"Wavescan" is a weekly program for long distance radio hobbyists produced by Dr. Adrian M. Peterson, Coordinator of International Relations for Adventist World Radio. AWR carries the program over many of its stations (including shortwave). Adrian Peterson is a highly regarded DXer and radio historian, and often includes features on radio history in his program. We are reproducing those features below, with Dr. Peterson's permission and assistance.
Wavescan N443, August 20, 2017
Eclipse Radio: Past & Present
Tomorrow, Monday, August 21, a spectacular total eclipse of the sun will be visible right across the United States, with the path of totality stretching from Oregon to South Carolina. The pathway of totality will be 70 miles wide, and the eclipse shadow will move along this narrow corridor at a supersonic speed.
The total eclipse of the light from the sun, due to the moon intervening in between the sun and the earth, will begin over the North Pacific Ocean at sunrise. In fact, at that location, the sun will rise in total obscurity, a very rare occurrence.
The eclipse will enter the United States on the Oregon coast at Lincoln Beach at 10:15 am local time at a speed of nearly 3,000 miles per hour, 2,955 miles per hour to be exact. The path of totality of the eclipse will travel across the United States in a slightly curved pathway for an hour and 33 minutes. It will then exit the United States at an isolated beach at Cape Romain in South Carolina at 2:49 pm local time at a speed of 1,502 miles per hour, a reduction in velocity of approximately 50%.
It is anticipated that many millions of people will view this spectacular cosmic event, and for many it will be a once in a lifetime occurrence. Many people who live and work near the pathway of total obscurity will travel into the curved pathway to view the total eclipse, and multitudes from other countries have poured into the United States for the occasion.
Then, of course, there will be many amateur radio operators who will sit at their electronic equipment during the time of the eclipse in their locality so that they can take advantage of the enhanced propagation during the 2-1/2 minutes of total obscurity.
So what happens to radio signals during an eclipse of the sun? Back on January 24, 1925, there was a spectacular total eclipse of the sun over the northern areas of the United States, and for the first time ever, radio scientists were able to make an intensive study of propagation conditions during the period of totality.
The signals from two radio transmitters at Schenectady in upper New York State were monitored in New York City for five days in a row; before, during and after the 1925 eclipse. The daily time for monitoring the signals from the two radio broadcasting stations was from 6:30 am to 11:00 am, remembering that the time of total obscurity on Eclipse Day itself was at 9:11 am, local time.
The two broadcasting stations whose signals were monitored in New York City were mediumwave WGY with 5 kW on a wavelength of 380 metres (790 kHz), and 2XI with probably just 1 kW on 75 metres (4000 kHz). The distance between the transmitters in Schenectady and New York City was approximately 160 miles.
By comparing the paper-tapes for the five days, upon which was etched the comparative signal strengths from both the mediumwave and shortwave transmitters, the radio scientists at RCA and AT&T in New York came to the following three conclusions:
The longwave signals from England on 12,500 metres (24 kHz) were also studied by RCA radio scientists at both Riverhead on Long Island and at Belfast in Maine. They discovered that the longwave signal behaved with the same sunrise-sunset pattern as the mediumwave signal, taking into account though that the eclipse traversed both localities, North America and England.
There was another eclipse of special radio interest that occurred over Europe and Asia on June 19, 1936. The signals from the following stations were studied by radio scientists in Japan:
|JOIK||830 kHz||0 kW||Sapporo|
As would now be expected, the monitoring observations in Japan in 1936 exhibited the same propagation pattern as normally experienced at sunset and sunrise.
For the festive events associated with tomorrow's 2017 total eclipse, Thomas Beebe in Marion Illinois has obtained a special short term amateur license for an eclipse radio station. His license for station W9E permits five days of amateur communication for all things related to the eclipse event.
A special news release from TV station WSIL in Carbondale, Illinois mentions amateur station W9E in Marion and its special eclipse coverage.
The United States Post office issued a special postage stamp earlier this year that focuses nationwide attention upon the 2017 total eclipse. This special stamp will change color if the warmth of the finger is applied to it.
What Happens to a Radio Signal During an Atomic Explosion?
It is very evident that there is no similarity between a Total Eclipse and an Atomic Explosion. A Total Eclipse brings an awesome darkness to the land, and an Atomic Explosion brings highly destructive devastation to the land.
