[Elecraft] Elecraft General Interest: SFGate: Robert Helliwell, radio science pioneer, dies

[Mike Cox]

  Just for a bit of nostalgia, I also had a CK722 (back in the day) 
which I paid about $10 for. My 2N107's legs had previously fallen off 
and this was what I replaced it with. I still have it so here's a 
picture of one of the prettiest transistors ever made sitting on the 
screen of a current production version of a truely classic scientific 
calculator.

http://ab9v.us/a1DSC_2047-1024.jpg

73,
Mike, AB9V


On 5/26/2011 13:42 PM, Jim Dunstan wrote:
> At 10:49 AM 5/26/2011 +0100, you wrote:
>
>>>    With great delight over the years, he regularly welcomed visitors to his
>>> lab to listen to what he called his "whistlers," the eerie electrical
>>> warbling generated by lightning flashes in Canada's Arctic and that had
> Hi,
>
> Just a short line (off elecraft topic ... forgive me) ... when I was15
> years old I bought my first CK-721 transistors (Raytheon) and built a
> '"whistler" receiver after reading a Scientific American article.  Maybe
> the article  was written by Professor Helliwell ... I can't recall.
>
> The receiving setup is a large 4' diameter loop of many turns (maybe 30-50)
> of copper wire (salvaged from old transformers) connected to a diode
> detector and high gain audio amplifier.  Essentially an audio frequency
> crystal set followed by a high gain audio amplifier.  I hung the loop
> vertically in the attic.  It was possible to hear "whistlers" from storm
> centers long before you could hear the thunder.  Whistlers appear to be
> electromagnetic waves that fall within the the audio frequency spectrum,
> but they cannot be detected directly by the ear.
>
> By the way the CK-22 which I originally ordered was priced at over $20.00
> ... by time I sent away for one, similar CK-721's were already surplus and
> I could get a handful for $5.00 ... an early indication of the speed of
> technological change !!
>
>
>
> Back to Elecraft topics hi
>
> Jim
>
> VE3CI
>
>
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