Issues, Problems, Pitfalls, & The Conclusion
When we left GB Part 2, I talked about the fact that things didn’t always go as expected during either the GB1 or GB2 builds and that we would take a look at some of the specifics in this 3rd, and hopefully final, post for this series. I apologize ahead of time that there are no pictures in this installment, mainly due to these ideas having been thought of in hindsight and no pictures documented the failures. Also, though it might seem strange, I have no problem discussing issues and mistakes made during the development or building of any of my projects. As a nuclear engineer and process analyst by trade, it is my day job to objectively review trends and performance data looking for problems and looking for the lessons learned in them. So this is familiar territory, and any DIYer worth his or her salt should embrace learning lessons from failure, whether it’s theirs or someone else’s. I believe that it was Elenore Roosevelt who once said,
“Life’s not about expecting, hoping and wishing. It’s about doing, being and becoming. It’s about learning from the mistakes of others. You can’t live long enough to make them all yourself.”
I can’t agree more. If you never try anything you will never make a mistake, however, you’ll never get anything done either! So with those thoughts in mind, lets take a look at some of the issues I encountered in both of the GB builds.
Issue #1 – Weight
At the top of the list is weight. Although I have never weighed either GB I know that their initial versions were both very heavy. Lets take GB1 for instance:
GB1
In its initial version, GB1 had 3 metal shelves, a battery pack, and internal power supply. This made for a lot of extra weight and complicated the wiring. On further evaluation I had to resolve myself to the fact that something would need to be eliminated in order to achieve a reasonable level of portability. In the end I was able to reorganize the contents, shed the battery but keep the power supply, and generally simplify the power side wiring.
One thing that allowed me the ability to remove the battery without significant loss of capability was my adoption and building of external, portable battery packs. These will be covered in future posts. I was also able to sit back and do a “clean sheet” reconstruct of the box to make better use of the space available, but keep all four radios.
GB2
GB2 was also plagued by battery weight. The internal battery also had the added detractor of not having a significant amount of available power to justify its continued use. So in the version 2 rebuild I removed it and used that space to uncrowd the power and control wiring.
Lesson Learned #1 – Weight is a significant factor to address when you are building something that is intended to be portable, and by that I mean that you can move it yourself without a lot of assistance.
Issue #2 – Building Materials
In the quest to build GB2, I ran into issues of how to mount the equipment into the Apache 4800 case so they wouldn’t move around and become damaged. There was also the initial goal of having the case be somewhat weather tight. To be honest, these cases are great, for their price, but I would honestly never expect them to be watertight in any manner. That’s not a knock on the item or brand, just a simple expectation. If I really wanted watertight, I would spend the money on the Pelican brand, buy the related accessories for mounting the gear in one, and call it a day. But as I’ve said before, I’m cheap and this case met my needs.
But that still left me with the need to mount the gear. Enter, the drill and cap screws. Most everything inside that is heavy (like the radio bodies) is bolted into the case using cap screws, through holes drilled into the case. Really not a big deal, as long as you don’t make a mistake and drill a hole in the wrong location. I think I did that twice (remember the battery in version 1?). The repair, if you want to seal it up can either be a glue/epoxy of some sort, or heating up and sealing the hole with an old soldering iron. Honestly, I did neither. I fortunately was able to reuse those holes to mount the power distribution strip.
Another point here is that, in most cases, if you still need the case to be somewhat water tight, you can easily seal the screw holes with a sealant such as silicone. Also, by taking care to drill the holes slightly undersized in the plastic, they will almost self-seal due to having to virtually thread the screws into the holes.
Lesson Learned #2a – Take care when laying out holes to be drilled in GB cases. Though not usually a major issue or problem if you get it wrong, it does ding the look and our egos just a little.
In addition to the heavy gear, I also bolted 3/8″ aluminum angle around the perimeter of the case to allow for mounting the front panel holding the computer screen. I was able to drill and tap the aluminum for cap screws to hold the panel in place and allow for easy removal if required. That leads me to the next problem in this issue – brittleness.
One problem when working with build materials is the disparity of characteristics in a particular material. Take the front panel of GB2.
