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This Week's Wireless News Headlines
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NO POLITICS HERE
This doesn't mean that nothing is ever published here that mentions a US political party—it just means that the editorial policy of this newsletter is to remain neutral on all political issues. We don't take sides.
A new issue of the Wireless Messaging Newsletter is posted on the web each week. A notification goes out by e-mail to subscribers on most Fridays around noon central US time. The notification message has a link to the actual newsletter on the web. That way it doesn’t fill up your incoming e-mail account. There is no charge for subscription and there are no membership restrictions. Readers are a very select group of wireless industry professionals, and include the senior managers of many of the world’s major Paging and Wireless Messaging companies. There is an even mix of operations managers, marketing people, and engineers — so I try to include items of interest to all three groups. It’s all about staying up-to-date with business trends and technology. I regularly get readers’ comments, so this newsletter has become a community forum for the Paging, and Wireless Messaging communities. You are welcome to contribute your ideas and opinions. Unless otherwise requested, all correspondence addressed to me is subject to publication in the newsletter and on my web site. I am very careful to protect the anonymity of those who request it. I spend the whole week searching the INTERNET for news that I think may be of interest to you — so you won’t have to. This newsletter is an aggregator — a service that aggregates news from other news sources. You can help our community by sharing any interesting news that you find.
Editorial Opinion pieces present only the opinions of the author. They do not necessarily reflect the views of any of advertisers or supporters. This newsletter is independent of any trade association. I don't intend to hurt anyone's feelings, but I do freely express my own opinions. |
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There is not a lot of news about Paging these days but when anything significant comes out, you will probably see it here. I also cover text messaging to other devices and various articles about related technology. |
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Remembering colleague and friend Judi Kanne
Judi Kanne regularly gathered compelling story ideas from her many conversations, travels and meetings, then dug into subjects with the knowledge of a nurse and the passion of a journalist. Combining both careers, her articles covered a fascinating range of topics: health literacy, essential oils, hospital laundry, paramedics and eating disorders. Some of her stories covered surprising medical breakthroughs, while others revealed the human side of healing. Always, Judi dealt with editors and interviewees with a cheerfulness and warmth that came naturally to her. She made instant friends of the people she met. Health care journalist, nurse, beloved wife and mother, Judith Leah Leonard Kanne died last week of Lewy body dementia at her metro Atlanta home. She was 78.
She had been a member of AHCJ since 2003. The organization was founded in 1998. After a series of puzzling and painful symptoms, Judi spent more than two months in two hospitals and a rehab facility earlier this year. Her husband, Barry, said it took some time for doctors to figure out her diagnosis because so many body functions were affected. Many people with Lewy body dementia develop movement symptoms as Judi did. She died peacefully at home among family members, Barry said last week. It’s a testament to her devotion to her dual nursing and journalism careers that while experiencing symptoms, she wanted her final story for Georgia Health News to be completed and published. Based on her reporting notes, the story was posted in May, about the upcoming launch of the Georgia Nurses Hall of Fame. A life of learning and workingA daughter of Polish immigrants, Judi was born and raised in San Diego. She married her sweetheart, Barrett Michael “Barry” Kanne, in 1962, and they celebrated 59 years together this past St. Patrick’s Day. Barry’s career at Motorola took them around the country. In 1970, they moved to the Chicago area, where they raised their two daughters. There, Judi enrolled at a community college, where she received an associate degree in nursing, and then worked at hospitals around suburban Chicago. In 1981, Judi and family moved to Dunwoody, outside Atlanta. Still interested in furthering her education, Judi enrolled at Georgia State University and earned a bachelor’s degree in journalism in 1992. She then focused on medical writing, working primarily for the CDC as a contracted communications specialist. A lifelong learner, Judi returned to school years later, after reaching “retirement” age. In 2012, she earned her second bachelor’s degree, this time from Clayton State in 2012. It was a degree in nursing. Her goal was to update her medical credentials and learn the latest clinical trends. At age 69, she was the oldest graduate in the history of the Clayton State University College of Nursing. As a freelance health care journalist, Judi began writing articles for Georgia Health News in 2013. She also wrote for Atlanta Senior Life and other publications. A zest for the truth . . . and funOver the past decade, Judi was a fixture at AHCJ’s Health Journalism conferences and at local Atlanta chapter meetings, often accompanied by Barry, who was her proofreader and occasional personal photographer. Jeanne Erdmann, an AHCJ board member and head of its Freelance Committee, said that during Judi’s work on the committee, “her gentle demeanor and her enthusiasm kept many of our projects moving forward.’’ “I can speak for all of our committee members when I say that we valued her kindness and the smile that always seemed to be there,” Erdmann said. “We’ll miss her greatly. I do hope that she knew her worth. Judi certainly meant a lot to us.” Former AHCJ Executive Director Len Bruzzese remembered Judi’s dedication. “Judi was such a devoted AHCJ member,” he said. “She was on our local planning committee for our terrific 2012 Atlanta conference, took part in local chapter meetings, helped out younger members and served on the nationwide Freelance Committee — always with a smile and friendly word.” In 2019 Judi earned a fellowship in geriatric medical writing from the Gerontological Society of America. She proved her mettle in this area, writing stories about mobility devices, mental health challenges, and seniors’ risks of falling. Fellow health journalist Katja Ridderbusch said: “Judi loved AHCJ — the learning opportunities, the brainstorming buzz, the fellowship of health care journalists. She would never miss an annual conference or a local chapter meeting.’’ “I remember us slithering across the icy roads of Cleveland in April of 2016, and a year later, running for shade in the garden of our Orlando conference hotel. I remember us sitting on the floor in a Phoenix conference hall waiting for our slots at the freelance pitch fest, laptops on our laps, frantically making last-minute changes and laughing in despair because we were always late, and we were always nervous, and in the end, it would always work out.’’
Ridderbusch remembers Judi as an adventurer who was always curious about people, places and “back stories.’’ “She was the happiest when she and Barry embarked on cross-country trips in their RV. From the road, she often sent selfies of them at quirky locales, with hearty food and funky drinks. She sometimes even traveled in the RV to an AHCJ conference — making an expedition out of a business trip.’’ In addition to her husband, Barry, Judi is survived by daughters Karen Kanne Ngowe and April Kanne Donnellan; son-in-law Paul Donnellan; grandchildren Athieno and Yosef Ngowe; and Claire and Sophie Donnellan. In lieu of flowers, please consider contributions to the Lewy Body Dementia Association or the Georgia Nurses Association. |
| Source: | Georgia Health News | K4JLK SK |
| Leavitt Communications |
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Think Apple Silicon is exciting now? Just wait and see what’s to comeBY KILLIAN BELL • 3:35 AM, AUGUST 2, 2021
Apple just reported a hugely successful quarter for the Mac — one of its best ever — and it looks like it’s only going to get better. A new report detailing the company’s Apple Silicon roadmap says the best is yet to come. In addition to new MacBook Pro models powered by faster Apple Silicon chips, which are still on track for this year, Apple is expected to roll out a high-end Mac mini before the year is out. Then, in 2022, we could see a “revamped, smaller Mac Pro” featuring custom Apple chips — and more. Apple Silicon has been a game-changer. It has not only made Apple’s most popular machines faster and more efficient than they ever were when running Intel chips, but it has completely reignited interest in the Mac. Despite supply constraints, the last year was the best ever for Mac sales. When it introduced Apple Silicon for the first time in November 2020, Apple said it would take two years to transition the entire Mac lineup to custom chips. It looks like reaching that deadline is going to be tight, but according to one reliable reporter, what Apple has planned will knock your socks off. The Mac is going to get even betterIn the latest edition of his Power On newsletter, Bloomberg reporter Mark Gurman predicts big things for the Mac for 2021 and 2022. It begins with the MacBook Pro upgrade we were already waiting for, which is expected to bring even faster “M1X” chips in the coming months. “Soon after that,” Apple will introduce a high-end Mac mini that’s likely to feature similar power upgrades, Gurman says. In 2022, Apple is expected to deliver a “revamped, smaller Mac Pro” powered by Apple Silicon, as well as a redesigned MacBook Air that will feature MagSafe support. Bloomberg previously reported that Apple is developing custom 20-core and 40-core chips for use in a future Mac Pro. It is believed the first Apple Silicon model could be around half the size of the current desktop. More for Mac ProIn the meantime, Apple will roll out one more Mac Pro refresh that will continue to feature Intel chips — likely the company’s new Xeon Ice Lake processors — Gurman writes. It’s not yet clear when that refresh will happen. If you’ve been lusting after an M1 Mac but haven’t yet pulled the trigger then, it might pay to wait a little while longer. You could end up with an even better machine when Apple’s new models roll out, or, at the very least, a nice discount on one of today’s models. |
| Source: | Cult of Mac |
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Paging Transmitters 150/900 MHz The RFI High Performance Paging Transmitter is designed for use in campus, city, state and country-wide paging systems. Designed for use where reliable simulcast systems where RF signal overlap coverage is critical.
