Signal Hound VSG25 - Modification for better frequency stability

Tests

Tests run at 162MHz nominal with 0dBm output power. Ambient Temp: 24C Deg
VCTCXO Freq is measured by Racal 2202R Universal Counter/Timer (it has a rubidium reference so it is reliable!)
Frequency drifting before modifications were over 500Hz
Frequency drifting after VCTCXO modification was 19Hz
- Initial freq: 162.000006MHz
- After 2.5hrs: 162.000025MHz and kept drifting
Frequency drifting after VCTCXO and heatsink added was 10Hz and stabilized relatively quickly
- Initial freq: 161.999983MHz
- After an hour frequency stabilised on 161.999993MHz