User Guide

RH-37
6(b) - RF Troubleshooting Instructions Nokia Customer Care
Page 34 Nokia Corporation Issue 1 07/04
The setup should now look like this:
The VCO chamber has a fixed shielding lid, which can only be opened by destroying it. To
enable measurements with a closed lid, holes are located at positions where the supply
voltage VR7, the tuning voltage Vc and the output frequency f
VCO
can be measured.
Figure 1: Test holes in the VCO chamber
The VCO frequency has to be measured with a special probe, which fits into the holes of
the shielding lid. A thin coax cable can be used for this purpose, where the outer conduc-
tor is removed for 2mm. The isolation and the inner conductor must fit into the hole of
the shielding lid and provide a capacitive coupling to the attenuator R7503 at the VCO
output. A spectrum analyzer is used to display the frequency.
Tuning voltage
Vc @ C7503
Output frequency
f
VCO
@ R7503
VCO supply voltage
VR7 @ C7500