Category Archives: Astronomy History

Laika’s Flight: November 3, 1957

On this day 60 years ago, November 3, 1957, Laika, a Soviet dog, became the first Earth creature to orbit the Earth.

Her survival was never expected, since the technology to de-orbit had not yet been developed. Little was known about the impact of spaceflight on living creatures, and some scientists believed that it would be impossible to survive the launch. Laika’s mission was designed to determine whether a living creature could survive the forces of launch and the micro-g environment of space travel.

The Soviets initially claimed that Laika was humanely euthanised by lack of oxygen. However, her actual cause of death was made public in 2002, when it was revealed that the spacecraft overheated, causing her death within a few hours.

Laika was originally a stray found wandering the streets of Moscow. It was thought that such animals were already well adapted to surivial. Three dogs were trained, and Laika was finally selected as the “lucky” winner to make the one-way trip to the final frontier. She was trained by being kept in progressively smaller cages. Before the launch, one scientist took Laika home to play with his children. He reported, “Laika was quiet and charming. I wanted to do something nice for her. She had so little time left to live.”

She was hooked to sensors, and on November 3, 1957, she was launched on her mission from the Baikonur Cosmodrome. When a piece of thermal insulation tore loose, the temperature of the capsule soon reached about 104 °F. Laika died of overheating on about the fourth orbit.

After 2570 orbits, the Sputnik 2 spacecraft, along with Laika’s remains, disintegrated during re-entry on April 14, 1958.


Calibrating Your Watch With The Stars

1947OctPSSeventy years ago, the October 1947 issue of Popular Science showed this method of making sure your watch was accurate.

While this method would not, by itself, give you the exact time, it would very precisely tell you the elapsed time.

The method was very simple. You simply installed a piece of tin with 1/16 inch hole on some fixed location, such as the side of the building. You used it to sight a vertical fixed object, such as a lightning rod or distant skyscraper. Then, you observed the exact time that any star was occluded by the object. Since the star is essentially a point of light, it would disappear suddenly. You noted the time.

Then, the next evening, you would observe the same star. It would be occluded exactly 23 hours, 56 minutes, 4.09 seconds later–one sidereal day. In other words, the time on your watch should read exactly 3 minutes 55.91 seconds before the previous night’s figure.  (For all practical purposes, a sidereal day is 364/365 of a solar day.  This makes sense, since the Earth itself has moved 1/365 of its way around the sun in 24 hours.)

Depending on whether your watch was fast or slow, you could thus adjust the spring.

If you knew the exact time the first night, then you could also create a table showing the exact time of occlusion subsequent nights. As long as you didn’t move the piece of tin, you would always know what time it is.

This method has two applications.  After the zombie apocalypse, presumably WWV will be off the air.  The stars give you a method to keep your clock calibrated very accurately.  It could also be the basis for a very interesting science fair project.

 

 



Sputnik: October 4, 1957

Sixty years ago today, the Space Age started when the Soviet Union stunned the world by launching Sputnik 1, the Earth’s first artificial satellite, on October 4, 1957.

Soviet news agency TASS made the official announcement:

As a result of very intensive work by scientific research institutes and design bureaus the first artificial satellite in the world has been created. On October 4, 1957, this first satellite was successfully launched in the USSR. According to preliminary data, the carrier rocket has imparted to the satellite the required orbital velocity of about 8000 meters per second. At the present time the satellite is describing elliptical trajectories around the earth, and its flight can be observed in the rays of the rising and setting sun with the aid of very simple optical instruments (binoculars, telescopes, etc.).

In addition to reminding the West that the satellite could be seen by anyone, TASS went out of its way to make sure that even radio amateurs could hear for themselves that the Soviets had won the race into space.  The official press release included Sputnik’s frequencies:

 It is equipped with two radio transmitters continuously emitting signals at frequencies of 20.005 and 40.002 megacycles per second (wave lengths of about 15 and 7.5 meters, respectively). The power of the transmitters ensures reliable reception of the signals by a broad range of radio amateurs. The signals have the form of telegraph pulses of about 0.3 second’s duration with a [312] pause of the same duration. The signal of one frequency is sent during the pause in the signal of the other frequency.

