Reception of the historical VLF-Transmitter SAQ Grimeton / Sweden.
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Hello everyone!
This is a short report of my activities, to receive the transmittion of the historical Verry Low Frequency-transmitter
"SAQ" in Grimeton / Sweden.
You can find a lot of information about SAQ on the internet, for example on the SAQ website:
https://alexander.n.se/
or on wikipedia:
https://en.wikipedia.org/wiki/Grimeton_Radio_Station
The most important part is the antenna. I chose a magnetic loop antenna, because it is the least sensitive to interference:
Matched loop-antenna with pre-amplifier.
I designed the preamplifier input with high impedance. There would also have been the possibility of decoupling the signal from the loop at low impedance using a coupling loop,
but with the high-impedance input of the preamplifier I have the option of also using an E-field antenna. This works quite well, but is more sensitive to interference.
The circuit diagram, with FET preamplifier and coax driver.
The pre-amplifier for the loop antenna has a separat housing, so that I can also use it for capacitive antennas.
As the receiver I chose the direct-conversion principle.
To recorde the Morse-code, I build a historic inspired line recorder:
I cut the paper stripe out of a cash register roll using a small homemade device.
December 3rd, 2023:
I build the receiver electronics in modules:
- crystal oscillator specifically for SAQ
- VFO for manual station select in VLF-band
- mixing down unit
- LF unit
- signal detector to control the line recorder
I also set up a small test transmitter.
Sum technical details of the test transmitter and local oscillator:
The frequencies are based on 8 MHz TTL oscillators. The divider chains are:
Test-transmitter: 8 MHz TTL-Osc., :5 (74LS90), :3 (HEF4017), :31 (HEF4024, HEF4081) = 17,2043... kHz
LO: 8 MHz TTL-Osc., :5 (74LS90), :7 (HEF4017), :7 (CD4017), :2 (CD4013) = 16,326... kHz
klick for video!
December 15th, 2023:
Here is the circuit diagram of the receiver:
The circuit diagram is based on a publication by DL1STO:
https://opppf.de/SAQ-Grimeton/index.html"
But I adaptet it to my requirements.
And the circuit diagram of the local oscillator with the VCO of the CD4046.
December 17th, 2023:
Now things are starting to get exciting, only a week left. That's why a first "field test" with all components was scheduled on our terrace:
Video first field-test:
Video "short and long strokes":
December 22th, 2023:
SAQ's test broadcast was announced for today, shortly after noon. A few fiends were with me, one with Morse knowledge.
Around 1:20 p. m. a clear and quite strong signal appeared and after a short adjustment its frequency few "...-" ("v") followed by "-.. ." ("de")
and the call sign "... .- --.-" ("saq") had to be recorded :-). We didn't expect such a clean signal.
Here is a short MP3 recording of such a sequence:
2023-12-22-MP3:
That was the first success. In the further course, the Christmas message transmission was for the morning of December 24th at 8 a. m. UT, that means 9 a. m. our time announced.
Unfortunately my line recorder didn't work. Because of other singnals, especially submarine communications, SAQ was not dominat enough.
For the future I need to add a sharper LF Filter. On the 24th I will record the Christmas message with the MP3 recorder and translate it "offline".
December 24th, 2023:
I got up early that day to have my reception system ready on time. The broadcast of the Christmas greetings began promptly at 9 a.m. CET.
Here is the MP3 recording of the message:
2023-12-24_2.MP3:
The signal was not as good as during the test broadcast two days earlier. Nevertheless, the content should be understandable if you can "read" it... ;-/
But that's why we have the screenshot from the SAQ website:
(permission for this is available)
You can also watch a recording of the broadcast on YouTube:
For YouTube broadcast
click on the image or this link.
(Not much happens in the first 5 minutes, you can safely skip them)
Here is a screenshot of my confirmation of receipt of the "SAQ Listener's Report Map" from their website:
And the link to the “SAQ Listener's Report Map”:
Click here for "SAQ Listener's Report Map"
(For my confirmation of receipt, click on the dark blue marking near "Heinsberg")
Then a comment about what I would do differently given my current experience:
Actually I don't have much to list here, it worked largely as I expected.
However, I would avoid the quartz-controlled local oscillator.
The VFO with 4046 is stable enough and the frequency setting for SAQ worked great with the small test transmitter.
So, at the end, of course, the E-QSL card also belongs here, as it has now arrived:
In any case, the whole thing was a great project and I will definitely continue to try to receive the messages from this very special station.
Many thanks to the SAQ team! I think it is important that such unique witnesses to the history of technology are preserved.
mail: reinhard.lauterbach[at]freenet.de