OptLowpass is one of the
programs included on the Bonus CD accompanying the
Released as 2.03
OptLowpass™ is a specialized program written to
expedite the design of transmitter output lowpass filters,
especially 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
- 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 Wizard.
- 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
- The inductors are assumed to be
toroidal and, given a user-chosen value of core material
AL, are specified in turns instead of the usual textbook
- With an option switch, the toroidal
inductance values can be adjusted by inductance value
(textbox entry or by percent steps, like the capacitors)
instead of by number of turns.
- The response using the current
component values can be saved and later retrieved and
overlaid on the current-value plots.
- 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 program.
- 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
- 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 Technology