From: Bill Powell on Feb 5, 12:41 pm

I'm seeking information about using 2 or more closely spaced SM
inductors (unshielded - not torid or shielded) in a bandpass circuit.

The application I'm thinking of would use two closely spaced SM
inductors and varicaps to tune both the center frequency and bandpass
and allow simple and repeatable construction without the need to
locate and wind torids or find specialty inductors.

Please - experiences and not pure speculation.

Experience with filters here indicates that EVERY filter design
BEGINS with speculation. :-)

Bandpass filters can be designed for specific bandpass without
using inductive coupling. Those with percentage bandwidths
less than 5% can be tuned around the bandcenter without much
change in bandwidth. What bandcenter and bandwidth were you
considering?

From a scan of several different manufacturers of SMD inductors,
they don't specify any coupling so it would be experiment time
to find it out as one has already observed in here. I've found
that trying to determine coefficient of coupling by experiment
is more difficult than designing and tweaking a non-coupling
filter. Mileage varies.

If you want a small program that does passive (non-inductive
coupling) L-C filters (low, high, band, reject) synthesis and
analysis (with ability to set individual component values and
simulate Q), ask me in e-mail for LCie4. Ain't flashy but it
works. Freeware.

Small-quantity toroid forms are available at reasonable prices
quickly from www.kitsandparts.com. For home use, I like Neil
Hecht's (www.aade.com) little L-C Meter for much-easier
zeroing-in on inductance values when winding toroids along
with checking out fixed, small-value capacitors.