Tag Archives: Linux

K8JTK Hub DVMIS Presentations

Presentation on the K8JTK Hub Digital VoIP Multimode Interlink System which integrates many Ham radio modes, both analog and digital.

Framework

The framework I chose to use for the presentation slides is called reveal.js. It is an HTML framework meaning it will run in any HTML 5 capable browser. Looks a little better than a PowerPoint presentation.

Navigation

Useful navigation keys in the presentation. In addition to navigating with the keys below, you can swipe (tables/smartphones) or use the navigation arrows on screen in the lower right.

Toggle full screen: press [F11].

Advance to the next slide: press [n] or [SPACEBAR].

Go back to the previous slide: press [p] or press and hold the [SHIFT] key while pressing the [SPACEBAR].

Display presentation overview: [ESC] then use the arrow keys or mouse to select a slide. [ESC] again will exit overview mode.

Links

Clickable links are colored in brown text.

Presentations

Three variations are available: presentation version is viewable in a browser. Printable version for printing or saving in a different format. Finally a PDF version.

They may take some time to load because I left original images untouched and some were a couple MB in file size.

Slides

The presentation is about 10 minutes in length which aired on the AmateurLogic.TV podcast on 11/13/2020 for episode 149.  It includes additional slides referenced in the video segment.

Presentation version
Printable version
PDF version

Segment:

Ohio Section Journal – The Technical Coordinator – May 2020 edition

One of the responsibilities of the Technical Coordinator in the Ohio Section is to submit something for the Section Journal. The Section Journal covers Amateur Radio related things happening in and around the ARRL Ohio Section. It is published by the Section Manager Scott – N8SY and articles are submitted by cabinet members.

Once my article is published in the Journal, I will also make it available on my site with a link to the published edition.

You can receive the Journal and other Ohio Section news by joining the mailing list Scott has setup. You do not need to be a member of the ARRL, Ohio Section, or even a ham to join the mailing list. Please sign up!

If you are an ARRL member and reside in the Ohio Section, update your mailing preferences to receive Ohio Section news in your inbox. Those residing outside the section will need to use the mailing list link above.
Updating your ARRL profile will deliver news from the section where you reside (if the leadership chooses to use this method).
Go to www.arrl.org and logon.
Click Edit your Profile.
You will be taken to the Edit Your Profile page. On the first tab Edit Info, verify your Email address is correct.
Click the Edit Email Subscriptions tab.
Check the News and information from your Division Director and Section Manager box.
Click Save.

Now without further ado…


Read the full edition at:

THE TECHNICAL COORDINATOR
Jeff Kopcak – TC
k8jtk@arrl.net

DSCF5081 K8JTKHey gang,

Well, this stay at home thing seems to have run its course – beginning week 11 soon. Unless you’ve been under a rock, you know by now Dayton Hamvention was canceled this year. First time ever in its history. Weekend events that had the resources were virtualized such as Contest University. Some vendors and manufactures ran Dayton specials regardless of the lack of a physical showing. Technical Specialist Bob – K8MD pointed out that one of the retailers ran a special on D-STAR repeater components for $299 apiece. That meant a full stack (controller, 2m voice, 440 voice, 1.2G voice, and 1.2G data) could be purchased for about $1,500. Wow. Just ONE of those items cost about that much retail. Is ICOM feeling the pressure from the Yaesu repeater giveaway, DMR, or is D-STAR II around the corner? Hmmm…

Unfortunately, I’m starting to see on-the-air happenings return to previous levels. I guess that means people are returning to work, going out more, and returning to their normal. For me, I knew early on I wanted to utilize the hunker-in-place order to knock out some long-standing projects and “to-dos” of mine. Others had the same idea.

Among my list of annoying issues was a problem with one of my Fedora systems. As I’ve written about in the past, I made the switch to Fedora Linux as the primary operating system on my desktop and laptop. Fedora is a cutting-edge operating system and employs a very aggressive release and end-of-life schedule. The project releases a new version twice a year in April and October. When a new version drops, they mark the version two behind it as end-of-life. Fedora 30 released in April of 2019 means Fedora 28 went end-of-life one month after that date, May 2019. No bug fixes, no package updates, no security enhancements. And everyone complains about Microsoft ending life of a 10-year-old OS. Well, I knew what I was getting into.

Fedora 31 released at the end of October, 2019. I usually wait 2-3 months for the major problems to be ironed out and updates made available before I upgrade. When I tried to update to 31, I ran into a problem. Using the Fedora 31 Live CD or doing the automatic upgrade, the boot process would hang on this line:

A start job is running for Monitoring of LVM2 mirrors, snapshots etc. using dmeventd or progress polling

This process neither finished loading nor failed to load after any amount of time. Off to the Internet I went. Searching “Fedora 31” and the message above brought me to a couple bug reports and forum posts about the same message. Unfortunately, none of the suggestions got me past this problem. Due to life and other responsibilities, I put it aside secretly hoping Fedora 32 would have fixed my problem, saying I would upgrade from 30 to 32. I saw Fedora 32 beta was available (now a full release) and downloaded the Live CD. Problem still existed. Darn!

Since this occurred during the boot process of both the Live CD and after upgrading a previous installation, I couldn’t look or pull stored logs easily to see if those provided any clues as to why the process was hanging. Live CD images are the lifeline go-to when the installed OS on the hard drive wont boot. In addition to installing the OS, they are used as a rescue method to repair a borked install. I couldn’t get the Live CD to boot so I was in trouble if this system ever became unbootable because I’ve never *cough* have done something that *cough* *cough* caused my system to become unbootable…

Storage server supporting RAID (Wikipedia)

The forum post above gave me a clue and I started exploring this as being an issue with my RAID array. RAID stands for Redundant Array of Inexpensive (or Independent) Disks. It’s a technology that combines multiple physical disks into logical units for redundancy, performance, or both. I tried messing around in the BIOS disabling other arrays, that didn’t work. I thought maybe something in the RAID information written to the disk was causing a problem. Backed up everything on the array and deleted it. Deleting a RAID array destroys all data on those disks!! When I recreated the array, the Fedora 31 Live CD booted! Problem solved!!? Yeah, no. It would boot successfully once then hang on subsequent reboots or after being installed to the hard drive.

After screwing around with it even more, I finally searched “Fedora 31 Intel RAID array LVM2 dmeventd” and found this bug report and how to work around the exact issue I was having. Whoo Hoo! Problem solved, well workaround provided. It took a while to get there. Simply searching a message, error, or problem may not return the most relevant search results for your issue. You might have to dig at it a bit by gathering other information to determine the real reason or peel back the right layer to discover the correct answer.

Work around involved masking the lvm2-lvmpolld.service via kernel load parameters and at the command line after install. Masking creates a link to the Linux blackhole /dev/null device so the service cannot be started by systemd or dependencies. The service is a polling system for the Logical Volume Manager (LVM). After all that, I was finally able to get Fedora upgraded to 31! Just in time as version 30 was about to go EOL. I noticed the data consistency validation scan no longer automatically occurs on the arrays, which is likely related to disabling the service. I initiate it manually every couple of weeks. The problem of not being able to boot has an active bug report that’s assigned. Hopefully gets attention from a developer and fixed.

