Metal - old style Diodes

[Heid the baw - goal!!]

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


Tam

 

[John Popelish]

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

Sure it is still possible. Google copper oxide rectifier
and selenium rectifier. You can still buy either,
occasionally on eBay, also. And if you heat a piece of
polished high carbon steel till it turns blue and touch that
surface with a nickel or chrome plated pin point I think you
get a detector diode.

 

[John Larkin]

Sure it is still possible. Google copper oxide rectifier
and selenium rectifier. You can still buy either,
occasionally on eBay, also. And if you heat a piece of
polished high carbon steel till it turns blue and touch that
surface with a nickel or chrome plated pin point I think you
get a detector diode.

The minerals galena and zincite were used as crystal radio detectors,
essentially point-contact diodes, in the 1920's. The "foxhole radio"
used a rusty razor blade. By the mid 1940's, microwave mixer diodes
were being made from germanium, silicon, and GaAs.

There were early electrolytic rectifiers, too.

I sort of doubt the fillings/house stuff.

John

 

[kell]

folklore has

I sort of doubt the fillings/house stuff.

John

Maybe not but you can get rectification in odd situations. I ran a
twisted pair about 150 ft to extend a phone line to an outbuilding and
started hearing a radio station on the remote phone.

 

[Jamie]

folklore has



Maybe not but you can get rectification in odd situations. I ran a
twisted pair about 150 ft to extend a phone line to an outbuilding and
started hearing a radio station on the remote phone.

You were not getting rectification.!.. I'm sure if you really
think about it, you'll figure it out.!~...

 

[John Larkin]

You were not getting rectification.!.. I'm sure if you really
think about it, you'll figure it out.!~...

How could he hear a radio station without rectification going on?

Cheap electronic phones (RatShack mainly) pick up AM and TV stations
pretty badly, but because the semiconductors inside are rectifying the
RF.

Lots of opamps will rectify RF and create nasty offsets.

John

 

[Homer J Simpson]

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.

 

[Robert Baer]

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

Also see coherer




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.

 

[Eeyore]

Google copper oxide rectifier
and selenium rectifier.

Just be prepared for a really bad small if a selenium rectifier 'blows' !

Graham

 

[Eeyore]

You were not getting rectification.!.. I'm sure if you really
think about it, you'll figure it out.!~...

Eh ?

Graham

 

[Homer J Simpson]

Concerning something vibrating to local stations, it is *not* rubbish; a
metal fire-escape ladder can do so thus:

You don't find those on too many homes.

 

[John Larkin]

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

 

[jasen]

Before semiconductors were invented we had Diodes for rectification which
were metallic of some sort. Does anybody remember?

prisoners of war used blued razor blades or coal as detectors in crystal
sets, conventional crystals are galena (mineral lead sulphide) which is
metallic in apearance. these days semiconductors are used.

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.

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

it'd happen, but it's unlikely to be a measurable effect.

Bye.
Jasen

 

[Barry Lennox]

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?

Yes, copper oxide, selenium and galena (Lead Sulfide) were common
before WW2. Galena was found in some types of coal, and that was used
in conjunction with a "cat's whisker" usually of tungsten wire, as a
point contact diode. I remember trying that with a "crystal set" back
in the 50's but got better results with a rusty razor blade. AKA the
foxhole radio, and also used in POW camps.

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

Have heard of it, but suspect it's urban myth stuff.

Barry Lennox

 

[Jan Panteltje]

How could he hear a radio station without rectification going on?

Cheap electronic phones (RatShack mainly) pick up AM and TV stations
pretty badly, but because the semiconductors inside are rectifying the
RF.

Lots of opamps will rectify RF and create nasty offsets.

John

Hum, nobody has mentioned that BIG metal rectifier workhorse:
http://www.tigercom.dsl.pipex.com/gallery.htm
Mercury is a metal after all

 

[martin.shoebridge]

SNIP
"> Also, some claim that a house can vibrate to local radio stations due to
the

metallic structure. Possible or rubbish?


Tam

Not rubbish at all, sort of. My wife can clearly hear the cable TV channel
when the TV is switched off. I can hear absolutely nothing and I'm talking
3am in the morning and you could hear a spider walk across the ceiling.
Any theories?

