Yet another tropical cyclone has to be reported, this one threatening the East coast of India, and called NIVAR. It struck the coastal provinces of Tamil Nadhu, Puducherry and Andra Pradesh, causing heavy rainfall and strong winds on Wednesday and Thursday. Rain was expected to continue on Friday and in to Saturday.

Other areas experiencing extremely heavy rain, and landslides, and causing casualties this week included Colombia, Vietnam, Sumatra and Kalimantan in Indonesia, Italy and North West England.

Meanwhile, the Natal Witness says that Council has declared Msunduzi a disaster area after the hailstorm earlier this month caused extensive damage to roads, electricity and water networks, as well as municipal buildings, including Pietermaritzburg’s historic town hall, whose roof has developed leaks. A trail of damage was left with services in suburbs cut off for several days in some parts.

Pictures circulated on social media of hailstones the size of cricket balls and the damage has been assessed at R2.8 billion!

Bridges, storm water drains and pavements were damaged, and sanitary reticulation interrupted. A long list of expected costs was published, and regrets were voiced that the damage was worse because of the aging infrastructure in the sub-council. A lot of the repairs to be done needed doing anyway. This storm had just made everything worse, and the urgency greater.

The state of disaster announced means that resources can be redirected to get the repairs rolling faster than might otherwise have happened.

Apart from the damage to fixed property, there must be a lot of vehicles in KZN dimpled like golf balls by the hail. The cost to owners for repairs is mind-boggling, and with the economy in the state it is, and job losses and unemployment running very high, a lot of these repairs are just not going to happen. Depressing indeed!

Greg, G0DUB, has confirmed the idea to have another Webex in December, and the 12th December has been chosen as the date. He is thus proposing that the virtual meeting takes place from 13h00 UTC until 15h00 UTC on that day.

He says he had hoped to have feedback from the exercises everyone had planned in October/November but these were beaten by COVID-19, so he will bring everyone up to date about how they are growing DMR usage in the UK, giving feedback from the IARU Region 1 conference, and so on.

He invites any involved participants to suggest other items they may wish to bring up at the meeting.

Brian Jacobs, ZS6YZ, tells me that HAMNET Gauteng held a training event on Saturday 14th November 2020 at the Arrowe Park Scout Centre on the East Rand.

The training event took place in the form of a fox hunt or Amateur Radio Direction Finding (ARDF) as it is formally known in the amateur world. Being able to locate transmitters whether it is a Fox that has been hidden, or an ELB which is an emergency locator beacon of a downed aircraft or a missing hiker, or a rogue interferer causing problems on the amateur frequencies, is a skill all amateurs should master as one never knows when you will need to use this skill.

Two transmitters were hidden within the grounds at Arrowe Park which were used to teach the basic techniques of radio location and then another two were hidden in Brakpan on the East Rand which required the searcher to be mobile and perform a search over a greater area.

The morning spent practising to locate the hidden transmitters was thoroughly enjoyed by both the new HAMNET members, who were taught how to do it, and the more experienced members who honed their skills again. This is certainly one training event that puts some FUN into the more serious work that HAMNET is always preparing itself for.

Thanks, Brian. The fact that this is an out-of-doors event means that social distancing and ventilation is easy to maintain. I hope there are more events like this during the summer.

Herald Mail Media reported last weekend that amateur radio operators helped race officials keep tabs on participants in the JFK 50 Mile race on 21^st November.

Mike Spinnler, race director, said members of the Antietam Radio Association play a key role in the nation’s oldest ultramarathon. The radio operators’ work at the race started in an era before cell-phones, he said, and it’s still needed.

“There are so many dead spots on that course where cell-phones don’t work,” Spinnler said. “[Radio Amateurs] don’t have any dead spots. They’re our safety nets.”

M.E. “Butch” Eigenbrode, president of the Antietam Radio Association, said at least 30 volunteers were assigned to Saturday’s race, the 58th annual event. Several were stationed along the course at various spots,

This year, because of the COVID-19 pandemic and limits on crowds, the runners started in three waves, spaced 30 minutes apart. Eigenbrode is a race veteran, albeit as a radio operator. “I’ve done a lot of things” in those years, he said.

