VCO:Ultra Negtive100kHz-100Mhz

Dec 22, 2011

Here is a awesome oscillator, negative resistance configuration. it so wide band , easy to start from around 100Khz and oscillate all the way to 100Mhz!!

At first try, i want to build this one as a VCO:( similar as EMRFD chapter 4 Fig4.13 C)

But, there is a big problem, if you use 1sv149 replace C1, you'll fond output waveform is very distortion: raise slop is arsing so fast, and became faster while it raising. And i final realized that it's because the tank energy is high, voltage on the C1 is then too high, the oscillating voltage dominated the varactor's bias!!

these 2 images is the quick assemble guide and the final circuit quick PCB.

NOTE:

BJT's Ft is limited the higher frequency it can operated on. 9014 work up to 10Mhz, 9018 work up to 100Mhz, use higher Ft, this oscillator will surprised you.
tank energy is very high, and so powerful, tank voltage can reach to double VCC
Not suitable for varactor style VCO, only for VFO
high tank energy given more stable more low noise , high S/N ratio.

MC1648 style Oscillator

I can't stop here because it's so amazing. so i searching and look around, finally i got this one. actually,it's the hart of MC1648, and popular used as simple but attractive small signal generator. MC1648 might have no real competitor from it's been crated, and widely used till now-day.

this is a low tank energy version of the first oscilator i built , voltage on tank limited around 0.6V.
here is a very small R6, then use R5 to adjust the work point. in a decent design R5 been replaced as a BJT for ALC purpose.
out put buffer is recommended, as it extract signal from tank directly.

the image for quick assemble this VCO.

(quick built pattern modified @2012/12/8)