[TenTec] Filters: ringing and insertion loss

[Bill Tippett]

Jason wrote:
 >I found some old threads about TenTec filters not ringing where INRAD
filters supposedly do.  I also noticed that the INRAD filters have less
insertion loss than the TenTec filters.

 >Can anyone explain what INRAD "ringing" is as compared to the TenTec
filters not ringing and whether the INRAD filters do in fact have lower
insertion loss?

         The following link is a copy of Ten-Tec filter specs in P/N 74089-C:
http://dayton.akorn.net/pipermail/tentec/2004-January/041510.html

         Inrad specs can be read by clicking "Performance Curve" here:
http://www.qth.com/inrad/tentec_menu.htm  Insertion loss is 2 dB per
small vertical division at the center frequency and shape factor is
in the data at the upper right box.

         Insertion loss is self explanatory and ringing is generally a
function of Shape Factor, especially at very narrow bandwidths.  I am
not aware that either the Inrad 760 or the Ten-Tec 219 ring.  Inrad
has a sharper shape factor due to being 8-pole instead of 6-pole, but
it also has wider overall bandwidth (315 Hz vs 250 Hz), and I would
doubt it rings.  Ringing is more typical for VERY narrow bandwidths
(<100 Hz) such as you find in DSP filters that have very sharp shape
factors, but even Orion's 100 Hz DSP filter does not ring.  It's
actual bandwidth is closer to 150 Hz and the shape factor is not very
sharp (intentionally I'm sure).

                                                 73,  Bill  W4ZV