Etherwave construction. Not enough variation through antennas

It is my first time posting here, but i've been lurking for info during the construction of an etherwave variant. I wanted to try and progress all that i could without consulting but i´m honestly kinda stuck right now so i might as well get help.
The main problem i´m having is that the antennas do not change the oscillators frequency enough. In the pitch section, I can properly adjust the potentiometer so the range of frequencies at the output is between 0 - 500Hz and in a very limited and close range of motion (like a hands lenght). It is my understanding that this dynamic range of frequency should be of about 3kHz and in a more extense range, is that right?
In the other hand, the volume oscillator does not move at all. I can only tell that the antena is connected because when i touch it the frequency drops a mere 10 Hz (atleast thats what the oscilloscope says). The frequency at which it's stuck makes the output of the volume antenna cicuit around -500mV. I couldnt find much explicit info about the caracteristics of this output but by the description of the VCA tunning in manuals and some simulations i thought it should vary between -12 and 0 V. Is that right?
 
I also changed the whole VCA part for something less complex, as i will process the signal digitally by other means, but i wouldnt think thats the cause the discribed issue.

In the last video i could take, the volume antenna inductors are not mounted, but the results mentioned above were made connecting them like in the video. All of the inductors not soldered directly like in the first photo are of the following type:

Using only one coil instead of 2 in series improve the movement range, but not so much the total frequency range. Of course for everything i relatively respected the values, but it did catch my attention that ussing massively off values (like 4Hy or 2mHy instead of 40mHy) for the antenna inductors had equally bad results, but not worse, compared to the correct value.

I tried to follow the common guidelines, using NP0  and air cores for the tanks. I'm satisfied with the amplitude and stability in frequency of the oscillators. I suspect the lack of sensitivity could be related to the series inductors for the antennas, as they are not 100% "air core". In that case, are there any methods so i dont lose my mind making a 40mHy coil?
I also tried to get everything reasonably away from grounded metal, but i must admit the cabling is quite messy and there is a lot of room for interference (but its difficult to know what is actually wrong or how to improve it).
 
Any feedback is welcome and thank you in advance.

Hello El Pepe,

Great post. I am not the sharpest marble in this forum and my theremin design days are over.

I do see you have some design conflicts.

You are working with RF energy which leaves the circuit by any conductive means possible. Get away from using that metal cart.

The pitch antenna begins at the circuit board so the connecting wire is a conflict.

You need a good earth ground, don't just assume you have one.

None of the oscillators must know the other ones exist or they will fight with one another for a harsh sound. Get distance between them.

Here is my authentic theremin sound after years of what did not work.

https://oldtemecula.com/+lights-go-down.mp3

My oscillators use a single NPN 2N3904, detection is a single 1N914.

The EWS approach over complicates theremin design.

What makes an RF analog sound special, it can be shaped on both sides of the detector diode for something more natural.

My own authentic theremin research is now in the hands of University of Massachusetts MIT graduates that will re-introduce the discovery/miracle of Lev Theremin which today is being lost if not forgotten, to theremin imitation.

Christophe
Old Temecula

El Pepe,

1. On the diagram, I don’t see any adjustment elements for tuning the oscillators anywhere. The Q5 and Q8 nodes don’t count – those are operational adjustment controls.

This is very important – accurately tuning the resonant frequency of oscillator's LC circuit relative to the antenna circuit’s own resonant frequency. Only then will you be able to achieve an audio range up to 3 kHz.

2. It appears your antenna coils are multi-layered. This means they have an unacceptably low self-resonant frequency. In this case, you will never be able to tune the circuit for proper operation.

P.S. I haven’t seen the video, as YouTube is blocked in Russia.

3. Using coils with a closed ferrite core is not the best idea. They are very sensitive to temperature changes. If you are going to use ferrite at all, it should be in an “open” configuration.

"2. It appears your antenna coils are multi-layered. This means they have an unacceptably low self-resonant frequency. In this case, you will never be able to tune the circuit for proper operation."  - ILYA

If true, this is likely the biggest problem.  You need high Q at the operating frequency, and it's not hard to measure as it's a direct multiplier of the input voltage.  So:

1. Drive one end of the coil with a function generator, the lower the impedance the better.
2. Stick a capacitor equivalent to the antenna capacitance (usually in the 10pF to 15pF range) to ground on the other end.
3. See what the voltage is at the LC junction is, preferably through a string of small capacitors and resistors in series.
4. Calculate the voltage backwards to the LC junction, knowing your 10x scope probe capacitance and resistance.  

