5. Log Amplifier Adjustments

4.Connect DVM to A4AlTPl and DVM ground to the IF casting. Connect the frequency synthesizer to the RF INPUT. Key in CFREQUENCY) 80 MHz and [AMPLITUDE) -86.98 dBm. The frequency synthesizer will now provide a 5OfI load.

Offset Adjustment Check

5.Adjust A4A2R79 ZERO for 0.0000 f0.0005 V dc. See Figure 3-34 for location of adjustment.

R79 R61R91R14

R62 Z E R O ATTEN - 1 2 VTV LG 20 RI8

A4A3

A4A2

L O G AMPLIFIER-

L O G A M P L I F I E R -

F I L T E R

D E T E C T O R

\

I

A4A2

R83

c55

R67

LG 10 C52

C53 CTR R66

AMPTD

A4A3

Figure 3-34. Location of Log Amplifier AdjustmentsBandpass Filter Center Adjustment

6.Press LOG (ENTER dB/DIv)

7.Set the frequency synthesizer for 7.6000 MHz at +5.0 dBm output level.

8.Adjust A4A3C55 CTR for maximum DVM indication. See Figure 3-34 for location of adjustment. If A4A3C55 is at an extreme of its adjustment range (fully meshed, maximum capacitance, or unmeshed, minimum capacitance), increase or decrease value of A4A3C52 and A4A3C53. Refer to ‘able 3-3 for range of values.

Note A4A3C52 is a fine adjustment, and A4A3C53 is a coarse adjustment. If A4A3C55 is fully meshed, increase the value of A4A3C52 or A4A3C53.

3.66 Adjustments