Fuseless
Member • Oct 17, 2010
PLL VCO Temperature Instability
I recently constructed a PLL synthesized weather band receiver. When I apply heat using a hair drier, the reference oscillator crystal remains on frequency. The VCO LO only remains on frequency for a short time until the VCO control voltage reaches its limit 7V, then the PLL drops out of lock.
Why does the VCO control voltage reach its limit so quickly at only 90 degrees F?
Why does the VCO control voltage reach its limit so quickly at only 90 degrees F?