--- In
Homebrew_PCBs@yahoogroups.com, "Leon Heller" <leon.heller@...>
wrote:
>
> ----- Original Message -----
> From: "kilocycles" <kilocycles@...>
> To: <Homebrew_PCBs@yahoogroups.com>
> Sent: Monday, February 20, 2006 11:50 PM
> Subject: [Homebrew_PCBs] Re: Film Caps at RF frequencies
---snip---
> Silver mica are difficult to find and very expensive. Film
capacitors aren't
> very suitable for RF, I use low-K ceramic plate capacitors, like these:
http://www.rapidelectronics.co.uk/rkmain.asp?PAGEID=80010&CTL_CAT_CODE=30151&STK_PROD_CODE=M32340&XPAGENO=1 > Leon
Leon,
Boy, I haven't seen anything like those over here. SM caps on the
retail market are typically $.50 apiece and above, but I get them from
a local surplus shop unless I need a specific value.
Some monolythic ceramics are available in temperature-compensated
values, typically NP0 and N750, but not the full range of the plate
capacitors listed in the data sheet, and certainly not 2% tolerance!
Mostly, the full range (2 pF on up) are NP0/C0G ceramic disc. They
are available in values that don't follow the E6 or E12 standard, such
as 5, 8, 9, 10 pF, and they aren't very expensive.
I am building the LCR meter from Everyday Pracical Electronics.
Originally, the only 1% cap (can't recall the required value at the
moment; .1 uF possibly) I could find was a fairly large Mylar axial
that would have been a problem trying to fit to the PCB, but I
recently found a monolythic replacement that is very small.
I guess this is another example of the differences in availability of
types of components in the US and the UK and Europe. For another
example, toroids are very widely used here in homebrewing, and Toko
inductors are not used much. Our suppliers have only limited values
of those, none of which match what I see in RSGB publications and
designs on the web.
73/72,
Ted KX4OM