LA75676V

No.A0831-6/9

V10, V11. Black noise threshold and clamp voltages • • • • [VBTH, VBCL]

1. Apply a DC voltage to the external AGC IF input (pin 17) and vary that voltage.

2. fp = 45.75MHz, 400Hz, 40% AM, 10mVrms (VIF input)

3. Vary the IF AGC (pin 17) voltage so that the noise canceller operates.

Measure VBTH and VBCL at test point A.

V12. Video signal-to-noise ratio • • • • [S/N]

1. Internal AGC

2. fp = 45.75MHz, CW, 10mVrms (VIF input)

3. Measure the noise voltage as an RMS level at test point A after passing through a 10kHz to 4MHz bandpass filter.

This is the noise voltage (N).

4. S/N = 20log

Video component (Vp-p)

Noise voltage (Vrms)

= 20log

1.12Vp-p

Noise voltage

= (dB)

V13. C/S beating • • • • [ICS]

1. Apply a DC voltage to the external AGC IF input (pin 17) and vary that voltage.

2. fp = 45.75MHz, CW ; 10mVrms

fc = 42.17MHz, CW ; 10mVrms - 10dB

fs = 41.25MHz, CW ; 10mVrms - 10dB

3. Vary the IF AGC (pin 17) voltage to adjust the output level at test point A to be 1.3Vp-p.

4. Measure the difference in level between the 3.58MHz and the 0.92MHz components at test point A.

VBCL

VBTH

Time

Video output

(V)

C/S beating

0.92MHz

3.58M 4.5M

Frequency (MHz)

Output

(dB)