Bo Bjerre wrote:
....
>
> Jeg har een af de helt gamle i min kælder. Dengang det var en rigtig
> krystal, og man sad og fiskede med "nålen" for at opnå den rigtige ensretter
> virkning. Min bedstefar brugte den i sin første "radio". Egentlig burde jeg
> aflevere den til et museeum..
>
> Bo //
Hej Bo
Faktisk sidder der stadig folk og fisker...mere om det senere...først
lidt overraskende nostalgi:
Jeg fik et chok for et stykke tid siden, da det viser at folk i
1920'erne anvendte dimser med negativ differentiel modstand - sikkert
uden nogen vidste hvordan det fungerede.
Dimsesystemet er let at genkende, da der er et batteri til at give
krystallet bias - jeg formoder at effekten er opdaget ved at man
oprindeligt blot ville lave lidt forward bias, men så "ramte" et
biasområde med negativ differentiel modstand med visse krystaller - og
så fik meget bedre signalmodtagelse - bladr ned til figur 4-7:
Cristadyne: Semiconductor archaeology or tribute to unknown precursors:
http://www.a-reny.com/iexplorer/cristadyne.html
Citat: "...In 1923, Oleg Losev [O. V. Lossev, Lossew] (1903-1942) ( See
link below ) managed to make a high frequency generator using such a
detector. But it was polarized. This indicates that this diode had a
characteristic curve in which a negative slope was present. And this
makes one think of the tunnel effect diode invented a half a century
later...These layouts where part of what one called CRYSTADYNE [eller
Cristadyne, Crystodyne] systems. But in those days, the technical
performance and industrial ease of the new increasing valve technology
made these layouts to be ignored, and then forgotten..."
Se f.eks. (
http://da.wikipedia.org/wiki/Negativ_differentiel_modstand ):
Radio News, September, 1924, pages 294-295, 431: The Crystodyne Principle:
http://earlyradiohistory.us/1924cry.htm
Radio News, September, 1924, page 291: A Sensational Radio Invention. By
HUGO GERNSBACK:
http://earlyradiohistory.us/1924sens.htm
-
I dag sidder der folk og "rister" møtrikker, søm eller galvaniseret blik
for at få dem til at virke som signalforstærkere til brug i oscillatorer
eller krystalmodtagere (møtrikmodtager?):
By Nyle Steiner K7NS 2001. Hjemmelavede dimser med negativ
modstandskarakteristikker:
Code Practice Oscillator made from Homemade Active Semiconductor:
http://home.earthlink.net/~lenyr/nraudio.htm
Citat: "...Heat treated galvanized nail and zinc chromate nut. Either
can produce oscillations. Nail was somewhat difficult to adjust but nut
was easy..."
Zinc Negative Resistance RF Amplifier for Crystal Sets and Regenerative
Receivers Uses No Tubes or Transistors:
http://home.earthlink.net/~lenyr/znrfamp2.htm
Citat: "...Taking a wild guess, I would suggest the possibility of these
dark spots being Zinc Ferrite Zn-Fe2-O4 or something similar, formed by
the interaction of heat, oxygen and zinc, reacting with the surface of
the iron..."
Zinc Negative Resistance Oscillator:
http://home.earthlink.net/~lenyr/zincosc.htm
mvh/Glenn