Built-in custom interface for Prism-IPX ipBSC Base Controller for remote control, management and alarm reporting.
Prism-IPX Systems LLC.
11175 Cicero Dr., Alpharetta, GA 30022
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The Wireless Messaging News
The Board of Advisor members are people with whom I have developed a special rapport, and have met personally. They are not obligated to support the newsletter in any way, except with advice, and maybe an occasional letter to the editor.
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Modern civilization would be lost without GPSby Anusuya Datta — August 3, 2021
Aircraft, cars, trucks, trains and ships rely on GPS for location data, while GPS timing signals underpin cellular communications and financial transactions. A 2019 report sponsored by the National Institute of Standards and Technology estimated the loss of GPS would cost the U.S. economy $1 billion a day, or $1.5 billion if the technology failed in the April-May planting season for farmers. Two years later, the costs could be even higher with the sharp rise in consumer solutions and location-based rideshare and delivery services. “Positioning, navigation and timing signals are important to so many stakeholders and for so many different applications that a disruption in these signals would likely be more economically significant today,” Alan O’Connor, senior economist and director of innovation economics at RTI International, the nonprofit research institute that prepared the 2019 report, said by email. GPS and its GNSS (Global Navigation Satellite System) counterparts — Europe’s Galileo, Russia’s GLONASS and China’s Beidou — play a vital role in myriad economic activities. India’s NavIC and Japan’s QZSS are similarly important in their respective regions. GPS is the oldest and mostly widely used PNT system. Many infrastructure networks still rely on GPS-only legacy receivers. Multi-constellation receivers are becoming a norm to provide for GNSS continuity and accuracy. Since these receivers pick up signals from any available GNSS satellite, irrespective of the constellation, they should theoretically provide service continuity in the event of GPS loss. However, because they rely primarily on GPS, it’s not clear how they would behave if GPS were lost for hours. “GPS is so important in our everyday lives. If it were to go away for a significant amount of time, I am sure lives would be lost,” Dana Goward, president of the nonprofit Resilient Navigation & Timing Foundation, said by email.
To date, GNSS outages have lasted less than one day, but a longer breakdown is possible. Galileo suffered a six-hour systemwide failure on Dec. 14, 2020, and a weeklong outage in July 2019. GLONASS failed in 2014 when its satellites broadcast corrupt information for 11 hours. Outages of individual GNSS satellites are common and the systems are often subjected to localized jamming and spoofing. In 2016, GPS-dependent timing equipment showed errors after an older satellite was retired. The 13-microsecond discrepancy affected police and emergency communications equipment in parts of North America for hours and caused power grid anomalies. One reason GNSS failures are farreaching is the timing element. GNSS satellites rely on atomic clocks for signal synchronization, which allows users to determine the time with nanosecond accuracy. As a result, banks rely on GPS to report the precise timing of financial transactions and cell towers use it to synchronize network nodes. “The U.K. is critically dependent on GNSS. These services are integral to the U.K.’s safety, security and prosperity, overseas territories and wider global interests,” Ian Annett, UK Space Agency deputy CEO, said by e-mail. THE SAME IS TRUE FOR THE UNITED STATES.If GPS were to fail, “it’s impossible to predict the exact sequence of events,” Goward said. “Transportation and first responders will suffer immediately. There could be more accidents. Cellphones and internet will begin to degrade, but it’s hard to say how much and how quickly.” The COVID-19 pandemic made the U.S. economy more reliant than ever on telecommunications infrastructure. “There is broader recognition of the role infrastructure plays in our economy, though many people are unaware of the connections between GPS, robust positioning, navigation and timing signals, and the apps and tools we use every day,” O’Connor said. ECONOMIC IMPACT OF DISRUPTIONA 2017 study commissioned by Innovate UK, the UK Space Agency and the Royal Institute of Navigation estimated a five-day GNSS disruption would have an economic impact of 5.2 billion pounds ($7.2 billion), with road, maritime and emergency service impacts accounting for 88 percent of the cost. Goward said the cost of disruption would be far higher in 2021 since location data has become pervasive. The UK Space Agency has commissioned an updated study to determine the potential economic impact. The past decade has seen a sharp rise in the value of GNSS, which largely