Of Free Software
Back when personal computers were new to the world and Basic was the common man's
programming language of necessity, there were hundreds of new little applets that
kept popping up to solve specific calculation tasks. It was great sport, as well
as a display of mental cunning, to develop such programs and then figure out a way
to make them available to the public. Remember that at the time (early to mid 1980s)
or a Commodore
64 would set you back a couple hundred dollars, and the Internet was just a
gleam in Al Gore's eye.
Eventually, new languages like Pascal, Fortran, and some really strange language
known as simply "C" arrived for MS DOS, and even for Apple DOS. I personally latched
onto Pascal simply because in the late 1980s when I was at the University of Vermont
working on my EE degree, that was the language du jour. Our microprocessor lab consisted
of an Intel 8088 proto board for machine language practice. One of our first Pascal
programming exercises was to create a routine that would convert a base-10 number
to a Roman numeral
(not as straight-forward as you might think once you get above 48 - try
converter). There was no such thing as an Integrated Development
Environment (IDE) or visual development tools. Performing a divide-by-zero operation
caused the entire computer to hang (however, rebooting took about 30 seconds due
to the small OS size, with no anti virus software to load, maybe a printer driver,
etc.). I was immediately smitten by the programming bug (no pun intended) and set
about to write routines for every application I could - or might - use in my daily
Eventually, spreadsheet files with calculation functions began getting posted
on bulletin boards along with the applets, but many people did not have access to
spreadsheets because they were part of rather expensive office packages. A lot of
the computers did not have the amount of memory required to load the spreadsheets,
and even worse yet, the vast majority of users did not know how to dial into or
use a bulletin board service. Even EasyCalc pushed the memory limits of early PCs. That put file
sharing - programs and spreadsheets - out of the realm for all but the most technically
savvy. Many people procured their non-commercially distributed software on 5-1/4"
floppy disks either via the mail (ordering from computing magazines) or via the
Sneakernet. Those were rough days to be a programming enthusiast.
Stored on a CD in my safe is a collection of many of those old DOS routines that
I used regularly. A few years ago I transferred everything from 3-1/2" floppies
onto CD. The downside of that is that due to migration in the plastic, most of that
data will over time become too corrupted for even error correction to handle, so
it will be lost forever. The upside (kind-of) is that by then, the 64-bit architectures
of new PCs will not even emulate 16-bit DOS to run them. As recently as sometime
around 2000-2001, I was still using a DOS program for designing transistor biasing
circuits that plotted gain, noise, and stability circles. Only fairly recently did
I replace a DOS-based Smith Chart program with a Windows version. Does anyone else
out there remember using the ground-breaking
program by Amplifonix (ported to Windows and improved by Spectrum Microwave), or
HP's AppCAD (also ported
to Windows and improved)? There was a program that Microwave Journal mailed out
to subscribers in the early 1990s, but I cannot recall its name; does anyone remember
Most of the popular old programs can still be located with a search engine, and
there are many, many websites with extensive lists of links to other websites that
host the programs. Of course, RF Cafe also maintains a list of its own - check out
the Calculators and
Software pages to see what I have. Since it would likely be considered
a copyright violation to actually store and offer them for download on RF Cafe,
there are links to other sites that either legally or illegally host the files.
The RF Globalnet
website has a huge collection of software that has been uploaded, supposedly, only
by copyright holders, so that is another good source. You will find that most sites
are replicas with a large percentage of dead links - especially for the DOS apps.
Throughout the years, hobbyists and professionals alike have continued the task
of creating very useful programs and applets that have made the lives of fellow
hobbyists and professionals much easier. Of course, the newer ones are written to
run either in Windows or Linux (some MacOS), and there is a whole host of online
apps that run in your Internet browser. One of the drawbacks of using the free programs
is that they do not provide for saving configuration files so that you do not need
to start over again every time you run the application. There is an advantage in
looking for calculators and simulators based in a spreadsheet in that the spreadsheet
program itself provides the ability to save your final configuration.
You do need to be aware of the fact that there are a lot of erroneous results
produced by these programs. It is amazing to me that even the most expensive commercial
applications get away with placing the onus of results on the user with a simple
disclaimer statement to the effect of, "It is the responsibility of the user to
verify that results meet the expectations, and shall not hold <company name>
liable for any damages due to incorrect results." I do not recall having ever heard
of a case where someone successfully sued over bad data produced from engineering
software - do you?
RF Workbench, originally marketed commercially as "TxRx Designer,"
was and still is my only major foray into the formal engineering software world.
When it debuted sometime around 1992-1993, RF Workbench was quite advanced insofar
as features. I wrote every line of code from scratch for the moveable windows, drop-down
menus, mouse driver, 2-D and 3-D graphical outputs, and even the printer driver.
Extensive error trapping was coded in to prevent any possibility of the user entering
data that would cause the system to hang or crash. Once the world went Windows,
I changed the name to its current incarnation as RF Workbench, and began offering
it as Shareware. The program has been included on countless disks and CD collections
of engineering software. If you go to RF Globalnet, where I uploaded the program
to their servers way back in 2000, you will see the following notice: "RF
Workbench is the most frequently downloaded software on the site." Although
I cannot prove it, I suspect it might be the most-used RF system design tool ever.
Maybe the price of $0 has had something to do with the phenomenon.
Another item that I have made available free of charge from RF Cafe is the
RF Cafe Calculator Workbook. It is an Excel spreadsheet that is
chock full of useful calculators that electrical engineers will appreciate. Some
of the more advanced programming features of Excel are employed to make the interface
a little more user friendly, like pull-down option lists, range checking, etc. There
is also a version that runs on the Calc spreadsheet that is part of the
OpenOffice.org office suite
While not created by me, there is another file that can be downloaded for free
Transmission Link Planning Tool, by Mr. Alok K. Tiwari, of Idea
Cellular Ltd. It is a very useful spreadsheet that runs in Excel. Alok has been
continually adding features.
Matching Network Designer is an incredibly sophisticated Smith
Chart spreadsheet provided graciously by Mr. Manfred Kanther. Chances are you have
never seen such a high degree of functionality programmed into Excel.
Although not to the level of the aforementioned spreadsheet, I offer my own
Smith Chart for Excel in two versions. One version takes complex
impedance values as input, and the other takes S-parameters. It is a great tool
for entering data from a product datasheet or from the output of a network analyzer.
Your suggestions for similar software or online calculators would be greatly
appreciated both by me and by other RF Cafe visitors. Because of the large numbers
of e-mail that I receive, it would be nice if you would look on the Calculators
and Software pages to see whether the item you are thinking of is