Hello everyone,
I'm building a radio transmitter with a Colpitts oscillator schema and everything works fine. I built the circuit and tested in the Oscilloscope and with L=470uH, C1=100pF, C2=100nF I created a 549KHz 6Vpp senoidal (with 5v as source), as we can see bellow:
Theoretically, the formula tells us that the frequency with these values should be around 734KHz, so I think we're close as I'm using a breadboard and it has parasite capacitance and others interferences.
But I want to increase the operational frequency because I can't built an antenna for this wavelength (546 meters), even with 1/4 wavelength (136 meters) it still not viable. So I'm trying to increase the frequency up to 70MHz because it's wavelength is 4.3 meter and it's 1/4 wavelength approximately 1 meter and it's feasible to build.
So my first try was to change the inductor to a tinnier one, I started to decrease the inductor value one by one to see if the frequency was increasing. But the circuit stops to resonate when L is bellow 13uH (5MHz), even though in the simulator works.
So my question is, what can I do to increase the operational frequency up to 70MHz with this schematic?
PS: This is a project I'm doing to adquire knowledge in RF for university. I don't intend to transmit data above the 100mW allowed by BR regulations.
I'm building a radio transmitter with a Colpitts oscillator schema and everything works fine. I built the circuit and tested in the Oscilloscope and with L=470uH, C1=100pF, C2=100nF I created a 549KHz 6Vpp senoidal (with 5v as source), as we can see bellow:
Theoretically, the formula tells us that the frequency with these values should be around 734KHz, so I think we're close as I'm using a breadboard and it has parasite capacitance and others interferences.
But I want to increase the operational frequency because I can't built an antenna for this wavelength (546 meters), even with 1/4 wavelength (136 meters) it still not viable. So I'm trying to increase the frequency up to 70MHz because it's wavelength is 4.3 meter and it's 1/4 wavelength approximately 1 meter and it's feasible to build.
So my first try was to change the inductor to a tinnier one, I started to decrease the inductor value one by one to see if the frequency was increasing. But the circuit stops to resonate when L is bellow 13uH (5MHz), even though in the simulator works.
So my question is, what can I do to increase the operational frequency up to 70MHz with this schematic?
PS: This is a project I'm doing to adquire knowledge in RF for university. I don't intend to transmit data above the 100mW allowed by BR regulations.