I did a little reverse engineering on the A Loomis filter. It is a 4 pole
Butterworth filter with a 3dB cut off of 1.59 Hz. You can easily change it
to a 15.9 Hz 3dB cut off by changing the 4 1MEG resistors to 100K. Any
other frequency can be chosen by appropriate scaling of the 4 resistor
values. You might also want to look at Larry's 10 Hz filter at
http://psn.quake.net/eqampd.gif 

Jim Hannon
http://soli.inav.net/~jmhannon/
42,11.90N,91,39.26W
WB0TXL

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