ALERT NEWSLETTER – December 2016

Hi Everyone,

I hope you made it through Thanksgiving and Black Friday unscathed or only slightly bruised. December will be a busy month for ALERT, as we look forward to Skywarn Recognition Day and the ALERT Christmas Party.

Skywarn Recognition Day was developed in 1999 by the National Weather Service and the ARRL to honor the contributions that Skywarn volunteers make to the NWS mission – the protection of life and property during threatening weather.

During the Skywarn Special Event, hams will operate from ham equipped NWS offices. The object of the event is for all participating Amateur Radio stations to exchange contact information with as many NWS stations as possible on 80, 40, 20, 15, 10, 6, and 2 meters plus 70 centimeters. Contacts via repeaters are permitted.

Starting at 6PM Friday December 2nd, the ALERT Team will bring up K4NWS as part of this special event and will operate until Saturday December 3rd at 1PM.

We will be operating on all bands & radios in the Forecast Station including 2-Meter, 220, 440, and D-Star,

We will be setting up an expeditionary HF system in the conference room with portable antennas in the yard.

Because of space limitations, this will be an ALERT Operational Members Only event.

Immediately following the event we will be celebrating the ALERT Christmas Party!

Johnnie, KJ4OPX is coordinating this event, which will feature ham, for the hams.

If you are available to help with the SRD, please respond to the callout that will be issued and also please coordinate with Johnnie in advance of the Christmas party at wxjohnnie@gmail.com.

Come on down and be prepared to have Christmas fun!

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Using Mirages For VHF / UHF Communications

You are driving along on a hot summer day. As you round a curve the road stretches ahead as far as the eye can see. Up ahead, maybe a couple of hundred feet ahead you see a pool of water in the road. You keep waiting to drive through it, but, you never reach it, as it seems to stay tantalizingly just ahead.

You are seeing a mirage.

In the desert, mirages have caused lost travelers to wander for miles trying to reach the illusion of cool water so they could relieve their parched throats. Other types of mirages have also allowed explorers to see distant lands far beyond the horizon.

Mirages occur when light rays are bent or in some cases trapped by layers of air of differing temperatures.

There are two basic types of mirages, an “inferior mirage” and a “superior mirage”.

These terms have nothing to with the quality of the mirage, but, rather which direction a light ray is bent.

An inferior mirage occurs due to the sharp temperature difference between warm or hot air at a low level and cool or cold air at a higher level, such as hot desert sand or road pavement beneath cooler air. This arrangement will bend light rays slightly upward making objects at higher altitudes appear beneath a lower object, for instance the blue of the sky appearing in the middle of a road. The image is distorted due to turbulence and usually inverted, so that it appears like a pool of water.

A superior mirage occurs when cold air is overlaid or trapped by warm air, which is a temperature inversion. In this case the light rays are bent downward, and the mirage appears above the true object. In some cases if the boundary between cold and warm air is sharp enough the light can be reflected off the boundary, back toward the ground, and reflected by the ground towards the boundary, or become trapped between layers of air, and follow the curvature of the earth making far distant objects appear on the horizon. Some believe this is how the Norsemen knew that Greenland existed and how once reaching Greenland they knew another larger landmass lay farther to the west, now known as North America.

I’ve seen this once myself, when the temperature in Birmingham was in the low teens. The mountains toward Blount County had an exact reflection, albeit upside down hovering above them.

What, if anything, does this have to do with radio communications, you may ask?

This mirage effect is the exact same process that creates our VHF and UHF band openings. In radio terminology we call it “tropospheric ducting”. A fancy name for what is basically a radio mirage.

Radio waves and visible light are part of the same electromagnetic spectrum and subject to the same rules, quirks and limitations. The only thing that makes visible light special is that we have organs that can detect the “visible” portion of the electromagnet spectrum, and further resolve the wavelengths into the primary colors. Below visible light lie infrared, microwave and radio frequencies. Above are ultraviolet, X-rays, gamma rays and perhaps other realms yet to be discovered.

Using filters and electronic processing we have blurred broad view into the infrared and ultraviolet range. Is it possible that the infrared and ultraviolet wavelengths are also divided into “colors” beyond our ability to detect? Who is to say not? Perhaps just as sound waves have octave after octave or harmonic after harmonic, you could have octave after octave and harmonic after harmonic of unseen colors. Just because you can’t detect something doesn’t mean that it doesn’t exist. For instance, you can’t see the magnetic field that moves a compass needle, yet it’s there.

