Paul Burridge wrote in message . ..
On 22 Mar 2004 22:01:47 -0800, (Tom Bruhns) wrote:

Of course, maybe you don't need such a high Q, Paul. Qu of 30 is
quite reasonable for small SMT RF inductors, at least the type I use.
In the following list, "series" means in series from the gate output
to the next gate input, in order, and "shunt" means shunt to ground at
that point. Anyway, try this (build it or SPICE it or RFSim99
it...add resistors to any simulation to account for the Qu. I'd
suggest 3 ohms series and 12k ohms shunt for each 1.8uH.)

Thanks, Tom. I've simulated the filter and posted the plot result to
abse. Looks promising. See if it meets your expectations....

Hmmm...I simulated it, and it looked fine to me. I don't do a.b.*
groups. I haven't actually built one; more pressing things to do.
But I expect it will work OK. It assumes no inductive coupling among
the coils. That's usually not too hard to get low enough in practice,
if you orient the coils properly.

BTW, check out Coil-Q inductors for commercial RF coils in small
shield cans with decent Q. 7mm square can, Qu around 100 for
inductances and frequencies in the neighborhood we're talking about
here.