Re: Cooking with the primary

["Tesla list" <tesla-at-pupman-dot-com>]

Original poster: "Ed Phillips by way of Terry Fritz <teslalist-at-qwest-dot-net>" <evp-at-pacbell-dot-net>

Tesla list wrote:
 >
 > Original poster: "Jim Lux by way of Terry Fritz <teslalist-at-qwest-dot-net>" 
<jimlux-at-earthlink-dot-net>
 >
 > Given the very long wavelength of TC emissions, compared to
 > cellphones/microwave ovens/radars, the nature of the RF power dissipation is
 > going to be somewhat different.  In the higher frequency case, radiated
 > fields get absorbed (and, fairly quickly), so things like antenna/head
 > geometry are important.  At the lower frequencies, you're probably more
 > worried about being part of an RF circuit, and having RF currents heat up
 > some part of your body (i.e. very localized, as in a burn, or generalized,
 > as in the well documented ankle/wrist symptoms ).  Skin depth at TC
 > frequencies, in a human body, is much greater than the thickness of the
 > body, so it's sort of a bulk conduction effect.

	Furthermore, only a small part of the incident RF energy is absorbed in
the body, most of it is reflected.  As for "touch burns" that's another
matter.  Example:  I have a small 180 kHz radio beacon here, running a
couple of watts.  The output is coupled through a series tuned loading
coil to a vertical antenna with a total capacitance of about 400 uufd
(talk about a top load for a coil).  The actual output stage schematic
is very much like a conventional TC - tuned primary, tuned secondary,
and (in my case) just slight overcoupling.  Even at the 2 watt level the
voltage on the antenna is over 1000 and touching it or the lead to it
gives one a nasty bite.  A screwdriver or other conducting object
scraped along it produces small sparks which are visible even in
daylight.

Ed