coincides with the rise in smartphones, smart devices and internet penetration, enabling a spurt in consumer solutions. “Satellite navigation systems are also important to unlocking future technologies such as driverless cars, smart cities and artificial intelligence — transforming the way people live, work and travel,” Annett said. The UK Space Agency is exploring innovative options for a UK space-based positioning, navigation and timing capability. HOW LIKELY IS A TOTAL GNSS BLACKOUT?A failure of all GNSS constellations at once is improbable. “The higher risk is attacks to GNSS systems from jammers or spoofers,” said Miguel Amor, chief marketing officer for autonomy & positioning at Hexagon, a Stockholm-headquartered information technology company. Anti-jamming and anti-spoofing technologies are available, but have generally been purchased by national security agencies rather than commercial customers, he added. Regional outages are more common. Geopolitical tensions have led to GPS signal loss near the Middle East. In July 2018, the NATO Shipping Center received reports from ships facing GPS interference while transiting the Mediterranean. NATO also reported similar issues in December 2019 when ships and aircraft in the Mediterranean could not access GPS or GLONASS signals. A U.S. Transportation Department report delivered to Congress in January identified technologies that can complement or backup GPS service. The report found no current replacement, though, for GPS positioning and navigation capabilities. To ensure resilience, the Transportation Department recommended critical infrastructure owners and operators adopt diverse positioning, navigation and timing technologies. Anusuya Datta is a Canada-based journalist who previously worked for Geospatial World. Debra Werner, SpaceNews senior correspondent, contributed to this story from San Francisco. This article originally appeared in the July 2021 issue of SpaceNews magazine. |
| Source: | Space News |
| PRISM IPX Systems |
With PRISM IPX Systems, Your message is delivered Secure & Encrypted
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| Easy Solutions |
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Providing Expert Support and Service Contracts for all Glenayre Paging Systems. The GL3000 is the most prolific paging system in the world and Easy Solutions gladly welcomes you to join us in providing reliable support to the paging industry for many more decades in the future. Easy Solutions provides cost effective computer and wireless solutions at affordable prices. We can help in most any situation with your communications systems. We have many years of experience and a vast network of resources to support the industry, your system and an ever changing completive landscape.
Please see our web site for exciting solutions designed specifically for the Wireless Industry. We also maintain a diagnostic lab and provide important repair and replacement parts services for Motorola and Glenayre equipment. Call or
Easy Solutions |
GLENAYRE INFRASTRUCTUREI would like to recommend Easy Solutions for Support of all Glenayre Paging Equipment. This Texas company is owned and operated by Vaughan Bowden. I have known Vaughan for over 35 years. Without going into a long list of his experience and qualifications, let me just say that he was the V.P. of Engineering at PageNet which was—at that time—the largest paging company in the world. So Vaughan knows Paging. GTES is no longer offering support contracts. GTES was the original group from Vancouver that was setup to offer support to customers that wanted to continue with the legacy Glenayre support. Many U.S. customers chose not to use this service because of the price and the original requirement to upgrade to version 8.0 software (which required expensive hardware upgrades, etc.). Most contracts ended as of February 2018. If you are at all concerned about future support of Glenayre products, especially the “king of the hill” the GL3000 paging control terminal, I encourage you to talk to Vaughan about a service contract and please tell him about my recommendation.
Click on the image above for more info about advertising here. |
INTERNET Protocol Terminal
The IPT accepts INTERNET or serial messaging using various protocols and can easily convert them to different protocols, or send them out as paging messages. An ideal platform for hospitals, on-site paging applications, or converting legacy systems to modern protocols.
Additional/Optional Features
Prism-IPX Systems LLC.
11175 Cicero Dr., Alpharetta, GA 30022 |
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Paging Data Receiver PDR-4 The PDR-4 is a multi-function paging data receiver that decodes paging messages and outputs them via the serial port, USB or Ethernet connectors. Designed for use with Prism-IPX ECHO software Message Logging Software to receive messages and log the information for proof of transmission over the air, and if the data was error free.
Prism-IPX Systems LLC.
