HP 8970B, Руководство по обслуживанию, Страница: 30 / 40

5-6 HP 8970B Option 020 Service Manual Supplement
Fault-Finding Tips
Second Convertor (5086-7909)
Second Convertor (5086-7909)
This part contains a X6 multiplier, a bandpass filter, a mixer and a lowpass filter.
The 3900 MHz is mixed with the 600 MHz (multiplied by 6) to give a 300 MHz IF.
Internally the 3900 MHz is bandpass filtered and the 300 MHz is lowpass filter to prevent
the generation of images.
Under no circumstances should the bandpass filter be adjusted as this is a very
complicated process and will impair the performance of the microcircuit.
1. J1 is the RF input at 3900 MHz.
2. J2 is the IF output at 300 MHz
3. J3 is not used
4. J4 is the LO input at 600 MHz. Power should be between -1 and +4 dBm.
5. J5 is the LO monitor at 3600 MHz. This is about -30 dBm with the above input
range for the 600 MHz.
The conversion loss between the 3900 MHz input at J1 and the 300 MHz output at J2 is
about 6 dB. With a -25 dBm input signal at J1 the output at J2 would be approximately
-31 dBm.
It is possible to verify these levels by using a signal generator and a spectrum analyzer.
The supply connections are shown in Figure 1-1.
600 MHz SAW Oscillator (08970-60093)
This board delivers the 600 MHz to the second convertor.
Figure 3-2 shows the adjustment procedure.
The frequency should be 600 MHz
±
50 KHz
The power should be > -3 dBm