Operating Notes – 12/9/12

Bad fists. When a CW operator sends sloppy, poorly-spaced code, or makes a lot of mistakes, he or she is said to have a “bad fist.” It’s one thing to have a bad fist, quite another to have one after many years of operation. It’s only a few guys that I regularly hear on the air, but there’s no excuse for it. If you hear me on the air, and I’m sending poorly, please let me know.

30m, 40m propagation. Propagation on 30m and 40m in the evenings has been just useless most nights. The band seems really long and the signals weak. I haven’t heard a European on 30m for weeks, it seems. Last night was a nice change. On 40m, between 0200Z and 0300Z, I made three contacts, including a couple of Europeans, and a nice long ragchew with WB2KAO.

More stations whose callsigns spell words. I recently purchased a Wouxoun KG-UVD1P dual-band hanheld. I’ve programmed it with the more popular local repeaters and have it scanning while I work. About a week ago, a guy pops up on the W8UM repeater. At first, I couldn’t believe I heard his call right. As it turns out, I was right. His call is KK4JUG. We had a nice contact as he drove by Ann Arbor. He was on his way to visit family further north.

Yesterday, down at WA2HOM, I first tried 10m, but when I didn’t hear a peep there, despite the contest, I  QSYed down to 20m. One of the first stations I ran across was VA6POP. He had a really nice signal, and we had a nice contact.

I hope to get both QSL cards soon.

Sun to cause problems for contest this weekend?

The Washington Post reported yesterday that there was a X-class solar flare, the most powerful type of solar flare, on Monday, and that more might be on the way. The article notes,

The X-class flare was not directed at Earth. But space weather forecasters caution the very active sunspot region – known as AR1598 – responsible for these flares is slowly rotating towards Earth in the coming days.

Extra Class question of the day: Aurora propagation, selective fading; radio-path horizon; take-off angle over flat or sloping terrain; effects of ground on propagation; less common propagation modes

One of the most interesting propagation phenomena is Aurora propagation. To make use of this phenomenon, radio amateurs actually bounce their signals off of the Aurora Borealis, also known as the “Northern Lights.” All of these choices are correct when talking about effects Aurora activity has on radio communications (E3C01):

  • SSB signals are raspy
  • Signals propagating through the Aurora are fluttery
  • CW signals appear to be modulated by white noise

The cause of Aurora activity is the interaction of charged particles from the Sun with the Earth’s magnetic field and the ionosphere. (E3C02) Aurora activity occurs in the E-region of the ionosphere. (E3C03) CW is the emission mode that is best for Aurora propagation. (E3C04) From the contiguous 48 states, an antenna should be pointed North to take maximum advantage of aurora propagation. (E3C11)

Normally, we think of the ionosphere as a mirror, reflecting HF signals back to Earth at the same angle at which the signal hits the ionosphere. While this is normally the case, sometimes the ionosphere does not get refracted sufficiently to return directly to Earth, but instead travels for some distance in the F2 layer before finally being returned. The name of the high-angle wave in HF propagation that travels for some distance within the F2 region is called the Pedersen ray. (E3C08)

While we say that VHF/UHF communications is “line of sight,” the distance that a VHF/UHF radio wave will travel is slightly longer than the line-of-sight distance. We call this distance the “radio horizon” or “radio-path horizon.” The VHF/UHF radio-path horizon distance exceeds the geometric horizon by approximately 15% of the distance. (E3C06) The radio-path horizon distance exceeds the geometric horizon because of downward bending due to density variations in the atmosphere. (E3C14)

Another phenomenon that sometimes makes VHF signals beyond the line of sight is tropospheric ducting. Tropospheric ducting is usually responsible for causing VHF signals to propagate for hundreds of miles. (E3C09)

One of the most frustrating propagation phenomena is selective fading. Selective fading is partial cancellation of some frequencies within the received pass band. (E3C05) It is frustrating because it sometimes makes portions of an otherwise perfectly readable signal unreadable.

