Ch70 Rx - Furuno FM-8800D Service Manual

2.3.4 SQ : xxxxx
This is a test for "SQUELCH" volume. Turning this volume will change the value in
every 64 steps turned ranging from 00000-65472(65536). Range of outputted voltage
(0-3.3V) is digitized by 10-bit A/D converter with built-in CPU and will be indicated.
When a position acquired on AUTO, 00000 will be indicated.
2.3.5 PTT : OFF/ON
This indicates the ON/OFF of PTT switch on the transceiver. When PTT is ON, ON
will be indicated and when it is OFF, OFF will be indicated.
2.3.6 HOOK : OFF HOOK/ON HOOK

3. CH70 RX

3.1 AGC
This is not in use.
This is only equipped in case checking AGC functions with "CHANNEL" knob or
[▲] [▼] key. This adjustment will change the voltage of J10-#25 and J8-
#12(AGC CONT) on CPU board.
AGC Test out
1.10V – 3.65V
<■■
EXT : EXT
3.2 LOOP
"LOOP P : 0
This is a look-back test where IF frequency of 37.5 kHz of CH70 TEST signal is
transmitted from U17: CODEC on CPU board to CH70 board and is checked on
U17: CPU board via R37 on CH70 RX board. This test checks the test signal
modulated by tone of 1300 Hz and then the signal modulated by the tone of 2100
Hz.
- "P" is an assessment of included tone and if is normal "0" will be indicated
and "1" if abnormal. Tone will be assessed OK with over 98 %.
- "A" is the amplitude of received signals and 6000 and above will be assessed
normal.
This test is carried out and assessed just the same as CH70 RX test is.
> 1.65
A : 9099"
8-12
8.3 T/A, TEST, RESET DSP