deForest did it, so can we.

[Bob Bruhns]

Wow, that's a cool looking tube.

  Bob, WA3WDR

----- Original Message ----- 
From: "hal" <hfeinstein at cox.net>
To: <tacos at amrad.org>
Sent: Monday, June 19, 2006 10:31 PM
Subject: Re: deForest did it, so can we.


> This URL is a picture of a home made audion. Its made from a bell jar. 
> An ashtray is used
> for the base. Rob, where do you order tantalum wire from? And is the stuff
> dangerous to heat up and work with?
> 
> http://www.sas.org/tcs/weeklyIssues/2004-05-28/review/art/triode2b.jpg
> 
> 
> 
> 
> Robert E.Seastrom wrote:
> > hal <hfeinstein at cox.net> writes:
> >
> >   
> >> (2) Next skill, what do you
> >> make the filament out of?  I think you can buy thoriated
> >> tungsten, yes, but  I wonder what old DeForest used for
> >> his filaments?  Nickel wire? 
> >>     
> >
> > wikipedia article:  http://en.wikipedia.org/wiki/Audion_tube
> > has a link to the patents.  841,386 says in part:
> >
> >    While various means may be employed for heating said gaseous medium I
> >    find it convenient to employ electrical means and, therefore, I prefer
> >    to employ as the electrode F a filament of carbon or metal and to
> >    connect the same in series with a battery B' and a rheostat R'.  I
> >    have ascertained that a filament of metal, especially one of tantalum,
> >    renders the oscillation-detector much more sensitive than one of
> >    carbon.
> >
> > it is not surprising that deforest would try tantalum as it was an
> > interim filament material in light bulbs after carbon lost popularity
> > and before tungsten was adopted (tantalum is pretty friendly to work
> > with whereas tungsten is not very ductile - not sure what was done to
> > be able to work it into light bulb filaments, but i suspect that it
> > probably involved super high purity and very carefully controlled
> > alloying).  according to sylvania's web site, the thoriated tungsten
> > wire is preferred for arc lamps and power tubes.
> > http://www.sylvania.com/BusinessProducts/MaterialsandComponents/ElectronicsDisplayProducts/TungstenWire/
> >
> > but i digress.  tantalum wire is not particularly expensive stuff,
> > considering the quantities of it we're anticipating using.:
> >
> > http://www.sisweb.com/ms/sis/wire4.htm
> >
> >                                         ---rob
> >
> >
> >   
> 
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