[Hallicrafters] Piesoelectric effect case in point.

[Robert Nickels]

On 1/3/2011 10:05 AM, Troglodite at aol.com wrote:
> But expose them to heat and they are gone

Hi Doug, and Happy New Year!

Moisture will kill them quickly too, as rochelle salt crystals have a 
strong affinity to wate.  They basically dissolve  - "deliquescent" is 
the fancy term for it.  One might wonder why they were so widely used if 
they were so touchy?  The answer is, potassium sodium tartrate (the 
chemical name for Rochelle Salt) was the first material discovered that 
had piezoelectric properties.  Interestingly, cane sugar crystals were 
another, although Rochelle Salt had a very high output and was also 
cheap and easy to make (using  baking soda and cream of tartar, for 
those who may be into kitchen chemistry).

And here's the radio connection: there is growing interest in "energy 
harvesting" to operate low-powered wireless sensors that can spend most 
of their time storing energy from the environment in order to transmit a 
short burst without batteries.  Linear Technology has just introduced a 
new power supply IC designed for this purpose that cleverly converts 
voltage spikes from a piezo element into enough energy to do something 
useful:

http://www.linear.com/pc/productDetail.jsp?navId=H0,C1,C1003,C1799,P90393

So it may not be long before a hiker or cyclist can capture enough free 
energy through his exertions to make a few QSOs!

73, Bob W9RAN