VLF,
I just checked the amplitude and frequency respose of the audio
transformer i use to decouple my signals between soundcard and antenna.
Just a simple test. They are in use in various applications, are cheep
and small.
Type, Distributor and datasheet:
http://www.reichelt.de/Trenntrafos/NFU-1-4/index.html?;ACTION=3;LA=444;GROUP=C54;GROUPID=3320;ARTICLE=73039;START=0;SORT=artnr;OFFSET=16;SID=32fRwi5qwQASAAACIkJWk502917f27b61570f9f85c5c030e3f831#av_tabdata
Looks they operate down to 5 Hz which is excellent:
http://dl.dropbox.com/u/19882028/VLF/Uebertragertest.png
Also the wide range looks fine up to 20 kHz:
http://dl.dropbox.com/u/19882028/VLF/Uebertragertest_wide.png
In the pictures, the upper SL instance is a frequency generator driving
the headphone output of the soundcard. The lower instance records
signals coming from the Mic input.
As a conclusion i found that the transformer is even suitable for ZEVS
receiving at 82 Hz.
73, Stefan/DK7FC
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