Nokia RH-37 Series Rf Troubleshooting Instructions page 35

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The VCO frequency is twice the Rx frequency in the GSM1800 band:
= 2 * 1842.8 MHz = 3685.6 MHz
f = 2 * f
VCO RX
The tuning voltage can be easily measured at the Vc input of the VCO. The corresponding
hole in the shielding lid enables the voltage measurement at C7503, which shows the
same DC voltage as Vc.
The tuning voltage should be 2.1V
The tuning sensitivity of the VCO is typically 250MHz/V. The typical relation of VCO fre-
quency and tuning voltage is shown in the following diagram:
4500
4000
3500
3000
0 0.5
Issue 1 07/04
Figure 2: VCO probe
DC
Figure 3: Typical frequency tuning curve for the FDK VCO
Temperature: +25°C
1 1.5 2
2.55V @ 24.4 .. 25.4°C
High limit
Nokia Corporation
6(b) - RF Troubleshooting Instructions
.. 2.6V
at f = 3685.6MHz.
DC
VCO
2.5 3 3.5 4
VCTRL [V]
2.7V @ 24.4 .. 25.4°C
Low limit
RH-37
4.5 5 5.5 6
2.85V @ 24.4 .. 25.4°C
Page 35