"K7ITM" wrote in message
...
If
you build a filter according to a design that either the AADE progarm
or Elsie gives you and it doesn't perform like you think it should,
don't be too quick to blame the program!

My experience is basically...

-- The behavior as-built will almost always be at lower frequencies than what
you designed for, due to the stray capacitances and inductances the simple
filters don't take into consideration. Similarly, bandpass filters will
usually end up narrower than you intended.
-- For bandpass filters, it seems just about as common that coupling between
elements, approaching self-resonant frequencies, and parasitics can help just
as often as they can hurt insofar as shape factor goes.
-- Taking a scrap piece of PCB material (or some other thin metal sheet-type
material) and placing it midway between pairs of inductors can give you some
qualitative idea as to how much coupling there is. (...and normally you want
to place consecutive inductors at right angles to one another... or perhaps
try the "magic" 54.7 degree angle like the old neutrodyne receivers used...)

If you need quite sophisticated filter designs, Nuhertz (aka, Jeff Kahler,
Inc. -- a man who can probably quote large portions of Zverev's book...) has
their Filter Solutions program, which is quite good... although only a very
basic version of it is free (apparently Jeff wants to eat every now and again,
and not just at Taco Bell).

---Joel "Yo quiero Taco Bell!"