To save some typing here is my response to another forum (with edits to apply to here) :
If the two rods are not one piece and bent into a hairpin shape the device is a replication of Lecher lines.
http://en.wikipedia.org/wiki/Lecher_lines--------
I watched Karl's video again and still see no signs of anything that isn't produced by transverse waves.
The video link provided by xxxx (yet another Lecher line experiment decalared a hairpin circuit) even makes statements something like 'and this cannot happen with EM'. Sorry to say but in almost every case exactly the opposite is true. It is confirmation that transverse waves are at play. The only exception is near the end with the column of water being drawn with the wire. This related more to things not discussed in the video.
One of the big problems here is folks can't see the difference between RE and RF(radio frequency energy).
An example of radiant energy is the light or heat radiating from a light bulb (longitudinal or LEM). Radio frequency energy can be LEM or TEM or both and always is (Transverse electro-magnetic like the ripples on a pond).
If the waves being sent up the Lecher lines were LEM the light being used for a shorting bar would not be brightest while the shorting bar is horizontal.
Folks get me wrong. I know LEM is possible and has the properties declared. I know Tesla was probably the greatest experimenter and inventor that ever lived. I also know Lecher invented this method and Tesla's hairpin circuit was a hairpin shape and included other things not shown by either of these videos.
Make no mistake. Both of these videos demonstrate the beginning of spark gap radio transmitter technology, hard and talented work but not much more.
---------
Addition:
People need to understand that Tesla had a broader understanding of induction. In the classic Faraday description the root is the relationship between the magnetic field and the conductor. In Tesla's understanding it also includes not considering the magnetic field - or using perpendicular induction. This is demonstrated in the coils by AgentGates of OU. This is where 'stout' rods come into play and Tesla describing a short conductor with high self induction with low frequencies. Using book induction this is impossible. Using Tesla's induction it is a fact.
Peeps call a Lecher line a hairpin circuit. This is wrong. Grumpy has provided links and pics of true hairpin circuits. If you look at those you will see there is more to the experiment than a demonstration of a basic spark gap radio transmitter.
As for how a short wire can provide high impedance..... Again - basic, standard transverse radio propagation principles.
You can connect a lamp across a short rod which measures zero ohms and light it easily. All it takes is pumping that rod with a frequency equal to 4 times the wavelength of the rod.
Like I said in chat:
Every one of my HAM antennas measure zero ohms at the feed point - with a DC ohm meter. However, some have impedances of 50, 75, 300 and 600 ohms at the operating frequency.
Again, nothing demonstrated in the referenced videos demonstrates anything than isn't correctly explained by a basic understanding of wave propagation and resonance.
This includes mention of tickling skin and purple or blue light under the skin. Folks should avoid that.