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



On 9/16/12 7:37 PM, Andreas Hahn wrote:
For Terry Fritz's antenna, he specifies a 20nF NPO ceramic capacitor.
The largest NPO I can get is 1nF; however, I can get 20nF in X7R or
polyester & polypropylene film.

While Fritz does say the value isn't critical, I suspect off by a factor
of 20 could hurt things...

On the other hand, he does say "it should be a high performance COG type
capacitor." (NPO and COG are equivalent, last I checked).

Should I just go with X7R? Or am I better off using the (perhaps more
inductive) poly film?


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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