Heathkit SB-10 Series Troubleshooting Manual page 5

s.2.1.Final Heterodyne Oscillator Alignment.........................................................................................................38
s.2.2.Driver Neutralization Adjustment..................................................................................................................38
s.3.LMO Shifter Adjustment.................................................................................................39
t)Uneven Response Across the Band / Bandpass Filter...........................................40
t.1.8395 to 8895 KHz Bandpass Filter..................................................................................40
t.1.1.Measuring the Bandpass Filter Response (Simple Method).........................................................................41
t.1.2.Measuring the Bandpass Filter Response (Sweep Analysis)........................................................................41
u)Signal Level Measurements......................................................................................44
u.1.Receive Signal Levels....................................................................................................44
u.1.1.Carrier and Heterodyne Oscillator Levels.....................................................................................................44
u.1.2.Receive Audio Signal Levels........................................................................................................................ 45
a)Disconnect speaker and connect an Audio Level meter to the speaker jack
(alternatively, an 8 load resistor and AC voltmeter can be used to measure the
levels)..............................................................................................................................45
v)Using an audio signal generator at 1 KHz, connect the generator to the top of
the AF Gain control and adjust the AF Gain control to provide 500 mw audio
output..............................................................................................................................45
v.1.1.Receive RF and IF Signal Levels.................................................................................................................45
v.2.Transmit Signal Levels...................................................................................................49
v.2.1.Transmit and VOX Audio Level Troubleshooting Guide...............................................................................49
v.2.2.Transmit RF Signal Levels............................................................................................................................50
w)Signal to Noise Ratio (SNR)......................................................................................52
w.1.Signal to Noise Ratio (Theory)......................................................................................52
w.1.1.Concept of signal to noise ratio SNR...........................................................................................................52
w.1.2.Signal to noise ratio..................................................................................................................................... 52
w.1.3.Effect of bandwidth on SNR.........................................................................................................................53
w.1.4.Signal to noise ratio specifications...............................................................................................................53
w.2.Measuring Signal to Noise Ratio (SNR).......................................................................54
w.2.1.Required Equipment.................................................................................................................................... 54
w.2.2.Test Setup.................................................................................................................................................... 55
w.2.3.Test Methodology........................................................................................................................................ 55
x)Testing Gain, S+N/N, AGC Threshold and Figure Of Merit....................................58
x.1.Testing............................................................................................................................. 59
x.1.1.Receiver Gain............................................................................................................................................... 59
x.1.2.(S+N)/N Testing............................................................................................................................................ 59
x.1.3.AGC Threshold............................................................................................................................................. 59
HW & SB Series Manual
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