Sputnik 1.jpg

Replica of Sputnik 1. Wikipedia photo.

Receivers for the 40 MHz signal would have been a rarity, but thousands of hams and SWL’s had receivers that would easily tune 20 MHz.  The frequency was cleverly picked to be close to WWV’s powerful 20 MHz signal.  Thus, even though most receivers weren’t calibrated well enough to show the exact frequency, the U.S. National Bureau of Standards unwittingly made sure that everyone knew exactly where to tune.

In addition, the signal was so close to WWV, then at Beltsville, Maryland, that the unmodulated carrier from the satellite would create a heterodyne with WWV, allowing it to be heard even if the receiver was a simple one without a BFO.

The national association of amateur radio operators, ARRL, was flooded with calls from reporters.  They gave instructions to listeners to “tune in 20 megacycles sharply, by the time signals, given on that frequency. Then tune to slightly higher frequencies. The ‘beep, beep’ sound of the satellite can be heard each time it rounds the globe.”

1957DecQSTThe December 1957 issue of QST included several photos of hams who had heard the satellite,  And in many cases, those hams made the signal available to local broadcast stations and news outlets.

In Chicago, it was 27-year-old ham Jerome Tannenbaum, W9JJN, of 5240 Harper Avenue. He was described in the October 5 Chicago Tribune as the owner of an electronic engineering consulting firm and radio operator since he was 15. He told the newspaper that he heard a steady stream of “dahs” on 20.005, and definitely believed that the signal was from Sputnik, based upon the fact that it faded out right when predicted.

Hams quickly figured out how to track the orbit and predict the next time the satellite would be in range.  Again, Moscow made sure they knew Sputnik’s orbital inclination of 65 degrees,  and orbital period of 1 hour 35 minutes, by including this information in the first announcement.  The simple locating device shown here was made at ARRL headquarters, merely by mounting a loop of wire around a globe.  Once the satellite was heard, it was a simple matter of predicting where it would be heard next by rotating the Earth 23.75 degrees, the amount it would move during one orbit.

Apparently, Sputnik had at least one deliberate QRM’er.  A letter in the December 1957 issue of QST reports that someone showed up on 20.005 MHz on October 7 with commentary such as, “this is the moon speaking,” sending the safety signal, and signing the call sign UA3ABD.  The letter writer, Dave Harris, K2RRH of Lyndhurst, N.J., hoped “that donkey realizes that he is on tapes all across the country.”

Sputnik 1 remained in orbit until January 4, 1958, having completed 1440 orbits of the Earth.  When it re-entered the atmosphere, WWV played another role.  Hams and others were already familiar with meteor scatter, the reflection of radio signals by the ionized gasses caused when a meteor enters the atmosphere.  Scientists and hams correctly guessed that Sputnik would cause the same phenomenon on re-entry.  As a convenient signal source, WWV was once again used, and as predicted, the WWV signal appeared or got louder as the satellite entered the atmosphere.  With this data, it was possible to track the satellite’s location until it completely disintegrated in the atmosphere.

Thousands of Americans were able to see or hear Sputnik.  In many cases, this sparked a lifelong interest in science, space, and/or radio.  I asked some of the hams at QRZ.com to share there stories about their experiences.  A number of hams posted there or e-mailed their recollections.

Glen Zook, K9STH, currently of Richardson, Texas, shared this story of hearing Sputnik as a 13 year old in LaPorte, Indiana, and he gave me permission to include it here:

Hallicrafters S-40

Hallicrafters S-40

There was a garage shop TV repair facility about a block south of my parents’ house. When Sputnik was launched and was operating, the frequency, 20.005 MHz, and the expected times when the satellite could be heard, were published in the LaPorte Herald Argus newspaper. Orville Hartle, the owner of the TV shop, had a Hallicrafters S-40 receiver and invited my father to come down and listen to Sputnik. I “tagged along” with my father.