Windows 7 Users: Take Heed

Broken Windows (Krebs on Security)

It’s become more imperative that you move to another operating system like Windows 10, Linux, or utilize a 3rd party patching service like 0patch. Unlike Windows XP’s end-of-life, there were not too many critical issues shortly after EOL. Microsoft did release patches for ‘really bad’ issues. XP, and any OS, always have an unknown number of undiscovered security problems. We were not so fortunate to run with Windows 7 as long without discovering major problems. There have been a number of significant critical issues each month since Windows 7 went EOL that affect Windows 7, 8, and 10, for which Microsoft has not (and likely will not) patch Windows 7.

My February OSJ article has information about how issues can affect ‘all versions of Windows’ and information on 0patch. March OSJ article covers upgrading to Windows 10 for free and check my Linux information article for choosing a Linux distribution. A reader previously tried to argue that exploits resided in browsers. Since the last official update for Windows 7 in January, these critical exploits are largely operating system based: ActiveX, Windows Installer, Graphics Interface, font rendering, and shortcut handling (.lnk files) with many being 0-day, meaning they are actively exploited in the wild. Could be a result of someone that has physical access to the machine, an application the user thinks are legitimate or an app that comes bundled with crapware/malware, or polled by an infected device on the network.

This month alone, 111 security holes were patched, 16 being critical, in supported Windows operating systems. Makes you wonder why anyone is still using a Microsoft Windows OS. Lack of software support and learning curve are probably the biggest. I have a few uses for Windows, ugh – thank you streaming services and your stupid ‘copy protection.’ Microsoft is looking at ‘containerizing’ the Win10 operating system. The belief being when a software component fails to update or creates a problem, it doesn’t affect other parts or crash the entire operating system – separate containers that only affect themselves. Or maybe Microsoft should focus on getting the operating system stable instead of “feature updates” no one cares about. </end rant>.

AmateurLogic.TV Sound Check Net

One of the nets created since the stay-at-home order is the Amateur Logic Sound Check Net. Amateur Logic.TV is a long-running monthly podcast featuring the latest in ham radio. There have been 5 nets so far. I became involved with the net because they wanted the ability to link D-STAR and DMR users to their EchoLink net. I was able to offer up my Digital Voice Multi-mode Interlink System Hub. Started utilizing only those three modes but quickly expanded to incorporate all. Users have checked in using all the modes each week, including Wires-X.

Previous net announcement with NCS K8JTK!

The AmateurLogic guys are using a local repeater in Mississippi connected to an Echolink node. I connect to their Echolink node and transcode audio to and from other modes: AllStar Link, Hamshack Hotline, D-STAR, DMR, YSF, and Wires-X. It has performed well as it mostly lives in the cloud and has data center level resources. Users and sponsors of the net have been impressed with how well it works and grateful to experiment with many modes to reach the net – one of the few, if not only, taking Hamshack Hotline checkins.

I was net control MC for a couple of their nets. It was my longest and most amount of checkins with about 40 at nearly 2 hours for a net. The net is on Tuesdays at 9pm eastern and should be running for at least a couple more weeks. Net can be reached by connecting to any of my hub nodes or checking ALTV social media for other connections. Everyone is welcome!

Thanks for reading and 73… de Jeff – K8JTK

Ohio Section Journal – The Technical Coordinator – September 2019 edition

One of the responsibilities of the Technical Coordinator in the Ohio Section is to submit something for the Section Journal. The Section Journal covers Amateur Radio related things happening in and around the ARRL Ohio Section. It is published by the Section Manager Scott – N8SY and articles are submitted by cabinet members.

Once my article is published in the Journal, I will also make it available on my site with a link to the published edition.

You can receive the Journal and other Ohio Section news by joining the mailing list Scott has setup. You do not need to be a member of the ARRL, Ohio Section, or even a ham to join the mailing list. Please sign up!

If you are an ARRL member and reside in the Ohio Section, update your mailing preferences to receive Ohio Section news in your inbox. Those residing outside the section will need to use the mailing list link above.
Updating your ARRL profile will deliver news from the section where you reside (if the leadership chooses to use this method).
Go to www.arrl.org and logon.
Click Edit your Profile.
You will be taken to the Edit Your Profile page. On the first tab Edit Info, verify your Email address is correct.
Click the Edit Email Subscriptions tab.
Check the News and information from your Division Director and Section Manager box.
Click Save.

Now without further ado…


Read the full edition at:

THE TECHNICAL COORDINATOR
Jeff Kopcak – TC
k8jtk@arrl.net

DSCF5081 K8JTKHey gang,

A ham in the section asked me about obtaining the latest Linux kernel. Not wanting to deal with problems found after the operating system install media was released, the latest stable kernel version available was what he wanted to be installed during setup.

Before I get started, if you are not familiar with Linux and have not read my April 2018 OSJ article, I encourage you to do so as some of the terminology defined will be used here.

There is not an easy answer to the question which version of the kernel is “stable.” The answer is: it depends. Depends on:

  • Definition of stable. There will always be bugs and constant fixes being released. Most IT personnel take ‘stable’ to mean: the least amount of issues after testing and polishing.
  • Linux distribution. How well does a kernel version work with the packages and drivers of a distribution. Availability of a new stable kernel depends on maintainers, developers, and the community’s time to update everything including programs, libraries, and drivers. Then test, document, ship, and address bug reports.

At kernel.org, there is a giant yellow button which indicates “latest stable kernel.” As of this writing, currently 5.3. Terminology on the Kernel Archives website for the different kernel types:

  • mainline = beta
  • stable = less issues
  • longterm = maintained and updated longer, typically for business production systems
  • linux-next = patches for the next version of mainline, stable, longterm

Logging into a handful of updated Linux devices I have around the house, their kernel versions:

  • Fedora 30: 5.2.14
  • AllStar Node (Debian 9): 4.9.0
  • Raspberry Pi – AllStar node (Arch): 4.14.97
  • Raspberry Pi – stock install (Raspbian Buster): 4.19.66
  • Wireless access point: 2.6.36

You’ll notice exactly zero are on 5.3. Even Fedora, which is considered a “bleeding-edge” Linux operating system will lag behind. Fedora is currently a single release behind the stable channel. Each distribution has their own definition of “stable” because it’s up to each distribution to maintain and update their releases.

A similar situation exists for software packages too. There will often be different versions of the same named package between different Linux distributions. Packages Managers almost always lag behind source code releases. For example, the Linux printing system software called CUPS for Common UNIX Printing System (cups.org), its latest is version 2.3.0. The latest in the Fedora 30 package manager is version 2.2.12. Therefore, 2.2.12 is the latest stable CUPS install for Fedora 30. Version 2.3.0 will be available when it is approved.

