LC Resonance Circuit VFO

High frequency and low frequency limits of this work tend VFO determined by the value of L1 and C1 (check the circuit diagram in the figure 2 above),besides of course the use of varactor. Calculation for determine the amount of L1, C1 and varactor type used seemed too complicated. However, in practice we can expect roughly taking into account L1 and C1 alone and with trial and error method we develop some results so that getting what we want. To think big about inductance L1 with a capacitance C1 we have specify, you can use the following formula calc Resonance :
f is expressed in MHz
L is the inductance coil L1 is expressed in uH.
C is the capacitance C1 is expressed in pF.
For example in VCO design specified the desired resonant frequency 12.700MHz, while the value of 30 pF C1 is selected, then the calculation according to the formula above the value obtained L approximately 5 uH.
To make a coil with the above values should be some experiment. Based on the results of the experiment the author, when used Koker former radio IF as shown in Figure below with loops of wire Koker's former hair, then to be able to obtain the value approximately 5 uH 8T empirically necessary.

Figure IF coil

By rotating the coil ferrite is, the value will change the inductance that can be adjusted to obtain the correct value. Please note that not all Koker have the same properties, so depending on the type of ferrite used. Experiments in above is done by using IF Koker RCL brand shop that there are many in the market,with other types of Koker will get different results.