Blogs / Cosmic Variance

Okay, it’s time to come clean – I am a ham. That is, I am an FCC-licensed amateur radio operator, call sign KI6GDQ. I got into it a few years ago because my wife’s parents and sister and brother in law are hams, and we all go camping in northern California every summer. Obviously a little hand held ham transceiver is not a bad way to communicate when there’s no cell phone coverage, though the range is limited to a few miles in the mountains up there.

And, living here in California, which a friend of mine notes is a beautiful land with a decidedly savage side, it’s not bad to have a means of communication that doesn’t depend on the grid, be it the electric grid or the Internet/phone grid. My in-laws live in Pacifica, south of San Francisco, which is hemmed in on all sides: the ocean to the west, mountains to the north and south, and the San Andreas fault to the east. A big earthquake could easily isolate them from the rest of the peninsula. So my father in law (N6FG) helps run a 2-meter repeater on a nearby mountaintop; he and and my mother-in-law (K6IIP) participate in local emergency response groups.

A friend of mine joked that amateur radio is the original social networking tool. (Well, unless you count the postal service.) Early in the last century, when radio was young, the advent of high-power vacuum tubes made it possible for amateurs to build transmitters that allowed them to talk to other hams all over the country, and around the world, ionospheric conditions permitting. At night, when the lower layers generated by solar radiation dissipate, a vast electromagnetic mirror called the F layer forms several hundred miles up. Signals from the surface can bounce off this mirror essentially all the way around the planet. Hard-core DXers still go to great lengths with antennas and legal-limit (1500 watt) transmitters to make contacts with Morse code. (And then there are the truly crazy ones who go on expeditions to remote islands off Antarctica solely for the purpose of making nearly 100,000 ham radio contacts all over the world.)

With the advent of transistors, and, more recently, digital signal processing, modern ham radio rigs can range from the relatively simple and inexpensive (like mine) to unbelievably complicated units going for over $10,000. So it’s one of those hobbies that you can get into at a number of different levels, you might say.

Electromagnetic bandwidth is limited by its very nature. And of course the governments of the world have to regulate who gets to use what portion of the available spectrum for what. The International Telecommunication Union coordinates this across borders. It’s pretty fascinating to study the US band allocation chart. When you do you’ll see that amateur radio has been granted little slices in a lot of different ranges: 160/80/60/40/30/20/10 meters, (the HF bands) and 6/2/0.7 meters (the UHF/VHF bands). By far the most popular among hams is the 2 m band, 144-148 MHz. The reason is that with a low power mobile unit, it’s easy to make contacts on 2-meter (144 MHz) FM repeaters which are scattered all over the country.

Repeaters listen on one frequency, and re-transmit the signal on another. This means that someone with a signal too weak to pick up with his or her mobile unit directly can be heard by the repeater, and then their signal can be sent out at much higher power, covering a big range, typically 50 miles or more. Sort of like a big megaphone. Often repeaters are run by local amateur radio clubs, and access is left open to whoever wants to use it. The clubs run weekly “nets” where all the members check in, news and announcements are shared, and so on. Ham clubs provide comm support for events like bike races, festivals, and so on, and there are also more official emergency radio amateur emergency services (RACES) that some folks help with.

There’s no “broadcasting” on amateur bands, and only licensed folks can use them legally. (Though there are a lot of renegade truckers out there, sick of the CB chatter, who are rogue 10 meter amateur band interlopers.) On the amateur bands one endeavors to make two-way contacts, and you are required to identify your station in any such contact, periodically.

The problem with UHF/VHF, though, is that propagation is limited to about 100 km at the most, typically. For making more distant contacts, you need the longer wavelength HF bands. The longer the wavelength, though, the less available frequency bandwidth there is. Building an antenna for 80 m operation, for example, is non-trivial; even a half wave dipole is 40 meters in length!

But then there’s the 40 m band, long enough wavelength for distant contacts, and short enough that it’s not hard to build a simple dipole antenna. On my roof I’ve built a simple one from parts I got from Home Depot and some coax cable from eBay, and a little gizmo called a balun I got from the radio store. I got a HF transceiver from my colleague and friend Tony Tyson (KQ2I) who has been a ham since before I was born. I put it all together, and have pulled in signals from Georgia, Quebec, Indiana, and someone speaking Spanish (Mexico?). I also have a half wave dipole for 2 m, and check in on the local nets.

But I have made no contacts yet! Why? My license needed upgrading…so I just took the ham General Class exam last Sunday, passed, and now can legally transmit on that band, though my rig only goes to 100 W. (Anyone interested in making contact? I need to lose my 40 meter virginity.)

Actually I have not done all that much with ham radio yet, but in fact the scientist in me is intrigued by the possibility of working on a large radio array to measure the highest energy cosmic rays. The Europeans have an advanced concept for a large scale radio array, E-LOFAR, which can actually form an image of a particle shower produced by an incoming proton with an energy of 10²⁰ electron volts (that’s 10 million times the energy of an LHC proton). The large Pierre Auger air shower array, in Argentina, has been recording such events with water tanks scattered over a county-sized region, combined with atmospheric fluorescence (AF) telescopes (mirror arrays pointed at the sky). Radio arrays have the potential to cover a much broader area, for a lot less cost. It also works 24 hours a day, rain or shine, unlike AF. Other people are proposing to sink antenna arrays into the ice near the South Pole; my bet is that this will not yield as big a sensitive area, but who knows?

Anyway, as the hams say, “73″ to you all…