As the expected time for the satellite to become in range, Orville started “fiddling” with the receiver. Nothing was heard! Finally, the “beep, beep, beep” from the satellite’s transmitter came faintly from the S-40’s receiver. Today, such a happening would be “ho hum”. However, in 1957 this was very exciting if, for no other reason, that the signal could be received by “Joe Blow” and not just by a very sophisticated scientific or military installation.

The repercussions from this evening, at least in my personal life, were great. Orville discovered that I had a serious interest in electronics which his son, who was about a year younger than I, had absolutely no interest. In fact, his son had very little interest in anything! Orville was an unusual character! He was a graduate EE but worked in the “tool crib” at the local Allis Chalmers plant, ran the TV shop evenings and weekends, and wrote books!

Orville started giving me as many old television chassis that I could “haul off” for the purpose of stripping for parts. I would take my sister’s “little red wagon” (she is 7-years younger than I) down to the TV shop and Orville would put 2, or 3, chassis in the wagon and I would bring them to my house. There were outside stairs to the basement and I would carry the chassis down and put them next to a workbench that my father had built next to the coal bin. My “experiments” were conducted, primarily, on that bench.

Thinking back, I cannot help but believe that Orville was a contributing factor to the fact that for Christmas, 1957, my parents bought me a used Heath AR-3 receiver (from Allied Radio Company in Chicago). Prior to that Christmas, I had been using an old TrueTone (Western Auto private brand) receiver with a shortwave band.

He was not an amateur radio operator, but he did encourage me to experiment with electronics and even gave me a television set, for my room, that was better than the one in my parent’s living room!

With the help of Dave Osborn, K9BPV, I passed my Novice Class examinations on my 15th birthday, 13 February 1959. It took over 3-months for the license to arrive in the mail. The license is dated 15 May 1959 but took an additional almost 2-weeks to come in the mail. I was just ending my freshman year in high school. In October, I took my General Class examinations at the FCC office in Chicago.

Then, in August 1962, between my senior year in high school and my freshman year in college, I took the examinations for my commercial radiotelephone operator’s license. My junior year at Georgia Tech, I got married and also got a job at the Motorola Service Station in Atlanta, Georgia. My senior year, I was hired directly by Motorola to establish, and then manage, the first Motorola owned portable / pager repair facility away from the Schamburg, Illinois, plant. After graduating, I was employed by the Collins Radio Company at the “new” corporate headquarters here in Richardson, Texas, and the “rest is history”!

All of this starting with the listening to Sputnik in October 1957!

Jim Allen, W6OGC, of New Braunfels, Texas, sent this account, which I share with his permission:

Sputnik went up in October, 1957, and lasted something like 3 months

One evening as we sat eating supper, the telephone rang. My dad got up and answered. He recognized the caller, the Superintendent of Schools, then became as flustered as I ever saw him. “Why, yes, he’s here. I’ll get him.”

He gestured to me, I got up and answered the phone. My dad hovered around with a look in his face, “there better be a heck of a good story for this!” He could not imagine why this big shot was calling for me, a 6th grader.

Hallicrafters SX-100. Radio News, ______.

Hallicrafters SX-100. Radio News, Feb. 1956.

The Super, W5FFE, said to me, “listen to this.” I heard the beep, beep, beep, that no one had ever heard before. He explained it was a satellite, the first one, and he was listening to it on his radio, an SX-100 as I knew. I had been watching the launches from Florida, none successful thus far.

A few of us had been going to Novice classes, he knew of it, and had called some of us, each pass.

I don’t think my dad ever forgot that.

One surprise for me was the number of hams (and other members of the public) who saw Sputnik with their eyes.  A number of such reminiscences were posted, although many of the viewers realized years later that they probably hadn’t seen Sputnik itself, but rather the larger covers that had been jettisoned from the smaller satellite.   But still, they were watching with their own eyes something the Soviets had put into orbit.

It shouldn’t have come as a surprise that so many people saw Sputnik (or the other parts of the spacecraft).  Today, when randomly stargazing, it’s not uncommon to see an artificial satellite cross the sky.  After all, there are thousands of them, and just by randomly looking up, you’re bound to eventually see one.  In fact, it’s almost mundane.  When I was growing up in the mid-sixties, it wasn’t uncommon for my parents to point one out to me.  It was already mundane, but there they were for all the world to see.  It did strike me as amazing.

