Shortening the distance between pitches

First off, hello!

I just acquired a temporary theremin and am going to try to learn it over the holidays. I'm a complete beginner, though I have much musical experience being a string student. 

Using a tuner, I noticed that I'm only getting a perfect 5th in range (from the farthest position I can reach to almost touching the pitch antenna). How can I shorten the distance between the semitones to get a greater range (at least an octave)? 

Thank you so much 

I have a Moog Etherwave theremin. 

hi yellow,

turning the front knob changes the low range massively and does nothing on the high part. do get more high notes you need to carefully retune the internals. but that would change the linearity and the spacing of the notes too. basically could make good things worse.

i could give you now the probably most stupid advice to grab a screwdriver and open the pandoras-box and retune the oscillators with the red fiddle-stick. if you know how, that's the way she goes. but because i don't know how much you know about the electronic inside and it's functions etc... i don't.

it's a bit a tricky thing, tuning for more octaves. much more difficult than most stringed instruments. there's a video by thereminist kip rosser somewhere in the www about tuning (but because if the front knob does not give back zero-beat, not to increase pitch range.) you can see how carefull he turns the slugs!

found it: the video