ARRL Field Day was June 27-28, 2020. As the ARRL says:

Field Day is ham radio's open house. Every June, more than 40,000 hams throughout North America set up temporary transmitting stations in public places to demonstrate ham radio's science, skill and service to our communities and our nation. It combines public service, emergency preparedness, community outreach, and technical skills all in a single event. Field Day has been an annual event since 1933, and remains the most popular event in ham radio.

Field Day was a little different this year due to COVID. Normally, we'd get together at remote sites in the field, and set up and operate. This year, amended rules allowed us to operate at home, and our clubs could still get credit for the contacts we made.

I only made 12 contacts operating 1 E (emergency power). The bands were pretty crowded for FT8.

The real success for me was improving my capability to operate in the field, especially using a Raspberry Pi as the computer doing the FT8 work and the logging.

The hardware setup

The Raspberry Pi 4, and the 12 V to 5 V converter (purple box)

The Raspberry Pi 4 has more than enough computing power to do FT8. It needs at least 3 A @ 5 V for power. Most cigarette lighter adapters only provide 2 amps. I bought a Drok buck converter with a USB port, which provides 5 amps. I created a case for the converter in Autodesk Fusion 360 (free for hobbyist use) and printed it on my Ender 3 Pro 3D printer. More on that in the upcoming series of blog articles.

The beauty of the Raspberry Pi 4 is that it takes only 5 watts when idling.

Battery box. 143 W‽‽ This must have been when I tried plugging in the laptop.

The battery box has a 50 Ah (600 Wh) LiFePO4 battery in it. I ran both Saturday and Sunday on one battery.

143.4 W must have been when I plugged my 13" MacBook Pro laptop in. I have an aftermarket DC-DC boost converter for the laptop, which is really useful when it works. The problem is that the laptop wanted to both run, and charge the battery. I think the boost converter can pull 65 W, and with the radio transmitting, that brings up the power quite a bit. I was also charging the iPad.

iPad as display and keyboard for the Raspberry Pi

For a display on the iPad, I used a 12.9" iPad Pro with a keyboard. I used VNC Viewer to connect to the Raspberry Pi (not shown, a Verizon hotspot acted as a portable WiFi access point, as well as providing Internet service). The whole screen works like a trackpad. The virtual display can be bigger than the iPad screen itself. And, the iPad runs on its own batteries as well as being recharged by the USB output on the battery box.

The iPad claims 10 hours of operation on a 38.5 Wh battery, so it draws about 4 W. Together the iPad and Raspberry Pi are around 10 W at rest, compared to the 30 W for the computer I'm writing this on.

Total energy usage

When I recharged the battery, I put 40.7 Ah back in.

When it was all over, I recharged the battery, and it took 40.7 Ah. I had made it 24 hours, with some sporadic contacts, but with many hours of the radio and the Raspberry Pi running.

Summary

While I didn't make a lot of contacts, to me, that's not all that Field Day is about. It's about gaining skills at operating in the field. Although I was in my apartment the whole time, I operated on emergency power. I made improvements to my field setup by using the Raspberry Pi, reducing the power consumption and increasing reliability and portability.