[SEDXC] Update on capacitor needed

[MIKE GREENWAY]

Hi Dave,   I am not sure you want to use the ceramic caps you mention.  Caps
in transmitting situations also need to have current considerations.  I use
some broadcast type caps here that have amperage rating stamped on the side.
You see these at hamfest sometimes.  They normally are rated around 5 KV and
3 to 5 amps.   I have had caps to burn up or get very warm due to not being
able to handle the current in some things I built.  I tried using silver
mica caps in a  100 w filter and they would burn up but swithced over to
microwave chip caps which are rated at several amps even though smaller than
the silver micas they handle the current nicely at 100 w.  The silver micas
I found out are rated at a very low amperage.  Current ratings on caps is
something you don't see much in print about but they do have one.
73 Mike K4PI

----- Original Message -----
From: "David L. Thompson" <thompson at mindspring.com>
To: <sedxc at contesting.com>; "secc" <secc at contesting.com>
Sent: Wednesday, August 13, 2003 1:07 AM
Subject: [SEDXC] Update on capacitor needed


> I am told to beware of door knob capacitors in high RF situations such as
> the antenna tuner.  I need to stick with either a 6 or 10KV ceramic or an
> old transmitting mica.   I am looking for 1000pf.  I currently use two
.0003
> (300pf) in parallel 3750Wvdc transmitting micas.
>
> I found the 10KV 1000pf ceramic for a mere .62 per each in my Antique
> Electronics Supply (the other AES HI).  The rub is they have a minimum
> purchase.   Fair Radio used to have big transmitting micas (I got a 470pf
> 10Kwvdc several years ago) but the only ones they have are
> real big ones now. I will try WB4GNT but he usually has to dig things out
> and I am sure he is going to both Huntsville and Shelby.
>
> Does anyone have something in their junk box I can use?
>
> 73 Dave K4JRB
>
>
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