This year, his main role was coordinating the volunteers and assigning them to positions and duties. Following the COVID-19 rules about masking and social distancing provided an added complication, he said.

On race day, Eigenbrode planned to be out on the course, making sure people had what they needed and that things were working smoothly. Among other duties, the radio operators identified the male and female race leaders at various checkpoints along the course.

“We relay that back to the race officials,” Eigenbrode said.

They also let race officials know if an aid station needed more supplies, and they provided whatever other communications were needed. If a runner became exhausted, injured or did not make the cut-off times, radio association volunteers called for a radio-equipped van to take the person to the finish.

A volunteer swept at the back of the race, following the final runners, Eigenbrode said.

This of course sounds exactly like what South Africans do during the Comrades and Two Oceans Marathons. Good to know that the same kinds of events need the same kinds of assistance! Thank you to Herald Mail Media for excerpts from their report.

This is Dave Reece ZS1DFR reporting for HAMNET in South Africa.

We are still seeing reports about Hurricane IOTA. On Tuesday of this week, the ARRL issued a communique requesting all unnecessary traffic to be kept away from 14.325 and 7.268MHz, being the frequencies used by the Hurricane Watch Net and WX4NHC, the National Hurricane Centre. Mention was made of the Honduran Emergency net on 7.180MHz and the Nicaraguan Emergency net on 7.098MHz.

On Friday, the GDACS daily news flash said that the passage of IOTA over Central America (northern Nicaragua, southern Honduras, Guatemala and El Salvador) on 17-18^th November had caused very heavy rainfall over the region, triggering floods and landslides that resulted in several casualties and severe damage, only a few days after the devastating impact in the area of Hurricane ETA. Maximum sustained wind-speeds of 250 km/h had been experienced.

In Nicaragua, 36 fatalities, more than 62,914 sheltered people, and 53,130 families without a water service were reported. In Honduras, around 10,326 people were evacuated, 71,228 people were in shelters and 3 affected bridges were also reported. One fatality was reported in Panama.

In Colombia, media reported 7 fatalities (of which 2 were in Providencia Island, close to the coast of Nicaragua, where nearly all infrastructures had been damaged or destroyed). Other parts of the country were also severely affected by heavy rain and floods associated with a “La nina” phenomenon.

Over the following 24 hours, very heavy rainfall was forecast over Central America from south-eastern Mexico south to northern Venezuela, in particular over north-western Nicaragua, Honduras, El Salvador, Guatemala, and Belize.

Meanwhile, the ARRL Letter for 19^th November reported that the Hurricane Watch Net was forced to suspend operations at 03h00 UTC on November the 16^th, because of what HWN Manager Bobby Graves, KB5HAV, described as “deafening interference from a foreign AM broadcast station that came out of nowhere at 02h00 UTC.” At the time, the net had shifted to its 40-meter frequency of 7.268 MHz, collecting real-time weather and damage reports via amateur radio.

“This was heart-breaking for our team, as the eyewall of Iota was just barely offshore,” Graves said. “The storm had weakened slightly to a Category 4 hurricane with sustained winds of 240 km/h.” After activating at 13h00 UTC, the net was able to collect and forward reports from various parts of Nicaragua and Honduras via WX4NHC throughout the day for relay to forecasters at the National Hurricane Center in Miami. Iota was the most powerful storm on record to make landfall this late in the hurricane season.

Graves said the very strong AM signal was on 7.265 MHz. “From my location, it was S-9,” he told ARRL. “You could not hear anything but the BC station.” Graves noted that other foreign broadcast stations were heard from 7.265 to 7.300 MHz and with splattering close by.

The offending signal appeared to be from a 500 kW broadcaster in Turkey. Graves said the HWN has a long history on 7.268 MHz, but that the net is now considering a 40-meter frequency below 7.200 MHz.