In version 1, this panel was cut from 1/4″ lauan plywood. A good strong material that cuts well and can be fabricated into most any part for a build such as this. However, it’s also flexible. So flexible, in fact, that I was afraid the flexing would result in a damaged screen. It also left sawdust residue where parts and cables rubbed against access holes. So in version 2 I opted for 1/4″ Lexan. This material is super strong, easily machined, and though flexible, not as much as the plywood within the dimensions of the box. All was great until the mounting hole in the upper left corner was drilled slightly out of alignment. In the struggle to get all of the screws to align and tighten down, this corner ended up cracking. Not the end of the world, but disappointing. Solution, epoxy the broken part back on, redrill the hole, and reinstall without the drama. Had this been the plywood panel, the flexibility would have allowed the misalignment with little grief.
Lesson Learned #2b – Make sure you understand and evaluate all of the characteristics of the materials you plan to use when building a project. Strength, flexibility, brittleness, UV resistance, to name a few, can all have an impact on the final project and its ability to meet your established goals.
Issue #3 – The Raspberry Pi In Portable Ops
It is no question that the Single Board Computer (SBC) has revolutionized the DIY/Maker landscape. Whether it’s an Arduino, Odroid, or Raspberry Pi, the fact that a significant amount of computing power can be housed on a small circuit board, smaller than the average cell phone, is amazing. The uses for SBCs include remote sensor and data gathering, robotics, automation, and of course portable computing. It’s in that vein that we employ a Raspberry Pi4 in GB1 and a Raspberry Pi400 in GB2.
In their basic form, each one uses a small Secure Digital, normally known as an SD card, to store not only the operating system, which is usually a smaller form of the linux operating system, but other files as well. These can include equipment manuals, emails, and documents. Add to this the available sizes of these small cards (128Gb+) and the capabilities begin to multiply significantly.
However, there is a drawback to this arrangement. SD cards have a limited number of writes and they are fragile if not handled properly. There is also the issue of wear and tear on the SD Card slot of the pi, and without a regular means of backing up the card, a bad card means total loss of your data and having to rebuild the operating system and programs from scratch. A process that can take upwards of 4-5 hours at least, depending on the number of programs installed and the data involved.
One solution or alternative that the generation 4 of Raspberry Pi readily supports is booting from an external USB or SS drive. This is a great solution and solves many of the problems presented by the little SD card. When coupled with the USB3 ports on the RPi4 series, the data throughput is not unlike that of a normal linux computer. Great! you might say. Problem solved! Well, maybe… It depends.
You see, there is a little dark secret associated with the USB3 port. I won’t get too far into the weeds on this here, but if you want to look into the gory details you can follow this link to an Intel article on the RFI issues that USB3 can cause. In a nutshell, USB3 is spread spectrum and causes significant interference in the 2.4Ghz band if the ports and cables are not properly shielded. You know, the band where wireless mice, keyboards, wifi, etc., operate? That can present a problem if you employ these devices in your build. It also interferes with GPS dongles that plug into USB, like the ones I use for obtaining grid square info in the Conky program. The solution I’ve implemented is that I purposely plug USB3 devices into the USB2 ports and non-USB3 devices into the USB3 ports. I know it seems counterintuitive but as long as the port doesn’t register a USB3 compatible device it won’t revert to spread spectrum, thus no RFI.
So in my GBs I still use a SD card in the GB1 pi and I use a 480Gb SSD in GB2. Overall both work great, and at some point I’ll break down and get a SSD for GB1 to keep from having to backup the SD card all the time.
Lesson Learned #3 – Understand the limitations and potential RFI issues related to SBCs, especially the Raspberry Pi 4 versions with USB3. Also, this is one area where spending a little money is likely a good plan when it comes to cables used with USB3 to insure they are properly built and shielded to minimize the RFI. If your plans do not include the use of wireless mice, keyboards, or GPS dongles, then the spread spectrum RFI from USB3 may not be an issue for you. Best advice, experiment and see how your system works and address the issues as you find them. However, do yourself a favor and do your testing at home so you’re prepared when you go portable with your GB.
Conclusion
Well the truth is I could go on for pages relating issues related to building these GBs but I think I’ve hit the highlights that I wanted to cover. As always, if you have a question about how these GBs were built or questions about an issue you’re experiencing drop me a line in the comments and I’ll get back to you as soon as I can.
73’s, The DIY Ham.
The DIY Ham 