I remember reading about the Lykov family, who, starting in 1936, lived in complete isolation from society in Siberia for 42 years.  According to one account,  They had noticed starting in the 1950’s that “the stars began to go quickly across the sky.” The father, Karp Lykov, surmised that “people have thought something up and are sending out fires that are very like stars.”

When Sputnik 1 went up, it wasn’t mundane, and the predicted times of orbits were published in newspapers.  Millions of people were looking up, expecting it.  It shouldn’t have surprised me that so many of them still remember.

 

 



1937 Parachute Jump for Young Comrades

1937OctPMThis photo should put to rest, once and for all, the myth that commie kids never got to have any fun. Eighty years ago, parents the world over apparently weren’t quite as concerned that their children be protected from all conceivable dangers. Today, we might worry that the playground slide is too dangerous, but at least it deposits Junior in very close proximity to terra firma.

But they didn’t worry about things like that in 1937, and they certainly didn’t worry about it in the glorious Soviet Union.

In this Moscow park, the slide ended twelve feet above the ground, and the kids just had to trust the laws of aerodynamics to see them safely to the ground.  The accompanying text in the October 1937 issue of Popular Mechanics notes that this was one of the park’s most popular features.

The first woman in space, Valentina Tereshkova, was born in 1937, so my first hunch was wrong, since the young comrade shown in this 1937 photo obviously wasn’t born in 1937. But Comrade Valentina Vladimirovna was an amateur skydiver when, as a textile worker, she was inducted into the Cosmonaut Corps.  And there is definitely a family resemblance.

RIAN archive 612748 Valentina Tereshkova.jpg

Cosmonaut Valentina Tereshkova. Wikipedia photo.

I’m sticking to my theory that the young comrade jumping from the slide is the future cosmonaut’s older sister.

In any event, if you have kids jumping off twelve foot slides, Hitler should have known that he didn’t stand a chance.



Get Your Eclipse Glasses and Hotel Rooms Now!

Path of Totality. NASA image.

Path of Totality. NASA image.

On August 21, 2017, a total eclipse of the sun will be visible as it passes across the United States from Coast to Coast. This is the first time an eclipse has been visible from coast to coast since 1918. I have seen partial eclipses, and they are a somewhat interesting phenomenon. However, I have never witnessed a total eclipse of the sun, and my family plans to travel to Nebraska to view it.

The total eclipse will be visible only on a band about 70 miles wide stretching from Oregon to South Carolina.  If you are not within this band, you might not even notice the eclipse if you’re not watching for it.  But within this band, the sky will become dark, stars will be visible, and only the sun’s corona will be visible.

During the approximately two minutes of totality, it is safe to view the sun with the naked eye.  But even if only a tiny portion of the sun is visible, then it is necessary to use eye protection.  Therefore, if you are planning to view the eclipse, two things are necessary.

1.  Get Your Eclipse Glasses!

First of all, you will want to get a set of eclipse glasses, such as the ones shown here.  With these glasses, which cost about $2, you will be able to safely view the eclipse if you are not in the path of totality, or if you want to look at the sun before and after totality.

During a 2015 partial eclipse in England, there was a shortage of the eclipse glasses.  In the days leading up to the eclipse, thousands searched in vain to find a pair, but there were none available, or they were available only at grossly inflated prices.  These glasses are still readily available online at reasonable prices.  I recently purchased 10 pairs of the glasses shown here, and they were shipped to me in about a week.   The total price for 10 pairs, including shipping, was about $17.  I’ll post a review in a few days, but they appear to be well made for what they are, and they have the appropriate ISO safety certification.

Unfortunately, I don’t know anyone else who has ordered in advance.  I suspect that, just like in England, there will be a huge demand at the last minute.  Stores won’t have them, and it will be too late to order online, or online suppliers will also run out.  Therefore, I strongly recommend that you order now while they are still available.  The set of ten that I ordered can be ordered from the following Amazon link:

Numerous other options are available on Amazon at this link.

