[AMRadio] Mica vs Paper

Michael D. Harmon mharmon at att.net
Thu Dec 14 22:29:40 EST 2017

According to the Construction Practices chapter in the 1955 ARRL 
Handbook, if you hold a 6-dot cap so the arrows point to the right, the 
upper leftmost of the 6 dots indicates whether the cap is a mica or 
'molded paper'.

If the dot is black, it's mica, if it's silver, it's molded paper. This 
designation is in accordance with the AWS (American War Standards) or 
JAN (Joint Army-Navy) specs.  If the cap has only 3 dots, it is ALWAYS 
an RETMA 500 volt 20% mica cap.
If there are 6 dots, and the upper-left dot is NOT black or silver, the 
cap is an RETMA mica cap.

I am attaching a PDF file of the page which describes these caps. If 
they don't come through, email me at mharmon at att dot net and I'll 
send it to you.

Mike, WB0LDJ

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This page last updated 17 Jan 2018.