Re: Concrete materials can act as a shorted turn

["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>

 > ----- Original Message -----
 > From: "Tesla list" <tesla-at-pupman-dot-com>
 > To: <tesla-at-pupman-dot-com>
 > Sent: Sunday, January 19, 2003 4:39 PM
 > Subject: Shorted loops of concrete reinforcing effect res freq?
 >
 >  > Original poster: "Christopher Rutherford by way of Terry Fritz
 > <teslalist-at-qwest-dot-net>" <Christopher.Rutherford-at-comindico-dot-com.au>
 >  >
 >  > Hello,
 >  > I recently move my coil outside of my garage to run it and have found its
 >  > working much better. I suspect that the loops in the steel reinforcing
 >  > under the concrete of may garage may have loaded it??
 >  > I don't think I should have to retune it now that its had these 'shorted
 >  > turns' removed, is this right?
 >  > Basically only the Q has gone up? ...is this thinking right?
 >  > Cheers & thanks
 >  > Chris

	Back in 1946 I was working at Naval Research Lab in the Washington
area, and someone arranged a trip to NSS, a giant VLF transmitting
site.  One of the things we were shown was the loading coil room, which
I remember (that's quite a while back) as being a cube around 30 feet on
the side, with a hole in top for the lead in from the antenna; the coil
filled a good bit of the room.  Anyhow, the guy who was taking us around
had a story which may or may not have been true.  According to him when
the building was built and the coil first operated the floor buckled up
because of eddy current heating of the rebar!  It was rebuilt with some
other form of reinforcement.  Of course, those guys were running about
500 kW at around 16 kHz, more than any home TC.

Ed