Re: Metal - old style Diodes

On Sun, 17 Dec 2006 03:24:38 GMT, Robert Baer
<robertbaer@xxxxxxxxxxxxx> wrote:

Homer J Simpson wrote:

"Heid the baw - goal!!" <mad@xxxxxxx> wrote in message
news:45848011$0$15484$88260bb3@xxxxxxxxxxxxxxxxxxxx


Before semiconductors were invented we had Diodes for rectification which
were metallic of some sort. Does anybody remember? I am interested if it
is
possible to make a Diode from two dissimilar metals. Why? Well folklore
has
it that in some rare occasions people have heard radio stations via two
fillings on top of each other in their teeth.


http://www.adonald.btinternet.co.uk/Crystal/Crystal.html

Also see coherer


Also, some claim that a house can vibrate to local radio stations due to
the
metallic structure. Possible or rubbish?


Rubbish.






One of the rectifier construts was made via copper and copper oxide;
not too efficent and (i think) low reverse voltage standoff.

Concerning something vibrating to local stations, it is *not*
rubbish; a metal fire-escape ladder can do so thus:
1) the iron structure is long enough to act as an antenna, especially
"local" to the transmitter
2) the rust on it creates the detector (iron/iron oxide)
3) that detector is "shorted" by the structure, allowing a reasonable
current to flow (in the order of 10-100 mA)
4) that current causes the fire-escape ladder to vibrate.
That had been confirmed, at least in downtown San Francisco after (a)
someone finally *listened* to a number of drunks and so-called crazy
people, (b) the station determined that their coverage in a certain
direction was greatly impared, (c) the station techs determined that the
fire-escape ladder was in line of the reduced coverage, and (d) anyone
near the ladder heard exactly what the station was transmitting: news,
music, etc.
Cleaning the ladder of the rust solved the problems.


That's crazy. If the station's coverage was "greatly impared", the
fire escape would have to be dissipating kilowatts. If one rusty fire
escape can affect the far-field radiation pattern of a radio station,
what would a tree do? A kid with a longwire antenna and a crystal set?
An electrical substation? The Bay Bridge? My company is in downtown
SF, and I wish I could steal a couple of free kilowatts.

And what's the sound transducer mechanism? The only radio transmitters
in SF are on Sutro Tower, and it's way up on the top of Twin Peaks, a
couple of miles + a couple thousand vertical feet from downtown.

http://www.jimprice.com/sutro/

Urban legand, and not a very good one.

John

.

Quantcast