The e-mail newsletter RF DesignLine has a series of articles in the last two issues on digital receiver design:
The 12/27/06 edition of the New York Times contains the article, “A Fading Signal.”.
Paul Saffo opines in his 12/16/06 journal entry:
It is tempting to conclude that the FCCâ€™s action spells the end of Morse, but I am certain we will see a very different outcome. Freed from all pretense of practical relevance in an age of digital communications, Morse will now become the object of loving passion by radioheads, much as another â€œdeadâ€ Language, Latin is kept alive today by Latin-speaking enthusiasts around the world. Latin fans eagerly tick off the practical benefits of speaking a dead language, but of course they pursue their study because it is fun and challenging, gives them a sense of accomplishment and links them to a community of other passionate speakers.
The demise of CW has been greatly exaggerated.
From the NARTE News, Winter 2007:
Cornell researchers have discovered that strong solar flares cause Global Positioning System (GPS) receivers to fail. Because solar flares are generally unpredictable, such failures could be devastating for “safety-of-life” GPS operations such as navigating passenger jets, stabilizing floating oil rigs and locating mobile phone distress calls.
“If you’re driving to the beach using your car’s navigation system, you’ll be OK. If you’re on a commercial airplane in zero visibility weather, maybe not,” says Paul Kintner Jr., professor of electrical and computer engineering at Cornell and head of Cornell’s GPS Laboratory.
Alessandro Cerruti, a graduate student working for Kintner, accidentally discovered the effect on while operating a GPS receiver at Arecibo Observatory in Puerto Rico, one of six Cornell Scintillation Monitor (SCINTMON) receivers. Cerruti was investigating irregularities in the plasma of the Earth’s ionosphere—a phenomenon unrelated to solar flares—when the flare occurred, causing the receiver’s signal to drop significantly.
To be sure of the effect, Cerruti obtained data from other receivers operated by the Federal Aviation Administration (FAA) and the Brazilian Air Force. He found that all the receivers had suffered exactly the same degradation at the exact time of the flare regardless of the manufacturer. Furthermore, all receivers on the sunlit side of the Earth had been affected.
The flare consisted of two events about 40 minutes apart. The first lasted 70 seconds and caused a 40% signal drop. The second lasted 15 minutes and caused a 50% drop. But this flare was moderate and short-lived; in 2011 and 2012, during the next solar maximum, flares are expected to be 10 times as intense and last much longer, causing signal drops of over 90% for several hours.
“Soon the FAA will require that every plane have a GPS receiver transmitting its position to air traffic controllers on the ground,” warns Cerruti. “But suppose one day you are on an aircraft and a solar radio burst occurs. There’s an outage, and the GPS receiver cannot produce a location. It’s a nightmare situation. But now that we know the burst’s severity, we might be able to mitigate the problem.”
The only solutions, suggests Kintner, are to equip receivers with weak signal-tracking algorithms or to increase the signal power from the satellites. Unfortunately, the former requires additional compromises to receiver design, and the latter requires a new satellite design that neither exists nor is planned.
“I think the best remedy is to be aware of the problem and operate GPS systems with the knowledge that they may fail during a solar flare,” says Kintner.
The team was initially confused as to why the flare had caused the signal loss. Then Kintner recalled that solar flares are accompanied by solar radio bursts. Because the bursts occur over the same frequency bands at which GPS satellites transmit, receivers can become confused, leading to a loss of signal. Had the solar flare occurred at night in Puerto Rico or had Cerruti been operating SCINTMON only at night, he would not have made the discovery.
“We normally do observations only in the tropics and only at night because that’s where and when the most intense ionospheric irregularities occur,” says Kintner. However, since no one had done it before, Cerruti was looking at “mid-latitudes” (between the tropics and the poles), where weaker irregularities can occur both night and day. As a result, SCINTMON detected the solar flare.
Cerruti reported the findings on September 28 at the Institute of Navigation Meeting in Fort Worth, Texas, where he received the best student paper prize. The full results of the discovery will be published in a forthcoming issue of Space Weather. O t h e r authors of the paper include D.E. Gary and L.J. Lanzerotti of the New Jersey Institute of Technology, E.R. de Paula of the Instituto Nacional de Pesquisas Espaciais and Cornell research associate Hien Vo.
Don, KB9UMT, moderator and owner of the HamRadioHelpGroup mailing list came up with the following chart:
Year___ %Ham__US Population___# US Hams
Don notes that the number of licensed amateurs has declined since 2003, and that the population of the U.S. has increased. If we use a figure of 300 million for the population of the U.S., then the percentage of the population that are hams in 2006 is 0.22%.