Stations handling emergency traffic during the response to Category 5 Hurricane Iota had requested clear frequencies on November 16^th to avoid interfering with the HWN and with WX4NHC, as well as with a Honduran emergency net operation on 7.180 MHz and a Nicaraguan emergency net operating on 7.098 MHz. It’s not known if those nets were also affected by interference from the numerous broadcasters on 40 meters.

In passing, remember IARU region 1 does not have access to the 40m band above 7.200MHz, and so the Turkish AM broadcast station had every right to be there. Sadly ionospheric conditions were so good that their AM signal was being heard in the Caribbean, just when it was not needed!

The meeting of HAMNET Directors and Deputy Directors seems to have gone well on Wednesday evening past, and a document has been prepared by Brian Jacobs ZS6YZ, laying out the exact emergency frequencies for all modes and all bands. The document needs a small amount of tweaking still, but will be distributed far and wide, once the final version is complete. Once you receive it, as a HAMNET member please have it always to hand, to be accurate when you call for emergency aid.

Sad news from the world of radio astronomy was received on Friday when it was announced that the fixed 350 metre Radio Astronomy dish at Arecibo in Puerto Rico is to be decommissioned, after it was damaged earlier this year. One of the supporting cables keeping the feed horns floating above the dish snapped, causing equipment to crash into the dish breaking a large portion of the reflector. The repair of the dish and the restringing of the cable have been deemed to be too dangerous to attempt, and so the dish will fall silent. This is very unfortunate for the entire team of radio astronomers who work there, as well as the amateur radio club established there, which has been lucky to make use of listening time on the dish. Remember though that China has in the meanwhile built a 500 metre fixed dish in the ground, called FAST, so all is not lost. We hope that radio astronomy will remain the shared science it always has been, and that FAST will provide time and listening to all who need it.

Those of you who look at the stars will have noticed the close association these nights, high in the sky, of a crescent moon, with Jupiter to the East of it, and Saturn only a little further East of that. Well, on 21^st December, if you remember to look, you will see Jupiter and Saturn separated by a distance only 1/5 of the diameter of the moon, making them look like a double planet. They will be more closely associated than they have been since the Middle Ages, and Patrick Hartigan, a Rice University Astronomer says you’d have had to go back to the 4^th March 1226, to see a closer alignment between these objects visible in the night sky.

The pair will be visible over to your West, and soon after sunset, and I’m not sure where the moon will be relative to all this, but I suspect it won’t interfere with viewing.

So a good pair of binoculars, or a small telescope, will give you an excellent display, all within one field of view. Mark your calendar now.

Oh, and the next available viewing like this? March 15^th, 2080. You have been warned!

This is Dave Reece ZS1DFR reporting for HAMNET in South Africa.

HAMNET in the Western Cape lost a long-standing member last week, when Henk Toxopeus ZS1ACD became a silent key (SK). We were notified by his wife Margareta, ZS1TOX that Henk has been in poor health for some time, and finally slipped away on Friday the 6^th of November.

Henk and Margareta were keen yachts-people, and had sailed the seas for many years before coming back to live in the Tableview area. Henk had not been active in HAMNET circles since before the Coronavirus pandemic started to take control of our lives.

Our sincere condolences to Margareta, a voice often heard reading the SARL Afrikaans News bulletin on local repeaters for the Boland Amateur Radio Klub (BARK).

I didn’t think I’d be telling you about the third Typhoon to strike the Philippines and go on to Vietnam in as many weeks, but now we have Tropical Cyclone VAMCO-20, which was expected to graze Catanduanes Island – which was devastated by Typhoon GONI less than two weeks ago – before making landfall on the most populous island of Luzon later on Wednesday or early on Thursday.

Destructive winds and torrential rain were expected in parts of central and southern Luzon, the state weather forecaster said.

About 50,000 people living in the typhoon’s path were to be ordered to leave their homes, said regional Civil Defence spokesman Gremil Alexis Naz.

The Bicol region, which VAMCO will cross as it heads towards Manila, is still reeling from deadly typhoons MOLAVE and GONI, which killed dozens of people and left thousands of families homeless.

Swathes of the region remain without power and with only limited or no telecommunication services after GONI – the most powerful typhoon this year – toppled power lines, destroyed houses and flooded roads.

