Re: coherers

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

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

Tesla list wrote:
> 
> Original poster: "Antonio Carlos M. de Queiroz by way of Terry Fritz
<twftesla-at-qwest-dot-net>" <acmq-at-compuland-dot-com.br>
> 
> Tesla list wrote:
> >
> > Original poster: "Ed Phillips by way of Terry Fritz <twftesla-at-qwest-dot-net>"
> <evp-at-pacbell-dot-net>
> 
> >         Your university seems to have a lot of really neat antiques!  That
> > sounds like the classic Marconi detector, particularly if it is in a
> > large flat box with the detector mounted on the top panel.
> 
> Yes, it has a label from the Marconi company. It is actually double,
> with a coil and two magnets at each side.
> 
> > IF the wire
> > is still there it would be really interesting if you could borrow it and
> > attempt to measure its properties, an in particular see what the "click"
> > really sounded like.
> 
> Unfortunately, the wire is missing... But it has no reason for being
> insulated. No current travels on it, and it doesn't touch anything
> conductive. The two pulleys are made of ebonite, and the wire
> passes inside glass tubes at the centers of the coils.

	What about eddy current losses?  Don't the turns make contact with each
other?

> > One claimed advantage of the device was that it
> > could produce quite a lot of signal current and operate several
> > low-impedance headsets in series, permitting multiple operators to try
> > to transcribe the same message under "difficult" conditions.
> 
> In that receiver, the same wire is used in two independent detectors.
> 
> Along with it is a box with a kind of tuning circuit with three
> cylinders
> at the top and several nice switches.
> 
> Antonio Carlos M. de Queiroz

	Sounds like a VERY valuable antique.  The last one I saw for sale went
for $4500 U.S., and had none of the features you mention.  Marconi
collectors are willing to pay an unbelievable amount for Marconi
antiques, more than $25,000 at a recent auction.

Ed