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Updated
10.21.05
Lev's Ultimate Antenna
"This antenna design is the True Beauty that was hidden in Simplicity" Christopher
This
preset tuning method worked excellent in my initial testing..
Lev's antenna
works perfect with my 850 khz RS
Theremin,
use two capacitors for 796 khz.
It "should" also work good with the
750 khz PAiA Theremax,
use three capacitors
for 650 khz |
Theory
The above schematic values tuned in at 650 khz well below
the Ultimate 2b theremins operating frequency and worked quite good.
Antenna tuning must always be lower than the oscillator frequency.
As I further study Lev's
antenna I find the antenna "spring coil" dominates the overall
effectiveness of linear tuning, the LC antenna tuning has the least
influence. If you double the spring coil length by adding another
spring in series, the outside lower octaves A1 & A2 become
"much narrower" than the inside higher octaves A4 &
A5. Using a single spring coil length balances the
inner and outer octave widths. My
Ultimate 2b low octaves
A1 & A2 could be made narrower than the upper A4 octave near the
antenna.
Stretching the spring coil about a 1/4"
to 1/2" equalized the
octaves, for linear behavior.
Keep the chokes away from
Ult-2b L2 coil
unless you want to reshape the audio sine wave for a different
sound.
| Yet to be tested
is changing the 100 pf C2
& C8 to 47pf on the
Ult-2b which raises the theremins operating frequency up above 1100
khz. The A4-A5 octave might come into better play
moved a bit more away from the antenna, I think? Then you would use one
100 pf capacitor and two 100 uh chokes for the Lev antenna
tuning. 10.21.05
This needs further study |
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Components: |
Quan |
RS Cat# |
Price |
Store |
| <= Chokes 100 uh |
2 |
273-102 |
1.29 |
Radio Shack |
| Capacitors 100 pf |
3 |
272-123 |
1.29 |
Radio Shack |
| Extension Spring |
1 |
see below |
4.97 |
Lowes Hardware |
|
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 - Sales #60954 |
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| What will perfect linearity
do? It allows the hand positions used in aerial fingering to create the same note
repeatability at 15" (38
cm) from the antenna as it does 5" (13
cm) from the antenna. Moving your hand away from the antenna moves you to a lower
register but the finger positions play the same!
rain-2-octave.mp3 (190k)
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The pitch or "null" adjuster allows you to narrow the octave width to match the size
of your hand for aerial fingering.
LINKS is short for "Linear Ideal Note Key Spacing". When
LINKS is achieved your theremin notes will match the piano keyboard key for
key from C1 to C4 with A2 at 16" (40.6 cm)
distance from the antenna.
Antenna Construction
My
Theremin Theory
.
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