K17: 50-Ohm Bk Relay Circuit; R44: 50-Ohm Dummy Load Circuit; Swr Detection Circuit - Furuno FS-1575 Service Manual

2. K17: 50-ohm BK relay circuit

The 50-ohm BK relay switches the T/R antenna circuit in order to use the T/R antenna
as a receiving antenna. The operating time of the relay is less than 10 ms.

3. R44: 50-ohm dummy load circuit

When conducting a self-test, power outputted from the TX FIL board is connected to the
"R44" 51-ohm /35W dummy load. The purpose of this connection is to raise the
accuracy of self-tests on the transmission circuit and prevent the radiation of RF signal .

4. SWR detection circuit

The V-SWR detection circuit on the input side is used as a signal to protect the PA
board when the TX FIL circuit of the TX FIL board causes a failure. The V-SWR
detection circuit on the output side is used as the input signal for the ALC circuit to
control TX output power.
Reference) LPF characteristics
1.6-2.3M LPF
3.2-4.5M LPF
CONFIDENTIAL (internal use only)
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.
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7-31
7.2 Transmission Circuit
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2.3-3.2M LPF
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4.5-6.6M LPF