Pre-emptive evacuations of around 400,000 people were credited with saving many lives.

Evacuation efforts on Catanduanes have been complicated this time, however, after GONI destroyed some of its emergency shelters.

VAMCO’s winds were expected to reach a peak intensity of 130-155km/h before it made landfall, the weather forecaster said. The typhoon was expected to dump heavy rain in Manila and nearby provinces as it swept across the already-sodden country.

The weather service also warned of flooding, landslides and storm surges several metres high along parts of the east coast and in the capital.

Friday’s news reports say 1.6 million people are affected by the storm, and at least 42 deaths have been reported. Windspeeds on Luzon were measured at 150 km/h, while storm surges reached the height of a double storey building.

Since yesterday (Saturday) it has been threatening the Vietnamese coast, and should make landfall today. Hopefully it will have dissipated a bit after its passage across the Philippines.

I also didn’t expect still to be talking about Hurricane ETA-20, which finally blew itself out after affecting Nicaragua, Honduras, Cuba, Florida, and finally dumping large quantities of rain on the Carolina States. It has proved to be the strongest hurricane since a Cuban one in 1932. It finally dissipated on Friday the 13^th, after giving the national Hurricane Warning Centre a hard time for longer than a week.

Hot on its heels, a Tropical depression started forming in the central Caribbean Sea on Friday, and is forecast to turn into Hurricane IOTA before approaching Central America early this coming week.

Once the storm nears Central America, it “has the potential to produce 500 to 750 mm of rain with a focus across northern Nicaragua and Honduras,” the Hurricane Centre said. “This rainfall would lead to significant, life-threatening flash flooding and river flooding, along with landslides in areas of higher terrain.”

Several Central American countries are still reeling from Hurricane ETA, which killed at least 120 people and left scores missing when it hit earlier this month.

“I am greatly concerned we may soon have another major disaster on our hands in Central America if this Caribbean tropical system pans out like we suspect,” Accuweather hurricane expert Dan Kottlowski said.

I’m pleased to inform you that, after a long delay caused by factors related to the pandemic, the SARL Council has formally appointed Grant Southey ZS1GS as National Director of HAMNET, and Brian Jacobs ZS6YZ as Deputy National Director. These fine gentlemen have been in acting leadership since the end of 2019, and it is nice formally to congratulate them on their appointments. HAMNET has been running smoothly for the past year or so, so clearly their appointment was a good idea!

As mentioned in last week’s bulletin, the Jonkershoek Mountain Challenge trail run last Sunday was affected by rainy and cold weather, but fortunately, due to the change in route announced last Friday, there were no serious incidents.

Some 290 competitors ran one of 3 distances, and 12 operatives, consisting of Mountain Club members, Medics, and HAMNET members were positioned along the route.

Strict COVID protocols were in place, and the runners of the longest race were required to carry bad weather protective gear and emergency sources of food and water in case they got stuck on the mountain.

The radios and frequencies of the Wildrunner organisation were used, and Michael ZS1MJT tells me that the organizers were most grateful for the efficiency of our team. He thanked each and everyone involved as, without them, the event would not have been such a success.

I’m relieved that conditions weren’t as bad as predicted, and that there were no casualties. Thank you for the report Michael!

On United Nations Day, October 24^th, the Alexanderson Alternator station SAQ in Sweden transmitted a message in CW on 17.2 kHz urging unity in the face of the COVID-19 pandemic. The message transcript follows:

“CQ CQ CQ DE SAQ SAQ SAQ This is Grimeton Radio/SAQ in a transmission using the Alexanderson 200 kW alternator on 17.2 kHz. The global COVID-19 pandemic challenges people and nations to unite, to minimize the negative consequences for individuals and societies, and to uphold the advancements in public health made in recent decades. Good health and wellbeing is a prerequisite for a peaceful and sustainable global development, and health equity cannot be achieved without peace and human security.”

The message was signed by Anders Tegnell, chief epidemiologist of Sweden’s Public Health Agency. SAQ received some 400 listener reports from all over the world, with just 20 reporting they were unable to copy the message. Reports came from Russia, Japan, and the US, as well as Tasmania, 16000 km away.

