Embedded Files
Morse character frequency analysis
16 May 2020
Comments by Tyler Van Slyke KE0CIW
Thanks for going on the little journey with me today about Morse character frequency analysis. The Excel sheet that I presented is attached [see link below on this page] if you want to play around with it. You can change the Morse representation of each character if you want, and the formulas will recalculate automatically. The calculations assume 1 unit of time for a dit, 3 units for a dah, and 1 unit for the space between them.
As I anticipated, someone else has created a very nice writeup about Morse character frequency analysis (https://www.johndcook.com/blog/2017/02/08/how-efficient-is-morse-code/). At first, the author did not completely account for a full space between the dahs. When he later did, he computed an average character duration of 6.0 units, which is very close to the 6.1 units that my Excel sheet is reporting. The difference is due to the corpus materials used to create the frequency analyses. I would be interested to see how prosigns and numerals in real CW communication would change the results. (It'd also be interesting to calculate using those real world timing differences between a paddle and a straight key that your ear can immediately recognize!)
The author came to the same immediate conclusion as I did about O being overly long, relative to high frequency in which it occurs. I was curious about how this came to be, so I started reading about Morse code history (https://en.wikipedia.org/wiki/Morse_code#Development_and_history). The original version was quite different than the ITU standard we know today. The original had many different character representations, including variable spacing between the elements. You can see a nice comparison here: https://upload.wikimedia.org/wikipedia/en/5/5a/Morse_comparison.svg. Interestingly, the original O was actually two dits, separated by a double space. This gave the original O a duration of 4 units, which is much shorter than the current 11 units. If I manually override O's duration in my Excel sheet to be 4 units, it brings down the average duration of the whole character set from 6.1 units to 5.6 units--almost a 10% improvement in efficiency. I'm sure no one wants to relearn Morse just for a 10% gain. It's probably easier for most of us to just focus on becoming 10% faster with the current scheme. :)
The unsolved mystery is why the O went from such a compact representation to one that is almost 3 times as long. The Wikipedia article offers some insights about how the ITU standardized our current Morse code, but I haven't learned the rationale of each character yet. O is used less frequently in European languages like French and German than it is in English. (In English, O is the 4th most common character. In French, O is the 10th most common. In German, O is the 15th most common.) Perhaps O wasn't perceived as an overall pain point in the overall ITU standard across all languages. There could be other troublesome characters for French and German speakers that we're not considering here. If anyone figures this out, please be sure to report back!
- Tyler
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AT&T Archives: Similarities of
AT&T Archives: Similarities of
Wave Behavior
Wave Behavior
Antarctic Activity Week QSO With Former U.S. Antarctic Research Program Civilian KG0PA
Mar. 4, 2015
by Jim KB0MZF
One of the greatest joys of Antarctic Activity Week special event is having the occasional QSO with someone who has a personal connection with or had spent time associated with Antarctica. During the AAW this year, Don (KC0WTT) had an interesting conversation with Mark about his time spent on the continent and how he got involved with ham radio there. With Mark's permission, this is what he said:
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I just had a nice QSO with Don about Antarctica, and he asked that I drop you an email. I lived on Antarctica 1979-1983. I was a civilian contractor working for what was then known as the U.S. Antarctic Research Program (USARP). My first 2 years I was in McMurdo Station serving as manager of the Berg Field Center - kind of like an REI store where we outfitted scientists, taught them survival and sent them out to do their research.
It was in this capacity that I visited South Pole, the USSR Station Vostok and of course the New Zealand station Scott Base, which is just a 30 minute walk over the hill from McMurdo.
The third year on the ice I was an administrator at McMurdo and the last year on the ice I was manager of a Dome Charlie Station, on the eastern Antarctic ice sheet. Dome Charlie is no longer there, and has been replaced by a French station. It was at a Dome C that I got into ham radio. I was assigned the call KC4AAK by the U.S. Navy. This eventually led to my getting a ham license here in the US.
That's my story. Thanks for the QSO, and thanks for supporting the great white continent.
