[AMRadio] Johnson Ranger Capacitor Question

[Bob Bruhns]

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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