The Alexanderson transmitter at Grimeton is a massive VLF one. It is a huge 500hp motor and gearbox that drives a alternator to produce a 17.2kHz signal. It transmits at various times of the year but only routinely on Christmas Eve and end of June / beginning of July. Its a fun thing to listen out for and is a good test of your VLF receiver. A decent SDR like the Airspy HF discovery + and a YouLoop or MiniWhip does the trick nicely when listening from Europe
July 2021 saw me break my YouLoop the night before but I still managed to receive nicely with the MiniWhip. RST was 559 in IO84. Software being used is GQRX, it works easily on Ubuntu, which I switched to this year. For Windows users the go to software is SDR#. Whatever your choice the output is similar. A chance to copy this unique piece of radio history in action.
The transmissions are accompanied by a live stream on YouTube of the start up sequence which is a great way of seeing, and hearing, the effort required to start up, synchronise and the optimise the system. Easy to forget when all I do is press the power button on my rig.
So, dates for your diary are generally Christmas Eve and around the first weekend in July. Normally a good copy in my QTH but just seeing how far VLF can travel is fun too. An amazing piece of equipment with a great team behind it.
The video below is of my reception in July 2020. I’d say this was a better reception than with the MiniWhip, although I did have the bandwidth very low. The software is SDR# in this instance.
At the time of this recording I played about with a few antennas. the W3EDP I have here, the YouLoop and a mini whip and the YouLoop was by far the best.
If you manage to receive the transmissions, and you can see from the 2010 map that they pretty much worldwide, then fill in the listener report and you’ll get added to the interactive map and a nice QSL card.
What I’d like to do next is to build a dedicated receiver. If seen a few VLF designs on the web, the Alexanderson Society actually sells a complete kit but I think It’d be nice to build my own and avoid the performance bonus I get with the SDR. Receive it the old school way. i.e.make it harder 🙂