Furuno FAR-2107 Series Service Manual page 95

Note 2. ARPA target lost (ver 2.43 and 2.50)
Differentiation and signal processing functions are incorporated in ARPA processor
independently from radar raw echo processing. This is to suppress sea clutter and as a
result, ARPA echo can be weakened too. To compensate it, the default of ARPA video
level threshold (6 ARPA PRESET – 4 ECHO LEVEL) is reduced from 16 (ver 2.40 and
before) to 13 (2.43 and 2.50).
1) ARPA video level setting is not overwritten when the program is updated, that is old
setting 16 remains after updating the program to 2.43 or 2.50. Check and set the level
to 13 after program update.
2) In case that the acquisition of smaller target at longer range is still weak at video level
13, differentiation and signal processing level in ARPA DETAIL data should be modified.
Factory default of differentiation and signal processing level with Ver 2.43 and 2.50 are
insufficient.
Remedy in the field:
ECHO LEVEL, CFAR TAP, D alpha and w_mtch_mod should be changed as shown below.
Item
ECHO LEVEL
CFAR TAP
D alpha
W_mtch_mod
ECHO LEVEL: It can be set in the [ARP PREST] menu. See photos at previous page.
CFAR TAP (No. 007): Refer to Remedy 2 of Note 1, Go to [ARPA DETAIL DATA] menu.
Select 9. DETAIL DATA and enter No. = 007 and DATA = 0007.
D alpha (No.097): Go to [ARPA DETAIL DATA] menu. Select 9. DETAIL DATA and enter
No. = 097 and DATA = 0003.
Item in MENU
ECHO LEVEL
007
097
038
Figure 2 ARPA VIDEO (QV) by ver 2.43
and 2.50 (Turn OFF EAV and ES)
Recommended settings
Ver2.43/50.06
13
7
3
18 see Note 1
Ver.2.50/50.12
13
7
3
0
3/4