Diplexer 2.09 was available to download from the developer's website when we last checked. We cannot confirm if there is a free download of this software available. The common filenames for the program's installer are diplexer.exe, DiplexerDesign.exe or DiplexerDesigner.exe etc.
Diplexer lies within Education Tools, more precisely Science Tools. According to the results of the Google Safe Browsing check, the developer's site is safe. Despite this, we recommend checking the downloaded files with any free antivirus software. This free program was originally created by James L. Tonne. The most popular version among Diplexer users is 2.0. You can launch Diplexer on Windows XP/Vista/7/8/10/11 32-bit.
From the developer:
This program is for designing diplexers of both the highpass/lowpass and bandpass/bandstop types.
This interactive program accepts for its inputs the crossover frequency (for the highpass/lowpass topology) or the lower and upper bandedges (for the bandpass/bandstop topology), the order (number of parts), the passband ripple and the system impedance.
You may want to check out more software, such as Wintree, f x -Viewer or FSAcars, which might be related to Diplexer.