Reception Testing; Reception Gain And S/N Ratio Measuring; J3E Reception Gain Measuring; J3E S/N 20Db Measuring - Furuno FS-1575 Service Manual

5.8 Reception Testing

5.8.1 Reception Gain and S/N Ratio Measuring

1. J3E reception gain measuring

1) Set a frequency to be measured, and then set RF gain to Max., AF gain to Max., and
AGC to ON (FAST).
2) Add a "Measured frequency + 1 kHz" signal generated by SSG to find a SSG signal
level at which the AF signal will come to standard output of 1 watt.

2. J3E S/N 20dB measuring

If no distortion meter is available, connect a low-frequency voltmeter in place of
distortion meter to make measurement of "S/N 20dB sensitivity" which is almost the
same measurement value as SINAD.
To make measurement of "S/N (20dB) = 20log
1) Set a frequency to be measured, set RF gain to Max. and AGC to ON (FAST), and
then make adjustment of AF gain to set noise level output to 100 mVrms.
2) Add a "Measured frequency + 1 kHz" signal generated by SSG to find a SSG signal
level at which the AF signal output power will come to 1V.

3. J3E AGC measuring

1) Set a frequency to be measured, set RF gain to Max. and AGC to ON (FAST), and
then make adjustment of AF gain to set AF signal to an appropriate level.
2) Add a "Measured frequency + 1 kHz" signal generated by SSG to find a SSG signal
level at which the AF signal output power will no longer increase.
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5.8 Reception Testing