[AMRadio] Johnson Ranger Capacitor Question

[Tony Golda]

Bacon,                                                                     
This may sound like a dumb question, but will the value of the caps change 
just "sitting there," or do they have to be in their application?
                                     Tony/ka7ius

>From: Bob Bruhns <bbruhns at erols.com>
>Reply-To: amradio at mailman.qth.net
>To: amradio at mailman.qth.net
>Subject: Re: [AMRadio] Johnson Ranger Capacitor Question
>Date: Sat, 19 Jan 2002 10:10:41 -0500
>
>Hi Bob,
>
>GMV means Guaranteed Minimum Value.  In your case, this spec must be for RF 
>bypass purposes, to make sure the bypass is effective under all conditions.
>
>Most common ceramic capacitor dielectic materials cause capacitors to fall 
>in value over time, especially the higher-dielectric materials normally 
>used for ceramic capacitor values over 500 to 1000 pF.  Also, you will 
>often see tolerance specs of +80 / -20%, which is also basically about 
>staying above some minimum value over temperature.
>
>Check out www.atceramics.com/pdf/technotes
>
>- a nice collection of informative tech notes about ceramic capacitors.  In 
>particular, look at dielectric_aging.pdf.  The ATC chart included in this 
>document shows Z5U (the most common capacitor material used in such disk 
>ceramic capacitors, in my experience) losing 20% of its capacitance in 
>10,000 hours (about 14 months).  Interestingly, the document states that 
>the industry standard process to restore a degraded capacitor to its 
>original value is to heat the capacitor to 150 C (302 F) for one hour.
>
>   Bacon, WA3WDR
>
>
>Bob Sova wrote:
> >
> > Hi folks,
> >
> > There are 32 capacitors listed in the Ranger's Parts List as:
> > .005 mfd GMV, 600VW, disc ceramic condenser
> > My question is what is the difference between a "GMV" ceramic disc and a
> > standard ceramic disc.
> >
> > Thanks,  Bob
> >
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