[Amps] Mica cap substitute \ alternative

Joe Subich, W4TV w4tv at subich.com
Wed Jul 12 18:03:42 EDT 2006


Be careful of Steatite ... several kinds will absorb moisture 
and cause problems.  I had to replace the feedline at a television 
station (1600'+ of 3 1/8" rigid line) a few years ago because the 
Steatite insulators had absorbed moisture over the years, increasing 
the loss and resulting in problems with arcing.  

73, 

   ... Joe, W4TV 
 


> -----Original Message-----
> From: amps-bounces at contesting.com 
> [mailto:amps-bounces at contesting.com] On Behalf Of Harold Mandel
> Sent: Wednesday, July 12, 2006 5:28 PM
> To: 'Gary Smith'; 'R L Measures'; g3rzp at g3rzp.wanadoo.co.uk
> Cc: 'Amps Amps'
> Subject: Re: [Amps] Mica cap substitute \ alternative
> 
> 
> Steatite, (porcelain); Corning Glass, PTFE....
> 
> -----Original Message-----
> From: amps-bounces at contesting.com 
> [mailto:amps-bounces at contesting.com] On
> Behalf Of Gary Smith
> Sent: Wednesday, July 12, 2006 5:18 PM
> To: R L Measures; g3rzp at g3rzp.wanadoo.co.uk
> Cc: Amps Amps
> Subject: Re: [Amps] Mica cap substitute \ alternative
> 
> At the risk of straying OT, what is a good insulator at 50 MHz or >?
> 73,
> Gary...wa6fgi
> 
> 
> ----- Original Message ----- 
> From: "R L Measures" <r at somis.org>
> To: <g3rzp at g3rzp.wanadoo.co.uk>
> Cc: "Amps Amps" <amps at contesting.com>
> Sent: Wednesday, July 12, 2006 3:46 AM
> Subject: Re: [Amps] Mica cap substitute \ alternative
> 
> 
> > It's called Dissipation Factor.  For example, Nylon, Delrin 
> and Vinyl  
> > are excellent insulators at 50Hz, but at 50MHz they are not.
> > 
> > On Jul 12, 2006, at 2:13 AM, Peter Chadwick wrote:
> > 
> >> Rich said:
> >>
> >> >Unlike barium-titanate dielectric (ceramic)  doorknob capacitors,
> >> whose current carrying ability increases from 5MHz to 30MHz, mica
> >> dielectric caps' current carrying ability decreases above 5MHz.<
> >>
> >> Yes, but WHY? What's the mechanism that allows mica to be a  
> >> perfectly good insulator in other application, way way up in  
> >> frequency?
> >>
> >> 73
> >>
> >> Peter G3RZP
> >>
> >>
> > 
> > R L MEASURES, AG6K. 805-386-3734
> > r at somis.org
> > 
> > 
> > 
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