In the Twin Cities area, I am only aware of these stores selling eclipse glasses.  They are:

2.  Make Your Hotel Reservations!

The other item you will want to consider is traveling to view the eclipse.   The partial eclipse that will be visible in most of the United States is certainly interesting, but for most, the total eclipse, visible only in a 70 mile wide band, is a once in a lifetime experience.  Most Americans are within a day’s drive, and it’s certainly worth the drive.  Surprisingly, some hotel rooms are still available, even though many cities along the path have been booked solid for months.  My family will be staying in Hastings, Nebraska, although that city is now completely sold out.

If all else fails, I would recommend simply driving to the path of totality, and sleeping in your car if necessary.  However, rooms are still available in many cities on and close to the path of totality.  The following table will give you some idea of what is available.  As you can see, the last hotel room in Casper, Wyoming, is a modest motel going for $800 a night.  But even though rooms are filling up fast, the following table gives you some idea of what is available.

This table shows availability at Hotels.com, as of June 16.  As you can see, many cities still have bargain hotels available.  This will certainly change as the eclipse gets closer, so. I encourage you to do as I did and make your reservation now.

I have included a link to the least expensive hotel in the city.  In some cases, this hotel might be a few miles from the path of totality, so you will still have to drive to the location of the eclipse.  But by booking a nearby hotel, you will make the process much easier, since you won’t have to worry about driving all night or sleeping in your car.  This chart shows availability for the night of August 20, the night before the eclipse.  The time of the eclipse will vary by location, but will be around midday on Monday, August 21.

As of today, inexpensive rooms are still available in Lincoln, NE, Kansas City, MO, Columbia, MO, Jefferson City, MO, St. Louis, MO, Paducah, KY, Nashville, TN, Greenville, NC, Columbia, SC, and Charleston, SC.  But I guarantee that will no longer be true in a couple of weeks!

Before I made my own hotel reservation last year, I did check on campground availability.  At that time, the campgrounds I checked were already sold out.  However, you may wish to check on campgrounds, including state parks on or near the path of totality.  (See the list of Nebraska State Parks at the end of this post.)

The links below are to the least expensive hotel in the area, as of June 16.  There might be other hotels that are more suitable or closer to the path of totality.  But this will give you an idea of what is available.

For constantly update hotel information, please visit the following posts:

City Lowest price City Percent Booked Link to Least Expensive Hotel
Salem, OR Not Available 100.00%
Jackson, WY Not Available 100.00%
Casper, WY $801 96%
1st Interstate Motel
Glendo, WY Not Available 100.00%
Alliance, NE Not Available 100.00%
Grand Island, NE Not Available 100.00%
Lincoln, NE $43.00 76.00%
Americas Best Value Inn Lincoln Airport
Kansas City, MO $42.00
Super 8 Lenexa Overland Pk Area
Columbia, MO $43.00 78.00%
Frontier Motel
Jefferson City, MO $50.00 Almost 100%
California Motel
St. Louis, MO $39.00
Motel 6 Hazelwood
Cape Giraredeau, MO Not Available 100.00%
Carbondale, IL Not Available 100.00%
Paducah, KY $180.00 98.00%
Wingfield Inn
Nashville, TN $50.00 72.00%
Super 8 Nashville Downtown
Greenville, NC $44.00
Days Inn Washington NC
Columbia, SC $42.00 74.00%
Budget Inn Express-columbia
Charleston, SC $60.00 93.00%
Econo Lodge North

 

Nebraska State Parks

It does not appear that there are any reservable campsites at Nebraska State Parks in the path of totality. But the following Nebraska State parks have sites available for reservation as of June 16. Most of these are north of the path of totality, some as much as a hundred miles or more. But for those visiting Nebraska from the north, one of these parks might be a good option, since you can camp there, and then drive to view the eclipse Monday morning.