For example, Wilhelm Röntgen didn’t invent X-rays; he just discovered something that had been there all along, but, until then was beyond our ability to detect.

Think of the question you ask when you see your dog or cat looking up and visually tracking something moving across the room, but, you see nothing. We can’t see anything, but, they obviously can. They can see things we can’t, just as they can hear things we can’t, which is why we use dogs as guard dogs. So it’s not as far-fetched a notion as it may seem.

But, that’s Mark’s Theory, for which my Nobel Prize has not yet arrived, and I’m drifting far off topic.

Our VHF/UHF band openings usually occur during two conditions. The first being when a cold front pushes through the area. Cold fronts are not shaped like a huge wall of cold air, but, rather a rounded boundary that tends to lift up the warm air ahead of it. This lifting process forces convection causing thunderstorm development and creates temperature inversions which create band openings.

Another, far more frequent occurrence, especially in the heat of late spring, summer and early fall, is around sunrise when the sun heats the upper levels of the atmosphere as it rises, but, the lower levels are still cold.

Every morning around sunrise you have a natural temperature inversion and a band opening. The opening may be a just few minutes or it can last for hours.

This can be a good thing, or a bad thing.

Many years ago, during the 1980’s when the Shelby County repeater first went on the air, finding a good frequency pair was a challenge due to interference with distant repeaters during band openings. One frequency pair they tried was 146.985 input / 146.385 output. Subtones weren’t widely used back then, during the Stone Age of crystal controlled 2 meter radios, and during a band opening the repeater would lock onto another repeater in Kentucky with the exact opposite frequency pair, and keep transmitting until they timed each other out, and then repeat the process over and over again all morning. Finally they chose the 98 frequency which they use today, which cured the problem.

Similarly, in the 70’s and 80’s the BARC repeater was on 146.94, with an input of 146.34, and was commonly referred to as the “34 94” repeater. The current repeater, 88, was privately owned by Ronnie Pitts. The only other repeaters back then were Hop Hayes & Henry Wingate’s 146.76 repeater, which they donated to HARC, the 147.74 “Hueytown Repeater” now on Red Mountain, a now defunct repeater on 147.94 & a short lived repeater on Lloyd Nolan Hospital In Fairfield on 146.66. The Lloyd Nolan repeater was ordered taken down by hospital authorities convinced it would interfere with hospital telemetry, which for some reason they didn’t seem to worry about with their own HEAR (Hospital Emergency Ambulance Radio) system, with which they talked to paramedics on 155.34 MHz. Fortunately such thinking has largely been overcome as witnessed by the very successful HCARC.

Anyway, frequently during severe weather outbreaks the band would open and BARC’s 94 and Huntsville’s 94 would interfere with each other. This problem was solved when 88 was donated to BARC. The 88 & 94 repeaters were identical, so they swapped crystals & 88 became the primary BARC repeater. 94 changed frequencies to 145.41 & later became the K4DSO D-Star repeater.

The younger generation of hams of the 70’s and 80’s, which would have include myself, the Spanos brothers, David Black, and others of our generation would stay on the BARC repeater. We were young, and assured by the older hams on the other repeaters that ham radio was dying and that we were the prime reason why. They didn’t like the FFC test we took nor did they like the way we conducted ourselves on the air, and were not hesitant to let us know. But, the truth was, we really didn’t do anything wrong, we were just young and acted young, and that made some, but, certainly not all, folk uncomfortable. In fact some told us we were the best entertainment on radio.

That generation of hooligans later founded SCARC, and ALERT and ended up being Presidents and officers of BARC, SCARC, ALERT and the state ARRL.

Back on topic, during these openings it may be possible to conduct usable communications with a distant repeater or station up to 800 miles away.

There are obstacles to overcome though.

If you attempt to communicate on a repeater using the same frequency as a local repeater, the local repeater will override the distant repeater. If the distant repeater uses a different subtone than that of the local repeater, you can use it until someone keys up the local repeater. Repeaters with no local competition are a piece of cake, as is simplex point to point operations. Simplex contacts, incidentally, are the only ones beside satellite contacts that count for the Work All States Award.

How far up and down the radio spectrum can this effect reach?

I have heard commercial FM stations in Oklahoma in the 89 MHz range and back in the days of analog TV, have seen distant stations on TV channel 2 just above the 6 Meter band. Can it extend another 20 MHz to the 10 Meter band? Maybe.

