Exploring Bit Error Rate with FLDigi

Today’s recommendation for teachers: A fun demonstration of bit error rate if all you have to work with is an A/V system and some laptops, sending text and images via audio using various digital modes in FLDigi. We used this demo in this morning’s EECS 351 (Digital Modulation) class, sending text and images from one end of the classroom to the other using only audio. Having a good microphone at the receiving end is helpful, but with a bit of adjustment it’s possible to use the built-in microphone in most laptops.


We sent text over BPSK, QPSK and 8-PSK and compared the error rates of the different modes. This was the sample text we used:

Parkin was quoted in an article titled “The Feminine Wireless Amateur,” which appeared in the October 1916 issue of The Electrical Experimenter:

“With reference to my ideas about the wireless profession as a vocation or worthwhile hobby for women, I think wireless telegraphy is a most fascinating study, and one which could very easily be taken up by girls, as it is a great deal more interesting than the telephone and telegraph work, in which so many girls are now employed. I am only fifteen, and I learned the code several years ago, by practising a few minutes each day on a buzzer. I studied a good deal and I found it quite easy to obtain my first grade commercial government license, last April. It seems to me that every one should at least know the code, as cases might easily arise of a ship in distress, where the operators might be incapacitated, and a knowledge of the code might be the means of saving the ship and the lives of the passengers. But the interest in wireless does not end in the knowledge of the code. You can gradually learn to make all your own instruments, as I have done with my 1/4 kilowatt set. There is always more ahead of you, as wireless telegraphy is still in its infancy.”[17]

We also sent the classic photo of Lenna over MFSK-16, as well as some images from the first demonstration of raster television.

Students may be interested in the SSTV Easter eggs hidden in the first Portal game. MMSSTV is a good program for sending and receiving messages over slow-scan television.

If you’re interested in adapting this demonstration in your classroom, leave us a comment and we’ll send lab materials and tips.

-Kristina KD8OXT

Go Go Gadget Box

The Case Alumni Association generously provided us with funding for a “Go Box” in September. Today it has come to life assembled.


All the major components are in the box here, but not completely secured.

Various parts of it have been “tested” at various points leading up to today.  The radio was put through it’s paces in an on air contest within days of our receiving it.

We had been using a transmitter from the estate of Jack Goldfarb, W8WGO, when we discovered the known failure mode… Apparently running the radio too long causes the main knob shaft encoder grease to fail and bind.  This has since been fixed with assistance from John Gibbons, N8OBJ, and the Sears Lab.

The box, battery, radio (again) & iambic Morse Code key were put through there paces at the Engineering Challenge Carnival:


Young radio operator in training…

Some of the smaller parts are not yet install in the go box.  This includes the Morse key.  They are non-essential, unless someone absolutely needs to send Morse Code, but will be installed soon.  However all the major components are now installed and secured.


Go Box “Tilt Test”.

The Go Box has wheels which will allow us to roll it where it needs to go.  However the handle for wheeling the box stows in the bottom, so to roll it the entire thing ends up rotated 90 degrees.  The tilt test was to ensure that all the equipment would stay put when it was rotated for travel.

The box has a single power input that will run everything from AC/commercial power.  The power input for the box is the gray cable in the front of the Tilt Test image.  However, it is worth noting that the box is not plugged in even though the radio is running.

The entire box can run without AC/commercial power.  In both images the radio is running on the battery installed in the back of the box.  The laptop will happily run off of its internal battery, and will be getting an option to be powered off the power supply battery arrangement as well.

There are some parts that still need adjustment/refinement.  Also we’ll need a way to contain the various bits and pieces that inevitably will accumulate in/with the box.

-Nathaniel KB1QHX