  • Branched Oak SRA
  • Calamus SRA
  • Chadron SP
  • Eugene T. Mahoney SP
  • Fort Robinson SP
  • Fremont SRA
  • Lake Wanahoo State Recreation Area
  • Lewis and Clark SRA
  • Louisville SRA
  • Niobrara State Park
  • Platte River SP
  • Ponca SP
  • Rock Creek Station SHP
  • Two Rivers SRA
  • Willow Creek SRA



John Glenn, 1921-2016

Glenn62.jpg

John Glenn. Wikipedia photo.

Mercury Astronaut John Glenn died on December 8, 2016, at the age of 95.  He was the first American astronaut to orbit the Earth aboard the Mercury 6 spacecraft, Friendship 7, on February 20, 1962.

The American orbital mission proved an opportunity for shortwave listeners to eavesdrop of the communications with the space mission.  This news flash from the May, 1962, issue of Popular Electronics confirms that many American SWL’s were able to tune into the communications to the space capsule, although at press time, it did not appear that there were any confirmed reception reports of the space-to-Earth downlink.

mercury

Voice communication from Earth was sent on HF frequencies, with 15.016 MHz being the most important in the Western Hemisphere. On that frequency, SWL’s were able to hear ground stations in Guaymas, Mexico, Corpus Christi, Texas, and others. It was believed that Glenn was transmitting on or near that frequency, although this had not been confirmed at press time. In the Eastern Hemisphere, ground network stations were heard on 7.575 and 10.61 MHz, with ships in the recovery operation above the 15.016 frequency.

The magazine noted that SWL’s probably enjoyed the mission more than TV viewers.

Godspeed, John Glenn.



Lunar Eclipse of July 15, 1916

A partial lunar eclipse took place on this date one hundred years ago, f July 15 1916.  The eclipse was notable for the effect it had on Sir Ernest Shackleton’s Imperial Trans-Antarctic Expedition, an attempted crossing of the Antarctic continent.  The expedition consisted of two parties.  One party, led by Shackleton aboard the Endurance, was to make the crossing from the Weddell Sea.  This party was the most famous, since after the loss of the ship, the party had to travel to Elephant Island, then to South Georgia island, and finally make a dangerous land crossing to a whaling station on the other side of that island.

 A man, fresh-faced with dark, brushed-back hair, seated among a group. He is wearing a naval officer's uniform with a high, stiff collar

Aeneas Mackintosh, Ross Sea party commander. Wikipedia image.

The other party was to enter the continent from the Ross Sea, and was led by Aeneas Mackintosh.  This party would head inland and establish depots for the party making the crossing.  In 1916, five of this party were stranded, and needed to reach the relatively safety of a hut at Cape Evans.  An attempt was made in May, but the ice was too thin.  They had to wait for colder weather, which also meant darkness.  The weather was bad during the full moon of June, but on July 15, conditions seemed good.  But when the moon rose, the men were surprised to find that it was about to be eclipsed.  Fortunately, even though the eclipse continued for two hours, it was only partial, and enough light remained to make the journey.

Read More At Amazon

 

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Happy Leap Day!

1908 Leap Year postcard. Wikipedia image.

Today is leap day. In order to accomodate the U.S. presidential election and the Summer Olympics, the years in which those events take place require an extra day, which is added on February 29. These events take place in years evenly divisible by four (2016/4 = 504), and for this reason, Pope Gregory decreed in 1582 that such years would contain 366 days, rather than the typical 365. The first leap year took place in 1584. Even though there was no presidential election or Summer Olympics that year, the new system showed incredible foresight.

The addition of a leap year also keeps the calendar in sync with the Earth’s orbit around the sun, which takes approximately 365-1/4 days. Without the modification to the calendar, the seasons would shift by about one day every four years.

However, the Earth’s period of orbit around the sun is not exactly 365-1/4 days. It is actually slightly more, but because of the effect of the Earth’s precession, it appears from the point of view of an observer on Earth to be slightly less, namely 365.24219879 days.

To get things properly in sync, a few more tweaks had to be made. Therefore, years divisible by 100 (which are divisible by 4, and would normally be leap years) are not leap years. Therefore, 1900 consisted of 365 days, and there was no February 29, 1900.