One article I read says this effect at UHF ranges is “nil”. I know this is bunk, because I’ve heard it numerous times on 440 MHz, and of course have seen visible mirages.

This is the effect of superior, downward bending radio mirages. What about the inferior, upward bending ones?

At midday VHF/UHF radio range decreases. This was explained to me through the years that as temperature increased; the air molecules absorbed the signal. Maybe this is true. But, I also wondered since warm air is less dense than cool air, why a warmer thinner atmosphere would absorb more signals than a cooler denser, higher humidity atmosphere?

Another possibility is that the signal is being bent skyward by the inferior mirage effect, just as visible light is. In this case, if you are transmitting a 50 watt signal, and 30 watts of it are being bent skyward, then only 20 watts is hitting your target area.

Then factor in the same distortion you see when you see objects shimmering in the heat. If the radio signal is subject to the same effect, then your remaining 20 watts is a signal being distorted and “blurred” or scattered by the heat, causing even less usable signal at the repeater site.

Another atmospheric effect is that the atmosphere near the horizon acts like a lens and bends light and radio signals over the horizon. This sometimes will cause the silhouette of distant mountains to be seen in front of the setting sun. With radio signals the effect is that the “radio horizon” is 15 % farther than the geographic horizon.

That is assuming you have an unobstructed horizon. If a mountain blocks the view of the horizon you are out of luck. Or are you?

Back in the 80’s I made and erected a cubical quad antenna for 2 meters. From my location I had never been able to hit the 76 repeater, I assumed due to the hills around Birmingham Southern College. With my beam my first target was 76, and much to my disappointment I still could not hit the repeater. One day I was swinging the beam and suddenly the repeater came in full scale. This is how I discovered that if I “off aimed” 30 degrees to the south towards Red Mountain, the mountain range would act as a reflector or “passive repeater” and I could “see” around the hills and hit the repeater.

Knowing these effects add more tools to your ham radio “bag of tricks”.

Try them and see how they work for you, as you chase that elusive VHF/UHF Worked All States Certificate.

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Mark’s Almanac

December was the tenth Roman Month, from whence it gets its name. Among many Native American tribes it was called “the moon of clacking rocks”, as it was the time when they prepared and manufactured stone tools, implements and weapons, since the growing season being over, and bad weather prevented them from hunting.

December is the cloudiest month of the year, with only 40 to 60% of possible sunshine poking through the clouds. It is also the stormiest month of the year for the Continental US & the Gulf of Mexico. By “stormy” meaning large-scale storms, not necessarily the tornadic storms that they bring, even though we are still in the Second Tornado Season.

A region of heavy rainfall usually forms from Texas to Northwest Florida to Tennessee and Arkansas. Cold waves bringing rain, snow, ice and occasionally tornadoes, sweep across the region.

December can be cloudy and cold, and, then it can swing into spring like warmth, luring plants to bloom early, only to have the frosts and freezes return and the plants are “nipped in the bud”.

Hurricane season is now “officially” over, however Mother Nature sometimes throws a surprise in to make life interesting. Since 1822 there have been 8 Category 1 hurricanes that either lasted into or actually formed in December. The last December hurricane being Hurricane Epsilon during the 2005 season, the year in which we ran out of hurricane names. That year also featured Tropical Storm Zeta, the latest forming Tropical Storm which formed on December 30, 2005 and lasted until January 7, 2006.

Looking towards the sky, Mercury, magnitude –0.5, is tucked in the glare of the sunset at the beginning of the month but by December 11 it will have risen to its highest point in the sky, or “greatest eastern elongation” of 20.8 degrees above the Sun. This is the best time to view Mercury since it will be at its highest point above the horizon in the evening sky. Look for the planet low in the western sky just after sunset.

Brilliant Venus, magnitude -4.2, shines brightly as the “evening Star” in the southwest during and after twilight.

Mars, magnitude +0.5, glows in the south-southwest at dusk, 25 degrees upper left of Venus, as he crosses central Capricorn.

Jupiter, magnitude -1.8, rises around 2 or 3 AM and shines brightly in the southeast in Virgo by early dawn.

Saturn, magnitude +0.5, is hiding deep in the glare of sunset, 30 degrees lower right of Venus, in Ophiucus The Serpent Bearer.

Uranus, magnitude 5.7 in Pisces is high in the southeast shortly after dark.

Neptune, magnitude 7.9 in Aquarius is high in the southern sky shortly after dark.

