Monthly Archives: August 2020

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.

RX-666: Listen to A Gamechanger!

Flying high: RX-666

Since Marco Polo, combinations of Italian and Chinese had proven fruitful. The Dragonfly RX-666 is such a combination or, at least, a very special “kind of”. It is a 16bit SDR, ranging 1 kHz to 30 MHz in a row with 16 bit resolution – plus some extra above 32MHz (1.5/1.7GHz) by the help of an R820T2-chip of RTL-SDR fame, but 8 bit only. Priced not much over US-$ 200 (if that) at some ebay sellers, it is a real gamechanger, offering for the first time 32 MHz streaming via USB3.0 at 16 bit resolution to ensure a competitive dynamic range.

32 MHz at a glance! And just 15% CPU load on an i7.

It has been built around LTC2208 chip and seems a clone, a twin or a pirate piece of a concept, literally layed/laid out by Oscar Steila, IK1XPV, an electronics engineer from Turin. Über-DXer Bjarne Mjelde has diven deep into the story and the receiver itself. I don’t want to repeat what he found out in only my own words. You simply must read his story here, and I can stress each and every word of it.

In this blog, I may add only some audio clips to give an impression of the reception quality in Northern Germany on the evening of August 11 and the morning of August 12, 2020. Antenna, as always, is the professional active dipole MD300DX, vertical with 2 x 5 m legs. Recordings were made with HDSDR software, but replay done with SDRC V3. Both, Bjarne and Oscar, helped me to get the SDR flying at all. Without their friendly hand, it would have been only another heavy paperweight on my desk …

Now for some twelve audio clips:

IRIB Ardabil/IRAN, 1512 kHz, 20:00 UTC in Farsi
RUssian Aero Net with control station like Samara and Ural, 4712 kHz, 20:05 UTC, each running 1kW with a low-hanging dipole; in Russian.
Echo of Hope, clandestine from Suwon/South Korea on 4890 kHz at 20:00 UTC in Korean.
BPM, Chinese time signal station in AM with CW-ID and voice ID in Chinese on 5000 kHz at 19:59 UTC. Please compare to reception during the same time on 10’000 kHz below.
Voice of America/Botswana on 6.080kHz duly doing for what they are payed for: Hail to the Chief, hail, hail, hail! 20:00 UTC
The other chief: TWR Botswana on 6130 kHz in Kimbundu language – Amen. 20:00 UTC
Singapore VOLMET on 6676 kHz with weather e.g. for Kota Kinabalu, Bali, Penang and Singapore/Changi, 19:50 UTC
BPM, Chinese time signal station in AM with CW-ID and voice ID in Chinese on 10’000 kHz at 19:59 UTC. Please compare to reception during the same time on 5000 kHz up.
World Christian Broadcast from Mahajanga/MALAGASY transmitter on 11’965kHz at 20:00 UTC
BBC via their Atlantic Relay/Ascension on 12’095kHz, 20:00 UTC
Radio Kuwait from their homeland on 15’530kHz in Arabic, 05:00 UTC
China Radio International from Kashi/Xinjiang on 17’720kHz in German

The range above 32 MHz is covered by an R820T2-chip at maximum streaming bandwidth of 8MHz only. Please see below a screenshot of a part of the FM broadcast band:

FM broadcast is covered with an R820T2-chip at a maximum streaming bandwidth of 8MHz only. Here you see a part of the FM broadcast band.