Power Measurement By Calculating Efficiency - Furuno FS-1575 Service Manual

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5.3.3 Power Measurement by Calculating Efficiency

Approximate ATU output power can be calculated from PA Ic and PA Vc reading, and

efficiency "η" set forth in the Factory Test Data.

The Test Data has found ATU output power using 50 ohm dummy load for the HF band

and 10ohm + 250 pF dummy load for the MF band. Since actual antenna impedance

varies with frequency bands, the efficiency also varies. Consequently, the calculation by

efficiency only produces approximate ATU output power.

Po = Vc × Ic × η

As a guide, take the following efficiency for "η" although it depends on frequency

MF: 30 to 40%, HF: 40 to 50%

Adjustment of TX output power

Calculate ATU output power from PA Ic and PA Vc reading, and efficiency "η" in the

factory Test Data, using the following equations;

Po = Vc × Ic × η

Ic = Po/(Vc × η)

For example, when adjusting ATU output power to 250 watts in the 4 MHz band,

supposing that Vc is 42.0V and the factory Test Data is 50%, PA Ic to be adjusted is

Ic = 480W/(42V × 50%) =11.9A

Then, adjust power data so that PA Ic will come to 11.9A.

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This confidential document is used only by FURUNO authorized persons.

It is strictly prohibited to reproduce the document in whole or in part without prior written permission of FURUNO.

5.3 ATU Output Power

Table 5.3.1 SWR Chart

Transmission

Fs-2575 Fs-5075