3414 planets beyond our solar system have now been confirmed as of November 17, per NASA’s Exoplanet Archive http://exoplanetarchive.ipac.caltech.edu/

The Geminid Meteor Shower, peaks on December 13-14. Geminids are one of the year’s best meteor showers. It is my favorite meteor shower. It’s a consistent and prolific shower, and usually the most satisfying of all the annual showers, even surpassing the more widely recognized Perseids of August. This shower typically produces 50 or more multicolored meteors an hour, or about one every minute.

As a general rule, the dazzling Geminid meteor shower starts around mid-evening and tends to pick up steam as evening deepens into late night. No matter where you live worldwide, the greatest number of meteors usually fall in the wee hours after midnight, or for a few hours centered around 2 a.m. local time. If you’re game, you can watch the Geminid shower all the way from mid-evening until dawn.

This year we will have one major drawback, as the nearly full moon will block out many of the fainter meteors this year, but the Geminids are so bright and numerous that it could still be a good show.

The Geminids is produced by debris left behind by an asteroid known as 3200 Phaethon, which was discovered in 1982. The shower runs annually from December 7-17. It peaks this year on the night of the 13th and morning of the 14th.

Best viewing will be from a dark location after midnight. Meteors will radiate from the constellation Gemini, but can appear anywhere in the sky.

Full Moon occurs at 00:06 UTC December 14 or 6:06 PM CST on December 13. As with last month’s full moon, this will also be a “Supermoon”, the moon being at its closest approach to Earth, and may appear slightly larger and brighter than usual. This will be the last of the three supermoons of 2016. This full moon was known by early Native American tribes as the Full Cold Moon because this is the time of year when the cold winter air settles in and the nights become long and dark. This moon has also been known as the Moon Before Yule and the Full Long Nights Moon.

Winter Solstice will be December 21 at 10:44 UTC or 5:44 AM CST. The South Pole of the earth will be tilted toward the Sun, which will have reached its southernmost position in the sky and will be directly over the Tropic of Capricorn at 23.44 degrees south latitude. This is the first day of winter in the Northern Hemisphere and the first day of summer in the Southern Hemisphere.

The Ursid meteor shower, a minor meteor shower, will peak on the night and morning of December 21 – 22 producing about 5-10 meteors per hour. It is produced by dust grains left behind by comet Tuttle, which was first discovered in 1790.

The shower runs annually from December 17-25. The second quarter moon will block out many of the fainter meteors. But if you are patient, you might be able to catch a few of the brighter ones before hypothermia sets in.

Best viewing will be just after midnight from a dark location far away from city lights. Meteors will radiate from the constellation Ursa Minor, but can appear anywhere in the sky.

New Moon occurs December 29 at 06:53 UTC or 12:53 AM CST when the Moon will on the same side of the Earth as the Sun and will not be visible in the night sky.

Looking towards the sky, the stars of Winter have begun drifting into the night sky. Low in the southern sky is the bright star Fomalhaut.

Whenever Fomalhaut is “southing” (crossing the meridian due south, which it does around 7 p.m. now depending on your location), the first stars of Orion are just about to rise in the east, and the Pointers of the Big Dipper stand vertical straight below Polaris, towards The North Star.

Orion is also valuable as a rough navigation aid as the two left stars forming the elongated square forming Orion always lie on a general north / south line, and the bottom two stars of the square lie on a rough east / west line.

‘’’’’’’’’’’’’’’’’’’’’’’’’’’’’’’’’’’’’’’’’’’’’’’’’’’’’’’’’’’’’’’’

Christmas

Christmas is my favorite time of the year.

Christmastime is a time of wonder & mystery. A time of bright lights, shining trees and the time of hide and seek, as presents are hid from inquiring minds and fingers.

A time one’s mind and memories drift back to days of childhood, and Christmases now long gone by. Remembering friends and family, some here, some now gone & longing that they were near once again, as it was once upon a time not so long ago. And, it is a time when, if we allow ourselves and don’t choose to “Grinch out” and be sour pusses, we can become kids once again.

Most importantly though, it’s a time to remember that the true “reason for the season” occurred in a manger, long ago on that first cold and chilly “Silent Night.”

So as you go about your Christmas preparations remember the magic that was there when you were a child & don’t let that magic die. Make it magic once again

For Christmas truly is “the most wonderful time of the year”.

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This month’s meeting will the Chritmas Party on December 3 at 1PM at the National Weather Service Forecast office at the Shelby County Airport.

Hope to see you there!
Mark / WD4NYL
Editor
ALERT Newsletter

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