These original Kirt's Cogitations™ may be reproduced (no more than
5, please) provided proper credit is given to me, Kirt Blattenberger.
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Cog·i·ta·tion [koj-i-tey'-shun] – noun: Concerted thought or
reflection; meditation; contemplation.
Kirt [kert] – proper noun: RF Cafe webmaster.
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) a
TRS-80 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
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 engineering chores.
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
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
Cascade 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 the name?
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
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
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?
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:
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 (also free).
While not created by me, there is another file that can be downloaded for free called
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
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
pages to see whether the item you are thinking of is already listed.