Rx Gain - Furuno FS-1570 Service Manual

7.5 RX Gain

Receiver gain is checked with a SSG connected to J1 (RX IN) connector on TX/RX
board. See Fig. 7.5.1.
Table below shows the ratings. The receiving signal is attenuated by PRESEL board 2
to 3 dB. If the distortion meter is not available, use a vacuum tube voltmeter. S/N
is about 20log V
10
level from the speaker is 100 mVrms. Adjust SSG level to obtain the 1 V AF output
level to speaker. When the SSG level is +3 dBuV or less, the receiver gain is normal.
See Fig. 7.5.3 for the location of the adjuster.
Check Item
J3E receiver total gain
(SSG level to obtain
4W speaker output)
J3E 20 dB SINAD
(SSG level for 20 dB
distortion), or
J3E 20 dB S/N (SSG
level for S/N ratio of 20
dB)
J3E AGC minimum
level
(same as S meter)
Fig.7.5.1 RX signal flow
/V . Adjust AF gain volume with AGC on so that noise
signal noise
Condition
4 MHz, J3E
AF and RF gain controls:
Maximum
AGC: ON
SSG output: F + 1 kHz
4 MHz, J3E
AF gain control: Midturn
RF gain control: Maximum
AGC: ON
SSG output: F + 1 kHz
4 MHz, J3E
AF gain control: Adjusted
RF gain control: Maximum
AGC: ON (Fast)
SSG output: F + 1 kHz
Table 7.5.1 TX Gain Adjusters
0 dBuV ± 3 dBuV
+3 dBuV or less
+10 dBuV ± 2 dBuV
7-18
7.5 RX Gain
(20 dB)
Rating Adjuster
None
None
R320 on
TX/RX