 

[Winfield Hill]

John Larkin wrote...

...

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.

Concerning something vibrating to local stations, it is *not*
rubbish; a metal fire-escape ladder can do so thus: [ snip ]
(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

[ snip ]

That's crazy. If the station's coverage was "greatly impared" ...

One not-so-silly effect coming from rusty metal near high-power
transmitters is "rust noise", which is wideband RF noise created
from non-linear RF current conduction of the rusty joints. This
nonlinearity is the same effect exploited in crystal detectors,
namely a quantum-mechanical tunneling junction. For this to work
one needs two conductors in close proximity, about 0.1 to 0.3nm,
but not touching. The conductance is nonlinear, and rectifying.
An example of a debilitating rust-noise effect is degradation of
RF receivers on a ship when one of the transmitters is operating.

 

[Ancient_Hacker]

Before semiconductors were invented we had Diodes for rectification which
were metallic of some sort. Does anybody remember?

No, I'm not quite that old, but there were many rectifiers in use
before silicon or germanium--

* Old crystal radios used crystals of various elements, often lead
(galena), or various carbides.

* For power rectification, early amateurs used some sort of
electrolytic cells, dissimilar metals in a conducting solution will
have a directional preference. These were not terribly efficient, as
there are many trales of boiling rectifiers, but they certainly were
cheap and effective and didnt require a billion dollar silicon foundry.

* Later on copper oxide came into use-- early auto and airplane
alternators had copper oxide rectifiers. Also many older AC voltmeters
have copper-oxide bridges.

* Don't forget mercury-vapor rectifiers! Old battery chargers from
the 1930's often had a Sylvania "Trygon" tube, basically a 10 amp
mercury vapor rectifier.

* Also most any kind of oxide can act as a rectifier. Many years ago I
lived about a mile away from a 50KW AM station. One night while
sneaking back home at 2AM I heard talking in the garage! Busted! I
thought. I wandered ahead, head down toward the talking, expecting to
get a talking-to from my parents. Turned out the voice was coming from
a rusty electrical box! It was the overnight talk-radio show from the
radio station, coming in loud and clear. A rusty hinge was rectifying,
and enough current was flowing through the metal cover to act as a
speaker cone. It went away as soon as I touched the cover. Weird.

 

[John Larkin]

Hum, nobody has mentioned that BIG metal rectifier workhorse:
http://www.tigercom.dsl.pipex.com/gallery.htm
Mercury is a metal after all

Beautiful.

There was also the ignitron tube, a pool of mercury with an igniter
electrode and a big graphite anode, usually water cooled. They were
used as very high power rectifiers and triggered switches. They were
usually ugly. In pulsed applications, they could handle up to a
million amps.

John

 

[John Larkin]

John Larkin wrote...

Homer J Simpson wrote:
...

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.

Concerning something vibrating to local stations, it is *not*
rubbish; a metal fire-escape ladder can do so thus: [ snip ]
(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

[ snip ]

That's crazy. If the station's coverage was "greatly impared" ...

One not-so-silly effect coming from rusty metal near high-power
transmitters is "rust noise", which is wideband RF noise created
from non-linear RF current conduction of the rusty joints. This
nonlinearity is the same effect exploited in crystal detectors,
namely a quantum-mechanical tunneling junction. For this to work
one needs two conductors in close proximity, about 0.1 to 0.3nm,
but not touching. The conductance is nonlinear, and rectifying.
An example of a debilitating rust-noise effect is degradation of
RF receivers on a ship when one of the transmitters is operating.

No doubt. Even the plating in new 7/16 connectors has to be right or
the nonlinearities can mess up cell phone sites. But the field
strength in downtown San Francisco is nowhere near what you'd see on a
ship, right under the antennas. We're in a pretty much rf-transparent
building, and we can see Sutro Tower out the back window, and the most
we see is a little fuzz on the faster scopes. And we *do* have a rusty
fire escape!

"their coverage in a certain direction was greatly impared" is still
unbelievable. No small-scale passive structure is going to poke a
significant directional hole in a far-field radio pattern. As I said,
a tree would have a bigger effect than a fire escape ladder, and no
radio station owners are going out chopping down trees.

John