VCO Tune

When I tune a VCO,i unconnect the resonator to the transistor,and there is a signal.Then i connect the resonator to the transistor,there is also a signal.and these two signals have neary the same values.what does this mean?

Liberal,

When you design VCO with CAD or practicaly built it you can find that it can oscillate on the different frequencies with little change. You have component in VCO that even without rezonator can oscillate on self resonance some componenets typicaly chokes.When you like to measure resonator it is necessary to turn off power supply for rest of circiuts and enabled weak connection to resonator to not distroy Q of resonator and than adjust it . If is rest of of VCO bad designed or chosen components which is not suitable for this frequency range you can obtain that VCO jump from one frequency to another or lost osillation with low(or high) tunning voltage. There is also one possibility that VCO oscillate on HF frequency and LF at the some time and signal is modulate like in AM modulator. Practicaly there is only one way to complete design VCO . First you put ideal components to find oscillation after that it is necessary to put all componenets with models and parasitic on PCB. After that really there is a small problem with corespodence design practical realization.

GL XTASA