Tour 6

Record data from kiwiSDR and analyze it using SCILAB tools to correct for sample rate error, and create an envelope for the pulses by overlapping the magnitude (using Hilbert transform) of several 1 second captures. Tune to RWM pulses on VFO B and also create envelope for PPS measurements. Thank you for the tour. It was more work than I had planned for, but I have learned a lot. (I hope I haven't been careless on this last tour.) I didn't want to resort to a kiwi but my reception in NA was nonexistent in any band for the last two tours.

Carrier: This time i used a GPSDO-modded SDRplay RSP1B with GNU Radio and some FFT magic PPS: GPSDO-PPS together with IC-7300 audio on a scope - cursor measurement (using calibration delay from 18.05.) Pulse: IC-7300 USB-audio recording in Tenacity to count samples

I have a homegrown C++ program that fetches data from the IC-705 built-in USB sound card and pushes it to a raw sound file, mono, nominally 48000 samples / second (it's actually about 47999,67). It turns out the Linux pipewire API hands out the sound samples in batches of 1024 samples at a time. Whenever such a batch comes in, the program fetches the "nanoseconds since the epoch" time stamp from the system and writes the number of bytes received and that time stamp to an auxiliary "marks" text file. The clock is NTP disciplined, or it was until about 16:36 UTC - then I goofed. I use the software chronyd for that. New: Yet another python program calls chronyd's control program chronyc every 10 seconds and writes timestamps of the call and chronyd's opinion of the state and precision of the system clock to yet another auxiliary text (CSV) file chrony.track. I experimented with using that information to fine-tune the timestamps retrieved from the marks files. The rest is a bunch of Jupyter notebooks and a bit of Python code. Running these notebooks is one of the rare occasions where I'm happy my PC has 16 GByte of RAM. As I learned the hard way, it is not wise to open several of them simultaneously. Normally, 80 m is best. Today with evening K=5, 40 m was best and the morning 20 m transmission also useful. The afternoon 20 m was weak, as was 80 m. I threw my whole bunch, raw files and software, into an archive and made it available as https://dj3ei.famsik.de/attic/2026-06-05-FMTLab/DJ3EI_FMTLab_2026-06-05_raw.tar.xz . That archive has a sha256sum of cff7505f7308f0805cc6e4e18354e5c7c7dea4f461e96945aa4a6ddfa5deb440 and a size of 538 MByte. I may eventually document the details a bit via my blog https://dj3ei.famsik.de/blog/ .

Measure frequency offset using SpectrumLab. Scope trigger 1pps from RFzero. Rx locked to 10MHz from GPSDO Measure pulse width and UTC offset on oscilloscope. Calibration using generator, counter and calibration transmissions.