I have nearly 2000 packages installed on one of my systems! That seems like a lot but some are very small and Linux is very modular. Some are programs I installed like VLC or YouTube downloader. Others, I have no idea. Those are likely dependencies for other packages or programs pre-installed by the distribution. Anything beginning with “lib” is a shared common library. Packages prefixed with a program name are modules of that program: “cups” is the core printing system while “cups-filters” are the printer libraries for CUPS. Some are required system packages. “tzdata” is time zone data – so the system knows about different time zones, changes DST correctly, and processes leap-seconds. “Mint-themes” are themes for the Linux desktop GUI Cinnamon.

Linux diehards will “compile from source.” To get the absolute latest and greatest features and fixes, this practice involves downloading the plain-text source code and compiling it into machine executable code manually. It takes alot of trial-and-error to get a successful compile. Not only is the program source needed but the source code for any dependencies and libraries will also be required. Most will say this is to validate the code, add their own custom modules to the kernel, or do kernel development.

Could someone download and compile kernel 5.3 for Fedora, Ubuntu, Mint, or any other distribution? Absolutely. Fedora has a process documented to update the kernel manually. It’s 15 pages. Or you can run a single command. You choose. But you have to deal with any issues that arise from using a custom version of the kernel and doing so is unsupported by most distributions. I have no reason to be on a later kernel version before it is made generally available by the Fedora project.

Unless there are bandwidth concerns, there is little reason to worry about installing the latest version of the OS. The package manager will handle all updates to the kernel, operating system, and programs. Updates through the package manager have been approved for that version of the operating system by those who maintain those programs. It does not mean updates are 100% bug free. There is no need to install updates the minute they are available – even every-couple-weeks will be OK. We’ve all been trained like Pavlov’s dog to install updates the minute we see that pop-up. Thanks Windows. Cherry-picking is not a good idea either – unless you have a specific reason not to install an update, like an incompatible version of Java with another program.

How to install the latest Linux OS updates? I’m a command line guy because I was brought up on the DOS and Linux command lines. Recent Linux distributions have both a CLI (command line interface) and a GUI (graphical) package manager. Once the Live CD install is complete, reboot. When logged in, open a terminal window.

For Red Hat based systems (Fedora, CentOS), run:
sudo dnf -y update
Replace dnf with ‘yum’ on older installs.

For Debian based systems (Ubuntu, Mint, Raspbian, etc), there are two commands:
sudo apt -y update
sudo apt -y upgrade

The -y option means “assume yes” to any download questions or repository updates. GUI versions vary but usually involve refreshing the repository data and selecting all updates. These should always be run after a fresh install. When complete, reboot the machine. I run these update commands about once a week, maybe more if I’m waiting for an update or fix. These can be run at any time after installation as well.

On the topic of operating systems, the much beloved Microsoft operating system Windows 7 will no longer be supported after January 14, 2020. Windows 7 reaching end-of-life means there will be no further security updates – in theory. Even after Windows XP reached EOL, Microsoft went back and patched some “really bad” vulnerabilities in all operating systems, including XP. I can’t say the January 14th date will be extended or moved beyond that date nor can I say how long Windows 7 will remain a safe operating system to use. For the first time ever at the beginning of this year, the number of Windows 10 users just passed the number of Windows 7 users. That means about half of Windows users are still running version 7. There was talk of hackers stockpiling Windows XP exploits that would be released the minute Microsoft stopped updating XP, bringing the world to its knees. That was more hype by the media than reality. Chrome and Firefox browsers continued to support XP until a time came when they decided it was more work than it was worth.

A conversation I had recently, this person was of the mind that Windows 7 is going to stop working all together after January. Not true. It will still work as normal after January 14. You may see nag screens saying Win7 is no longer supported encouraging update to Windows 10. This is not a requirement to continue using your computer because Windows 7 will continue to run fine, you know, until the machine dies. There will be problems installing 7 on certain newer hardware because Microsoft thinks regression testing and customizations for Windows 7 security on modern hardware will introduce more problems. This time may, however, be the last chance you can upgrade to Windows 10 for free, for the life of the computer. If you qualify and have the latest Windows 7 updates installed, you will receive a pop-up from Windows saying ‘Microsoft recommends upgrading to Windows 10.’ This is a similar promotion to the one I talked about in April 2016.

In general, users have grown numb to the constant updating and bloatware of Windows 10. Believe it or not, Microsoft solved all the real problems with Windows 10. It’s called Microsoft Windows 10 LTSC (Long-Term Servicing Channel). It’s fantastic. It doesn’t force you into feature updates, doesn’t have the Windows Store crap, Cortana junk, or Customer Experience tracking. Feature updates can be delayed 18-24 months instead of having to be applied every 6 months. Not to mention Microsoft has frequently pulled back feature updates nearly as soon as they are released due to lack of adequate testing. The gotchya is you need access to a costly MSDN subscription. This version is out there if you look for it. Microsoft heavily criticizes the use of LTSC saying ‘users want feature updates.’ No, they don’t, that’s why users are seeking out a usable version of your crappie ‘modern’ operating system.

Time Code Generator for WWVB (wwv100.com)

The oldest continuously operating radio station in the world deserves a grand celebration. The Northern Colorado Amateur Radio Club (NCARC) will operate a special event amateur radio station with the call sign WW0WWV, on the WWV property starting September 28 and going 24-hours a day through October 2. For information on the Special Event Station visit: wwv100.com. In addition, HamSCI and the Case Amateur Radio Club of Case Western Reserve University (W8EDU) will sponsor a “Festival of Frequency Measurement” on WWV’s centennial. They are hoping to measure 5 MHz propagation over a given day and compare measurement techniques. HamSCI’s first attempt at measurements occurred during the total solar eclipse in 2017.

Jim – W8ERW, Technical Specialist for the Ohio Section, gave an informative presentation at the Wood County Amateur Radio Club in August about ARDEN MESH networking. He talked about generations of devices used for MESH networking, including the infamous Linksys blue-box, and brought many pieces of his own equipment for demonstration. Seneca county is getting involved and finding plenty of uses for MESH. If you would like a presentation for your club about MESH, get in touch with Jim.

Thanks for reading and 73… de Jeff – K8JTK

Ohio Section Journal – The Technical Coordinator – December 2018 edition

One of the responsibilities of the Technical Coordinator in the Ohio Section is to submit something for the Section Journal. The Section Journal covers Amateur Radio related things happening in and around the ARRL Ohio Section. It is published by the Section Manager Scott – N8SY and articles are submitted by cabinet members.

Once my article is published in the Journal, I will also make it available on my site with a link to the published edition.

You can receive the Journal and other Ohio Section news by joining the mailing list Scott has setup. You do not need to be a member of the ARRL, Ohio Section, or even a ham to join the mailing list. Please sign up!

If you are an ARRL member and reside in the Ohio Section, update your mailing preferences to receive Ohio Section news in your inbox. Those residing outside the section will need to use the mailing list link above.
Updating your ARRL profile will deliver news from the section where you reside (if the leadership chooses to use this method).
Go to www.arrl.org and logon.
Click Edit your Profile.
You will be taken to the Edit Your Profile page. On the first tab Edit Info, verify your Email address is correct.
Click the Edit Email Subscriptions tab.
Check the News and information from your Division Director and Section Manager box.
Click Save.

