[NLRS] 220pf 1kv cap

[Dr. Gerald N. Johnson]

Most likely the makers chose different coating colors, but there can 
also be wild variations in temperature coefficient, voltage coefficient, 
and piezoelectric properties. Some high dielectric constant ceramics can 
loose 80% of their capacitance at 50 degrees C. Some also loose a lot 
with applied voltage, and some are so piezo electric they modulate 
signals from acoustic waves or when bypassing the plate feed for an AM 
transmitter they talk enough to be heard outside the transmitter. One 
time I had a .01 uf disc ceramic that would show several volts on an 
analog VTVM when gently tapped with a hammer while laying on the anvil 
part of a table vise. It didn't survive the experiment trying for more 
voltage. I should have tried a scope but didn't have a scope and anvil 
in the same room that day. About that same year I tried to build a 
compact vacuum tube receiver tucking little dogbone (not temperature 
compensated) ceramics between the pins and the center post of the 7 pin 
tube sockets and the heat from the tubes drastically detuned my IF 
strip. I try to only acquire NPO or N050 capacitors when the value is 
critical.

73, Jerry, K0CQ

On 9/16/2016 8:39 AM, S. Earl Jarosh wrote:
>
>
> Dumb question: What or is there any difference between brown ceramic caps
> and the blue ones?
>
> S. Earl Jarosh, N0HZ
> SEJ Industries, Computer and Business Consulting
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