11175 Cicero Dr., Alpharetta, GA 30022 |
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7 Mac Backup Solutions That Aren’t Time MachineTIM BROOKES @timbrookes AUG 2, 2021, 8:00 AM EDT | 5 MIN READ
Every Mac comes with Time Machine, a backup solution that makes it easy to create a snapshot of your computer on an external drive. However, we recommend you seriously consider an additional backup or two. Today we’ll look at some alternatives to Time Machine for creating backups that will ensure you don’t lose your data. Why Not Use Time Machine?Time Machine is a great backup tool that works with virtually any external drive or networked Mac. It can be used alongside other backup solutions (like the ones mentioned below) to ensure you have more than a single backup if something bad happens. You can even use a Time Machine drive for both storage and backup. Apple’s backup solution is easy to use, but it comes at the cost of customization. You can choose to omit certain folders and system files, but that’s about it. Every time you connect your drive the backup will run unless you stop it, indexing the disk and backing up intelligently to ensure files aren’t duplicated to save space. Time Machine is a local backup solution. Your Time Machine drive likely isn’t far away from your Mac most of the time. If something goes wrong with your Mac, Time Machine allows you to restore any lost data. But what if something happens to your Mac and your Time Machine drive, like a flood, burglary, or house fire? This is where the 3-2-1 backup rule comes in. You should have three copies of your data, two of which are local (on different devices), with one copy off-site. In the case of your Mac, two local copies already exist in your home or office (one on your Mac, another on your Time Machine drive). A third backup can be added using online storage, for true off-site security. Also worthy of consideration are cloning tools, which can help you get up and running in record time if you suddenly need to restore a Mac. While Time Machine creates archives of just your data and applications, cloning software can back up the entire drive so that it can be copied back in its entirety should the worst happen. Time Machine AlternativesSome backup tools try to do it all, while others have very specific use case scenarios. You should find something that works for you, and use it religiously to ensure data is never lost. Easy Bootable Backups: SuperDuper! (Freemium)
SuperDuper! is a free and easy way of creating a complete backup of your Mac’s hard drive that is fully bootable. You can download SuperDuper! free of charge and use its core features forever. This allows you to copy the contents of your Mac to an external drive, which can then be copied back to your Mac if something goes wrong. Upgrading to SuperDuper! for a little over $30 will net you some more useful features like Smart Update, which indexes files and copies only the changes (like Time Machine) as well as scheduling and scripting features. If you’re planning on using SuperDuper! to regularly back up your Mac, the upgrade is worth it. SuperDuper! is compatible with Yosemite through to Big Sur, with an Apple Silicon build in beta testing (as of this writing in July 2021). If you suspect something is quickly going wrong with your Mac, SuperDuper! could be a life-saver. Sync Files Between Devices: ChronoSync ($49.99)
ChronoSync does many things including making off-site file backups and bootable clones of your hard drive. You can use it like Time Machine with local drives and network locations, and it has powerful scheduling tools that can initiate backups stealthily in the background. But ChronoSync’s main draw is its ability to keep data synchronized between two or more devices. For example, say you have a Mac at home and a laptop for use at the office. With ChronoSync, you can keep the same set of files in sync between those two devices. This is ideal if you’re working on a project in more than one location as is often the case for creatives, video editors, and designers. Online backups can be performed to Amazon S3, Backblaze B2, and web servers via SFTP. If you don’t need the off-site backups, consider the cheaper ChronoSync Express ($24.99) instead. Time Machine on Steroids: Carbon Copy Cloner ($39.99)
Carbon Copy Cloner is a jack-of-all-trades backup tool that presents itself as a more powerful version of Time Machine. Backups are recorded as snapshots on a calendar (just like Time Machine) and can take place on local drives or networked Macs. Indexing ensures that backups happen quickly so that files aren’t unnecessarily copied more than once. The real strength of Carbon Copy Cloner lies in how customizable it is. You can choose exactly what to back up, when to back it up, and even employ smart tricks like watched folders to ensure that important files are always covered. If you find Time Machine useful but limiting, take Carbon Copy Cloner’s free 30-day trial for a spin. Bring Your Own Storage: Duplicati (Free, Open Source)
If you already have online storage that you want to use for an off-site backup, Duplicati is a free and open-source solution that lets you do so. The cross-platform app works on Windows, macOS, and Linux; allowing you to store all of your backups in one place. These backups can take place using a wide range of protocols and services, including FTP, SSH, WebDAV, Backblaze B2, Amazon S3, Tardigrade, Microsoft OneDrive, Google Drive, Mega, and more. The app focuses solely on creating and storing secure online backups using AES-256 bit encryption, with no local backup features to speak of. Duplicati uses a web-based interface to manage your schedule, initiate backups, and access your files. If you get stuck you can turn to the user forums to get help from the community. Duplicati is a great way to save some money if you know what you’re doing. Premium Off-site Backups: Backblaze, IDrive, CarboniteIf you don’t already have online storage available to you, or you’d rather not go to the hassle of managing your own backups, premium online backup services exist. Most of these offer the same fundamental service for a flat monthly or annual fee. Backblaze is one of the most competitively priced online solutions at $6 per computer, per month. There are no limits on data, no limits on file size, and an option to recover your data faster via a shipped hard drive in the post.
