APRS iGate

Digital

Last night I set up an Automatic Packet Reporting System (APRS) iGate to listen on 144.390 MHz for packets and report them to APRS Internet Service (APRS-IS). This is like a listening station that will improve my area APRS coverage.

My receive-only APRS station on https://aprs.fi

This can be done relatively inexpensively with a Raspberry Pi (~$35), a RTL-SDR receiver (~$26), and some opensource linux software available online.

The latest RTL-SDR v3 is a capable little Software Defined Radio (SDR) receiver that can even receive to HF frequencies. For much cheaper than a standalone HF receiver, you can get the kit that includes a whip dipole, extension SMA cables, and mounting hardware. I lengthened the whips to 2m resonance (~19 inches each side).

Using software in linux: rtl_fm and direwolf, one is able to listen for APRS traffic on 144.390 MHz, decode it, and with the Raspberry Pi  connected to the Internet, can send what it hears to the main APRS servers for visibility on aprs.fi.

Note one guy here sharing his heart rate and blood oxygen levels while on the road.

Now that this is up, I can monitor the firehose of digital packet information that is constantly on the frequency, and relay some close-by transmissions to the rest of the world.

Special thanks goes to my friend briandef (who is studying and may soon become a ham) for his insight and pre-struggle with SDR opensource software to help me debug out how to cleanly set up the RTL-SDR dongle.

Learning Morse Code

CW

I’ve found that learning CW is hindered by my preconceptions I’ve had about Morse code. When initially starting on the Koch Method using HamMorse, I would turn the sound I heard into a mental picture of dots and dashes, then I’d do an internal lookup of what that picture in my mind was against the alphabet.

As you can imagine, this takes way too long, and takes too much concentration to effectively work in real-time CW translation.

After many hours of trying and listening, I realize now what others have said all along about Morse: Just relax, and let the sounds come in on their own. The sounds need to reflexively become letters with little mental effort; Don’t try to visualize dots and dashes. Just listen, practice, and let the sounds become letter representations in your mind.

The above sound file says: CQ CQ CQ DE KF6UJS KF6UJS KF6UJS PSE K

That is what my CW general call to the world would be if I wanted to start a conversation with anyone listening on the frequency. CQ means a general call; DE means “from”; PSE means “please”; K means “go” (i.e. invite to respond).