Amateur radio operators may sometimes use ground-wave propagation to communicate. One important thing to know about this type of propagation is that the maximum distance of ground-wave propagation decreases when the signal frequency is increased. (E3C12) Vertical polarization is the best type of polarization for ground-wave propagation. (E3C13) So, if you really want to make a contact via ground wave, use a vertical antenna on the 160m band.

To take advantage of some of these phenomena, or to just make your antenna work better, you should know how antenna’s performance changes with changes in its design or installation. For example, the radiation pattern of a horizontally polarized 3-element beam antenna varies as the height above ground changes. What happens is the the main lobe takeoff angle decreases with increasing height. (E3C07)

The performance of a horizontally polarized antenna mounted on the side of a hill will be different from the performance of same antenna mounted on flat ground. Specifically, the main lobe takeoff angle decreases in the downhill direction. (E3C10)

Extra Class question of the day: Propagation and technique: trans-equatorial, long path, gray-line; multi-path propagation

There are a number of interesting types of propagation that occur on the HF bands.  They include transequatorial propagation, long-path propagation, and gray-line propagation.

Transequatorial propagation is propagation between two mid-latitude points at approximately the same distance north and south of the magnetic equator. (E3B01) The approximate maximum range for signals using transequatorial propagation is 5000 miles. (E3B02) The best time of day for transequatorial propagation is afternoon or early evening. (E3B03)

Long-path propagation is the type of propagation that occurs when the longer of the two direct paths between stations is better for communications than the shorter path. The type of propagation that is probably occurring if an HF beam antenna must be pointed in a direction 180 degrees away from a station to receive the strongest signals is long-path. (E3B04) 160 to 10 meters are the amateur bands that typically support long-path propagation. (E3B05) 20 meters is the amateur band that most frequently provides long-path propagation. (E3B06)

Gray-line propagation can be described as long distance communications at twilight on frequencies less than 15 MHz. (E3B11) Gray-line is the type of HF propagation is probably occurring if radio signals travel along the terminator between daylight and darkness. (E3B08) Gray-line propagation is most likely to occur at sunrise and sunset. (E3B09) Gray-line propagation occurs because, at twilight, D-layer absorption drops while E-layer and F-layer propagation remain strong. (E3B10)

Another interesting propagation phenomenon is echoes. While not strictly a type of propagation, echoes are the result of propagation conditions. Receipt of a signal by more than one path is one condition that could account for hearing an echo on the received signal of a distant station. (E3B07)

Extra Class Question of the Day: Earth-Moon-Earth communications

One of the more exotic things that amateur radios do is earth-moon-earth (EME) communication, sometimes called “moon bounce.” As this name implies, radio amateurs actually bounce their signals off the moon. This is the ultimate DX. The approximate maximum separation measured along the surface of the Earth between two stations communicating by Moon bounce is 12,000 miles, as long as both can “see” the Moon. (E3A01)

Because the signal travels such a long way, you need to do everything you can to avoid signal loss. So, for example, scheduling EME contacts when the Moon is at perigee will generally result in the least path loss. (E3A03) Perigee is the point at which the Moon is the closest to Earth.

Because the signals are so weak, it’s also important to use equipment with very low noise, so that the signals don’t fall below the noise level. That being the case, the type of receiving system that is desirable for EME communications is equipment with very low noise figures. (E3A04)

EME communications can take place on both the 2m band and the 440 MHz band. The frequency range that you would normally tune to find EME signals in the 2 meter band is 144.000 – 144.100 MHz. (E3A06) The frequency range that you would normally tune to find EME signals in the 70 cm band is 432.000 – 432.100 MHz. (E3A07)

As you can imagine, there are not many operators working moon bounce. You don’t just get on an call CQ—generally you set up a schedule with another operator to contact one another via moon bounce. At the appointed time, the operators take turns transmitting, while the other listens. Time synchronous transmissions with each station alternating describes a method of establishing EME contacts. (E3A05)

One interesting phenomenon is libration fading. Libration fading of an Earth-Moon-Earth signal is a fluttery, irregular fading. (E3A02) This fading is caused by the irregular surface of the Moon, and the peaks can last for up to two seconds on the 2m band. These peaks can actually help operators make contacts when they would otherwise be impossible.

