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Greetings:
Here is my latest Kirt's Cogitation. Your comments are encouraged.
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 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).
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 drive, 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 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 Cascade program by Amplifonix (ported to Windows and improved by Spectrum
Microwave), or HP's AppCAD[/url] (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 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 (also free).
RF Cascade Workbook 2005 is an advanced spreadsheet
that is a system level simulator for calculating most of the commonly needed cascaded
parameters for RF receiver (and transmitter) design. It accommodates frequency-dependent
parameters for filtering and mixing (frequency translation). Although it would be nice
for my bank account if you decided to purchase the Excel version, I have ported RF Cascade
Workbook 2005 to the OpenOffice.org Calc format, and that may be obtained at no charge
by sending me an e-mail requesting it.
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 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 and Software pages to see whether the item you are thinking
of is already listed.
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Thanks for reading.
_________________ - Kirt Blattenberger
 RF Cafe Progenitor & Webmaster
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