Amateur Radio with KC7MM
NOTE: this page is under construction. I'll add to it as I work my way through testing the substitute systems.
The Raspberry Pi has become a very popular system in the Ham shack. Unfortunately, disruptions to the electronics supply chain have made them both scarce and expensive, selling at scalper prices.
One of the participants in the Linux User Net recently asked about possible less expensive alternative systems. That led me to an exploration of what might be available to fill the Pi's shoes at a modest price. The project is only partially complete, but I'm far enough along that I thought it worth posting – I'll update this page as I progress.
A Pi replacement needs to be at least as capable as the Pi, and no more expensive. So, I limited the search to systems that:
I selected possible units based on the above, keeping in mind three categories of common Pi usage in Amateur Radio:
So far, I have obtained the following units for testing:
Also included is the Raspberry Pi 400, which is essentially a Pi 4 embedded in a keyboard.
The following table compares their specifications the the Raspberry Pi.
|RPi 4/400||HP Cbook 11 G5||Dell Cbook 11 3189||Acer CBox CXI2||Dell WYSE Dx0D||NUC DN2820FYK||Surface Pro 3|
|Storage||16GB SD card||16GB SSD||16GB SSD||32GB SSD||Varies||Varies||128GB|
|USB ver.||3, C||2||2||3||3||2, 3||2|
|Screen||No||11“||11.5” touch||No||No||No||10.5“ touch|
|Audio||Jack||Spkr + Jack||Spkr + Jack||Jack||Jack||Jack||Spkr + Jack|
|Power||USB 5v 3a||19v DC||19v DC||19v DC||19v DC||12v DC||12v DC|
|Cost||$80 MSRP||$50 EBay||$50 EBay||$35 EBay||$30 EBay||$45 Ebay||$79 Ebay|
The Pi 400 is available as of July 2022 at list price: $70 for the base unit, $100 for the complete kit.
The primary difference from the Pi 4 is the form factor: embedded in a keyboard. The GPIO pins are exposed on the 400, but Pi hat plugin boards won't fit. So, if you need to use a hat or rely on the compact form factor of the Pi 4, it's not a suitable substitute. Otherwise, it has all the capabilities of the Pi 4, at its normal price
The price is slightly above my $80 limit, but it might be worth the extra few dollars for a drop-in replacement that's ready to run Pi software right out of the box.
One of the first things I noticed while looking on Ebay for budget machines was the large number of used Chromebooks and Chromeboxes selling for around 50 dollars. Further research brought me to GalliumOS, a Linux distribution for ChromeOS devices. After looking at the hardware compatibility page, I decided the give that a try.
The next step was to check out the custom firmware for Chromebooks and Chromeboxes at MrChromebox. This can install UEFI boot firmware, which in turn allows the installation of an operating system. I decided early on to use it replace the factory firmware. I consulted the supported devices table when selecting test machines.
That done, I purchased two Chromebooks and a Chromebox to see what I could do with them.
|Operating System:||GalliumOS, Debian 11, Manjaro|
This is a conventional clamshell-style laptop, with an 11.5-inch screen, keyboard, and touchpad.
For a discussion of the conversion process, see my entry on groups.io. I initially installed GalliumOS, but switched to Debian 11 in order to get more current software (GalliumOS is based on Xubuntu 18.04). I then moved to Manjaro XFCE minimal in order to get the latest version of PipeWire audio software so I could do some tests with it. All three distros ran well, though only GalliumOS worked with the internal sound card. I left Manjaro on it.
Server: Lacking Ethernet and with slow USB, this unit isn't particularly well suited to work as a server. Its 16GB storage is on a par with many Pis. Still, it probably would be adequate for the for the low-volume services typically used in the shack.
Workstation: As a workstation for the shack this unit can do pretty much anything the Raspberry Pi can, and the built-in keyboard and screen are a genuine advantage. (See the update, below, for more on this.)
Portable use: The built-in battery is a plus here. With networking and Bluetooth turned off, it should last a long time. The down side is the 19V power supply, which makes recharging in the field a challenge. An inexpensive power inverter, though inefficient, might fix that. –
I passed this unit on to a Ham friend who is new to Linux. He wants to work FT8 on a portable rig, and was looking for a computer he could use for that. He was able to install WSJT-X to run under Manjaro, then connected to his Yeasu HF rig via USB, using a SignaLink USB box.
I helped him set permissions to access the USB port, which consisted of granting membership in the
uucp group (this works for Arch Linux and derivatives such as Manjaro). That done, the software connected with the radio and started showing stations received – but experienced decoding errors, apparently due to inaccurate timing. That led to the final tweak, of turning on network time updates, which apparently had defaulted to being off. Running
timedatectl set-ntp true in a terminal took care of that, and FT8 now works properly.
htop to check the program's use of system resources, and found that WSJT-X used about 90 percent of the CPU for a second or two when decoding the incoming signals, and 8 percent or less the rest of the time. That's acceptable for his purpose, and should give decent battery life in the field.
For the few dollars invested in it, I believe this unit to be a fine value.
|Operating System:||LineageOS (Android), Manjaro|
This is a step up from the HP. It has a 2-in-1 form factor, which means it works as a conventional laptop with keyboard and touchpad, or the screen can be folded back 360 degrees for use as a tablet with the touchscreen. It also has twice the storage capacity at 32GB.
Conversion to Linux was similar to the HP Chromebook, save for opening the the case and locating the write-protect screw.
