Shortwave Radio Diversity Reception
Shortwave radio diversity reception provides a way to combine several fluctuating signals and get a solid result. It provided the foundation for most radio news received in America for years.
During World War II, most countries around the world relied on Britain’s shortwave radio broadcasts for the latest news from Europe. In the days before transatlantic audio cables or satellites, distant news traveled fastest by radio. Networks in the America’s, Australia, New Zealand and elsewhere re-broadcast shortwave radio news domestically.
Getting reliable, good quality audio programs over shortwave is always a challenge because of fading. As signals bounce off the ionosphere, they split over multiple paths. Often they fade and flutter, sometimes significantly, as the nature of the layers change with time. Here are several examples of shortwave signals fading, so you know what it sounds like. Skywave radio signals are subject to complex patterns of travel and interference.
Eventually, domestic networks found a clever way to get better audio from these distant signals.
[…]Diversity reception works like this. Instead of one signal, you monitor several signals at once and blend them together. Harold Beverage and RCA pioneered work on shortwave radio diversity reception in 1920’s. Commercial solutions arrived by 1933. Typically, you would use three receivers with three different antennas, spaced 1,000 feet apart. When antennas are widely spaced, signals arrive with different fading. Just combine the signals and let the strongest signal dominate. As long as the fading is not correlated across all three antennas, improvement can be significant.
Diversity reception can be achieved in several ways. The most popular – spatial diversity – is described above. Other methods include frequency diversity – mixing together the same program received on several different channels.[…]
I am very happy to share that the BBC Radio 4 program Wireless Nights, Series 5, features our own community member London Shortwave this week. The show aired tonight (March 27) and the audio is now available to stream via the Radio 4 website. I’ve also embedded the audio below:
Here’s the description of the show from Radio 4:
Jarvis Cocker navigates the ether as he continues his nocturnal exploration of the human condition.
On a night voyage across a sea of shortwave he meets those who broadcast, monitor and harvest electronic radio transmissions after dark.
Paddy Macaloon, founder of the band Prefab Sprout, took to trawling the megahertz when he was recovering from eye surgery and the world around him became dark. Tuning in at night he developed a ghostly romance with far off voices and abnormal sounds.
Artist Katie Paterson and ‘Moonbouncer’ Peter Blair send Beethoven’s Moonlight Sonata to the moon and back, to find sections of it swallowed up by craters.
Journalist Colin Freeman was captured by the Somali pirates he went to report on and held hostage in a cave. But when one of them loaned him a shortwave radio, the faint signal to the outside world gave him hope as he dreamed of freedom.
And “London Shortwave” hides out in a park after dark, with his ear to the speaker on his radio, slowly turning the dial to reach all four corners of the earth
Jarvis sails in and out of their stories – from the cosmic to the captive – as he wonders what else is out there, deep in the noise
Producer Neil McCarthy.
I found Megahertz absolutely captivating! I’m very impressed with how all of the personal adventures in radio, including an array of motivations, were weaved together.
And brilliant job, London Shortwave! It was fun to go on a park outing with you and your spectrum capture gear!
(Source: CatholicCulture.org via London Shortwave)
As Vatican Radio ends short-wave broadcasts, others expand
As Vatican Radio closes an era by ending its short-wave transmissions, other broadcasters are stepping up their involvement in the short-wave field, notes Sandro Magister of L’Espresso.
Msgr. Dario Vigano, the prefect of the Vatican’s new Secretariat for Communications, has cut off short-wave broadcasts—long the heart of the Vatican Radio operation—in a move to cut costs and move toward emphasis on communicating through the internet. But Magister observes that short-wave transmissions retain their “unique ability to arrive as a free and true voice even in the most geographically and politically inhospitable places of the world.”
The Italian Vatican-watcher reports that other broadcasters are expanding their short-wave offerings. BBC has invested £85 million (almost $105 million) in a drive to expand its short-wave capacity. And Japan’s NHK network has inquired about purchasing the broadcasting station at Santa Maria di Galeria, just outside Rome, that Vatican Radio will no longer use.
Read this article at CatholicCulture.org.
This article originally appeared on the London Shortwave blog.
As many of my readers and followers will already know, these days I mostly enjoy listening to shortwave radio via the outdoor spectrum captures I make in my local park. Although I have built a system that helps me deal with urban radio interference at home, some of the weaker signals still can’t make it through the indoor noise. Since I have a limited amount of time for making outdoor trips, capturing entire portions of the spectrum allows me to record a lot of shortwave signals simultaneously, which I can then explore individually at a later time. However, these trips still need to be carefully planned because the time of the day and the time of the year both affect long-distance signal propagation, and do so differently depending on the frequency range. For example, signals on the 16 meter band are usually at their strongest during the daylight hours, whereas the 31 meter band is at its busiest around sunrise and sunset. Because my current portable recording set-up allows me to capture only 10% (3 MHz) of the shortwave spectrum at any one time, I decided to carry out a systematic exploration of activity on the shortwave bands to help me time my outings so as to capture as many signals as possible during each trip.
