vlf
Differences
This shows you the differences between two versions of the page.
Next revision | Previous revision | ||
vlf [2023/12/23 08:50] – created ei3jdb | vlf [2023/12/23 12:01] (current) – [Setup and Testing] ei3jdb | ||
---|---|---|---|
Line 2: | Line 2: | ||
Although there are no ham bands for VLF, there are VLF transmissions that hams can receive. | Although there are no ham bands for VLF, there are VLF transmissions that hams can receive. | ||
+ | |||
+ | ===SAQ Grimeton=== | ||
+ | |||
+ | The Grimeton transmitter is the last surviving example of an Alexanderson transmitter, | ||
+ | |||
+ | The transmitting station is now a [[https:// | ||
+ | |||
+ | ===Soundcard SDR=== | ||
+ | |||
+ | The receiver described here is a computer soundcard and GNURadio Companion combined to make a VLF Software Defined Radio. | ||
====Hardware==== | ====Hardware==== | ||
You will need | You will need | ||
- | * an antenna | + | |
- | * a soundcard | + | * a soundcard |
- | * a computer. | + | * a computer. |
===Antenna=== | ===Antenna=== | ||
Line 22: | Line 32: | ||
===Soundcard and Computer=== | ===Soundcard and Computer=== | ||
- | The connection should probably go into the microphone input of the soundcard or, failing that, the line in. The | + | The connection should probably go into the microphone input of the soundcard or, failing that, the line in. Soundcards with better resolution (e.g. 16 bits) will be more sensitive. |
+ | |||
+ | Any computer able to run GNURadio will probably do. I used a Raspberry Pi 4 running Debian 64-bit, but that is much bigger than the minimum platform. The Python executable ran on about 30% of one ARM core and consumed about 220M of space. | ||
====Software==== | ====Software==== | ||
- | I used GNURadio Companion to produce a SDR using soundcard input. | + | I used GNURadio Companion to produce a SDR using soundcard input. |
+ | |||
+ | The GRC file is {{grimeton.zip|here | ||
The SDR is a simple direct conversion receiver. | The SDR is a simple direct conversion receiver. | ||
Line 36: | Line 51: | ||
====Setup and Testing==== | ====Setup and Testing==== | ||
+ | To do setup and testing, I used an audio signal generator and an attenuator to produce a 17.2kHz carrier at about 100 microvolts. | ||
+ | |||
+ | |||
+ | ===Linux Setup=== | ||
+ | |||
+ | First find your soundcard. | ||
+ | |||
+ | So an '' | ||
+ | |||
+ | {{grimeton-aplay.png}} | ||
+ | |||
+ | should become an input to the Audio Source properties like this | ||
+ | |||
+ | {{grimeton-audiosource.png}} | ||
+ | |||
+ | Then you may need to enable your input with '' | ||
+ | |||
+ | When it is correct, you should see signals in the waterfall. | ||
+ | |||
+ | Here is what my input looks like with 100 microvolts at 17.2kHz | ||
+ | |||
+ | {{grimeton-siggen.png}} | ||
+ | |||
+ | and here is what it looks like when connected to my antenna | ||
+ | |||
+ | {{grimeton-ant.png}} | ||
+ | |||
+ | To connect the output of GNURadio to another application, | ||
+ | |||
+ | After that, you should be all set. | ||
+ | |||
+ | The Grimeton transmitter seems to schedule tests on the day before the actual transmission, | ||
+ | |||
+ | |||
+ | ===Windows Setup=== | ||
+ | |||
+ | To find your soundcard in Windows please follow [[https:// | ||
+ | |||
+ | ===QSL?=== | ||
+ | If you heard the transmission, |
vlf.1703321449.txt.gz · Last modified: 2023/12/23 08:50 by ei3jdb