What if I can’t afford an oscilloscope? (+Variable inductor issues)

I’m new to this and everyone says I should have an oscilloscope if I want to do this but I don’t have $800 or a job (I’m trying to get one but nobody is hiring me), and I don’t know if the cheap handheld ones are good or not. Another issue I’m having is finding the variable inductors listed on the 1996 schematic. Everywhere I look says something different and I’m not at all sure what to do. 

"I’m new to this and everyone says I should have an oscilloscope if I want to do this but I don’t have $800 or a job (I’m trying to get one but nobody is hiring me), and I don’t know if the cheap handheld ones are good or not."  - JasonLuiten

Everyone is right, you need a scope to really know what's going on, but don't get a cheap hand-held one.  I'd stick with names like Rigol, Siglent, or maybe Hantek.  You won't need more than 2 channels.  Spend maybe $250 and get something decent.

Can't help you with the variable inductors, it seems all IF transformers and RF chokes suitable for Theremin use have turned into unobtanium.

I'd stick with names like Rigol, Siglent, or maybe Hantek.  You won't need more than 2 channels.  Spend maybe $250 and get something decent.

The cheapest one I could find from any of them is $375, which I can’t afford 

Hello Jason,

The Authentic Theremin design is based upon principles of early AM Radio. Lev Theremin did not use a scope at first rather his “ear” listening to the heterodyned audio wave-shape.

Use an analog Am Radio as a digital radio will not work for this testing. Listen to your oscillators creating a blank spot in the static somewhere on the radio dial. Tune the oscillators to where they line up in the same spot.

You want distance/isolation between your oscillators so they do not interact/fight with one another creating a distorted sound.

The main thing the theremin teaches is what does not work, over and over.

A good performing theremin design requires special knowledge learned over time. Cost wise it will be more cost effective in the long run to just buy the modern-day theremin model you want than go through the theremin design learning curve.

I am a computer coder beating the US Stock Market and I assure you digital imitation will replace all human performances with “AI” or intelligent coding . . . kind of like what the perforated paper roll did for the player-piano but now with digital you can have very complex precision.

"With digital coding used "wisely" you could instead double your money annually by making 6% profit a month. A single $1000 will earn you $1,000,000 in profit in 10-years. My 777 intelligent coding data, freely shared, gives you The Weekly Answer updated several times during the trading  day."

The Authentic Theremin Phenomenon really is as simple as seen in this image why there is real beauty in a good performance. 

Hello Jason,The Authentic Theremin design is based upon principles of early AM Radio. Lev Theremin did not use a scope at first rather his “ear” listening to the heterodyned audio wave-shape.Use an analog Am Radio as a digital radio will not work for this testing. Listen to your oscillators creating a blank spot in the static somewhere on the radio dial. Tune the oscillators to where they line up in the same spot.You want distance/isolation between your oscillators so they do not interact/fight with one another creating a distorted sound.The main thing the theremin teaches is what does not work, over and over.A good performing theremin design requires special knowledge learned over time. Cost wise it will be more cost effective in the long run to just buy the modern-day theremin model you want than go through the theremin design learning curve. I am a computer coder beating the US Stock Market and I assure you digital imitation will replace all human performances with “AI” or intelligent coding . . . kind of like what the perforated paper roll did for the player-piano but now with digital you can have very complex precision."With digital coding used "wisely" you could instead double your money annually by making 6% profit a month. A single $1000 will earn you $1,000,000 in profit in 10-years. My 777 intelligent coding data, freely shared, gives you The Weekly Answer updated several times during the trading  day."The Authentic Theremin Phenomenon really is as simple as seen in this image why there is real beauty in a good performance. Authentic Analog Sound same parts used as seen

Im just doing this because I enjoy making electronic stuff and I like a challenge. 

If you're patient, you can find oscilloscopes on Craigslist for under $200. If you're really patient you can show up to amateur radio swap meets and find one for under $100. There's usually someone willing to make some space in their home/garage/shop.

I recently found having an oscilloscope very handy while building my tube theremin based off Moog's 1954 article. It's possible to work without it but you need to be even more patient  while you try to figure out what frequency your oscillator is operating at. An all-band radio can sometimes help with that but you may tune to a harmonic.

im likely going to bite the bullet for a rigol i found for 300 dollars myself although there are hantek models that have the needed spec i would just rather spend the extra for confidence in the name. as for the inductors ive been wondering are most people these days winding their own?

im likely going to bite the bullet for a rigol i found for 300 dollars myself although there are hantek models that have the needed spec i would just rather spend the extra for confidence in the name. as for the inductors ive been wondering are most people these days winding their own?

I wound my oscillator coils on pill bottles with enameled wire and coil dope to hold it in place. For the antenna loading coils I was fortunate enough to stumble on some old TV horizontal oscillator coils.

"as for the inductors ive been wondering are most people these days winding their own?" - alder6

I started out using PVC plumbing.  Now I 3D print just about any custom form that I want.  And if you set the Z-step height grooves to be slightly larger than the wire diameter, they can guide the winding process.

Late to this thread, but I work at a university, and they can't get rid of old scopes fast enough.  We have a storage room full of them, and the next time we get an infusion of new scopes for the teaching labs we'll be struggling to find a use for the current ones.  I'm not talking about ancient scopes from the 80s, but DSOs that are way more than capable of handling what you need for building a Theremin.

Thus I recommend you reach out to a local college, university or community college and ask if they have any older scopes taking up dust that you can at least borrow, that they might have been planning to send to e-waste.  You might just get lucky.

Regarding the variable inductor, I have a student building a Theremin from the Etherwave schematic and we were unable to find 47uH variable inductors.  Instead we used a trick that is commonly used in amateur radio auto-tuners:    we just put 6-7 fixed inductors in series on a breadboard spaced well apart, each inductance twice the previous one (values commonly available in inductor assortments,) and then we plug in wire jumpers to bypass whichever inductors we want in order to select the variable inductance in "binary".   This is nice because it's cheap, because you can reliably go back to a previously chosen inductance, because you don't touch or budge the actual inductors while performance the adjustment, and because using the jumpers you can adjust the oscillator while it's running without breaking the tank circuit.