====== Signal Hound VSG25 - Modification for better frequency stability ======
{{:projects:signalhound_vsg25:20240513-121755.jpg?direct|Signal Hound VSG25 - Disassembled}}
{{:projects:signalhound_vsg25:20240513-121921.jpg?direct|Signal Hound VSG25 - Modification Closeup}}
{{:projects:signalhound_vsg25:20240513-122256.png?direct|Signal Hound VSG25 - Mod Schematic}}
{{:projects:signalhound_vsg25:20240513-124435.png?direct|Signal Hound VSG25 - Mod Layout}}
===== 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