J• With the attenuator and the Model 4 1 6A SE T TO FULL SC ALE con-
trol at the settings made during calibration, the circuit now is set
up to measure the re l ative fr eq uency response of the amplifier.
As the signal frequency is varied, the transfer function is meas -
ured. Note, for examp le, that at the 3 db points the ratio wi ll be
down 1. 5 db on the mete r. T his is because the meter is calibrated
to read th e square root of the a c tua l i nput vo l tag e ratio, as stated
in the Requirem e nts pa ragr aph , above.
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