IDrive works a little differently in that you pay around $70 per year for 5TB of storage which can be used across an unlimited number of computers. This includes snapshots and file versioning (so you can access old versions of files), plus an option to get your data backed up and retrieved using a drive in the post.
Carbonite is another option, starting at $4.99 for the most basic plan (billed annually). There’s unlimited storage space with remote access provided for any device, including via mobile apps. If you spend a little more you can get external hard drive backup too.
These are just three of many such services, each offering something slightly different in terms of pricing. Be sure to shop around if you’re looking for an online backup provider, especially if speed is of concern to you. How far away the servers are from you can have a big impact on backup speed. Never Leave Home Without a BackupWhich backup software or online provider you use ultimately doesn’t matter, provided your data is being backed up. Time Machine is perfect for most people, but solutions like ChronoSync and SuperDuper! add another level of safety. |
| Source: | How-To Geek |
Brad Dye, Ron Mercer, Allan Angus, Vic Jackson, and Ira Wiesenfeld are friends and colleagues who work both together and independently, on wireline and wireless communications projects.
Click here Note: We do not like Patent Trolls, i.e. “a person or company who enforces patent rights against accused infringers in an attempt to collect licensing fees, but does not manufacture products or supply services based upon the patents in question.” We have helped some prominent law firms defend their clients against this annoyance, and would be happy to do some more of this same kind of work. Some people use the title “consultant” when they don't have a real job. We actually do consulting work, and help others based on our many years of experience. “If you would know the road ahead, ask someone who has traveled it.” — Chinese Proverb
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Remote AB Switches ABX-1 switches are often used at remote transmitter sites to convert from old, outdated and unsupported controllers to the new modern Prism-IPX ipBSC base station controllers. Remotely switch to new controllers with GUI commands. ABX-1
ABX-3 switches are widely used for enabling or disabling remote equipment and switching I/O connections between redundant messaging systems. ABX-3
Common Features:
Prism-IPX Systems LLC.
11175 Cicero Dr., Alpharetta, GA 30022 |
| Leavitt Communications |
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| Source: | Inside Towers newsletter | Courtesy of the editor of Inside Towers, Jim Fryer. Inside Towers is a daily newsletter by subscription. |
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| LETTERS TO THE EDITOR |
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| TECHNICIAN'S CORNER |
I had dinner with my good friend Ira Wiesenfeld last week. In the midst of our most enjoyable conversation, Ira told me one of his success stories; about how he solved a serious coverage issue on a public-safety two-way radio system. It was so interesting that I asked him if I could have a copy of the tutorial article he wrote (some years ago). I thought here in the Technician's Corner would be the perfect place for it. So with Ira's permission, I have edited and updated his paper. It is a little too long to put it entirely in one issue, so I will include it here — as a series — in sections. I had been taught that vertical antennas mounted on the side of a tower didn't have their radiation pattern affected very much, if at all. Ira proved this to be false. Since most of us think in pictures, I have added the “bottom line” of the paper — in the form of a graphic — right here.
A side-mounted omnidirectional antenna on a tower — illustrating how shadowing is created by the tower, partially blocking the signal.
