The distance between zero beat region and the pitch antenna seemed a bit small (about the length of an A4 sheet of paper. It’s since got smaller when I started it yesterday. I was expected the sound to start a couple of feet away.
Can't it be compensated with the pitch knob? Turning it counterclockwise should bring the zero beat region more far away from the pitch antenna
Also is it normal that when I move further away from a Theremin past the zero beat region the pitch starts rising again? This has since happened.
Yes, that is absolutely normal.
I think I need a tune or do I have a broken Theremin?
As long as you can adjust the pitch field for convenient size and tone spacing with the pitch knob, there is no need to fiddle with the internal adjustments, the risk of making things worse is too high!
I found this online… do you recommend? Any tips? http://www.wolinlabs.com/blog/etherwave.tune.html
Noooo! It's ways too complicated and as I wrote above, there is a risk of messing things still more up. If the pitch knob does not longer allow to bring the zero beat zone to about 60cm from the antenna when positioned somewhere between 9 and 3 o'clock, open the lid, take the red plastic special tuning tool which came with the theremin, locate the variable inductor L6 and adjust it as follows: If the pitch knob is too much clockwise, turn L6 an eighth of a turn counterclockwise. If the pitch knob is too much counterclockwise, turn L6 an eighth of a turn clockwise. Don't touch the other inductors! Close the lid, let the theremin warm up for at least 5 minutes and check if the zero beat zone can now be correctly adjusted with the pitch knob. If needed, repeat the above procedure.