73,
Mark KG0PA
* * * * *
Thanks Mark for sharing that with us. It is truly a pleasure to work this special event each year simply drawing attention to the work being done by the international scientific community there under some of the harshest conditions on the planet -- and, of course, having fun with radio. We do hope you will join us next year for the AAW, 13th Edition.
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Dipoles and Balanced Feed-Lines
Date: Tue, 22 Apr 2014 12:01:28 -0500
Post from Larry’s List by Larry Staples W0AIB <lstaples@kc.rr.com>
One local Ham who is a P. E. told me, ‘don’t confuse symmetrical with balanced’. I had to think about that quite a while but in essence, it doesn’t matter if a dipole is resonant, fed in the center, off center, or even end-fed. The balanced feed-line is separate and balanced and if not balanced with equal currents in each conductor, it will radiate which alters the antenna’s pattern and may make things in the shack ‘hot’.
Current baluns of the Guanella type will perform better when mismatched. Most tuners that have ‘Balanced Output’ use voltage baluns of the Ruthroff type which are auto-transformer wound. I have been inside a dozen tuners by MFJ and Ameritron and they all used 1:4 Voltage baluns. A 1:1 or 1:2 balun would be a better choice for a dipole that’s up a quarter wave or higher. NVIS antennas, or any that are mounted lower or close to conductors, will have a much lower impedance than 50 Ohms. Reversing a balun is NOT the solution. The balun needs to be designed for 50ohms to 25 or 12.5 ohms to work properly and stay balanced.
Baluns do NOT belong inside the tuner and Palstar has now put them outside the box with options for ratio, or even use some other brand balun or type. I like to keep the balun and the lightning on the other side of a well grounded bulkhead entry. Coax length to the balun is not important unless the balun is badly mismatched, and it will be for multiband use. Ladder-line length will make a huge difference: half-wave line will show the real impedance of the antenna while a quarter-wave lenth will invert the impedance. Ladder-line is difficult to use because it needs to be kept away from conductors and ground and you cannot roll up the excess like coax.
Baluns are convenient but balanced tuners, like the old Johnson MatchBox, are far better ways to handle the RF. I measured my W2AU baluns and other bargain ones and they are toast. If you plan on anything above 100 Watts then go with the ‘good stuff’ from DX Engineering or a few others. High power amplifiers do NOT like a smoking balun.
The multi-band problem is: Operating 75M is NVIS and 25 Ohms while at 40M it might be 40 Ohms and 20M is 75 ohms. One size does not fit all ----no matter what the advertising tell us. Multi-band will always be a compromise but you should try it. A lot of DX has been worked with antennas that didn’t perform perfectly.
73 de,
Ken Shubert, K0KS
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W0AIB comment: With Beth’s message and now this one from Ken we have some good discussion about antennas and feed lines. Perhaps others would like to wade into the discussion.
Previously I failed to define NVIS (Near Vertical Incidence Skywave) for the many of us who have not got a clue to what we are talking about. See: <http://en.wikipedia.org/wiki/Near_Vertical_Incidence_Skywave>
Thanks, Ken, for continuing the discussion.
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Post suggested by Scott Lorimor KE0EFX
Very interesting video of physical demonstrations and illustrations from Bell Labs of standing wave behaviors, including standing waves, reflected waves and impedance mismatch, etc.
https://www.youtube.com/watch?v=DovunOxlY1k
On an elementary conceptual level, this film reflects the multifaceted scientific hyperthinking that was typical of a Bell Labs approach. Host Dr. J.N. Shive's presence as a lecturer is excellent - it's understandable by a layperson even when he branches into equations, because he uses copious amounts of real-world examples to bolster the material.
Shive's role at Bell Labs was more than just a great lecturer: he worked on early transistor technology, inventing the phototransistor in 1950, and the machine he uses in the film is his invention, now called the Shive Wave Machine in college classrooms.
