Re: coherers

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

Original poster: "davep by way of Terry Fritz <twftesla-at-qwest-dot-net>" <davep-at-quik-dot-com>

>>My coherers don't. They also "cohere" without DC bias across them.
>>They change resistance once triggered, and keep the condition until
>>being shaken.
>>But there were coherers that would decohere spontaneously some time
>>after triggered, without need of tapping. Some old texts mention
>>a kind of coherer used by the Italian navy that had this property.

> The "Italian Navy Coherer"

	errrrr.
	Both my vintage 1910 references describe, explicitly
	the Italian Navy coherer as a mercury bubble between
	iron end plugs in a glass tube.  Strictly like a
	classic filings coherer.

> used a rotating wheel dipping into the surface of a small

> pool of mercury, which had oil on the top to keep it
> from oxidizing.  I've always intended to make one and see if

> it work, but haven't yet gotten enough ambition.  There's

> been a lot of discussion concerning Marconi's possible patent

> infringement, as he used them in some of his early work.

	The rotary one was an ENGLISH (LODGE & MUIRHEAD)
	invention.  cf my post earlier.  I looked it
	up, Zenneck & Seelig.


> On the subject of "old wireless" stuff, here's a question for Antonio:
> 
> Have you ever built a "magnetic detector"?  I've read of them a lot, but
> have never seen a single statement about their sensitivity.  They were
> reported as "less sensitive than a coherer" [if that is possible] but
> much more stable, and were standard Marconi equipment for several
> years.  I've always wanted to make one but can't find the fine,
> insulated iron wire.
	Insulate some.  rust, or thin varnish or ....

	The voltages are teensy.

 	<FX as dwp staggers to bookshelf>

	Mumble.  Z&S talk all around it, but never compare

	magnetic to others.  My impression:

	more stable, less sensitive.

	best
	dwp

...the net of a million lies...
	Vernor Vinge
There are Many Web Sites which Say Many Things.
	-me