This is an amazing feat for the transmitter which is now 110 years old.

This is Dave Reece ZS1DFR reporting for HAMNET in South Africa.

Since Monday the 2^nd, storm watchers have been viewing Hurricane ETA-20 with alarm as it bears straight down on Nicaragua from its East. At first wind-speeds of 185 km/h were forecast and 133000 people were in the red zone of danger in front of the category one hurricane. By Thursday, wind-speed forecasts were upped to 240 km/h, and Honduras was also predicted to be in its path.

On Tuesday, Greg G0DUB reported that the Emergency Services of Radio Amateurs and Emergency Networks were active in Nicaragua, Honduras, and Guatemala, using HF comms on 7098, 7120 and 3798 kHz, as well as DMR Talkgroup TG710. Amateurs are asked to avoid these frequencies if they do not have emergency traffic to pass.

The ARRL reported on Tuesday that WX4NHC at the National Hurricane Centre (NHC) activated, monitoring 14.325 MHz and 7.268 MHz, the frequencies used by the Hurricane Watch Net (HWN), as well as the VoIP Hurricane Net, Winlink, APRS, and other modes.

As of 21h00 UTC on Tuesday, the eyewall of what the NHC was calling “extremely dangerous Hurricane Eta” was making landfall just south of Puerto Cabezas, Nicaragua. The NHC warned of a life-threatening storm surge, catastrophic winds, flash flooding, and landslides across portions of Central America. Eta was moving to the west at a rather sluggish 5 km/h. The NHC said Eta was forecast to move farther inland over northern Nicaragua through Wednesday morning, and then across central Honduras by Thursday morning.

“This will be another historic hurricane to hit this area during a historic active season,” said Assistant Amateur Radio Coordinator Julio Ripoll, WD4R, at the NHC.

Ripoll asked stations to relay any reports from stations or ships at sea in the affected area, with or without weather data, for use by NHC forecasters.

“NHC appreciates all the surface reports from the affected area during hurricanes as they fill in gaps of not just weather data, but also give them real-time, first-person perspective of what is actually happening on the ground,” Ripoll said.

News reports on Saturday afternoon report as many as 2150 deaths so far.

Grant Southey ZS1GS, National Director of HAMNET, has invited his Regional Directors and their deputies to attend a virtual meeting on Wednesday the 18^th November. Subjects to discuss include feedback from the National Director, ongoing projects and new memberships. I wish them well in their deliberations next Wednesday.

The weekly ARRL Letter for 5^th November says that Researchers at the National Institute of Standards and Technology (NIST) have devised and demonstrated a system that could dramatically increase the performance of [fibre-optic] communication networks while enabling record-low error rates in detecting even the faintest of signals. This has the potential to cut the total amount of energy required for state-of-the-art networks by a factor of 10 to 100. The proof-of-principle system consists of a novel receiver and corresponding signal-processing technique, entirely based on the properties of quantum physics and able to handle extremely weak signals with pulses that carry many bits of data.

“We built the communication test bed using off-the-shelf components to demonstrate that quantum-measurement-enabled communication can potentially be scaled up for widespread commercial use,” said Ivan Burenkov, a physicist at the Joint Quantum Institute, a research partnership between NIST and the University of Maryland. Burenkov and his colleagues reported the results in Physical Review X Quantum.

“Our effort shows that quantum measurements offer valuable, heretofore unforeseen advantages for telecommunications leading to revolutionary improvements in channel bandwidth and energy efficiency,” Burenkov added.

Modern communications systems work by converting information into a laser-generated stream of digital light pulses in which information is encoded — in the form of changes to the properties of the light waves — for transfer and then decoded when it reaches the receiver. The train of pulses grows fainter as it travels along transmission channels, and conventional electronic technology for receiving and decoding data has reached the limit of its ability to precisely detect the information in such attenuated signals.