Dr. J.N. Shive of Bell Labs demonstrates and discusses the following aspects of wave behavior:
Reflection of waves from free and clamped ends
Superposition
Standing waves and resonance
Energy loss by impedance mismatching
Reduction of energy loss by quarter-wave and tapered-section transformers
Original audience: college students
Produced at Bell Labs
Footage courtesy of AT&T Archives and History Center, Warren, NJ
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NVIS (Near Vertical Incidence Skywave)Antennas
Tue, 22 Apr 2014 14:36:13 -0500
Post from Larry’s List by Larry Staples W0AIB <lstaples@kc.rr.com>
The discussion of balanced and unbalanced dipoles, etc. has been interesting, but one question some may ask is "why do I want a NVIS antenna - doesn't that defeat the point of a good antenna by limiting the distance it can transmit?".
Good question, and I'm sure there are lots of answers, but here's one that should be of importance to those interested in emergency communications.
One of the lessons learned from the 2013 Simulated Emergency Test (SET) exercise related to the difficulty in using HF to communicate over medium distances. For Kansas RACES, our objective for the exercise was to communicate various bits of info to the State EOC in Topeka and various other Kansas counties. What we found was that, on HF frequencies, we could communicate with adjacent counties, but that our signal was bouncing over everybody else. We eventually used a station in Georgia to help us relay information to Topeka!
If your dipole is set up for DX, you want the main lobe of your transmitted power to be at a low angle to maximize the distance you get on each bounce off whatever layer in the ionosphere is working for that frequency. If you're trying to work somebody 100 miles away, you want that lobe to be almost straight up (NVIS) so that it bounces off and comes back down closer to where you are.
Note that there are lots of regular opportunities to test the performance of your NVIS antenna using weekly HF nets that occur locally, on the State level, and nationally.
Thanks,
Herb Fiddick, NZ0F
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Interesting...
>From an Emergency Services perspective, it might be worth considering that before the "Digital Age", most State and County Public Safety Agencies used FM Simplex on VHF Lo Band in the 38.00 to 45.00 MHz Range for point to point communications across the state. Local operations took place in the 155.000 Mhz or UHF bands.
In Nebraska, the Statewide Law Enforcement Frequency was 39.90 Mhz. From Kearney, Nebraska, I could communicate with Omaha to the east, Ogalala to the west, and Alliance and Norfolk to the north. On a good day, mobile units with 100 watts and a whip antanna could expect a range of about 100 miles. The same went for the State Patrol in the 42.00 Mhz range.
So taking a look at this from an Amateur Radio perspective, would 6 meters on FM be better suited for communicating at a distance across the state for Emergency Services’ (I believe the State of Kansas used, or may still use 39.50 or 39.58 MHz back in the day as a mutual channel of some sort... We'd hear them sometimes.)
When the skip was in, we'd get Louisiana, Montana, and Ohio on 39.84 MHz, North Hollywood Division of LAPD on 39.82 Mhz, (the Real Adam-12,) and the Los Angeles County Emergency Management Office issuing SMOG Alerts on 39.98 MHz!
<http://purplesage.biz/LawEnf/RadioSkip.htm>
Randy Schulze, KD’HKD
Kansas City, Missouri
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NVIS also lets you get out to the surrounding couple hundred miles or so even if you're in the bottom of a narrow valley or canyon, or surrounded by skyscrapers. (Guy at the other end will need an NVIS antenna to get back to you, given your operating spot limitations.)
Visualize your NVIS antenna as operating like a fountain that shoots water straight up, with your signal coming down like rain for a couple hundred miles all around you ... as opposed to a ground wave or long-distance ionospheric bounce. On 40 or 80 meters (NVIS doesn't work much at 20 meters and higher freqs), an antenna that's lousy for DX because it's not high enough often is good for NVIS.
I've gotten good results with a wire thrown over some two-foot bushes and an HF mobile whip mag-mounted on a (parked) pickup truck roof, bent over horizontal ... 25 watts or less. There's lots of discussion online on what's the best NVIS antenna height above ground.
Ernie Murphy, NH7L/0
Merriam, KS
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