April 20, 2018: APRS Roadtrip with APRSDroid and the Baofeng UV-5R

I’m flying down to Santa Barbara on Monday to meet my family for a few days. They’re returning from a motorhome trip, and I’m lending a hand by driving their car back up to Oregon. It’s a great chance for me to complete some experiments with APRS.

The Automatic Packet Reporting System (APRS) is a digital ham radio system for broadcasting short messages. The APRS network has both a physical and an internet component: messages sent by radio are broadcast to all listening stations, and rebroadcast by all receiving repeaters; some repeaters function as internet gateways, injecting the messages they receive into the APRS internet backbone. The internet gateways also provide a limited form of routing, selectively rebroadcasting messages from the internet backbone into their local radio region.

An APRS frame contains the call sign of the sending station, and may optionally be addressed to another station’s call sign. But most APRS messages are status reports that broadcast information about a sender’s location, movement, or local weather conditions. Here’s APRS data from the Seattle area, with a great deal of it sourced from internet stations.

Following a few YouTube videos and blog posts, I’ve begun transmitting a bit of APRS location data. The simplest setup involves a smart phone, a handheld VHF radio, and an audio cable to connect the two. The smart phone collects GPS data and constructs APRS data frames, sending them out through the radio via the audio cable. And of course, an amateur radio license is required as well.

The Baofeng UV-5R, my handheld radio, is inexpensive and popular, but a little finicky for this application. I tried strapping the whole setup to my bike for a ride last week, and somehow neglected to transmit any data. This road trip will be a great chance to work out the kinks. You just might be able to follow my progress with this APRS.fi tracking link.

When I’m done, I’ll write it up. My ultimate goal is to create an APRS beacon for bike, backpack, and sailboat. I’m working on a goal-tracking server, and it would be pretty awesome if it could automatically consume this location data off of the APRS internet backbone to see when I’ve completed recurring goals like finishing a bike century or summiting a 12k+ peak.

April 17, 2018: Passing the Amateur Extra Class Exam

I passed the ham radio amateur extra class exam last night. The extra class exam is the third in a series of three licensing exams. And though the extra class endorsement opens up some extra band privileges, I wanted to pass the final test so that I could volunteer to administer exams to other licensees.

Many of the answers in the first two exams are common sense, or can be guessed at given some background knowledge in electronics. There are also only about 400 questions in each pool of available questions for the technician and general class exams. On the other hand, the extra class exam has a pool of about 700 questions, and many of these are about very specific circuits, regulations, and scientific effects. Whereas there were maybe 100 questions I committed to memory for the first two exams, there were about 500 questions on the extra class exam that I needed to memorize.

Here was my strategy:

  1. I downloaded the list of test questions and created a flash card deck for Anki.
  2. I borrowed the ARRL Extra Class License Manual from the library.
  3. One chapter at a time, I read the book for some combination of familiarity and understanding: some chapters I was able to read for full comprehension; for difficult chapters it was my goal just to become familiar with that chapter’s words, images and concepts.
  4. At the end of each chapter, the ARRL license manual lists all of the test questions that were covered in that chapter. When I finished a chapter, I tagged all of those questions in my flash card program with their corresponding chapter and added them to my study deck.
  5. Just before sitting the test, I did a bit of cramming by searching out all of the questions I had a difficult time remembering: prop:ease<2.5. I tagged these questions–about 150 total–and moved them into a special “cram” deck.

It took me a week of studying and I correctly answered 45 out of 50 questions!

I’m always surprised by the number and diversity of people that come to Ada’s to become certified. In the thirty minutes that I was at the test I saw maybe ten people in the exam room, and I got the impression that more would be showing up. It was a real diversity of age, gender, and race. My own interest in ham radio has to do with sailing and a general interest in electronics, communication, small-scale disaster response. And, I guess, it’s also nice to be part of a community of geeks.

After the test I talked for a while with a guy who had just passed his general class exam: he was using amateur radio to talk with his daughter, and also to hedge against TEOTWAWKI. I wish I could have asked more people why they were there that night.