However, in spite of the massive differences between a Total Eclipse and an Atomic Explosion, there is one common occurrence for them both. A Total Eclipse and an Atomic Explosion: They both produce changes in the upper atmosphere that impact the propagation of radio signals.
Johnston Atoll is a cluster of four small coral islands 860 miles south west of Hawaii, with a total area of just one square mile. There has never been a local population on the atoll, though at times there have been a thousand or more American service personnel on duty on these islands.
During nearly a score of years running from 1958 to 1975, the United States conducted many rocket fired nuclear tests in the atmosphere, at high levels and low levels. Radio monitoring in Hawaii, Japan and New Zealand demonstrated that the propagation of radio signals across the explosion zone at almost all frequencies was greatly reduced, as was also the local atmospheric noise (QRN). It was stated that apparently the nuclear explosion produced an absorption effect of all radio transmissions, R/T and QRN.
Immediately after a nuclear explosion, all R/T and QRN disappear, though soon afterwards there is a partial recovery, though full recovery may not become evident, sometimes for days or even weeks. One report stated that the disturbance pattern for all radio signals and all atmospheric noise was similar to that which occurs during a violent sun flare.
At Rarotonga in the Cook Islands, an international radio monitor there reported a complete blackout of all radio signals for around five days, except for enhanced signals at the very high end of the radio frequency spectrum, and also at the very low end of the electronic frequency range even during the day. The Quartz Hill Receiving Station in Wellington, New Zealand reported an enhanced signal strength from the BBC transmission in England on 25 MHz (11 metres).
Interestingly, the United States installed a special shortwave transmitter on Johnston Island specifically for the low level atmospheric nuclear tests in 1962. This transmitter was on the air with specific tone signals on 12020 kHz, similar to the tones from the chronohertz station WWVH in Hawaii.
At the time of the explosion at 0900 UTC on July 9 (1962), Quartz Hill in New Zealand heard a click from the Johnston Island transmitter, and then total silence. We are not aware that any international radio monitors received any QSLs for the broadcasts from this unique transmitter.
During this nuclear test explosion, Quartz Hill was also listening to 2UE Sydney on 950 kHz, their own 1YA in Auckland on 760 kHz, Radio Australia, Shepparton on 7190 kHz, VOA Honolulu on 9650 kHz, and WWV in Boulder, Colorado on 10000 kHz. In all cases, at the time of the explosion, the signal was either completely lost, or seriously diminished. (It should be noted that WWVH in Hawaii was off the air for 3 minutes after the top of each hour back in those days.)
A listener in Invercargill at the bottom of the South Island of New Zealand reported that the only mediumwave station in the North Island that could be heard down south was the powerful 100 kW 2YA which was on 570 kHz back then. However, even then, the 2YA signal was noted at a much lower level than normal.
During the months of August and September in the year 1958, the United States conducted a series of secret nuclear tests in the South Atlantic. These tests were performed at an extremely high altitude, though the results as far as radio propagation was concerned were very similar to other known nuclear tests in the South and Central Pacific.
We express appreciation for all of the above information on radio propagation after a nuclear explosion to websites that are readily accessible on the internet. We are grateful also to the New Zealand Journal of Geology and Geophysics for indirect quotations from their information which is available for research and teaching purposes.
QSL Letter Verifies Nuclear Radio Station
At the end of our program last week, we did indicate that our QSL of the week for this week would be a QSL card from a Mediterranean Station heard in South America. However, we have come across a QSL letter verifying the reception of programming from a nuclear radio station. So let's postpone the usage of the information about the Mediterranean radio station, and instead, we will present the information about the nuclear radio station. This is the story.
The United States conducted a series of atomic tests at the Mercury site in Nevada in May 1955. They installed a mediumwave station into a building at the site and it was on the air several evenings beginning on April 26, and it was blown off the air at the time of the nuclear explosion on May 25.
The programming from this unique radio station consisted of a test announcement on a repetitive tape recording; and the antenna system was a vertical long wire attached to a 150 feet tall guyed mast.
Mr. Norman Maguire of Albuquerque in New Mexico was fortunate enough to hear the transmissions from this temporary experimental station and he sent a reception report for which he received a letter of confirmation. The full page letter from the Federal Civil Defense Administration in Battle Creek, Michigan verified the broadcasts from experimental station KO2XDN with 250 watts on 1240 kHz.