This correction by itself would make the average year measure 365 + 1/4 – 1/100 = 365.24 days. However, to refine the formula even more, another exception is made. Years divisible by 400 are leap years, even though they are divisible by 100. Therefore, 2000 was a leap year, and there was a February 29, 2000.

With this added factor, the average year length is now 365 + 1/4 – 1/100 + 1/400 = 365.2425 days, which is only 0.0003013 days more than the actual length of the year. This means that it will take 3319 years for the calendar to be off by only a single day. But that seems to be an adequate distance to kick the can, and our descendants can deal with the problem then.

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Victory Eclipse of 1945

1945EclipseSeventy years ago today, July 9, 1945, a narrow strip of Idaho and Montana experienced a total eclipse of the sun.  From its sunrise beginning in the northwestern United States, the path of totality passed through Canada, Greenland, Scandinavia, and the Soviet Union. The photo here was taken near Butte, Montana, were the sun rose almost fully eclipsed, with totality a few minutes later. The photo was taken by Peter A. Leavens, and appeared in Life Magazine on July 23, 1945.

Critical frequency during eclipse.

Critical frequency during eclipse.

Ionospheric scientists at Tromsø, Norway, only two moths after liberation, took the opportunity to measure the effects of the eclipse on the ionosphere. Their results show a pronounced dip in the critical frequency during the eclipse.

Interestingly, their report also notes that the Germans had an ionospheric station at Kjeller, used to determine radio communication frequencies after the war. When the station was taken over by Allied forces, the German peronnel were ordered to continue their work, and observations were made at that station as well.

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DX’ing From Outer Space

PopElecApr77

For about the past century, the planet Earth has been sending out into the cosmos radio signals, and it’s not uncommon to wonder whether anyone has heard them. The subject sometimes comes up in science fiction. For example, in the 1997 movie Contact, the first message received from an extraterrestrial source was, of all things, a speech by Hitler (conveniently complete with both audio and video). It was reasoned in the movie that this was one of the first television broadcasts from Earth, and as soon as the TV DX’ers in some other part of the galaxy received it, they sent it back. Presumably, I Love Lucy and other programs would follow within a couple of decades.

For the reasons explained below, this is relatively implausible. While it would be a relatively easy matter for another civilization to detect the presence of our signals, actually demodulating them (not to mention sending them back) would be considerably trickier. But it’s not totally impossible.

DX’ing From The Moon

But there’s another related question lurking here, and that is how difficult it would be for me to receive radio signals from Earth if I decided to visit the moon or some other place in space. Obviously, radio communications is possible at very great distances, since NASA does this on a daily basis. The question is what those of us with more modest equipment would be able to do.

The question is answered by an April 1977 Popular Electronics article written by Glenn Hauser.

Hauser’s focus in this article is primarily on the moon, and he convincingly shows that reception of FM and TV signals would be relatively easy to accomplish with reasonably good receivers and antennas. When the subject comes up, naysayers frequently point out that very few terrestrial stations use antennas that radiate very much energy “straight up.” It turns out, though, that this is actually the reason why many signals could be heard on the moon. After all, the moon is rarely “straight up.” It can be at many points in the sky, and at some of these points, it’s within the main lobe of broadcast stations on Earth.

Most FM and TV stations use what we think of as “omnidirectional” antennas: In other words, antennas that radiate equally strong signals in a full 360 degrees. But most of these antennas have a certain amount of gain: The effective radiated power of the signal is greater than the transmitter’s output power. This is because the “omnidirectional” pattern of the antenna is not omnidirectional at all. Instead, most of the power is concentrated into a single plane. It’s “omnidirectional” in the sense that it’s headed off toward the horizon in all directions. But it’s directional when you think of it in three dimensions. All of the energy is concentrated toward the horizon. This makes sense for the broadcaster, since all of their listeners are located on an (approximate) plane, bounded by the horizon.

This means that a station’s signal is being beamed toward the moon at two times per day: At local moonrise and local moonset. From the point of view of the listener on the moon, this means all of the stations along the Earth’s approaching and receding limbs, a narrow band circling the Earth. A station located at the North or South Pole would have its antenna pointing at the moon on a constant basis. Every other station on Earth would have its antenna pointed at the moon approximately every twelve hours.

