This morning greeted me with this nice little video, where Diana Eng demonstrates the pattern generated by dipole and Yagi antennas by a simple detector consisting of a dipole antenna with a small flashlight bulb wired across the feed point:

It does actually uncover one of my pet peeves: in describing the action of the reflector element of the Yagi, Diane claims that the reflector “reflects”, but when she added a director, she claimed that the director “focuses”. But if you are a clever person who maybe doesn’t understand much about how antennas work, you might reasonably ask how that actually works. After all, the elements are identical in composition, and are essentially placed the same distance from the antenna. Why does the director direct, but the reflector reflect?

If you can actually answer this question, you’ve begun to understand how antennas really work.

Well, there wasn’t anything terrific on TV tonight, and I’ve had a little program kicking around in my head for a while, so I decided to set down and see if I could make some headway on it in a single evening of programming.

I used to have some Morse code practice cassette tapes a while ago. It used the Koch method, and was progressive. They began with just two letters, say K and M that were sent using Koch spacing (the space between letters were sent as if they were 5wpm, but the letters themselves were sent at 13wpm.) The tapes themselves were thus the combination of regular speech (giving you instructions) and Morse code. But I can’t find the tapes anymore, and even if I did have the tapes, I don’t have a cassette player, so they wouldn’t be of any immediate use. I went to HRO to see if they had any such thing on CD so that I could listen to them in my car, but ironically, the bottom seems to have fallen out of the Morse Code CD market, and they didn’t have any in stock.

So, I thought to myself, what would it take to make my own?

I’ve written programs to generate Morse code before. And most of the computers I use have some kind of speech synthesis capability (either the “say” command on Mac OS, or the festival speech synthesizer on Linux) so generating some reasonable if not exactly pleasing speech wouldn’t be that hard.

So, I tossed together a simple scripting language to wire the two together. It takes a simple script which consists of text which it translates directly into Morse code. The exception is any text which appears in double quotes. It gathers that text up, and passes it to the system speech synthesizer, and generates a sound file, which it then reopens, resamples to the same output rate as the rest of the morse code, and then returns to Morse mode. This isn’t all that hard because of the excellent libsndfile and libsamplerate libraries. There is some work left to be done, but the basics work. Here is the contents of a simple test script that I wrote:


"This is a test of the emergency broadcast system."
If this had been an actual emergency,
you would not have been using Morse code.


And here is the resulting .mp3 file, synthesized on my Macbook:

Morse synthesized by my “mscript” program (MP3)

The basics all work, but there are some additions to be made, to insert arbitrary wav files perhaps, to adjust timing, to implement Koch spacing and flexibility in changing the speed of Morse code inside a single document, and just other bits of cleanliness. Oh, and the Morse doesn’t have any shaping at all, so the transitions are a bit clicky. I can fix that pretty easily. Still, not bad for a couple of hours of tinkering with C, yacc, and lex.

Tonight, I’m currently hearing station DP1POL, from grid IB59uh on 40m. Where is that, you might ask? Antarctica. He’s heard my beacon before, but I think this is the first time that I’ve received him. The distance is nearly 15,000 km. Verah nice.

The more things change, the more things stay the same:

MR. B. N. BURGLUND, whose description of the wireless station at the University of Michigan, appeared in our March number, writes us an interesting letter on the part played by wireless amateurs during the recent floods in the Middle West in March. He has much to say in praise of those who did good work and rendered efficient service; and he also condemns, in no uncertain terms, the meddler who, we are sorry to admit, appears to be always on the job and gets in his fine work at such times. One of these individuals, possessed of a powerful transmitter, and ignorant of the code except to the extent of being able to recognize a few well-known calls when he heard them, persisted in calling the station at the University of Michigan while the operator there was trying to handle messages from the flooded districts. He was told, repeatedly, to keep out, but being ignorant of what was said to him, and thinking his calls were simply being recognized, kept on calling. And he kept it up for over six hours. The wireless law provides a heavy penalty for offenses of this sort, but he did not sign an understandable call and will probably never be caught.

via The Wireless Amateur in Times of Disaster (1913).

The early history of radio is quite fascinating, and luckily, lots of books from this early period are out of copyright and are available for free on the Internet. As an example, check out The book of wireless telegraph and telephone by A. F. Collins. This was radio in its infancy, when the use of vacuum tubes to create continuous oscillations was “the new wireless”, and the majority of stations were still using spark gaps. While you can’t legally operate spark anymore, it is still interesting to read these kinds of books, which offered pragmatic advice to the experimenters of the day on how they could construct and deploy their own wireless stations. Very nice.

The book of wireless telegraph and telephone : being a clear description of wireless telgraph and telephone sets and how to make and operate them, together with a simple explanation of how wireless works.