Furuno FS-1503, Service Manual

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2. Matching Process (TUNE/BUSY Signals)
1. When PTT switch is depressed or TX KEY is turned ON by an external device after
the frequency change, or when TUNE switch is depressed, "TUNE" is displayed on the
main unit and "TUNE" signal inputs to the antenna coupler.
2. The relays K1 and K2 are turned ON, and the detector circuits are switched ON. That
is, RF input frequency detected by ATT, Vf/Vr (V SWR) detected by T1, and the
phase detected by T2 input to U8 (MPU).
3. During matching, an about 10 W signal with a selected frequency is input to RF circuit
in USB mode (Tone: 1500 Hz).
4. MPU drives the relays K3 to K22 in accordance with the data from the detector circuit
and changes the constants of L/C in L-type matching circuit.
5. If SWR is less than 1.5, the matching data is stored in the internal RAM of U8. If SWR
is more than 2.0 or it takes longer than 15 seconds for matching (time out), the match-
ing circuit is bypassed.
6. The matching results are informed to CPU of the main unit by H and L levels of BUSY
signal.
7. RF signal is stopped, the matching results are displayed, and the condition of the main
unit is returned to that when the matching was started. If SWR is less than 2.0, TUNE
OK appears, and if it is 2.0 or more, error sounds (three beeps) occur with the indica-
tion TUNE ERROR.
TUNE
BUSY
TX RF
200 msec or more
40 msec
20 msec 20 msec
H: TUNE OK
L: TUNE ERROR
Max: 15 sec
(Tunning )
See note.
(= 10 W USB)
•
•
Note)
If the level remains "H" for one second, TUNE ERROR is to result.
Figure 2-24 TONE Operation Timing Chart