I love how this project is only about 5 miles from my house! Maybe I should go up to their store?

@FaultyWarrior

Just build a slightly larger coil and contact him at 8.97 kHz :P

Make a numbers station!

Wait? Didn’t tesla say that the resonont frequency of the earth was 8.97Hz? Well then, scale it up and build a new wardenclyffe tower

33km band….interesting. Reminds me of the ULF stuff that the US Navy used to run, real slow transmissions of very long wavelength…. could cover the globe from just a few locations.

Not that I Have a whole lot of personal interest in firing up an antenna like this….

HOLY CRAP, Thats a big coil!

@mrgoogfan
The resonant frequency of ‘the earth’ varies depending on the material at the site you are trying to resonate as well as the material next to/below that primary material. The size of a certain vein of stone would also determine its resonant frequencies.

In general, “The Earth” as a planet is made up of too many dissimilar materials mashed together to have a single resonant frequency. You may be able to do it, but you’d likely be talking a resonator larger than any building presently in existence.

But yes, a tesla coil would be an immense use of this coil. I don’t personally see any benefit to 8.9kHz transmission.

So will they be making a Laptop version?

the dust over the coil may be a kinda high voltage induced by some appliance near by or earth magnetic field?

I was really hoping it was a gigantic coil gun :(

@Benj:

The antenna would work much better if it were that length, but it doesn’t have to be. If it did, car AM radio antennas would need to be about 160m long.

The length of the wire in the coil is unrelated to the wavelength. When W1VLF says “resonant” he means that at the specified frequency, the reactance (imaginary component of the impedance) is zero. If your antenna is too short for your specified frequency, the reactance will be negative (capacitive reactance) and so you can add an inductor of equal and opposite reactance to reach 0j ohms. It’s not the case that the wire length in that inductor is related to the wavelength, though. You just solve the equation 1/(w*C) = (w*L) where C and L are the inductance and capacitance, and w=2*pi*frequency. That’s what he’s doing when he measures the coil as being 168 milliHenries. The real component of the impedance (measured in regular ohms, not imaginary axis ohms) has two parts: the loss from the wire measured as a resistor at DC (where he said 60 ohms for his first coil), and the “radiation resistance” which is also expressed in ohms, and shows what gets “lost” from the antenna by being radiated into space. Assuming reactance X=0, the efficiency is calculated just like a resistor divider, with some power being lost in the coil as heat, and some being radiated. Efficiency = Rr/(Rl+Rr). The Rl=60 ohms is quite large, since the radiation resistance of such a drastically shortened antenna is probably in the milli-ohm range, so his efficiency is probably on the order of 1e-3/(60+1e-3) =~ 16e-6 or about -110dB of loss. So (assuming the milli-ohm radiation resistance guesstimate is OK) his 50W in actually radiates around a milliwatt.

See http://en.wikipedia.org/wiki/Antenna_%28radio%29#Resonant_frequency and
http://en.wikipedia.org/wiki/Antenna_%28radio%29#Efficiency

Anonymouse:
>>It looks more like it’s been optimized for resonance than for radiation.

It has. Check the article. This is just the loading coil to match to the electrically short antenna supported by his 120 foot tower (turns out that a 33km antenna just isn’t practical).

Wow… This is AWESOME!

My 706 only goes down to 30Khz… Wish I had something that receives at 9khz.

Low-and-Slow is the way to go!