Luckily, I didn’t need to make any of my own measurements for this. For over a year, the wide-band WebSDR at the University of Twente has allowed its users to see what the shortwave spectrum has looked like over the past 24 hours in a single image. More recently, however, the creator of the service, Pieter-Tjerk de Boer PA3FWM, has opened up his spectrum image archives, so it is now possible to see the past conditions of the bands on any single day in the last two years. Intrigued by how band activity changes depending on the time of the year, I created a timelapse animation of these images by taking two from each calendar week and lining them up in sequence. With Pieter-Tjerk’s kind permission, I share this animation below.
First, a really fast version to illustrate the broad effects the time of the year has on peak activity times across the bands:
The X axis represents the frequency and the Y axis is the time of day, starting at the top. Conventional wisdom about band behaviour can be easily confirmed by watching this video: the 60m, 49m and 41m bands are mostly active after dark, with the 60m and the 49m bands being generally busier during the winter months. The 31m band is most active around sunset, but carries on all night until a few hours after sunrise. The 25m band is active during sunrise and for a few hours afterwards, and around sunset during the winter months, but carries on all night during the summer. Peak activity on the 22m and 19m bands is also clustered bi-modally around the morning and the evening hours, though somewhat closer to the middle of the day than on the 31m and the 25m bands. The 16m band is mostly active during the daylight hours and the 13m band is quiet throughout the year except for the occasional ham contest.
It almost seems as though someone positioned in the middle of the image’s right edge (corresponding to noon UTC) is shining two flashlight beams on the bands in a V-shaped pattern, and is changing the angle of this pattern depending on the time of the year: wider in the summer and narrower in winter. Here’s a slower version of the animation that shows some finer week-on-week changes:
Thanks to this data being made freely available, visualising and understanding these dynamics will help me schedule my spectrum capture outings in the weeks and months ahead.
(Source: RNZ Press Release via London Shortwave)
Press release: Following the ABC’s decision to cut shortwave radio transmission in the Pacific, Radio New Zealand International wants to reassure our listeners that we are committed to our Pacific broadcast partners.
Radio New Zealand International (RNZI) continues to serve people across the Pacific region, delivering essential day to day news and information and providing a vital lifeline in times of natural disaster.
RNZ CEO, Paul Thompson, has confirmed that there will be no reduction in Radio New Zealand’s commitment to its Pacific broadcast partners. His reassurance comes as Radio Australia closes its international shortwave transmission service to Papua New Guinea and the Pacific.
Paul Thompson has emphasised the importance of RNZI’s 25 year relationship with New Zealand’s Pacific neighbours.
“Remote parts of Papua New Guinea, Solomon Islands and Vanuatu who may be feeling the loss of the ABC can rest assured RNZI will continue to provide independent, timely and accurate news, information and weather warnings as well as entertainment to its Pacific listeners.”
RNZI has been broadcasting since 1990 to the Pacific and is regarded as the authoritative voice of the Pacific. It can be heard across the region and has proven to be a vital lifeline during times of disaster. In 2007 RNZI was named international Radio Station of the Year by the Association for International Broadcasting (AIB).
RNZI broadcasts timely cyclone and tsunami warnings via shortwave and can continue to be heard should local broadcasters go off-air due to a cyclone or other disaster.
Paul Thompson said the essential nature of Radio New Zealand’s role in the Pacific has been regularly underlined by the positive feedback to RNZI following cyclone and tsunami alerts.
“A Vanuatu villager has told our reporter Koroi Hawkins that he knew to take shelter during Cyclone Pam just because of the warnings broadcast on RNZI. At times like this we are the essential voice of the Pacific ” See attached photograph.
RNZI’s coverage of the aftermath of Cyclone Pam in Vanuatu in 2015 won RNZI reporter Koroi Hawkins a silver medal at the prestigious New York Festival Radio Awards in 2016.
RNZI broadcasts in digital and analogue short wave to radio stations and individual listeners across the Pacific region.
Around twenty Pacific radio stations relay RNZI material daily, and individual short-wave listeners and internet users across the world tune in directly to RNZI content.
The RNZI signal can sometimes be heard as far away as Japan, North America, the Middle East and Europe. RNZI also provides rich content for online users through our website
How to listen to RNZI
For further information contact:
Walter Zweifel, RNZI News Editor +644 474 1432
Adrian Sainsbury, RNZI Technical Manager, +644 474 1430 email@example.com