by Peer-Axel Kroeske
Offsets (minimal frequency deviations of AM carriers) help to identify extremely weak signals long before hearing any audio, especially on medium wave. The free Pskov software offers the ability to process the whole MW in one large WAV file produced by a software defined receiver (SDR). While the Praat software helps to analyse these exact frequencies, Pskov shows interference patterns. Here you can easily find out the difference between twi interfering carriers with a precision of 1 millihertz.
This image plots the amplitude on 963 kHz, recorded on 23/12/2023 at 1405 UTC in Handewitt, Germany. From left to right 1.160 seconds, line for line, showing a constant signal fading. Pskov allows to manually adjust the time span by 1ms. IThere are 8 peaks resulting in 0.145s per circle or 6.896 Hz difference between the two carriers - Sunrise Radio in London last logged at 962.9975 kHz and Asian Sound from Haslingden on about 963.0044 kHz.
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