Grimeton Radio Station was listed as a world heritage site because, its original equipment is an exceptionally well-preserved example of the development of communication technology. In fact, it is still in working order.
Grimeton (call sign SAQ) still transmits a message to the world twice a year: at the Alexanderson Day (Sunday at the end of June/beginning of July) and at Christmas Eve. The frequency is 17,2 kHz CW.
I received fading signals from SAQ on the second transmission of 5th July 2020 which began with a Startup and tuning at 13:30 (11:30 UTC) with a transmission of a message at 14:00 (12:00 UTC)I used a homebrew E probe based on a design by DL1DBC ( http://dl1dbc.net/SAQ/homebrew_e-field.html#_Testing_the_Homebrew ).
I built a VLF upconverter using a 33.4MHz TXCO - SBL-1 Mixer and a MiniCircuits T1-1 RF Transformer as the Galvanic Isolator which passed through a stage of 30dB amplification before the receiving RTL-SDR V3 using SDR# software.
Sample rate was 2.4MSPS, no AGC of course combined with a large FFT resolution of 262144 which pulled the weak signal out of the noise.
Here in an image of the signal and superimposed is the youtube video showing the operator.
[ RIGHT CLICK IMAGES AND OPEN IN NEW TAB ]
I recommend checking the Alexanderson Association Website for videos of the whole events and lots of information about the 1920's transmitter.
https://alexander.n.se/?lang=en
Here are annotated image of other VLF stations received here in Kallista
Here are pictures of the E probe construction.
Here is a picture of the VLF Upconverter
As I build other probes I will provide further Blog entries
