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INSTRUCTION MANUAL
AH-8055
HIGH GAIN HORN ANTENNA
1912 1 E l T o ro R d
●
Si l vera do, Ca lifo rni a 9 26 76
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(9 49) 459 -96 00
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co m-p o wer. com
REV051517
4.2 Preamplifier
Gain
Factors
Our second category of correction factors are gain factors for preamplifiers.
Preamplifiers are used to increase measurement sensitivity by increasing signal to
noise ratio. This is necessary when measuring low signal levels which would
otherwise be buried below the inherent noise floor of the measuring instrument,
typically a spectrum analyzer or EMI receiver. Ideally, input signals levels are
increased proportionate to the preamp’s gain, without significantly increasing the
overall system noise level.
Since the amplitude of the measured signal has been increased by the gain of
the preamplifier, the gain value must then be subtracted from the measured
value in order to obtain the ‘corrected’ value. Hence, our field strength formula
is modified as follows:
4.3 Insertion Loss Factors
As discussed previously, our third category of correction factors is insertion loss
factors. These factors can include the insertion loss values of coaxial cables,
band-pass or notch filters, attenuation pads, connecting adapters, etc. Basically,
it includes any measurement system component (cable, adapter, combiner,
divider or any other device) installed in-line with your measurement path having
inherent insertion loss over the frequency range of the measurements,
intentionally or unintentionally, beyond that which is considered to be negligible.
If the exact insertion loss factors (or values) are unknown for one or more
component(s) of your measurement system, refer to section 4.3.1.
Insertion loss factors (or values) must be added to the measured values in order to
obtain the ‘corrected’ values. So, we can update our field strength calculation
formula as follows:
Antenna Factor (dB/m)
+
Measured Value (dBμV)
Field Strength (dBμV/m)
=
Preamp Gain Factor (dB)
-
Insertion Loss Factors (dB)
+
Antenna Factor (dB/m)
+
Measured Value (dBμV)
Field Strength (dBμV/m)
=
Preamp Gain Factor (dB)
-
