Paul,
If you are trying to keep things small, have you considered one of the high
speed versions of the 4046 PLL/OSC? Some manufacturers spec these up to 20
MHz. No coils. If you go with the LC, and you have any fixed capacitors in
parallel with the inductor, use decent capacitors, like mica or RF approved
ceramic. I have seen cheap ceramic caps meant for bypassing just not work in
applications like yours.

Tam
"Paul Burridge" wrote in message
news
On Fri, 19 Mar 2004 17:46:43 GMT, "Harold E. Johnson"
wrote:


I don't think you can get away
with short cuts at RF, especially if you're a non-expert.

3 MHz is practically DC. Why don't you ask one of your friends at the BBC
to
build it for you.

I was told 40Mhz is "practically DC" too. I guess it depends on where
you're coming from.
Actually I've dumped the factory inductor as suggested by Tom and
wound-up a large, air core job on 15mm plastic water pipe. It's made
a big difference. I'm happy to report I've now got the 5th! Could be a
little cleaner but who cares? Tom made a big deal out of the
importance of high-Q so it was the obvious thing to try. Fortunately,
it's worked. God knows how I'm going to squeeze this monster coil onto
the board, though! :-|
Can I infer from this experience that SMD inductors of over a few uH
are a waste of time?
--

The BBC: Licensed at public expense to spread lies.