[AMPS] Re: Need info on mica caps

[Rich Measures]

>
>> >Just as a ball park reference, in my hand is a 258 pF 8KV 7A @ 3mHz. It
>> >measures 3X3X2 1/4 inches.
>> >
>> €  As I understand it, the current handling ability of mica caps 
>> decreases above 3MHz.  
>
>> Rich...
>
>Not according to the data I see in about a half dozen places. 

€  got any URLs, Tom?

> Many mica capacitors continue to increase in current with frequency, 
>depending on the style of construction and value, way up into VHF.
>
>Multi-layer micas are a very common high current  VHF capacitors.

€  I never saw a mica capacitor that wasn't multi-layer.  
>
>Mica does not become a poor dielectric at 3 GHz, let alone 3 MHz. 

€  Who said that it becomes a poor dielectric at 3MHz?  In my collection 
of mica transmitting caps, current rating is often speced at a few MHz 
and/or a few hundreds of kHz.  The info on derating mica above 3MHz came 
from Lenk at Hiway Sales in Oceanside, California.    

> . 
>Especially Ruby Mica, which is used in some of the lowest ESR 
>capacitors available for microwave.

€   Impressive.  So why isn't ruby mica dielectric used in HV  caps. for 
HF amps.?

-  cheers, Tom


Rich...

R. L. Measures, 805-386-3734, AG6K, www.vcnet.com/measures  


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