A.H. Systems SAS-551 Manual de operação - Página 10

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A.H. Systems Model SAS-551 Passive Monopole Antenna

CALIBRATION

Equivalent Capacitance

It is our recommendation to use a 12 pF for the ECSM fixture for an element height of 41" (1.04

meter) as per ANSI C63.5:2017 and CISPR 16-1-6:2017. Our telescoping rod with a BNC connector

that is supplied with the SAS-551 has an average radius of 2.223mm. The formula for calculating the

capacitance is (per ANSI C63.5:2017 and CISPR 16-1-6:2017):

where:

h = actual length of the monopole element (adjusted to 1.04m), m

a = average radius of the antenna element (6.17mm), m

λ = wavelength in meters

= capacitance of the dummy load

NOTE - Other fixtures with different capacitance are available as an option.

Effective Height Calculation

The correction factor for the calibration is dependent on the effective height of the monopole. The

effective height calculation is:

where:

λ = wavelength in meters

h = Telescoping element height in meters

Examples:

•

For a 41" (1.04 Meter) length, the effective height would be 0.52 meters (up to approximately

2 MHz) and the correction factor should be 20*Log(0.52) = -5.68 dB.

•

For a 1 Meter length, the effective height would be 0.5 meters (up to approximately 2 MHz)

and the correction factor should be 20*Log(0.5) = -6.02 dB.

= (55.6 h) / (ln(h / a) – 1) * (tan(2 π h /λ)) / (2 π h /λ)

(λ/ 2π) * tan(2 π h /λ)

e =

Eq 1

Eq. 2