There would still be a slight problem, however, since even on this narrow band, there would be multiple stations on any given frequency. I suspect that on some popular frequencies, this problem would be insurmountable, since the QRM would be just too great.

But there would be some signals that would be quite easy to copy, since they have the frequency to themselves, or share it only with much lower powered stations. Two examples given in the 1977 article is no longer relevant, but they’re good illustrations. Prior to the switch to digital television in the United States, TV channel 68 was occupied by only one station, KVST-TV in Los Angeles, with an ERP of a million watts. And on channel 67, WMPB, the Baltimore PBS channel, was in a similar position. These channels would be relatively easy to monitor from the moon whenever it was moonrise or moonset in Los Angeles or Baltimore. Hauser notes other such examples in Europe and Brazil.

Most of the FM band would be more cacophonous, but there would be some stations operating on relatively clear channels. Due to the FM capture effect, some of these would be relatively easy to hear, even if there was a bit of other activity on the same channel. For example, he cites a number of cases in the educational portion of the FM band (88-92 MHz), where there’s a single high-power station in the United States, with other stations on that channel having much lower power. In those cases, the dominant signal would be easily heard. He also cites a number of high powered Canadian stations operating on channels where only low powered stations existed in the United States. Since the FM situation has been relatively static since 1977, most of these stations would remain fairly easy catches from the moon.

Hauser does point out that longwave and mediumwave (standard AM broadcasts) would be unlikely to penetrate the ionosphere.  Only signals above the maximum usable frequency (MUF) could be heard outside the confines of the Earth.  Therefore, he notes that it’s unlikely that we had much radio leakage to speak of prior to about the 1930’s, when relatively strong shortwave stations started coming on the air.  Since most of these stations operated on regular schedules, it’s likely that they were still radiating, even when the MUF dipped below their transmitter frequency.  Those signals would radiate into space.  Hauser cites one example of a BBC transmission from the VOA station in Delano, California, being copied by a satellite.

DX’ing by Extraterrestrial Civilizations

The issue raised by the movie Contact is touched on by Hauser, but it’s studied in scholarly detail by a NASA report entitled Eavesdropping Mode and Radio Leakage from Earth by Woodrull T. Sullivan III.  While this report doesn’t show a date, it appears to be written post-1978.  It answers the question of what extraterrestrial listeners, with equipment comparable to that available on Earth, would be able to hear.  It turns out that those extraterrestrial viewers would be able to determine quite a bit, although it’s unlikely that they would be able to demodulate the video of speeches by Hitler.

Even though they might not be able to watch our shows, extraterrestrial monitors within several light years of the Earth would be able to make quite a few reasonable deductions about the Earth, even if they were equipped with only Earth-level receivers and antennas.  At least they would have been able to.  It turns out that the best source of information would be the video carriers of UHF television stations.  With the switch to digital television, some of those extraterrestrials might have concluded that the Earth has gone dark.

But those UHF carriers from a few years ago are still working their way through space, and it’s possible that someone is analyzing them.  The article makes clear that the modulation of those signals (the actual audio or video) would be too weak to decode with Earth-level technology.  But the presence of the carriers would be apparent.  And even with this information, extraterrestrials would be able to come to some intelligent conclusions.  They would be able to figure out which star the signals were coming from.  And by keeping close track, they would be able to figure out the diameter of the Earth’s orbit around the sun.

They would even be able to figure out the approximate latitudes and longitudes of individual stations.  This is because the signals would come and go on a regular schedule as the Earth made its 24-hour rotation.  As noted above, stations near the poles would be audible most of the time.  As stations got closer and closer to the equator, they would be audible for shorter periods each twelve hours.  The Doppler shift of received signals would give further clues as to the latitude of the signals being heard.  Eventually, the extraterrestrials would be able to crunch the numbers and figure out the approximate terrestrial locations of the stations.  If the correctly assumed that the locations of these signals were close to the locations of greatest human population, they would even be able to roughly map out the population distribution of the Earth.

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