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Lev's Ultimate Antenna

This Lev Tuning works best from the 850 kHz to 900 kHz range.  

Use your AM Radio to find where you are in frequency, this is a tuned phenomenon.

 "3 Octave Jump" .mp3  (270k)
From 8 years ago, very crude but you get the idea!

Linearity allows the hand positions used in aerial fingering to have the same note intervals outside at say 15" (38 cm) from the antenna to the same width right up "next" to the antenna. 


Something Beautiful is
Hidden in Simplicity


"Immediately you will notice while approaching the antenna something mysterious is occurring."


<= Lev's Antenna
, a concept never revealed to RCA

Notice the Levitating jewel

Perfect is to bring to completion; finish.

Linearity is the measure of having an output that is directly proportional to a piano keyboard layout.

When you have Perfect Linearity, you set one octave width to match the size of your hand for aerial fingering and all the other octaves widths will also match right up next to the antenna! 

The proximity of Musical Notes can be evenly spaced to match piano key spacing, note for note.


Note: Use a 1/4" to 1/2" (13 mm) stretch on the spring to create a tuned coiled antenna. The spring has an light insulating coating between turns. I grind off the loops at each end.

No inline antenna chokes are used which simplifies design.


"True beauty is hidden in simplicity"
From the Vision of 2003

 

A theremin MUST have a good earth ground, often achieved by using your main power amp that has a three prong power plug into the wall receptacle.

The Lev Antenna setup is connected "directly" to the collector of the variable pitch oscillator transistor, no other capacitors or chokes must be in the path.


The number of linear octaves a theremin generates is proportional to the amount of energy the pitch oscillator delivers into the pitch antenna. Normally three to five. 

Read "opinions" of what causes

 Perfect Linearity 
.

Once the Lev Antenna concept is better understood, others will refine it, maybe into something  like beautiful art!   Christopher
If someone wanted to validate the Lev Antenna, begin with the parameters of my circuit board that have been shown to work. On the Phoenix board touch your frequency counter probe at screw A on the T1 terminal in the 3 x 3 section.

* Use the proper spring coil with a max of ˝” (13mm) stretch.
* The LC tuning on earlier models was necessary, but now… not always?
* Operate your pitch oscillator at 875 kHz.
* Use Hartley oscillators made with NPN bi-polar transistors or vacuum tubes.
* Use ferrite oscillator inductors instead of air core.
* Oscillator LC capacitor = 47pf for 875 kHz
* Use a good earth ground!

I prefer an un-stretched coil measurement end to end outside coil edge of 15 3/4"

There seems to be a 3/8" (10 mm) variation in spring lengths from different vendors.

The washer size is 6 mm, slipped within the ends of the antenna spring to place the internal dowel or 3/8" PVC pipe against, this is to expand the spring for the needed 1/2" or less stretch. This more for insulating the coil turns from one another even though there is a slight insulating coating already. A bit larger than 6 mm would be nice. (7 mm) 8 mm is too large and stick out the side of the spring preventing insertion into the outside clear plastic tube.

Materials for the Lev Antenna

Lowes Spring = Hillman/Resorte 9/16" x 16-1/2" x .054"  (This is the Antenna)
Zinc Plated, add a stretch of 1/2" or "about" 16 turns per inch.
My Lowes still had this as of  2013  for $4.97

Century Extension Spring
C-253
$4.97 usd  9/16" x 16-1/2" x .054" (14.3 mm x 419.1 mm x 1.372 mm) Bar Code 3859? 00253   

16 turns per inch (approx. 252 turns at a ˝" I.D.diameter)

Amazon has something that might work.

Walmart maybe $7.87

I have seen them at Home Depot on the nuts & bolt isle near the metal rods. Verify the dimensions!   9/16" x 16-1/2" x .054" 


For the best look as seen above, use 5/8" thin wall clear aquarium pipe on the outside and a 3/8" inside PVC pipe or wood dowel against two small washers on each end of the spring to get the 1/2" stretch.  Use fine emery cloth to clean the contact area between the spring loops for the washer. The RF connecting wire solders to one of these washer. Use (Lowes) PVC mounting brackets to hold the antenna to the outside of your enclosure.

Or use:

5' PVC pipe 1/2 x 5'  98 cents - Use the full length of the PVC until your ready to mount it. This way you can stand it on the floor while experimenting. Use an alligator clip connected to the brass screw on the Lev Antenna that holds the spring in place.

I would also recommend 5' PVC pipe 1/2 x 5' High Pressure PVC which can be found in the plumbing section of a hardware store. This has a slightly larger inside diameter and will fit snugly over the coupling nuts like those used on the EtherWave Standard elbow.

Use a 1/2"
(ideal)  on the spring in the PVC pipe as seen in the picture to the left next to the brass screws. This gives you about 15 turns per inch. To much stretch the outside low octaves could become "narrower" than the inside high note octaves.

Hold your un-stretched spring next to the PVC pipe to get your screw markings.

You need two 1" brass screws and nuts to hold the spring stretched in the PVC pipe, or use two 2" brass screws and have your spring mounted on the outside of the PVC.

"With the Lev Antenna tuning it is possible before adjustment that the octave next to the antenna could be "wider" than the outside lowest octave, this is one of the interesting antenna phenomenon's."


Below is a Comment by Greg "gnsmith116" at Theremin World

When reviewing the LEV antenna write-ups I realized that I was not using the specified spring!  My spring (Home Depot primeline) was 15/16" in diameter and about 1/2 inch shorter.  I have the specified spring on order from Amazon (no local hardware store chain or not has it in stock) and I also found a spring at Lowes that has the same specs and is probably the same spring so I bought that last night.

At about 900 kHz I hung a scope probe about 1 foot from the LEV antenna (with the idea of using it as a relative field strength meter) with the Lowes spring and watched or field strength changes as I extended and retracted its coils.  I did find a relationship and a power change of about 4dB that came up as I stretched the spring by about (1/4") or 6/24 (24 thread per inch adjustment screw) and then stayed constant as I extended the spring further.  Also somewhere around 6 or 7 turns of extension the side lobes dropped and then went back up past 8 turns.  (I wouldn't put a lot of trust in this measurement or methodology but I wanted to see if there was something there.) It is 9/16" dia x 16-1/2" x .054"

Then I measured the distance of the coke can to the antenna from C1-C8 for a stretch of 0 to 14 turns and all the results were the same except for a stretch of 6 and 7/24's of an inch which showed improved linearity on the low end but no change from C5 - C8.  So of course, I will zero in with smaller adjustments in that area and see how good I can get the linearity.  I suppose that I should also change the frequency as well.

The Home Depot spring is not all that much different it seems as though it should do something too but I couldn't find a response at 900kHz and not at any other frequency between 700 to 1250 kHz (but just by spot checking). It is 15/16" dia and about 1/2 inch shorter?

The Rest of the Story
8.05.12

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