 | | Winter SWL Fest
The very popular annual gathering of DXers, sponsored by our sister organization NASWA, will be held this year in Plymouth Meeting, PA (just outside Philadelphia) on March 4 and 5. It's not just about shortwave, either. TV, AM broadcast, and longwave are some of the other topics usually covered as well. For information, see
swlfest.com.
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| | The LOWDOWN This Month
In the February 2011 issue of the club publication:
- "DX Downstairs" Kevin Carey presents members' LF and VLF loggings.
- "On The Air" Experimenters operating on the 160-190kHz and 136kHz bands ... and...
- "The Top End" MedFER and HiFER beacon lists... and...
- "Operator Contact List" How to reach the ops ... and...
- "The LF Notebook" Conducted by John Davis. News of LF radio happenings for, from, by, and about LWCA members.
- "Natural Radio" Conducted by Mark Karney.
- "News From the Old World" Alan Gale keeps us informed of LF experimentation on the "other side of the pond."
- "Testing Compact LF Antennas for VLF Sensitivity" by John Reed. Third part of his series on compact loops and active antennas; how these particular models perform below 30 kHz.
Interested in subscribing? Click here for address, rates, and remittance information (including PayPal).
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| | Whatsa Antimatter You?
Here's the creepy part: it's right over our heads!
No longer confined to the Big Bang, particle accelerators, and sci-fi starships...it now appears the creation of antimatter is a clever feat our own planet performs on a daily basis. Thunderstorms are the laboratory it uses. And, the upper-air lab demonstrations include proof of the interchangability of matter and energy, showing that e=mc2 works in both directions on earth, as it does in the heavens.
It hasn't been all that many years since scientists were astonished to discover gamma ray bursts coming from our upper atmosphere. Nuclear detonations were once thought to be the only event on earth that could produce such flashes, but satellites monitoring for atomic blasts encountered bursts from below that could not be of human origin. These military birds, as well as later gamma ray observatories created to study such astrophysical powerhouses as supernovae, were witnessing something odd going on in the tops of energetic thunderstorms--storms of the sort that interest Natural Radio observers--although it took a while to explain how such a thing was even possible in nature outside of an atomic nucleus. The best theory to date is that the electric fields above a thunderstorm are so strong that cascades of free electrons can sometimes be accelerated to relativistic speeds in an avalanche, releasing photons of such high energy that they are, in fact, gamma rays. They now have a name that distinguishes them from the deep-space gamma ray bursts the scientists were originally hunting: Terrestrial Gamma Flash, or TGF for short. Pretty heady stuff by itself, but there's more!
On Monday, 10 January, the Fermi Gamma-ray Space Telescope team from the University of Alabama at Huntsville announced that these gamma ray flashes also appear to be responsible for antimatter production. When an energetic gamma ray photon passes near enough to the nucleus of an atom, it can transform itself into physical matter in the form of a particle-antiparticle pair; specifically, an electron and an anti-electron (aka a positron), which dash off at high speeds. Since antimatter particles are vastly outnumbered by the "normal" matter in our universe, even in the rarified upper atmosphere near the edge of space, eventually the positrons will encounter lurking electrons. Both will be annihilated, resulting in the generation of new gamma rays having a specific energy level: 511,000 electron volts (511 keV). In a gamma ray spectrometer, the presence of a line at that wavelength is a clear signature of electron-positron annihilation, and the one aboard the Fermi satellite has detected that signature as part of TGFs coming from above large storms.
In four cases, the storms were quite distant, and the 511 keV gamma rays were the result of positron beams striking the satellite itself. Being charged particles of equal (light) mass, both electrons and positrons created during a TGF are guided equally well by the earth's lines of magnetic force, but in opposite directions because of the different polarity of their charges. This separates the surviving electrons and positrons into two beams. It was thus possible to observe the positron interactions well beyond line-of-sight of the originating storms, as explained in the Science@NASA article announcing the discovery. Included in the article are some graphics illustrating how the process works.
Fermi is one of the few orbiting (civilian) observatories also able to study gamma rays of terrestrial origin, but it is certainly not the only one hunting 511 keV signatures. Some years back, we talked in The LOWDOWN about the European Space Agency's INTEGRAL spacecraft, and especially its gamma spectrometer and imagers. A map of the sky as seen at 511 keV has been compiled, showing a stunningly bright region of positron annihilation at the very core of our Milky Way galaxy. Is this antimatter a consequence of the supermassive black hole at the galactic center, or is it (as some theorists propose) related to the mysterious dark matter and dark energy that is now thought to permeate galaxies? That's too big a question to answer with our present knowledge, but it is amazing to realize a phenomenon linked cosmic events of such grand scale as supernovae, black holes, and the Big Bang itself, also takes place in more modest form right above us on our own planet. (Click to learn more about INTEGRAL and its mission, or take a peek at the 511 keV all-sky map.)
Additional information on this story can also be found in Mark Karney's Natural Radio column in the February LOWDOWN.
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| | Related Longwave Sites
•William Hepburn's DX Information Centre features many kinds of DX resources, including much on services found at LF and VLF; for example, regularly updated lists of NAVTEX and TWEB (Transcribed Weather) stations, LF/VLF time signals, and longwave broadcasters. Visit the site at its new location:
DX Information Centre. Don't overlook the pages for higher frequencies, and the propagation forecasts as well.
•Radio Waves Below 22 kHz Renato Romero's eclectic collection of topics pertaining to both manmade and natural radio signals from near DC to the upper end of audibility. Includes the VLF Open Lab, and articles by many contributors...some fairly orthodox, and some not. Visit: www.vlf.it
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| | QRSS and WOLF Software
Rik Strobbe's QRSS software (for transmitting extremely slow CW) is usually available from our file library, but while it is temporarily out of service, you can obtain QRSS and Rik's other useful software at the ON7YD download page.
Continuing Development of Argo. Alberto di Bene regularly posts the latest version of Argo, a receiving tool for displaying slow CW, that performs FFT spectral analysis and displays it in ways optimized for QRSS. Many of the transoceanic LF amateur records were set using Argo at the receiving end. Argo has somewhat similar performance to Spectran, but interacts better with the user's soundcard and is customized for QRSS modes.
Slow CW for Linux. Claudio Girardi (IN3OTD) has released the next version of his Slow CW software for users of the Linux operating system, alpha 0.3.1. The program (called glfer) contains both transmit and receive capability, the latter including an FFT-based spectrum analyzer somewhat similar to those found in popular Windows Slow CW programs.
As with much open-source software in the X-world, you have to compile the C source code yourself. Users will also need additional code libraries. Links to those, plus downloadable source code, can be found at Claudio's glfer page.
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