Through Signal; System Setting: 9921; "Through" Operation - Furuno FS-1503 Service Manual

4. THROUGH Signal

The antenna coupler control depends on the system setting 9921 ("through"-signal of an-
tenna coupler). The through-signal brings the characteristics of the matching circuit to a
through condition, and is not a static H or L signal but pulse signal.
The through-signal turns OFF the relay for controlling the coils K3, K7, and K10, turns
ON the relay for other coils, turns OFF the relays K13 to K22 for controlling the capaci-
tors, and makes the frequency characteristics of the antenna coupler flat by adding L1, L5,
and L8 in the line between TX IN/RX OUT and the antenna terminal.

System setting: 9921

0: sets to "through" in the following receiving conditions. (THRU not always)
1. MF: frequencies in transmitting and receiving are different.
2. HF: bands in transmitting and receiving are different. (1.2 MHz or more)
3. Receiving in scanning and sweeping modes.
4. Receiving frequency is less than 1605 kHz.
1: always sets to "through". (THRU always)
System Setting
9921
At power on
Changing RX frequency
TX/RX under non-thru
THRU not condition
always
TX/RX under thru con-
dition
Under TUNE ERROR
At power on
Changing RX frequency
THRU always
TX/RX under thru con-
dition
Under TUNE ERROR
Remark)
1) The different frequencies mean the transmitting and receiving frequencies in the
"through" condition "0" of the system setting 9921.
2) Refer to above system setting: 9921.
Table 2-7 "Through" Operation
Condition
Same TX/RX frequencies.
Different TX/RX frequencies.
Switched to different frequencies.
In TUNE mode, switching between TX
and RX.
End of TUNE
After TUNE, start and end of TX.
End of TUNE ERROR
After TUNE ERROR, start and end of
TX.
Same TX/RX frequencies.
Different TX/RX frequencies.
End of TUNE
After TUNE, start and end of TX.
End of TUNE ERROR
After TUNE ERROR, start and end of
TX.
2-33
THROU
Remarks
Signal
No
Yes 1
Yes 1
No 2
2
Yes
1
No
1
Yes
1
No 1
2
Yes
2
No