From my Twitter stream – 5/9/12

This is cool. What a great concept. (key lending library) http://t.co/fyNvn1Lt
Heathkit Educational Systems Closes Up Shop: For the second time since 1992, Heathkit Educational Services (HES)…http://t.co/DWsxlgYm
GM8LFB
Solar Alert big time two M class flares plus Aurora alert. http://t.co/4Oekkfov

Solar storm a dud

Forget all those dire predictions of widespread power failures, satellites going belly up, and flight cancellations. What was touted to be the biggest solar storm in years is apparently a dud.

The Associated Press reports:

Hours after the storm arrived, officials said there were no reports of problems with power grids, GPS, satellites or other technologies that are often disrupted by solar storms.

National Public Radio (NPR) reports:

The forecasters weren’t aware of any significant impact to electrical or technological systems, but said there was a two-hour blackout of high frequency radio communications — affecting mainly ham radio operations — stretching from eastern Africa to eastern Australia.

Seeing as how that swath is not really a hotbed of activity, I think we can safely say that we can all go back to chasing DX now.

Two Gems from G0KYA

10m Slim Jim antenna

At more than 9m tall, this antenna isn't very stealthy, but if you have a tall tree to hang it from, it should be a great performer.

Steve, G0KYA blogs about HF propagation and antennas. Recently, he posted plans for a 10m “Slim Jim” antenna made from 450-ohm ladder line. At more than 9m tall, this antenna isn’t very stealthy, but if you have a tall tree to hang it from, it should be a great performer.

While you’re on Steve’s site, make sure you check out his two books, Stealth Antennas, and Understanding LF and HF Propagation. The latter is a compilation of articles he wrote with Alan Melia G3NYK for the Radio Society of Great Britain’s (RSGB) RadCom magazine.  You can’t beat the price. It’s a free download!

Extra Class question of the day: meteor scatter propagation

Perseid meteor

Amateur radio operators use many different ways to get signals from one spot to another. Perhaps one of the most interesting is meteor scatter propagation.

Meteor scatter propagation is possible because when a meteor strikes the Earth’s atmosphere, a cylindrical region of free electrons is formed at the E layer of the ionosphere. (E3A08) 28 – 148 MHz is the frequency range that is well suited for meteor-scatter communications. (E3A09)

Unfortunately, these ionization trails are relatively short-lived, so to communicate via meteor scatter, you need to either be able to detect when these paths are available or be transmitting when the paths are available. All of these choices are correct when talking about  good techniques for making meteor-scatter contacts (E3A10):

  • 15 second timed transmission sequences with stations alternating based on location
  • Use of high speed CW or digital modes
  • Short transmission with rapidly repeated call signs and signal reports

For more information on meteor scatter, go to:

Rugged Transistors, Designing Radio Systems

Here are a couple of links to articles in electronics engineering trade magazines that I’ve run across lately that I think are of interest to amateur radio operators:

  • Some new transistors can withstand VWSRs up to 65:1.Gauging Ruggedness In RF Power Transistors. This article, written by editor Jack Browne, who is himself a ham, covers some of the new power transistors on the market. Some of them are capable of withstanding VSWRs on the output of up to 65:1!
  • The Radio Link: A Tutorial. This series of articles is a bit heavy on math for most radio amateurs, but the point of the series is to think of radio communication as a system whose behavior can be predicted. Thinking about how we use radio in this way could help us to become better radio amateurs.

And here’s something entirely out of left field. Scientists have published a paper that shows that random noise can actually make signals clearer. The process is called stochastic resonance, and while the article doesn’t explain the theory in much depths, and I’m not sure that it’s something that’s applicable to radio communication, it seems like it might be something to look into.