Here's my medium voltage probe: http://www.thereminworld.com/forums/T/28554?post=219658#219658

Here's my coil Q testing jig: http://www.thereminworld.com/forums/T/28554?post=224020#224020

Here's an easier ringdown method of Q measurement: http://www.thereminworld.com/forums/T/28554?post=219626#219626

Single layer solenoids have the highest Q and most temperature stable (hence Theremin himself using them, though that was before the invention of ferrite) but they end up being quite physically large at these values (20mH or so).  For instance, here's my 19mH coil: http://www.thereminworld.com/forums/T/28554?post=224555#224555

Thank you for answering, Old Temacula

Get away from using that metal cart.

Its actually a plastic cart, I was carefull about that.

The pitch antenna begins at the circuit board so the connecting wire is a conflict.You need a good earth ground, don't just assume you have one.

Yes, the method i used to make the double sided PCB let me no chance to include ground pads. I heard placing a grounplate directly under the board helps, is that true?

None of the oscillators must know the other ones exist or they will fight with one another for a harsh sound. Get distance between them.

I see, another reason for remaking the board, maybe i will.

-El Pepe

Thank you for answering, ILYA

1. On the diagram, I don’t see any adjustment elements for tuning the oscillators anywhere. The Q5 and Q8 nodes don’t count – those are operational adjustment controls.

Yes, TOKOs are on the way, i couldnt find any other adjustable inductor locally, so i thougt these handmade ones would be enough. They are not

2. It appears your antenna coils are multi-layered. This means they have an unacceptably low self-resonant frequency. In this case, you will never be able to tune the circuit for proper operation.

I see, i though that being air-cored was the only important aspect. Im not familiar with the term but they clearly look "multi-layered"

3. Using coils with a closed ferrite core is not the best idea. They are very sensitive to temperature changes. If you are going to use ferrite at all, it should be in an “open” configuration.

would a "closed" ferrite be a toroid and an "open" ferrite an axial one, like the ones used in the etherwave?

Thank you for answering, Dewster

All the posts you referenced are very useful and i will measure the Q of current and future coils through those methods.

Single layer solenoids have the highest Q and most temperature stable (hence Theremin himself using them, though that was before the invention of ferrite) but they end up being quite physically large at these values (20mH or so).  For instance, here's my 19mH coil.

I understand that single layer air core selenoids may be the idea in terms of raw parameters, but is there any alternative that isnt flat out wrong (like the multilayers im using right now) that could give me a good enough Q value in a smaller size. For example, the Bourns 6310-RC Q you measured with your rig. I get that its an industrial component, but is is it realistic to try to replicate something similar with an open ferrite and my own wire?

"I understand that single layer air core selenoids may be the idea in terms of raw parameters, but is there any alternative that isnt flat out wrong (like the multilayers im using right now) that could give me a good enough Q value in a smaller size. For example, the Bourns 6310-RC Q you measured with your rig. I get that its an industrial component, but is is it realistic to try to replicate something similar with an open ferrite and my own wire?"  -- El Pepe

I have little idea how to design something like the Bourns 6310, though I wish I knew exactly how to maximize the Q and self resonant frequency.  The "donuts" measure dimensionally like a Brooks coil, though with a basket weave.  The spaces in-between the donuts are on the order of the width of the donuts.  Who knows what the ferrite formulation is?  Also unclear is the spacing width to the ferrite provided by the paper sleeve.  I suppose you could experiment by 3D printing a coil form and just scramble wind it by hand?

Here I tested the tempco of the 6310: http://www.thereminworld.com/forums/T/28554?post=202481#202481  
Here is one of my air core coils: http://www.thereminworld.com/forums/T/28554?post=224025#224025

800ppm/C for the 6310 is pretty horrible for Theremin use!

Okay then, i will try to make the 40mHy coil as a single layer air core (0.15mm wire),  or maybe start with one of the samller ones