Now without further ado…


Read the full edition at:

THE TECHNICAL COORDINATOR
Jeff Kopcak – TC
k8jtk@arrl.net

DSCF5081 K8JTKHey gang,

Hi. My name is Jeffrey and I am a Windows user. Yes, I migrated my laptop a couple years ago from Windows 10 to Fedora Linux and six months ago did the same for my main desktop. Windows applications are better. THERE I SAID IT. I can hear the hate mail rolling in. Anyway, I’ve encouraged readers to check out Linux as a Windows alternative. These are my experiences moving to a (mostly) Linux world over the last 6 months.

My goal was to move to Linux as my daily operating system. That is done. In that transition, find Linux programs equivalent to the Windows applications I was using. Anything I couldn’t find suitable replacements would be run in a Windows virtual environment.

In previous articles, I’ve written about the disaster that has become Windows 10 and my desire to find a less restrictive and obtrusive operating system. I settled on Fedora Linux because the virtualization worked better in my experience over Ubuntu. Moving my main desktop away from Windows was the last hurtle. This PC serves the duties of: audio & video recording (DVR mostly), ripping, editing and playing, graphics editing, web site editing, file storage and backup, virtual environment, web surfing, ham radio programming, and experimentation station. That pretty much covers it. You could throw in gaming about 10 years ago – who has the time? Also, the occasional document (image) scanning. This will become important later.

In my experience, what does work?

  • Linux works. I have not had any issues getting Fedora to work on stock laptops or my custom-built desktop machine. With few drivers to install, all hardware works including USB 3.0. Most of the pre-installed programs (graphics viewer, LibreOffice, music & video player) are very usable programs.
  • Package manager. This keeps the operating system and programs updated when approved by maintainers of the distribution. When I can, programs are installed through the package manager and I’ve accepted all updates when made available. I may have had a Kernel issue once or twice but simply selected a previous version at boot time.
  • Customization. I spent some time trying out different desktop environments because I cannot stand tablet-style interfaces in desktop environments on non-touch screen devices. Gnome, I’m
    Oh My Zsh customized terminal

    talking about you! Cinnamon is probably the closest to a Windows desktop-like feel with start menu, taskbar, and system tray. This is the one I choose. Customization tools import and apply different theme options. I replaced the bash shell with Oh My Zsh. Came for the themes. Stayed for the awesome autocomplete.

  • Virtualization works very well with VirtualBox. I’m looking at getting virt, virt-manager, and KVM working in the future.
  • Cross-platform apps. I’ve had good experience with applications that have a strong user base and are ported to different platforms. These apps would include VLC (formally VideoLAN), HandBrake, Thunderbird, Firefox, VirtualBox, and VeraCrypt. This is likely because development efforts contributed to the project benefit all platforms.
  • Web apps. Many services today are moving away from software installed on a PC to web based services. Having a modern web browser is all that is needed to interact with these services.

Where have I run into issues?
(Lack of) Popularity, including vendor support. This covers 75% of my issues. According to StatCounter Global Statistics, looking over the last two years at desktop and laptop platforms used to browse the web, Linux hasn’t passed the 2% mark and is currently holding steady at about 0.8% in the U.S. In comparison, OS X is at about 20% and Windows about 75%. Servers typically don’t browse the web so these numbers represent users running Linux to do a common computing activity, like browsing the web. When there are financial decisions to be made on developing an app or service, you’re going to go where the customers are. Linux hasn’t gained any significant market share when compared to that disaster operating system or the hardware priced out of the budget of average users (Windows & Mac).

Fedora Cinnamon spin

Vendors are simply not focusing a lot of their resources on a small segment of users when others like Windows eclipse that 2%. I’ve run into a couple examples. First being the drivers for the NVidia graphics card in my desktop. The process of getting this driver installed is a fairly complicated process. It’s dependent on system BIOS and involves editing Kernel boot options – not something average computer users are comfortable doing. If you’re lucky, you’ll magically end up with an NVidia driver that works with the installed Linux Kernel. The open-sourced driver, Nouveau, generally works for me but I notice flickering on some screens like ones with dark gray backgrounds. Nouveau has crashed a couple times when I had a bunch of applications running at once. A sinking feeling knowing how many applications I had open and not knowing when I last clicked save is not my idea of a good time.

I installed the Epson Linux image scanning driver for my flatbed scanner. The app very closely resembled the Windows application which made it familiar to use. However, though the manual indicates I should have been able to scan multiple pages and save them as a single PDF file, I did not have this option. I tried the native Fedora app, Simple Scan. It was way too simple. Automatically scanning the next page of a multi-page document after a selectable 3-15 second interval didn’t make any sense to me. Others I tried created ginormous sized PDF documents, 50MB file vs 3MB using the Epson Windows app. There is no reason to have files that large and some email systems have attachment limits of about 25MB.

In August, Dropbox announced they were dropping support for almost all Linux file systems. Many users were upset. Speculation was Dropbox had to support a wide variety of Linux distributions, file systems, desktop environments, and Kernels where they didn’t see any return on this investment. Companies often take a chance hoping users purchase paid subscriptions to support further developments in these areas. Linux users weren’t subscribing to sustain further development and support, so it was dropped. Most Linux users like free stuff because, well, the operating system itself is free.

I would say the remaining 25% of my issues are round quality of applications. While there are video ripping, editing, and authoring tools available, they don’t hold up to the Windows tools I’m using. Most users are on Windows so that’s where companies devote their time. Application authors who set out to make equally good tools in Linux may run into problems or lack of interest either in terms of downloads, support from the community, or through life, job, or family changes. Handbrake and VLC work as well in Linux as Windows. Video stream repair and splitting, DVD and Blu-Ray authoring, DVR, and audio ripping – not so much. Still using Windows applications. Not saying all Linux tools are bad because there some really powerful ones.

My desktop was the big obstacle to accomplishing my goal of getting Linux as my daily operating system. 99% of the time that system is running Fedora. I do have a number of virtual Windows machines for things like MS Office, radio programming, SDR programs, and my cord-cutter service – which says it will work in Chrome, but its only Chrome running on Windows. For applications and hardware interactions that didn’t work well in a virtual environment, I resized my original Windows partition down to about 30 GB and boot into Windows only when I need it. My shack PC is going to stay on Windows 7 because some of my ham activity is tied to programs only available on Windows.

These have been my experiences in moving away from the Windows disaster into an alternative desktop & laptop platform – Fedora Linux. These might motivate you to try Linux or some other Windows alternative. It will be like learning something new for most people. I had ideas of what the experience would look like and challenges having supported and programmed in Linux environments for the better part of a decade. The Mac platform has really become popular with great applications and great support from Apple. If you’re not willing to drop a significant amount of money on their devices, consider looking at Linux as an alternative.

