Step 4: Receiving...
You can try and experiment with different turns ratio's of the coils and see what kind of performances you get! This has to do with resonance, and step-up / step-down ratios.
Try adding more voltage, and see if you get more distance; another way of possibly increasing distance is to increase the resonant frequency a bit. Increasing the frequency should give you more distance, with additional current draw.
To increase the frequency, just lower the capacitor values. Personally, the lowest I'd go would be around 1 uF. Make sure when you lower the cap value, you do it for both the receiving, and the transmitting ends!
Also, remember, the idea does not have to apply only to USB. I've noticed that due to resonant rise, the filter capacitor charges to the peak of the output sine wave....
At 12 volts into the transmitter, I was getting around 24 volts at the receiver end! (this isn't the effective voltage however; once you put a load on it, it drops a bit) At 15 volts in, I was getting 35 volts on the receiver! (wow, that's quite a bit of a jump, huh?)
This means that you should be able to power other things as well. Use whatever your mind comes to!