Re: Metal - old style Diodes

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.
.