Differences

This shows you the differences between two versions of the page.

--- vlf [2023/12/23 12:01] – [Setup and Testing] ei3jdb
+++ vlf [2024/06/30 14:06] (current) – [Setup and Testing] ei3jdb
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 ====Introduction====
-Although there are no ham bands for VLF, there are VLF transmissions that hams can receive.  This page is about how to receive the transmissions from the Alexanderson transmitter at Grimeton in Sweden, sent on Alexanderson Day (2nd July) and Christmas Eve (24 December) every year.
+Although there are no ham bands for VLF, there are VLF transmissions that hams can receive.  This page is about how to receive the transmissions from the Alexanderson transmitter at Grimeton in Sweden, sent on Alexanderson Day (Sunday closest to the last day of June) and Christmas Eve (24 December) every year.
 ===SAQ Grimeton===
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 To connect the output of GNURadio to another application, I used the PulseAudio Volume Control tool.  The input of the application should be the monitor of the output that GNURadio is using -- probably your active sound device.  I was able to set this up with FLDigi, although FLDigi doesn't like mode switches, so set to CW before selecting the input.
-After that, you should be all set.
+After that, you should be all set.  If you are able to receive other VLF transmissions then SAQ should be OK.  I have been able to receive the RDL station in Krasnodar, Russia on 18.1kHz. This is an interesting station as the output is intermittent and the modulation mode varies. Most of the submarine stations send with military-grade encryption but RDL sometimes sends codes in clear using CW-FSK — Morse code encoded as CW. By choosing narrow band and tuning off-centre it is possible to receive only the mark signal and filter out the space signal, which makes it possible to decode the Morse by ear or with fldigi.
+If you can receive RDL you should be able to receive SAQ.
 The Grimeton transmitter seems to schedule tests on the day before the actual transmission, so you should have a chance to test your rig before the transmission day.
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 ===QSL?===
+Here is a recording of the afternoon transmission on 30th June 2024: {{ :grimeton-20240630.mp3 |}}
 If you heard the transmission, the Alexanderson Association have an online QSL form for your signal report on their [[https://alexander.n.se/en/|home page]].