The signal pulse can dwindle until it is as weak as a few photons — or even less than one on average. At that point, inevitable random quantum fluctuations, called “shot noise,” make accurate reception impossible by normal (“classical,” as opposed to quantum) technology because the uncertainty caused by the noise makes up such a large part of the diminished signal. As a result, existing systems must amplify the signals repeatedly along the transmission line, at considerable energy cost, keeping them strong enough to detect reliably.

The NIST team’s system can eliminate the need for amplifiers because it can reliably process even extremely feeble signal pulses: “The total energy required to transmit one bit becomes a fundamental factor hindering the development of networks,” said Sergey Polyakov, senior scientist on the NIST team. “The goal is to reduce the sum of energy required by lasers, amplifiers, detectors, and support equipment to reliably transmit information over longer distances.”

Southgate Amateur Radio News has reported that German TV broadcaster WDR aired a news story about radio amateur Theresa DC1TH who is part of the Neumayer-III base 2021/22 overwintering crew.

She is expected to be on-the-air from Antarctica with the callsign DP0GVN using the QO-100 geostationary satellite amateur radio transponder. Theresa DC1TH visited AMSAT-DL at the amateur radio facility at the Bochum radio observatory for some brief training in the use of QO-100 before traveling to the Neumayer III base.

AMSAT-DL provided the QO-100 satellite ground station for DP0GVN nearly a year ago, and it has already been operated by Roman HB9HCF.

It intrigues me that satellite QO-100’s geostationary signal can be heard by stations even at the North and South Poles. I’m sure the Yagi’s needed to complete the QSO’s at 90 degrees latitude need no elevation rotators to access QO-100. In fact their signals might need just to brush the surface of the snow to be received by the satellite!

Finally, Michael ZS1MJT tells me that today’s Jonkershoek Mountain Challenge trail run has had its route altered to a safer one, as a result of a strong cold front with heavy rain and strong winds which has battered the Western Cape since Friday. Northerly winds gusting at 60 km/h at sea level, and nearly an inch of rain between Friday and Saturday, may contribute to treacherous running and dangers of hypothermia in the Jonkershoek pass today.

This is Dave Reece ZS1DFR reporting for HAMNET in South Africa.

There has been a string of Typhoons in the area of the Philippines and bearing down on the East coast of Vietnam. Last weekend, news started to arrive of Typhoon Molave approaching Vietnam, with the potential to cross into Laos and Cambodia. A day or two later, Typhoon Goni, with maximum expected wind-speeds of 278 km/h, whipped across the Northern tip of the Philippines and headed off towards Vietnam as well. And on Friday, Dani, YB2TJV, reported that the Philippines EmComm organization was standing by for Typhoon Rolly, with expected wind-speeds of 200 km/h. Their EmComm coordinator, Mr Jojo DU1VHY is requesting all operators to avoid 7.095 MHz and 7.110 MHz, the IARU Region 3 EmComm frequencies.

On the other side of the globe, Hurricane Zeta has spent time in the Bay of Mexico this week, potentially coming ashore on the coastline of Louisiana, expected to affect about 850000 people living there with wind-speeds up to 176 km/h. The
ARRL reported that WX4NHC at the National Hurricane Centre in Miami was activated at Midnight UTC on Tuesday to monitor 14.325 and 7.268 MHz as well as the VoIP Hurricane net and other resources from there on.

Not to be outdone by violent windstorms, Turkey and Greece were struck by a magnitude 7 earthquake at a depth of 10km, just offshore in the Mediterranean at about midday UTC on Friday. Sotirios, the Amateur Radio Head of Greece’s EmComm Agency, reported to Greg, G0DUB, that there were some injured people being transported to Samos Hospital, and there were damaged houses in the Karlovassi area. Sotirios said his operators were online with Greek Civil Protection, and also had ham operators in their Operation Centre.

Greg G0DUB has also announced that IARU Region Two (the Americas) has appointed a new Emergency Communications Coordinator in the person of Dr Carlos A Santamaria CO2JC. He succeeds Dr Cesar Pio Santos HR2P, who recently retired after 12 years of service.