Late breaking for FT8 users: if you operate either the very popular FT8 or MSK144 digital modes, please update your version of WSJT-X to 2.0 by January 1, 2019. These protocols have been enhanced in a way that is not compatible with previous versions of WSJT-X. After that date, only the new version of those modes should be used on the air.

Thanks for reading. Happy holidays, Merry Christmas, and Happy New Year!

73… de Jeff – K8JTK

Ohio Section Journal – The Technical Coordinator – April 2018 edition

One of the responsibilities of the Technical Coordinator in the Ohio Section is to submit something for the Section Journal. The Section Journal covers Amateur Radio related things happening in and around the ARRL Ohio Section. It is published by the Section Manager Scott – N8SY and articles are submitted by cabinet members.

Once my article is published in the Journal, I will also make it available on my site with a link to the published edition.

You can receive the Journal and other Ohio Section news by joining the mailing list Scott has setup. You do not need to be a member of the ARRL, Ohio Section, or even a ham to join the mailing list. Please sign up!

If you are an ARRL member and reside in the Ohio Section, update your mailing preferences to receive Ohio Section news in your inbox. Those residing outside the section will need to use the mailing list link above.
Updating your ARRL profile will deliver news from the section where you reside (if the leadership chooses to use this method).
Go to www.arrl.org and logon.
Click Edit your Profile.
You will be taken to the Edit Your Profile page. On the first tab Edit Info, verify your Email address is correct.
Click the Edit Email Subscriptions tab.
Check the News and information from your Division Director and Section Manager box.
Click Save.

Now without further ado…


Read the full edition at: http://arrl-ohio.org/news/2018/OSJ-Apr-18.pdf

THE TECHNICAL COORDINATOR
Jeff Kopcak – TC
k8jtk@arrl.net

DSCF5081 K8JTKHey gang,

In all the ragging (er, discussion?) on Windows 10 last month, Bill – K8RWH had some good points and questions about Linux that I decided to write a follow up this month. There is a lot to parse, especially different terminology. The most useful website for Linux information is called DistroWatch, short for Distribution Watch. Most of the information here will come from that site. Let’s get to it.

History

Linux came out of the Unix operating system implemented by Ken Thompson and Dennis Ritchie (both of AT&T Bell Laboratories) in 1969. “Linux began in 1991 with the commencement of a personal project by Finnish student Linus Torvalds to create a new free operating system kernel. Since then, the resulting Linux kernel has been marked by constant growth throughout its history. Since the initial release of its source code in 1991, it has grown from a small number of C (programming language) files under a license prohibiting commercial distribution to the 4.15 version in 2018 with more than 23.3 million lines of [code] … ” (Wikipedia).

Tux

I’d be remiss if I didn’t mention the official Linux mascot. “Torvalds announced in 1996 that there would be a mascot for Linux, a penguin. This was due to the fact when they were about to select the mascot, Torvalds mentioned he was bitten by a little penguin on a visit to the National Zoo & Aquarium in Canberra, Australia. Larry Ewing provided the original draft of today’s well known mascot based on this description. The name Tux was suggested by James Hughes as derivative of Torvalds’ UniX, along with being short for tuxedo, a type of suit with color similar to that of a penguin” (Wikipedia).

Crash course in Linux terminology

GNU/GPL – software licensing methodologies frequently used by Linux and Unix variants.

Open Source – anyone can see the building blocks of a project known as the source code. This is beneficial because anyone with skills can fix and improve upon an open source program.

Kernel – is the core to any operating system (not only Linux). It interacts with and controls the computer’s hardware (mouse, keyboard, monitor/graphics, hard drive, USB devices, network). It is the lowest level of the operating system.

Operating System – collection of kernel and software that make a computing device work. Most operating systems include drivers, text editor, file manager, and a method for installing & removing applications (known as a “Package Manager” in Linux).

Architecture – type of processor an operating system can run. 64-bit, 32-bit processors, Raspberry Pi and mobile devices are examples.

Live CD/Medium – the operating system can be run from a CD or USB drive without installing to a hard drive. This is useful in testing different operating systems or to aid in recovering an inaccessible system.

Dual-boot – in contrast to “live CD,” installation of one or more operating systems on the same computer. My experience: install Windows first, then Linux. The Linux boot-loader plays nice with Windows but not the other way around. Reinstalling Windows will also break the Linux boot-loader. It can be repaired but will stress your Google and command line-fu skills.

Distribution – similar to “Operating System” but often targeted for a specific purpose or category: servers, desktops, beginners, education, gaming, multimedia, security, utilities, telephony, etc.

Checksum or Hash – applies an algorithm to data. It is used to track errors introduced in transmitting data or storing data. Checksum programs are standard in Linux operating systems. A third-party program like HashTab or QuickHash GUI are needed to verify a checksum in Windows.

Desktop environment – how a user interacts with multiple applications at once. This is a matter of personal preference. Popular desktop environments are: Cinnamon, GNOME, KDE, MATE, and Xfce.

Popular Linux Distributions

DistroWatch has just short of 900 Linux distributions in their database. Over 300 are considered active (updated in the last 2 years). Only about a handful are useful to average users. For a complete guide see “A Guide to Choosing a Distribution.”

Linux Mint

Linux Mint – launched in 2006 to address many of the drawbacks associated with a more technical operating system such as Linux. Using the Ubuntu distribution as a base, many beginner enhancements were created for usability. I had read about security concerns with Mint and began to steer users away from it. However, DistroWatch published a “Myths and Misunderstandings” debunking many of those points. If you’re a noobie and want to dive into Linux as an alternative operating system, start with Mint.

Ubuntu – Launched a few years earlier in 2004, this project took off faster than any other distribution and was touted as the way to get average people to use Linux. Learning from the mistakes of other projects and taking a professional approach to its users made it a popular choice. Excellent web-based documentation and an easy to use bug reporting facility was created. Though frequent major changes and the Unity interface – more suited for mobile devices – have driven users away.

Elementary OS – This one is for Mac users. It emulates MacOS and puts a lot of focus into ascetics.

Debian – base for the above and 120 other Linux distributions. Debian is remarkably stable due to its high level of quality control. It has support for many software packages and processor types making it a great choice for older systems. Due to that level of processor support it lacks newer technologies.

In the 300 other active Linux distributions, specialized versions serve an intended purpose:

Windows Compatibility

Users who’ve switched to Linux or Linux users that need to run a Windows app might ask: can I run Windows applications on Linux? Yes, there are a couple ways to accomplish this.

Run a virtual machine program like VirtualBox. A virtual machine emulates hardware and the functionality of a physical computer. Similar to dual-booting it requires a full installation of the desired (guest) operating system. Emulation is resource intensive for the physical (host) operating system hardware. It doesn’t make much sense to have a multi-gigabyte Windows virtual install to run a small application.

