April FTX AAR

And testing power consumption of comms gear

The April AmRRON field exercise was a week long “stress test” of your ability to operate off grid based on a scenario where loss of cellular and internet due to cyber attack progresses to a grid down situation. It was very Commstat focused and I am not a Commstat station as getting that program to work has been a challenge to say the least, but I will be interested to see what other corps operators have in their after actions and lessons learned. It is striking to me is that the very concept of this exercise would have been a struggle to execute just a few months ago! Recent solar upgrades to my system (more on that here) however made this week long test a breeze, as well as a great opportunity to gather some real world data on power usage that has improved my understanding of the strengths and limitations of the equipment I have available.

The following is certainly not meant to be exhaustive, I can only test the various equipment that I have on hand. All data is from the Powerwerx watt meter, which I highly recommend, and averaged over time as much as possible to represent real world consumption. When I say “running comms programs” I mean the following: FLRIG, FLDIGI, FLAMP, FLMSG, & JS8CALL.

• Raspberry Pi 5: .18 Amps average consumption while running comms programs. Having the Pi create its own wireless network caused no additional measurable consumption of power. Adding a 7” portable screen to the Pi increased total drain to .23 amps.

• Raspberry Pi 4: This one was a surprise. I had considered it to be more efficient than the Pi 5, but while it idled lower with nothing running it ran at .23 amps while running comms programs.

• Linux Mint “mini PC”: .22 amps at idle, .4 amps while running a 7” screen, and around .9 amps with the screen and comms programs running.

• HP Comms laptop: tested in both Windows 11 and Linux Mint 20.3.

  • Both OS’s (this surprised me, I expected to see a difference) used approx 15% of the battery per hour while accessing the RPi via VNC, and 20% per hour while directly running the suite of comms programs.

  • Charging the laptop requires about 2.31 Amps, with losses from the inverter being .25 amps of that. The battery is replenished at approx 20% per hour while running.

• Xeigu X6100: .84 amps! Even with the internal battery fully charged, it draws .84! Powered off and showing full charge it draws .56, I ran this thing for hours thinking it would slow the rate of consumption but it never did. It appears that its battery management circuitry takes .56 amps, so I suspect that the rest of the radio uses the difference of .28 and that number might reflect the drain you would see in the field off the internal battery, if that is the case going from 5 watts off the internal to 10 watts off external will be costly…

• Xeigu G90: .58 amps

• Lab599 TX500: here’s where this little radio earned its place in my “go bag” in spite of the wire mess for digital modes. It draws so little power on receive that at times the meter actually can’t measure it. When processing a bunch of incoming signals it peaks up to .13 amps, but settles back down to around .10. Less than .10 and the meter can no longer measure it, and it frequently reads 0.00. Its also the most rugged radio in my inventory.

• ICOM 7300: 1.02 amps

• Yaesu 857D: .61 amps

Pairing the Pi5 with the TX 500 along with a distribution block to power them gave me a 10 watt digital system that consumed an average of .4 amps by itself and .5 amps with a 7” screen. Even a diminutive 3 AH battery could probably power this system for close to 6 full hours if transmitting is kept to a minimum. On TX total draw is about 2.5 amps.

You might be wondering, as I did, how the math works. .18 for the Pi and .12 for the radio don’t add up to .40. But after re-checking everything in isolation I settled on the conclusion that when moving where you measure back in the system you add in all the little losses from the wires, connectors, distribution block, and so on. One more reason, as if you needed one, to keep your field gear as simple as possible.