GalliumOS did not enable the touchscreen. LineageOS and Manjaro do, to varying degrees.
This device is a capable replacement for the Raspberry Pi, with the notable addition of built-in keyboard and screen. The down side is the 19V power supply, which is offset to a fair degree by the built-in battery.
This unit pretty much matches the HP Chromebook for suitability of purpose. The 32GB of storage could be an advantage under certain circumstances, as could the touchscreen and 2-in-1 form factor.
Note that LineageOS is an open source version of Android. It's prepared for use on Intel architectures by the Android-x86 project. It has the potential of running Android apps for Amateur Radio. I didn't try any of them. but I might at some point load LineageOS back on to check them out.
Another promising class of machines is thin clients. These already run Linux, and used ones can cost even less than Chromeboxes.
There are lots of small, inexpensive computers, housed in a tiny box and using an external power supply. Some older ones are available at prices that make them possible substitutes for the Pi.
|Operating System:||clear Linux|
Intel has has been producing the NUC (Next Unit of Computing) since 2013. This unit drew my attention because it runs an Intel CPU on 12 volts DC. Just about all the other compact computers I looked at – including newer NUC models – require 19 volts.
I found one on Ebay for $45, less power supply and disk drive. I had a 120GB SATA SSD on hand, and was able to pull a suitable PS from my bin of orphaned wall warts. A similar SSD can be had for $20, and a power supply for about $10, so it fits comfortably into the Pi-substitute price range.
The challenge I faced was in finding a Linux distro that would install on it. Manjaro installed all its files, but couldn't install the boot loader. Debian 11 didn't go even that far, freezing midway through the install. The one that worked in the end was Intel's own Clear Linux – that went on without a hitch.
I've been using Clear Linux for some time on a newer model NUC as a headless server to run Docker containers, and it has worked flawlessly. It's unusual in that its software repository consists not of individual packages, but as functional “bundles” of packages. To get the software that does the work you want, you install one or more bundles. For example, on the server I installed the docker bundle with one command, and had a full-featured Docker environment when it finished.
To test this box as a desktop system, I installed two bundles:
amateur-radio. That installed the Gnome desktop, along with wsjt-x, Fldigi, Dire Wolf, Xastir, and others. I added myself to the
dialout group, ran a USB cable to my IC-7100, and started flrig as a test application. I was able to configure flrig to connect to the 7100 and take control. From that I infer the other digital mode software would work, as well.
The primary drawback here is the fact that only Clear Linux would load on it. I don't think that's much of a problem for use a server, given my success with it on a NUC. But as a workstation it could prove to be a limitation if you want to run software that's not in a bundle. In either case, setting up Clear Linux requires a modest level of command-line system administration prowess.
Server: This would work well as a server. With 4 gigs of RAM and a plug-in SATA SSD for high-speed storage, it should be more capable than a Pi.
Workstation: The interface seemed a bit slow, but I expect it would be a suitable alternate to a Pi for running digital modes. I don't recommend it for general-purpose use; for example, Firefox wouldn't run.
Portable use: Running on 12 volts makes it well suited for portable operation from a battery supply.
I decided to have another try at installing Manjaro, and succeeded. With the help of this Manjaro Wiki article, I was able to install Grub while running live off a USB drive. Now I have a very nice XFCE desktop machine.
I also discovered that Amateur Radio applications are available for Manjaro via the AUR (Arch User Repository) and Flatpak – nice! These repos can be activated by setting Third-party preferences in the Add/Remove Software utility (
pamac). AUR apps install themselves by downloading source code and compiling it, while Flatpaks work as they normally do. I installed Flrig from AUR and was able to connect to the USB devices on my IC-7100.
With Manjaro installed, this would be be a fine station computer, for either base or portable use. I successfully installed and ran NoMachine (in the Manjaro repository), so this could be used on a remote station, as well.
Here's an article on other used NUCs as a Raspberry Pi substitute.
|Operating System:||Linux Mint 21 Cinnamon|
This one came as a surprise to me. I occasionally look in on the Explaining Computers channel on YouTube to see what Chris has been working with, and found that he had installed Linux Mint alongside Windows on a Surface Pro. I searched for more relevant videos and found another two about Linux on a Surface tablet, both of which were very helpful. The first, Pop!_OS on Surface Pro 3, showed me how well it could work.
The second video, How to Install Linux on a Surface Pro 3, was the one I followed for my install. Instead of Pop!_OS, I installed Linux Mint 21 Cinnamon edition. In order to get Mint to install, I had to do one thing in addition to what's in the video: format the UEFI partition to FAT32. I did that using Gparted from the live Mint session running off the USB key.
The result of my efforts was a fully-functional Linux tablet, which would work well in any station. Audio, camera, wifi, touchpad, and touchscreen worked out of the box. The MS pen is hit-and-miss, but a third-party stylus works fine. My tablet came with the optional snap-on keyboard, which also works well. Performance is good with its i5-3317U CPU. I/O ports are a bit limited, with one USB 2, a 3.5mm phone audio jack, and a micro SD card slot. In all, a fine Linux tablet for $79!
Two items to be aware of: power supply and battery. The power supply connector has a proprietary form factor and attaches magnetically – only one made for the Surface will work. The battery is not replaceable, so if you want to operate on battery make sure you get a good one.
Here are links to other Raspberry Pi substitutes.