WINE running Media Player Classic and SumatraPDF (Wikipedia)

This is where WINE comes into play. Wine stands for Wine Is Not an Emulator. It’s not a virtual machine but rather a compatibility layer to translate Windows system calls into Linux system calls. WINE takes a considerable amount of configuring but programs like PlayOnLinux and Winetricks make life much easier. Neither solution is perfect and won’t succeeded in cases of complex applications or ones requiring specialized hardware.

In terms of ham radio, Windows was the overwhelming platform of choice for Morse Code and digital mode applications because everyone was using it. Older Windows only applications (MMSSTV, DigiPan) are going to run well on that platform. The good news is programs like Fldigi and QSSTV are viable replacements on Linux and, in many cases, better than their dedicated Windows counterpart. In addition, the Ubuntu package manager has an entire category dedicated to Amateur Radio applications. If you’re someone whose fed up with the badness and frustrations of Windows 10, give Linux a try.

Thanks for reading and 73… de Jeff – K8JTK

Bridge a Remote Site Network with OpenVPN Access Server

Having access to your devices over the Internet is a requirement for any admin deploying a project. Instead of running to a remote site to administer devices (making changes, applying updates and patches), it’s easier to connect remotely and make changes. Remote access poses many issues and concerns.

Security

First and foremost is security. You always, always, ALWAYS want devices connected to the Internet behind a router with a built-in firewall (NAT router). A firewall filters traffic between two networks (your ISP and home for example) and will block attempts to connect to your internal (private) network.

Device manufacturers take security for granted. Little testing and auditing takes place because the analysis is expensive for throw-away devices. This is noted in many stories including Bug Exposes IP Cameras, Baby Monitors where simply clicking “OK” on the login dialog allowed access to the Internet connected video camera. It is trivial to find these devices on the Internet because of Shodan. Shodan is dubbed the “Internet of Things Search Engine.” If you’re not familiar, think of it as the Google for devices connected directly to the internet. These could be: web servers, printers, cameras, industrial machines, bitcoin mining… Putting devices behind a firewall minimizes the risk because anything trying to peer into the network would be blocked by the firewall.

This holds true for networks you don’t control (granted access on someone else’s network). Put your stuff behind a router/firewall so they can’t see your devices and you can’t be exploited by devices on the other network.

Port Forwarding is a popular technique to only allow traffic on a specific port to a device you specify in your firewall (router). This provides little security as it still allows a potentially vulnerable service to accept incoming connections from the Internet.

Choose a good router

Couple of tips for a good router:

  • You get what you pay for. Don’t opt for cheap.
  • Opt for ones that support third-party firmware like DD-WRT and Tomato or setup a dedicated computer running pfsense or Untangle. These have proven to be more secure than stock firmware in addition to offering a more complete feature set.
  • Stick with popular models as found on Amazon, Newegg, or other tech store. They’re more likely to be reliable, well updated models.
  • Look for ones that accept USB cellular modem dongles for installations that have no accessible network connection like a remote site.

Virtual Private Network

The preferred way to connect to a remote network is to use a VPN. A VPN connects to a private network securely over the Internet. It allows the user to exchange data, use services, and connect to devices as if they were directly connected to that network. An open-source project that implements VPN technologies security is OpenVPN. OpenVPN is an application that allows for secure point-to-point communication. There are many implementations of OpenVPN including using it in many third-party router firmware (mentioned above). OpenVPN Access Server is one of the many implementations and the one used for this project.

This project was inspired by Hak5 1921 – Access Internal Networks with Reverse VPN Connections. As an Amateur Radio operator into the newer computer and digital technologies, more devices are located at remote sites.

This setup consists of:

  1. A remote network behind a firewall where devices exist you want to access. This will be a Linux server on the remote network that will act as the gateway and persistently connected to the bridge. This could be a full desktop computer purposed for something else or Raspberry Pi. Also on the same network will be a Windows machine.
  2. An unsecure/unknown network, AKA the Internet.
  3. A private server that will act as the bridge between the remote network and a device you choose.
  4. A device in a separate location that will connect to the cloud server and will be able to access the remote network. I will use a Windows machine to act as a ‘home’ computer.

This setup works in nearly all cases because the only device receiving incoming connections is the bridge server in the cloud. Firewalls block incoming connections by default. Very few block connections originating inside the network out to the Internet (egress). If a device along the way filters by content, connection attempts will be blocked. Many corporate networks are doing this kind of filtering. Otherwise the traffic looks the same as secure web traffic on port 443. No port forwarding is used.

Hosting

I recommend using an infrastructure hosting provider for the bridge server. This can cost anywhere from $5-$15 per month. The device can be anywhere on the public Internet. It must accept multiple connections on different ports but only by a couple users at a time are needed. Minimal configuration is more than sufficient. Bandwidth, latency, and up-time of all points in this setup effect reliability. My personal recommendations for infrastructure hosting providers are: Rackspace and DigitalOcean.

IP addressing

All remote networks and the home user networks cannot overlap in address space. That is they need to be differently numbered. For example, typically home networks have addressing as 192.168.1.x. The remote site(s) can’t have the same numbering (192.168.1.x). It must be different. I suggest making the remote site different enough to not cause conflict with any home users’ networks. Remote sites as 192.168.25.x, 192.168.26.x, and 192.168.27.x would work fine when the home users’ networks is addressed 192.168.0.x, 192.168.1.x, 192.168.2.x, and so on (except 25-27). Similarly addressed networks create routing conflicts and the packets will not reach the correct network.

Downsides

Cost.

In addition to hosting, a downside to using OpenVPN Access Server is licensing. While OpenVPN is Open-Source Software and OpenVPN Access Server is free, the license allows for only two concurrent tunnel connections at any one time. This means the remote site counts as one connection and the home device the second. If a second person (third device) needed access to the remote network, they would get a message saying ‘Access Server has reached its concurrent connections limit.’ The first person would need to disconnect first before the second could connect otherwise current connections will begin to be booted. Additionally, connecting two or more remote sites and a home user is not possible without purchasing licenses or running an additional bridge server. Additional licenses can be purchased for “$9.60 License Fee Per Client Connection Per Year. Support & Updates included. 10 Client minimum purchase.” $96 per year.

An alternative to OpenVPN Access Server is to setup your own (roll your own) OpenVPN server which is free. I hope to do an OVPN server setup at some point in the future.

Assumptions

This guide is step-by-step in nature, meant for beginners, with brief explanations of the steps. It will help to have an understanding of Linux commands and scripting. Capitalization is important in Linux! Understanding of basic networking concepts including determining network prefixes and CIDR notation is also required.

Program versions

I used a Windows 7 64 bit PC for configuration (and Home PC). Applications and versions used in this writeup:

  • OpenVPN Access Server 2.0.24
  • Putty 0.67
  • Ubuntu 14.04 x64 (bridge and remote servers)
  • Filezilla 3.16.0

Running Fldigi Flmsg and Flwrap on the Raspberry Pi 2

With the popularity of the Raspberry Pi and the growing need of NBEMS, I wondered if it was possible to run NBEMS programs on the Pi. This maybe of interest to those who want to make a Go Kit (box) with digital or a club wants to replace older computers in their operations center with more efficient devices.

