SVCfilter™ is a program designed to expedite the design and analysis of lowpass (and highpass) filters with nearest 5% component values.

Here are some pertinent features:

• SVCfilter is 32-bit Windows® electrical filter design software nicely written to help the radio amateur, technician or engineer design and analyze lumped-element lowpass and highpass filters.
  
  
• Order, topology and family are all entered by clicking on buttons.
  
  
• If the Chebycheff or Cauer family is chosen then three options for passband ripple (.01, .044 and .200) are available.
  
  
• If the Cauer family is chosen then four options for stopband depth (30, 40, 50 and 60 dB) are available.
  
  
• Cutoff frequency is entered in the usual text box and can be from audio through UHF.
  
  
• Cutoff frequency can be as low as 0.1 Hz, allowing the value of .159155 [ i.e., 1/(2*PI) ] to be used. This, in conjunction with a termination value of one ohm, yields parts values for the textbook classic "normalized" design.
  
  
• System impedance by default is 50 ohms but a textbox allows entry of any value of your choice, for example 600 ohms for audio.
  
  
• Inductor Q values are set by default to a value of one million. A textbox allows entry of any value of your choice in the range of 10 minimum to one million maximum.
  
  
• The graphic output draws the schematic of the filter you have designed, and also plots the responses of that filter (both transmission and reflection). It selects the nearest 5% values for the capacitors and shows those values as well as the exact values and overlays the response plots for the nearest values on top of the original exact-value plot.
  
  
• Tuning buttons allow stepping the cutoff frequency up or down in 1% steps and immediately seeing the new performance of the redesigned filter on the plot.
  
  
• Place the cursor anywhere on the plot and see the transmission, reflection, VSWR and envelope delay values for that frequency.
  
  
• Inductors are retuned as necessary to maintain the response of Cauer filters after nearest capacitors are chosen.
  
  
• To maintain the high level of quality of the graphic output, the outputs to the printer are not "screen dumps" but instead are from a set of dedicated routines which write directly to the printer. The quality of the graphics as delivered by the printer will be limited only by that printer, commonly several hundred pixels per inch. The printer output on one sheet contains the schematic with parts values along with the set of responses.
  
  
• Click on the "Write Elsie File" button to write a file to drive Elsie the filter design and analysis program for followup filter examination in even greater detail.
  
  
• Click on the "Write Spice schematic" button to write a file to drive the LTspice simulator. (Tonne Software has no connection with Linear Technology Corporation.)
  
  
• This program was written to simplify the sometimes difficult task of lumped-element lowpass (and highpass) filter design by automating or setting as default some of the more frequently-encountered options. But it also includes analysis, uncommon for such an application.