[600MRG] WIMA capacitors

[Ben Gelb]

My experience in amp building is pretty short (so take it for what its
worth).

I think the big consideration here would mostly be ensuring that the
capacitance value at applied voltage is what you're expecting (not sure
about the WIMA ones, or PP in general, but many caps are derated 2x or more
when full rated voltage is applied) and sufficiently low ESR to avoid a lot
of heating (and/or destruction of) of the cap (suggestion of 100V "minimum"
in linked schematic seems like it would be marginal... since class E is
nominally ~3.5x Vcc on the drain).

I have been using some C0G MLCC caps in my current class E project - with
1000-2000V ratings - (not for 630m, but for 7MHz) at ~800W power level,
seems to have been working ok so far.

Here's an example:
https://www.digikey.com/product-detail/en/kemet/C1210C682JDGACAUTO/399-14852-1-ND/7364184

I think 5% tolerance would be fine, though w/ class E some tweaking often
required due to parasitics and such.

On Thu, Jan 4, 2018 at 8:51 AM, N1BUG <paul at n1bug.com> wrote:

> I had one night of glory before my amplifier decided to act up again. I
> spent an afternoon building the thing and now have close to 200 hours into
> trying to make it work. I'm calling it a lost cause at this point. Into the
> dead project heap with it! The bear of it is, I can't confirm positively
> the amplifier is the problem and not some other gremlin in my station.
> Short of trying a different amplifier I have no way to determine that.
>
> Anyway, at some point I will want to try again with a more well proven
> design. I was looking at the (modified) GW3UEP 100W class E amplifier. I
> have all the parts except capacitors, but the specified WIMA FKP2
> capacitors appear to be unavailable. I can't afford silver micas in those
> values!
>
> So I went looking for alternatives. The WIMA FKP1 series is readily
> available in the proper values and voltage ratings, but I am not sure they
> can be successfully substituted in this application. Also they are not
> available in any tighter tolerance than 5%.
>
> Kemet offers an extensive line of pulse rated polypropelene caps, but they
> are so much cheaper I assume they are not appropriate here?
>
> Any suggestions?
>
> 73,
> Paul N1BUG
>
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