Fldigi is the program used and developed for Narrow Band Emergency Messaging System, but it does so much more. It’s also the standard for many Ham Radio operators because of the number of modes the software will operate.

Fldigi stands for Fast Light Digital modem application created by W1HKJ (David Freese, Jr.) and associates. Flmsg is a forms manager with standardized forms like MARS, plaintext messages, Radiograms, Red Cross, and Weather report forms. Flwrap is a file encapsulation and compression tool allowing for reception of a file exactly like the original.

The Fldigi application is open source, public license software meaning it’s free and available for auditing. With the source code available for Linux, I wondered if it was possible to compile the application on the Raspberry Pi.

At first I had some problems with the project. After (wasting) alot of time on it, I had given up. Only to find out the power supply I had been using was the cause of the issues.

Requirements

Work with my SignaLink USB. As a standard with my projects, the Pi can administered through SSH and VNC if needed. On Windows, I use PuTTY and TightVNC.

Assumptions

This guide is step-by-step in nature, meant for beginners, with brief explanations of the steps. It will help to have an understanding of Linux commands and scripting. Capitalization is important in Linux!

Check my other posts for setup guides on using your radio interface (though written for Windows) and Fldigi, Flmsg, and Flwrap.

Program versions

Applications and versions used in this writeup:

  • Windows 7 64 bit
  • Raspbian Jessie 2015-09-24
  • Win32DiskImager 0.9.5
  • PuTTY 0.65
  • TightVNC 2.7.10 64 bit
  • Fldigi 3.23.04
  • Flmsg 2.0.12
  • Flwrap 1.3.4

Build times

I did a face off for build times between the later model Pi versions: B+, 2, and 3. Later iterations will be faster. The results are in the format of the Linux command time, which contrary to it’s name does not set the time. It gives statistics about this program run. They consist of the elapsed real time between invocation and termination, the user CPU time, and the system CPU time. Later versions than listed above were used in this face off: Raspbian Jessie 2016-05-27, Fldigi 3.23.10, Flmsg 3.0.0, Flwrap is the same at 1.3.4.

Raspberry Pi B+

Failed. Apparently there is an issue running the Make command for Fldigi with versions later than the ones I originally used in this writeup. By the error messages this is an internal g++ compiler error. Make does not fail on the Pi 2 and 3 which probably means it’s a hardware issue (out of memory).

The error is “Warning: partial line at end of file ignored” for dialogs/fldigi-confdialog.o.

Raspberry Pi 2

real 21m49.783s
user 72m9.970s
sys 2m39.290s

Raspberry Pi 3

real 12m50.129s
user 42m8.980s
sys 1m19.160s

Parts list

Listed below are all the parts needed to get this project working. It is noted when items can be left out or substituted.

That’s all the parts needed for this project. Check out the AdaFruit Raspberry Pi page for other hardware that might be useful, like the USB to PS/2 adapter for example. Many of these parts are included in the Raspberry Pi Starter Pack.

If the Pi is setup where there may not be Internet, want to consider purchasing a Real Time Clock (RTC) addon. The Pi will keep time after power has been removed. Of course the time would just have to be set each time.

Flmsg custom forms

In order for custom forms to be used in Flmsg, version 2.0.17 or later must be used. There was a bug in previous versions that didn’t allow the forms to be parsed correctly. In addition, another browser needs to be installed as the default is unable to connect to the webserver created by Flmsg. Thanks to Ken – W0KAH for determining this issue and getting it resolved with the program author.

Linux package installer

The version available from the package manager could be installed but that version is several revisions behind which won’t have the latest enhancements. Some repositories don’t have Flmsg and Flwrap which makes it hard for NBEMS operation.

sudo apt-get -y install fldigi

sudo apt-get -y install flmsg flwrap
If it doesn’t work, you’ll get a message like:

E: Unable to locate package flmsg

Getting Started with Fldigi – Including Flmsg and Flwrap

Updated: 03/26/2017

Table of Contents

Introduction – page 1

Download and installation – page 2
-All 3 programs

Configuration – page 3
-Fldigi
-Flmsg

Receiving
-Fldigi – page 4
-Flmsg – page 5
-Flwrap – page 6

Transmitting
-Fldigi – page 7
-Flmsg – page 8
-Flwrap – page 9

Introduction

This document will show installation, setup, and basic use of Fldigi, Flmsg, and Flwrap. Fldigi stands for Fast Light Digital modem application created by W1HKJ (David Freese, Jr.) and associates. Flmsg is a forms manager with standardized forms like MARS, plaintext messages, Radiograms, Red Cross, and Weather report forms. Flwrap is a file encapsulation and compression tool allowing for reception of a file exactly like the original.

The Fldigi suite has many applications and can operate many, many different modes. For the list of modes, click the “Op Mode” menu in Fldigi. A quick description of the Fldigi suite from W1HKJ:

Fldigi – Digital modem program.
Flarq – AutomaticReQuest file transfer program (works with Fldigi).
Flamp – Amateur Multicast Protocol file transfer program.
Flwrap – File encapsulation for error free transfers over amateur radio.
Flmsg – Formatted message manager – 25 forms including Radiogram.
Flrig – Transceiver control program.
Flwkey – Winkeyer control program.
Fllog – Logbook program – works with Fldigi, Flwkey etal.
Flnet – Net management and database program.

The Digital Net typically operates Fldigi using NBEMS standard methods for VHF and UHF communication. NBEMS stands for Narrow Band Emergency Messaging System (or Software) (http://www.arrl.org/nbems). NBEMS VHF/UHF operating mode is MT63-2KL and Olivia 8/500 or 16/500 for HF operation. HF digital operation is considerably different than VHF/UHF FM digital. HF station operating tips are not covered however application usage is similar.

Flwrap is no longer considered part of NBEMS but is a useful program to send small files.  If only operating NBEMS, Flwrap can be omitted and ignored.

This is written with the beginner in mind and many concepts outlined step-by-step. It will provide direction for further experimentation on your own or on the net and direction for troubleshooting.  For SignaLink and audio setup, visit the Radio Interface Setup post.

Prepared for The Lake Erie Amateur Radio Association’s Digital Net (http://www.leara.org/).

Program versions

Program versions used in this document.

Windows 7 – 64 bit

Fldigi 3.23.21

Flmsg 4.0.1

Flwrap 1.3.4

Resources

http://www.w1hkj.com/beginners.html – Beginners guide to Fldigi.

http://www.w1hkj.com/FldigiHelp/index.html – Fldigi help.

http://www.w1hkj.com/flmsg-help/index.html – Flmsg help.

http://www.w1hkj.com/Flwrap/index.html – Flwrap help.

Calibration

Sound card calibration for some modes Fldigi supports is important; it is recommended regardless of mode. See the “Sound card clock calibration” section in the “Radio Interface Setup – For getting started with Ham Radio Sound Card digital modes” document. Fldigi method: http://www.k8jtk.org/2015/10/19/nbemsfldigi-sound-card-calibration/.

