Starting out with RF Engineering

[DrLuke]

Hello everyone!

I am in third semester at Uni studying EE. The dry theory is getting on my nerves, so I am trying to apply some of it where possible. I already have some experience with microcontrollers and basic analog electronics, but none with RF yet. Ergo I am trying to expand in that direction now.
The first thing I want to do is build a simple RF transmitter which allows me to shift the frequency a little bit so I can transmit simple data packets. The Problem I am stuck with is the VCO. I've looked all around the internet to see if there are ready to go VCO modules, but the only ones I could finde were over 30$ a pop, which is way too much for me.
Can anyone point me in the right direction? I was thinking about using 433 MHz as a frequency, since that's a license free band. As the frequency shift, I would like to see a shift of a couple kHz at most, so I could theoretically just listen to the audio output on my SDR dongle.

Cheers,
DrLuke

[SeanB]

Use a varicap diode to do the FSK direct with the RF oscillator. Pretty much any signal diode will do as a demo, but you can get proper low capacitance varicaps ( 2-20pF) if you want to try. Easy enough to roll your own varicap one you have the inductor and tuning capacitor and use the varicap to add a little more capacitance.