Dr Santamaria has extensive experience serving as Federacion de Radioaficionados de Cuba coordinator of the National Emergency Network (REN) both in exercises and communications during activations in the event of hurricanes and even earthquakes, maintaining contact with the coordinators of other Caribbean countries to protect emergency frequencies.  He also advises the Cuban headquarters of the United Nations Organization on Emergency communications during disasters, so is an ideal candidate for the post. I am sure we join all countries in wishing Dr Santamaria well in his new post.

HAMNET in the Western Cape will be assisting next Sunday the 8^th of November in the running of the Jonkershoek Mountain Challenge cross-country race. Eight operators have been asked for, and Michael, ZS1MJT, our Regional Director tells me all posts have been filled. I hope to have a report of the race in the bulletin two weeks from now.

It seems strange to be discussing these effects only in 2020, but Brett Carter, writing in MENAFN on 27^th October, talks about the effects of atomic bomb tests on our upper atmosphere, and the potential to damage the ionosphere. He says:

“Indeed, surface and atmospheric (high-altitude) detonations of nuclear weapons can have short-term and long-term effects.

“One short-term effect was a temporary blackout of long-distance high-frequency (HF) radio communication over the surrounding area. But this radio communication blackout was not a result of the nuclear explosions destroying the ionosphere.

“On the contrary, the nuclear detonations temporarily increased the natural level of ionisation in the upper atmosphere.

“In long-distance HF radio communications, the radio waves are bounced back and forth between the ionosphere and the Earth’s surface. This means you don’t need to establish a line of sight for HF radio communication.

“Many applications, such as emergency services and aircraft/maritime surveillance, rely on this mode of HF radio propagation.

“But this radio communication scheme only works well when there is a reflective E or F layer, and when the absorbing D layer is not dominant.

“During regular daytime hours, the D layer often becomes a nuisance because it weakens radio wave intensity in the lower HF spectrum. However, by changing to higher frequencies you can regain broken communication links.

“The D layer may become even more dominant when intense X-ray emissions from solar flares or energetic particles are impacting the atmosphere. The absorbing D layer then breaks any HF communication links that traverse it.

“Nuclear detonations also produce X-ray radiation, which leads to additional ionisation in all layers of the ionosphere. This makes the F layer more reflective to HF radio waves, but, alas, the D layer also becomes more absorptive.

“This makes it difficult to bounce radio waves off the ionosphere for long-distance communication soon after a nuclear explosion, even though the ionosphere stays intact.

“Beyond additional ionisation, shock waves from nuclear detonations produce waves and ripples in the upper atmosphere called ‘atmospheric gravity waves’ (AGWs).

“These waves travel in all directions, even reaching the ionosphere where they cause what are known as ‘travelling ionospheric disturbances’ (TIDs), which can be observed for thousands of kilometres.

“Bomb blasts are not the only things that cause disturbances in the atmosphere.

“In September 1979, there were reports of bright flashes of light off the South African coast, igniting theories South Africa had nuclear weapon capabilities.

“Analysis of ionospheric data from the Arecibo Observatory, in Puerto Rico, confirmed the presence of waves in the ionosphere that corroborated the theory of an atmospheric detonation. But whether the detonation was artificial or natural could not be determined.

“The reason for the ambiguity is that meteor explosions and nuclear detonations in the atmosphere both generate AGWs with similar characteristics.

“The 2013 Chelyabinsk meteor explosion in Russia generated waves in the ionosphere that were detected all across Europe, and as far away as the United Kingdom.

“Volcanic eruptions, such at the 1980 Mount St Helens eruption in the US, and large earthquakes, such as the 2011 Tohoku earthquake in Japan, are other examples of energetic processes at the ground impacting the upper atmosphere.

“Another well-known source of ionospheric disturbances is a geomagnetic storm, typically caused by coronal mass ejections from the Sun or solar wind disturbances impacting Earth’s magnetosphere.

“In summary, nuclear detonations can impact the upper atmosphere in many ways, as do many other non-nuclear terrestrial and solar events that carry enormous energy. Fortunately, the interference isn’t permanent.”

Well, after all these years, this news is certainly reassuring!

This is Dave Reece ZS1DFR reporting for HAMNET in South Africa.