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Table of Contents
Dave's Thoughts and Ideas
Etymology in Today's World
When people send LOL, did they really laugh out loud? What if I really laughed out loud? Should I send LLOL: Laughed Literally Out Loud.
But wait, did I mean literally literally or did I mean literally figuratively?
LLLOL.
ARRL FMT setup
(edited after 2025-04-17 fmt)
The ARRL runs a neato contest twice a year - the Frequency Measuring Test (FMT). The objective is to measure a transmission's unknown frequency as accurately as possible. There are 4 transmissions: 2 different geographical locations on 2 different bands (40m and 80m). The tests are run in the evening when the ionosphere is changing which adds an unpredictable element (doppler shift) to the results. Like any good “contest”, it's part skill and part luck!
The results are reported in accuracy windows:
- <= 1 Hz
- > 1 Hz to <= 5 Hz
- > 5 Hz to <= 10 Hz
Greater than 10 Hz doesn't get reported in a window but does get reported in your results listed by callsign.
You'll notice there's a method/soapbox with each callsign. If the contestant chooses, they can report their setup. Some of the setups consist of some amazing gear. My setup is basically my radio station with the addition of a GPS disciplined oscillator, namely the leo bodnar.
Here I'll note how I did my measurements so I can remember for future contests. I'll update this as I learn new things.
44net: amprd IPIP on Fedora 40
(EDIT: correct recommended subnet mask for 44. Of course it's no longer /8. It should be within either 44.0.0.0/9 or 44.128.0.0/10.)
The amprd package installs directly from the fedora repository. The configuration is straightforward, however getting firewalld and NetworkManager configured is a little tricky.
The amprd documentation refers to requiring the ipip_redirector for 4.13+ kernels. It's not required for the 6.8.9 kernel that comes with Fedora 40.
Note for the most part the commands require root so put sudo in front of the commands or become root with 'sudo -i'
FFT scaling factor
What's often confusing about the FFT is that the transform seems to have numbers that are too big. Let's call this the “FFT scale factor” problem (it's a reasonable google search). The frequency domain seems to have much more energy (much higher values) than one might expect from the time-domain waveform from which it originated.