Тур 3

Measure frequency offset using SpectrumLab. Scope trigger 1pps from RFzero. Measure pulse width and UTC offset on oscilloscope. Offset calibration using locked Siglent SDG1062X and confirmed using RWM.

Recorded audio from FT-710. Using SCILAB to: correct audio for ppm sampling error, BPF to remove QRM, analyze spectrum of CW, overlap multiple seconds of time domain to extract pulse edges. Using CHU Canada for PPS. Using Bodnar GPSDO to correct rig tuning error. Received FMT signal deep in the noise. Similar to Tour 2. No luck with RWM reception. I've improved my analysis tools but if probably not accurate to better than a couple milliseconds. Thanks for the calibration signal to help identify doppler. Thanks again for putting it on!

The 80 m band transmission was again by far the strongest, so I exclusively used that. But I wasn't able to find the correct frequency until about 2.6 minutes into the transmission, as it deviated considerably from the previously advertised one. So I missed the initial transmission at a well-known frequency. As I had calibrated my rig with the RWM time signal transmitter that day, I hope to be reasonably fine anyway. I recorded audio with well-known USB dial frequency, and record timestamps each time a 1024 audio sample batch comes in from the rig. All error boundaries are just educated guesses. With FFT from scipy, I found the audio frequency 2312.586 Hz ± 0.1 Hz. My trx was set at USB 3563400 Hz, I estimate its true frequency as 3563399.950 ± 0.5 Hz and allow maybe another ± 0.5 Hz for ionosphere instability. So 3565712.536 Hz ± 1.5 Hz. For the pulse length, I used a convolution each to find the rising and falling edge of each pulse. As far as I can tell, FMTLab did not send the full 360 pulses, but sometimes left out some at end of a pulse minute. For each pulse minute, I determine the median of the pulse length and throw out all pulse lengths that deviate from it by more than 2 ms (QSB). A total of 245 samples survived, the average is 43.239 ms pulse length. I notice that the same way to measure the pulse length of the 100 ms and 50 ms pulses produces values about 1.1 ms too short, so my pulse length value is 44.339 ms ± 2 ms. I have measured the total RWM delay to be 31.9 ms ± 0.7 ms, estimate the propagation delay 5.85 ms ± 0.2 ms, so my processing delay comes out at 26.05 ± 1 ms. The propagation delay to FMTLab's QTH is estimated at 2.4 ms ± 0.2 ms, so the total FMTLab delay is 28.5 ± 1.2 ms. Measuring when the 100 ms pulse starts yields an average value of 40.631 ms into the full second (compared with the PC's NTP disciplined clock). Subtracting the FMTLab delay yields 12.159 ms with an error bound of maybe ± 3 ms.

Used webSDRs to record WAV files, used Scilab scripts and Excel spreadsheets to analyze data.

RX AM 1 kHz below. Generator tuned to 1 kHz audio and then measured. Delay and time measured with scope cursor.