Oscillator 400~600 MHz

Hi, I need help, for a final proyect we have to build an antenna the problen is that we also have to design the oscillator and it has give a signal within 400 and 600 MHz range. The main problem is that I live in Mexico city and its not so easy to find those kind of oscillators, I have only found a 40 MHz so far...
So can any one give me a reference, or send me a diagram for this kind of problem? Or some soart of tip?

Thanks a lot

Check this:

**broken link removed**

Good for you. Oscillators are a lot of fun, and demonstrate interesting things about small and large signal effects and noise.

There are basically two types of oscillators designs that use transistors: reflection and transmission feedback.

Reflection oscillators involve taking a transistor, putting some feedback element (like and inductor between emitter and ground) on it to make another of the terminals have a negative resistance, and attach a resonator (of the right phase and not too much loss) to that negative resistance terminal, and it oscillates. This is a very popular type of oscillator, and you see them sold commercially by companies like ZComm, etc. The trouble for a student is that after you design and build such an oscillator is if it does not start up on the first try, then what do you do to change it to start oscillations?

Transmission feedback oscillators have a 2 part design. You first design and build an amplifier with at least 10 dB of gain in your desired frequency of oscillation. You measure the S21 of the amplifier, paying particular attention to the forward phase shift. Next you design a tunable transmission resonator--that is a resonator with an input and output connector that acts like a tunable narrowband bandpass filter. You tune it with a varactor diode replacing what would normally be a fixed capacitor in the bandpass filter design. You also measure the resonator's S21, and make sure that its loss is less than the amplifier's gain, and note the resonator phase shift. Finally, you connect the amplifier and resonator together, but add a phase shifting element between them (coax cable line length, or a lumped element tunable phase shifter). Now comes the easy part, You hook the amplifier, phase shifter, and resonator together all in a row and measure the combined S21. At the frequeny that the resonator is tuned to at the moment, if the magnitude of S21 is greater than 0 dB, and the phase shift is approximately 2nΠ, where n is an integer, it will oscillate when you connect the output to the input! If it does not oscillate, simply break the loop again and see if the loop gain is too low, or if the phase shift is too far off from 2nΠ.

I rocommend the transmission feedback approach for a first oscillator, since it is testable during the design process.

Some references:
www.odyseus.nildram.co.uk/RFMicrowave_Circuits_Files/Feedback_Oscillator.pdf

www.mimixbroadband.com/PDFfiles/9OSC0315.pdf