Should we be disturbed by this? I’m not sure. I don’t think we should go out and recruit new hams just to pump up our numbers. I think that we’ll find that if we recruit new hams for good reasons, such as increasing the number of hams capable of providing emergency communications or to just share the fun of ham radio, then we’ll be more successful and draw more active, interesting people into the hobby.
I worked a guy down in GA a couple days ago, and we got to talking about a bunch of different things. It was such a good QSO that he asked me to e-mail him so that we could continue the discussion.
Well, as it turns out, one of his hot buttons was the Amateur Extra license class. His contention is that it’s not really that “extra” anymore, and that he wanted the FCC to create a new class of license whose requirements would include a 25 wpm CW test and a “really hard” written examination.
I replied that it probably would be next to impossible to have volunteer examiners administer such a test. My thought is that if we really want to recognize someone’s technical or operating skills, we should perhaps put more emphasis on programs such as the A-1 Operator’s Club and the various technical awards.
Then, it hit me that our club should have such a program, and I ripped off an e-mail to our Board of Directors. In the e-mail, I proposed the following awards:
- Club Service Award. This award would recognize a club member who has gone above and beyond in promoting, organizing, and running club activities.
- Public Service Award. This award would recognize a local radio amateur–not necessarily a club member–who has excelled in providing public service, including emergency communications, community outreach, etc.
- Technical Award. This award would recognize a club member who has done something excellent from a technical point of view, for example designing and building a custom interface for the repeater or building a cool dual-band J-pole antenna or has perhaps helped fix radios for guys whose rigs have died.
How does this sound to you? Do you have any suggestions for other awards that we should give?
Also, does your club have an awards program? If so, what kinds of awards do they give out? How often do they give them out? What are the criteria?
Jack, AB8RK, my partner in the Ann Arbor Hands-On Museum Project, is hot to get the Boy Scouts involved in amateur radio. This seemed a natural extension of the museum project, as they hold they have activities there frequently. Jack’s idea was to have a session at the museum that would guide scouts through the activities needed to get the radio merit badge.
With that in mind, we met with James McClelland, program director of the BSA’s local council. He suggested that instead of doing this at the museum, we do this on a Saturday at one of their camps. In fact, he more than suggested, he really pushed the idea.
The way he explained it, it makes a lot of sense to do it at the camps, rather than at the museum. First of all, they like to use the camps, and an activity like this will draw troops to the camp. Second, there’s plenty of room at the camp, so facilities will not be a problem. Third, there will be scouts there just camping, and we may get some interest from scouts who just happen to be there.
So, we set the date – March 31 at Camp Munhackie. Now, we have to see about “being prepared.”
Fortunately, the Boy Scouts of America make this easy. McClelland gave us a brochure on merit badge counseling, as well as the Radio Merit Badge handbook. The handbook is compact and well-written. And, as it notes, once a Scout has mastered the material in the handbook, they know just about all they need to know to get their Tech licenses.
I think our task will also be made easier if we can get the materials used by hams at the 2005 Boy Scout Jamboree. As reported in the article, “K2BSA at the 2005 Boy Scout National Jamboree” (March 2006 QST), they were able to teach everything the scouts needed to know in three, one-hour sessions.
McClelland suggested that we break this down even further into smaller “mini sessions” that small groups of scouts would visit in round-robin fashion. I like this idea a lot, too. Now, the trick will be to get enough hams for each to take responsibility for and teach each mini-session.
To top it all off, I think it will be fun to also set up a station at the camp to just make contacts. Once we’ve finished with the merit badge classes, we can follow things up by having them talk on the radio and/or give Morse Code demonstrations. This looks like it will be a fun event.
UPDATE: 1/25/07: Gary, K2GW, has just pubished a Radio Merit Badge Web page. This is a very complete resource, including not only the materials needed to conduct the session, but also ideas on how to promote the event and a suggested timetable for the event. Thanks, Gary!
From the Science@NASA website:
Evidence is mounting: the next solar cycle is going to be a big one.
Solar cycle 24, due to peak in 2010 or 2011 “looks like its going to be one of the most intense cycles since record-keeping began almost 400 years ago,” says solar physicist David Hathaway of the Marshall Space Flight Center. He and colleague Robert Wilson presented this conclusion last week at the American Geophysical Union meeting in San Francisco.