ADS-B Decoding with RTL-SDR, ADSBSharp, and Virtual Radar Server

Update: ADSBSharp (ADSB#) is no longer available and has been deprecated.  Copies can be found by doing some searching.  It is not available from the authors site as described in this post for the RTL-SDR. A program like RTL1090 or Dump1090 (or any of its forks) can be substituted.  The author is focusing on AirSpy devices and ADSBSpy is available from the same site as SDR#.


An interesting project I came across using the RTL-SDR dongle is to decode ADS-B data.  ADS-B stands for Automatic dependent surveillance – broadcast allowing aircraft to be tracked by ground stations and provide situational awareness to nearby aircraft.  It is part of the FAA’s NextGen project and mandated by agencies across the globe.  ADS-B uses a frequency of 1090 MHz.

Thanks goes out to Robert Nickels – W9RAN and his article in the January 2014 edition of QST which covers this project and how to make a Collinear Array for 1090.  HAK5 also did a couple episodes showing how to make an antenna and configure Virtual Radar Server.

adsb-hub-diagram
Block diagram of the ADS-B Hub setup. From: QST, January 2014.

Program versions

I used a Windows 7 64 bit PC.  Applications and versions used in this writeup…

SDRSharp: 1.0.0.1330
ADSBSharp: 1.0.11.1
Zadig: 2.1.0.658
Virtual Radar Server: 2.0.2
SBS Resources: 6.7

Parts list

Listed below are all the parts needed to get this project working.

Antenna with receive coverage of 1090 MHz.
RTL-SDR dongle.

I had a ham radio antenna that I used.  It is the MP Antenna 08-ANT-0860 Ultra Mobile Antenna if you’re interested.  To build an antenna, see the QST article above.  The one that comes with the dongle will work but at short range.

Dongle Bits: RPi B+ and $20 SDR

This article appeared in the The Lake Erie Amateur Radio Association newsletter The Spirit of ’76 and ’88 August 2014 edition and The Wood County Amateur Radio Club newsletter CQ Chatter September 2014 edition.

Read the rest of the series in the Dongle Bits articles category.


Before we begin talking about the RTL-SDR dongle as promised, some big news broke. The Raspberry Pi Foundation released the Raspberry Pi Model B+. They point out this is not a “Raspberry Pi 2” but an evolution of the model B board. Price is the same at $35. Key improvements are:

  • More GPIO: 40 pins with the first 26 pins the same as the Model B.
  • More USB: 4 USB 2.0 ports with better hotswap and overcurrent behavior.
  • Micro SD: SD card socket has been replaced with a micro SD version.
  • Lower power consumption: Reduced power consumption by 0.5W to 1W.
  • Better audio: The audio circuit incorporates a dedicated low-noise power supply.
  • Neater form factor: Aligned the USB connectors with the board edge, moved composite video onto the 3.5mm jack, and added four squarely-placed mounting holes.
Raspberry Pi Model B+

For more details, diagrams, and videos, please visit Introducing Raspberry Pi Model B+. Because of the new configuration layout many accessories for the B board will not work with the B+ board.

Now, RTL-SDRs: RTL-SDR is a term used describe a very cheap software defined radio. Other names for this device are: RTL2832U, DVB-T SDR, or “$20 Software Defined Radio.” RTL refers to Realtek Semiconductor Corp most widely known for their computer IC network controllers, card readers, and very popular High Definition Audio codec used in many laptop and desktop computers.

SDR refers to “software defined radio.” Typically radio components like mixers, filters, amplifiers, modulators/demodulators, and detectors are implemented in hardware level components. In SDRs these components are implemented by way of software running on a PC or embedded system. The most widely known SDR in ham radio is FlexRadio.

RTL-SDR Dongle

The RTL-SDR is a DVB-T TV tuner dongle based on the RTL2832U chipset. DVB-T stands for Digital Video Broadcasting – Terrestrial used in the eastern hemisphere (Europe, Asia, Africa, and Australia) as their over-the-air broadcast standard. In contrast, North America uses ATSC (Advanced Television Systems Committee) standard for digital television transmission over-the-air, cable, and satellite networks (sources: DVB-T and ATSC).

Antti Palosaari, Eric Fry, and Osmocom were hackers playing around with these receivers and found the signal data could be accessed directly. This allowed a cheap DVB-T TV tuner to be converted into a wideband software defined radio via a new software driver and used as a computer based radio scanner. Add in software packages to expand the capability and you have a system that would cost hundreds or even thousands of dollars.

RTL-SDR Internal Hardware

The current popular dongle is the NooElec NESDR Mini SDR & DVB-T USB Stick (R820T). It comes with an antenna that only works well for very strong signals. Yes, it does come with a Remote but you don’t need it for SDR. They guarantee the NESDR will have an electrostatic discharge diode (ESD) in their dongles. This is useful when handling the dongle or traveling where the possibility of frying it is greater. However, as I found out, if you drop one of them upon returning from Dayton you’re better off getting another because it just won’t work the same!

Let’s dive into some specifics:

  • RTL2832U Chipset close-up

    Frequency range: depends on the device and chipsets used. The NooElec NESDR has a receive range of 24 – 1766 MHz. The previous Elonics E4000 hotness covered 52 – 2200 MHz. However, that company went out of business making the dongle rare and more expensive.

  • Sample rate: maximum theoretical sample rate is 3.2 MS/s (mega samples per second). The optimal sample rate (without any dropped samples) is 2.4 MS/s.
  • Analog-to-digital conversion resolution: 8 bits.
  • Input impedance: 75 Ohms. The mismatch loss when using 50 Ohm cabling is minimal.
  • Connector type: most use an MCX connector. The E4000 uses a
    MCX Connector

    PAL connector.

These $20 dongles only receive. Other dongles offer better performance but come at a higher price. The FunCube Dongle is an example of this. HackRF (10 – 6000 MHz) and BladeRF (300 – 3800 MHz) are SDR radios that will transmit over their given frequency range. That’s right, wideband transmit! These are even more expensive at $300 – $650 (sources: About RTL-SDR and Buy RTL-SDR Dongles).

What about HF? The dongles themselves don’t cover HF. There are two options for reception: use an upconverter to receive the frequency and convert it up to a frequency the RTL-SDR dongle can receive. Make a hardware modification to allow “direct sampling mode.” HF upconverters are anywhere from $50 – $100 (cheaper if you build your own) and offer better performance over the hardware mod. KF7LZE has a round-up of HF upconverters.

This quickstart guide shows how easy it is to setup and start receiving signals. Windows users will probably start out with SDRsharp (also written SDR#) to receive signals. Linux users have a couple options; GNURadio being the best though it is unwieldy because you build out the SDR from scratch.

These make it easy to receive FM broadcast (WFM), NOAA weather radio, amateur radio, or public service frequencies that are still analog. I will show uses and applications of these SDR receivers including a reason you might want to get two (or more) dongles. Hint: it’s not to replace one after Dayton!