Current version is 2.05
OptLowpass™ is a specialized program written to
expedite the design of transmitter output lowpass filters,
written specifically for the HF amateur radio bands.
Here are some pertinent features:
- OptLowpass is 32-bit Windows® electrical
filter design program written specifically to help the
radio amateur design transmitter output
harmonic-suppressing lowpass filters.
- It is based on the author's article "Harmonic
Filters, Improved" which was in the September/October
1998 issue of QEX, an ARRL publication.
- On startup, the program presents pre-designed
lowpass filters for each of the HF amateur bands, using
ideal parts values as outlined in the above-mentioned
article. You may also recall the last design session,
recall a previously-saved design or invoke the Design
- The design page shows the schematic of the filter
as designed and a plot of the responses of that filter
(both transmission and reflection).
- The capacitors' ideal values can then be adjusted
by entering values in textboxes or they can be "tuned"
upward or downward in 1% steps with the results
immediately replotted right on the same screen.
- The inductors' values can be adjusted by inductance
value (textbox entry or by percent steps, like the
- A design as edited can be saved using a
user-specified name and path for recall later.
- All of the various data files are in ordinary text
format for ease of editing or examination outside the
- Pressing the Monte Carlo button results in an
examination of the filter using a user-specified
percentage plus/minus random parts distribution.
Worst-case values are clearly shown.
- Items that are probably going to be used "globally"
(on all bands, for a given installation) are stored in
a Global Default file and are read into the program at
startup. These can be edited and saved by the user.
Examples of the items stored in the global defaults
file are system impedance (50?), inductor Q values
(200?), capacitor Q values (2000?) and so on.
- For maximum quality of printed output, the output
to the printer is not a "screen dump" but instead is
from a routine which writes directly to the printer.
The quality of that printout 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 plot of responses and
essential design information.
- Click on the "Elsie" 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 "LTspice" button to write a
ready-to-run LTspice file to drive the LTspice
simulator for further examination, especially involving
component voltage and current stress issues.
(Tonne Software has no connection with Linear
- Now includes 600 meter and 2200 meter band lowpass