Re: [TCML] Capacitor in Terry Fritz's plane wave antenna

[Andreas Hahn <andreas.hahn@xxxxxxxxxxx>]

Unfortunately I don't live in an area where Digi-Key shipping is 
affordable.

Seeing as the main differences between NP0/C0G and X7R are dC/dV and 
temperature coefficient, it sounds like the best route is to use X7R 
ceramics instead. The antenna isn't going to experience temperature 
changes of any magnitude between calibration and use, and the voltage 
across the capacitor will hopefully be small compared to the rated 
voltage.

(One additional issue is frequency coefficient, but hopefully the resonant 
frequency of the coil won't change much...)



On Mon, 17 Sep 2012, Jim Lux wrote:
> I would think that inductance in this circuit is a *bad thing*, but so is 
> changing the value of C2, since that is the bottom of a capacitive voltage 
> divider formed by C3 and C2
>
> Terry gives a part number from Digikey for the cap 399-1835-1-ND  (and you 
> need two, since they're 10 nF each)
>
> it is true that they show as "non-stock" at Digikey this afternoon (unless 
> you wan to buy 2,500 of them at about 36 cents each)
>
>
> The ROHS equivalent is in stock for small quantities at $1.39 each. 
> 399-4520-1-ND
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