Switching-on HF Transmitters: Step by step

Voice of Turkey, Emirler, signing on: 9880 kHz, The ABB transmitter SK5SC3-2P is switched to full poer [500kW] in five steps within about three seconds.

Recently, I came across the different sign-on ceremonies of different transmitters. The idea is to understand this workflow in which obviously several stages of the transmitter are switched on consecutively. See at the top one example, where Voice of Turkey is swithcing on their transmitter on 9880kHz in five steps within about three seconds.

The diagram was made with Simon Brown’s unique software SDRC V3. I used the Signals Analyser module, providing a (needed!) time resolution of down to just one millisecond, or 1000 values of level vs. frequency in just one second! These data (CSV) had been exported and visualized in QtiPlot software.

I would like to encourage other people to join these observations. One goal can be toi fingerprint no only a transmitter, but also the workflow of the people at the transmitter. Please refer to this website for a database of broadcasters and their transmitters plus galore of associated data.

In the meantime, I already observed a couple of different workflows/transmitters. Please keep in mind that all these measurements (better: estimations), of course, are prone to fading. You may also see some effects during sign-on in the spectrogram, see below.

Radio Saudi, signing on, 17’615kHz at 12:57 UTC on 02APR2020. You clearly see at least three different steps of power plus some transient when switiching to full power.

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