Lev Antenna - Two New Discoveries   (My Vision of 2003 revealed the theremin I would build would not have antenna's, now I understand how this could be done.)

After years of observation I have never fully understood why the dry spring coil stretched ~1/2" worked so effectively. My theremin operating at ~922 kHz has advantages but I think the real mechanism for pitch field linearity is geometry rather than algebra. To state it simply, to un-cram the musical notes near the antenna you want the antenna surface area to be as small as possible (skinny), to tighten up the outside musical low notes you want the antenna to be longer and maybe bowed towards the Thereminist. This also applies to volume control so using a metal plate trashes the possibility of achieving the maximum shading and control. Viewing photos of the research of Anthony Henk reveals he also made these observations but may not have taken it far enough. 

The two new Lev Antenna discoveries are environmental auto thermal antenna tuning and flipping it on its side for a more natural and comfortable playing pitch field. At first a sideways pitch antenna seems absurd until you try it and then the geometry of play makes perfect sense.

Fascinating: With the antenna wire connected at the center of the spring coil the pitch or tone rises with the temperature rise, but connected to the outer left side the tone decreases with temperature rise. Somewhere in-between is the sweet spot where the pitch remains the same over a 10 degree F room temperature change. When I say the same I mean less than a 10 cycle drift at 300 hz in a room with a 10 degree temperature change. I leave the setup running overnight. (I may have that direction reversed but you get the idea)

This sideways Lev Antenna will come to be known as "The Abbot" in memory of my friend Dana Abbott. (SewerPipe)

Very few remember the magic of what an authentic theremin should sound like? Listen.mp3 460k

This is theremin direct to sound card, no speaker/mic setup or reverb Band-Aid. Ask anyone designing a digital theremin for a sound byte and you decide which one is the toy. This may not be fair as I am in a league of my own. (-'  

Nearly all thermal pitch drift comes from a mismatch in transistor characteristics. Using my tube/valve boards for the antenna thermal drift testing makes for an excellent setup to explore these two new Lev Antenna characteristics.

A properly designed solid-state theremin would not need a warm up. There should not be anything designed within the enclosure that allows unnatural temperature change to occur around the RF oscillators. This includes not having voltage regulators, etc. in the same compartment.

Below here is about design accessories for various improvements, now or later.

Phoenix Control Board * This is a Phoenix add-on.  This can be also be used with my Dragonfly tube/valve setup. This board allows the Pot-4, Pot-5, LED-1, LED-2 and a mute switch to all be centrally located. How I use it will be shown in photos later. The Pots and Switch mount through the pcb with the nut on the copper track side. The LED's also mount on the copper track side. * When a DPDT Mute switch is used it will turn on the Red LED-3 which was originally suggested by djpb at LEVNET * A pitch preview amp is on the board, use an earphone or small speaker. <=dumb * As some of you know the Phoenix boards can transform into my tube/valve theremin. The G8-out jack is used with that set-up. More info on my tube/valve design will be released after my theremin gets a test drive by Charles Lester in Los Angeles. I work very slow and don't want anyone grabbing the brass ring ahead of me. LOL

My tube/valve boards use optical tuning of the RF oscillators which can eliminate the use of any variable inductors or variable capacitors and opens up the door using various other RF oscillator inductors. If ever I ordered more Phoenix PCB's I would want to add optical tuning to the pcb. Also this method allows the tuning knob to be mounted on the other side of the room if you chose to. (-' This voltage regulator  I cannot praise enough, it seems to run cold no matter how much input voltage overhead is present with theremin current requirements being very low.  This output voltage stability of this regulator to the left is ideal for stable optical oscillator operation.    All future theremin designs should use this type of voltage regulation, it operates cold to the touch.

I now use an Analog to Digital converter to pass my theremin audio through a Toslink cable to my sound card which eliminates several subtle issues of concern. Using the regulator above, which is small, will drop my 9 volt supply down to 5 volts to power the optical converter. This replaces the wall-wart that comes with the converter. Feeding theremin audio into optical converters and a Toslink cable from my tube/valve theremin to my computer sound card eliminates any ground loop hum concerns and adds complete isolation from higher voltage circuits.  Frequency response across the theremin audio band is level, no loss on the low end. Analog to Digital Converter   Digital to Analog Converter Toslink Cable 10' Adapter Plug  (bag of 10) These setups are not normally needed but can add benefits in certain situations.

I purchased a touch relay kit for muting the Phoenix sound and it seems to work adequately but I think I prefer a mechanical switch. I may install both.

In the future I want to go back to using two 100 uh chokes per oscillator for the coil, they add a remarkable increase in linear octave depth. Optical tuning allows their use to be practical. They have very High Q which allows more energy at the pitch field, I know this from previous practical applications.