Seibt: Visualizing Standing Waves on a Resonator by Corona

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Original poster: Kurt Schraner <k.schraner@xxxxxxxxxxx>

Hi all,

while the Seibt-Experiment is not spectacular, in the sense of making
"big bangs or sparks", it's quite rewarding, to show the behavior of a
resonator, by _very basic means_ of provoking corona discharges, along a
winded wire, to speak: a very thin and long coil plus a corona wire
along it (H/D=38). If I'm not mistaken, you won't find a lot about googling 
the "Seibt coil", except perhaps at Antonio de Queiroz site:

http://www.coe.ufrj.br/~acmq/mk95939.jpg

I made my own Seibt-Coil, winding the 4187 turns for one coil, with my 
friend Andi within one hour, (including 50% beer pause, having a good time 
;-)). We made 2 of the coils, to be seen at:

http://home.datacomm.ch/k.schraner/Dscn1740k.jpg

The feeding circuit was in very traditional style 19th century mode, first 
following the maggie-configuratin of Antonio's display, with a 158-turn 
secondary. However, in practice it was discovered, simple 
autotransformer+galvanic coupling proved more effective, as seen in the 
schematic diagram at:

http://home.datacomm.ch/k.schraner/Seibt_schema_3.gif

...which I have realized as:

http://home.datacomm.ch/k.schraner/Dscn1760c.jpg

In the picture, the spark gap, set fairly wide at about 20mm, is seen 
firing. This gap needs to be covered, and the room totally darkened, in 
order to observe the faint corona phenomena along the Seibt-coil. But the 
human eye can easily adapt, and see it nicely. Unfortunately I've not yet a 
convincing picture of the coil in operation, due to using a digital camera, 
which is not allowing manually setting the needed long exposure times. 
Anyway, here is, what I've currently available:

http://home.datacomm.ch/k.schraner/Dscn1750b.jpg

The ring-shaped figure at left is corona at one of the Leyden-jars. You may 
be able to distinguish the 5 corona zones along the coil at right. This is 
to be interpreted as 2 full waves along the coil (= 8 quarter waves), as 
made plausible in this diagram:

http://home.datacomm.ch/k.schraner/Stehwelle5b.jpg

The primary resonance had to be tuned to ~2.3MHz, which corresponds nicely 
to 8 times the measured 287kHz quarter wave base frequency of the 
Seibt-coil. It is also possible to generate 7 glowing zones on the coil, by 
tuning the primary to ~3.5MHz, corresponding to 3 full waves along it. 
Well, I hope bringing better corona pics, when having finished and 
developped the film on my conventional camera, which allows manually set 
long exposures...

Best regards,
               Kurt Schraner