TOWER SHADOWINGByIra Wiesenfeld, P.E.INTRODUCTION A [few years ago], I was contacted by a municipality who had just upgraded their single-site 800 MHz enterprise public safety trunking radio system to a two-site simulcast system. Instead of getting more range on the new system, the range was reduced considerably and the cities sharing this system were in desperate need of help. This system was designed by one of the major manufacturers in the business. The city did choose the towers that were available and must be used, and the manufacturer used that fact as the basis for the system needing more towers to be effective. In trying to solve the problem at hand, I did make a detailed analysis of what it would take to fix the problem. I wrote a 24-page report on the system and how to fix the problem, and the manufacturer wrote a 68-page rebuttal that did not address the problem but suggested that my analysis was wrong, and the city just needed more sites. My initial diagnosis of the problem was that tower shadowing was blocking the radio signals, and the engineers from the radio manufacturer and from the antenna manufacturer immediately accused me of being wrong. The radio manufacturer had convinced the city that I was wrong, and more sites were needed. This required me to conduct a thorough study of the system to prove to the city and the radio manufacturer that they did not install the antennas for optimum coverage. I was hindered in supporting my point of view because there is little literature that is published that explains tower shadowing. Hopefully, this article will aid others with similar problems. Every day since the system went on the air, hundreds of police, fire, EMS personnel, and other city employees were putting their personal safety in jeopardy due to the poor radio coverage in their jurisdictions. I have worked in public-safety communications for over four decades, and I know that this system was a danger to those people who put their dedication to others before their own needs. In the end, my only concern is for the users of the system and not the “SITYS” (SEE-I-TOLD-YOU-SO). This article is written to explain to engineers, technicians, and radio system managers what tower shadowing is, and how to use it properly. ANTENNA PLACEMENTS In every radio system, the antenna is the most important component that sets the range of the system. The height of the antenna sets the theoretical maximum range, but the actual range is usually reduced by obstructions, such as trees and foliage, buildings, hills and ground elevation obstruction. In addition, the mounting location on the tower or rooftop has a lot to do with the range. Sometimes, engineers use the tower shadow to protect against interference to and from other systems. This section will look at the effects of antenna placement of the mounting structure in relation to the antenna’s performance. The ultimate place to mount an antenna is the top of a tower with no other antennas near the antenna. In real life, most towers have multiple antennas at the top, and since the side of the tower has plenty of room, there are as many antennas in use on the sides of towers as there are on the top of the towers.
The lone antenna at the top of a tower will have a 360-degree radiation pattern called OMNI-DIRECTIONAL. If you place any object near the antenna, whether it is another antenna or the side of a tower, the pattern will then have an offset pattern. The pattern can be predicted and is usually shown in the catalogs from the antenna manufacturers as how the pattern is distorted from the tower. The same goes for buildings rooftops. In fact, buildings have an advantage in that each antenna has less distortion from the other antennas, as there is usually enough room at a building site as to not have the antennas crowding each other and causing severely distorted patterns. There is also less attenuation on the coaxial transmission line on a rooftop location for most sites. In some systems, it is desirable to have the antenna have a directivity so that all of the power to and from the system is in one or two directions, and the directions where the signal is not needed or wanted is reduced substantially. Some of the antennas that are designed to have a concentration of power in one direction and have substantial attenuation in other directions include:
If you have another system on the same channel (called co-channel) and you want to reduce the interference with this other system, you would normally use the tower to shade the signal in the direction of the co-channel system and this normally does fix many co-channel problems. You can also use the tower to shield one system from the other on the same tower by placing the antennas on opposite sides of the tower and letting the tower shadow keep each signal down by 20 dB (x 100 power) or more. You can also use the vertical separation by placing the antennas vertically apart which provides a great deal of isolation from each other electrically, usually in the order of 40 dB (X 10,000) or greater. In these last two examples, the tower shadow or vertical separation is used to enhance the operation of the system. In the system for this municipality, the tower located in the north part of the territory had the transmitting antenna mounted on the north side of the tower. This cast a large shadow to the south, where most of the users are located. The south tower had the receiving antenna on the south side of the tower, and all the users are located north of this tower. In addition, the transmitter antenna for the south tower was mounted on the west leg, and the cities to the east had minimal coverage from this site. In summary, more than 60% of the cities in this system were affected by the tower shadows. One of the cities was in the shadows from both sites, and their radio coverage was so bad, the police department had to use cellular telephones for keeping up with their field units. A second city called just a [few years ago,] and again, the initial diagnosis after making a field visit to the municipality was that the tower shadow was the problem here. Just as the radio manufacturer denied the problem in the first case, the other manufacture had the exact same reaction here. Again, I made a detailed study of the signal strength at exactly 1 mile from the tower at 30-degree intervals, and the results were quite revealing as to the problem. The area where the town was having problems was exactly the area that was found to be shadowed by the tower. The first city uses the 800 MHz band, while this second city uses the 460 MHz band. This just proves that the problem with shadows is not band specific. [To be continued next week.] If you can't wait for the next issue, the whole paper is here.
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