[600MRG] WIMA capacitors

[Larry]

I have tried ceramics.

The usual disk ceramics are horrible.

The big transmit ceramic "doorknobs" can be used in some applications 
but are usually not much better.

Some C0G/NPO chip ceramics are OK for receive applications if you don't 
mind your filters being a bit lossy. The real issue with chip caps is 
that the good ones are just not available in the large values needed for 
137/475. The "good" ones run 2 or 3 bux apiece and it makes little 
financial sense to parallel a dozen or more to make the required C 
values. Of course if you have access to them at little or no cost, then 
they become more attractive!

73, Larry - W7IUV


On 05-Jan-18 6:16 AM, J Mcvey wrote:
> Ceramics ought to work well, no?
> Have you tried any of them?
> There are COG and 5% types ...
> 
> 
> On Friday, January 5, 2018 8:49 AM, Larry <larry at w7iuv.com> wrote:
> 
> 
> Recently I had the opportunity to look close at some caps for 475/137
> filter use.
> 
> I measured the Q at the approximate operating frequency.
> 
> The best is silver mica caps. Expensive but usually worth it for
> critical applications. Unfortunately not usually available in the values
> needed for 137.
> 
> Next best is the 715P "orange drops", expensive and sometimes hard to get.
> 
> Third on my list is the WIMA MKP1 series. Seems to be OK in all my
> applications so far and is affordable.
> 
> I have had bad luck using the FKP1 series caps. The ones I looked at had
> higher ESR, lower Q and got hot in my filters.
> 
> Kemet and other vendors didn't seem to be much good, at least the types
> I had access to.
> 
> YMMV....
> 
> 73,
> 
> Larry - W7IUV
> 
> 
> 
> On 04-Jan-18 10:32 AM, lstoskopf at cox.net <mailto:lstoskopf at cox.net> 
> lstoskopf at cox.net <mailto:lstoskopf at cox.net> wrote:
>  > Take a look at the graphs for the WIMA FKP1 series.  At 472 kHz they 
> seem to fall off pretty fast.  I'm in the same boat....have some picked 
> up here and there, but haven't used them so anxious to see what the big 
> boys say.  N0UU
>  >>
>  >> 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%.
>  >>
>  >
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