<html xmlns:v="urn:schemas-microsoft-com:vml" xmlns:o="urn:schemas-microsoft-com:office:office" xmlns:w="urn:schemas-microsoft-com:office:word" xmlns:m="http://schemas.microsoft.com/office/2004/12/omml" xmlns="http://www.w3.org/TR/REC-html40"><head><meta http-equiv=Content-Type content="text/html; charset=iso-8859-1"><meta name=Generator content="Microsoft Word 14 (filtered medium)"><style><!--
/* Font Definitions */
@font-face
{font-family:Calibri;
panose-1:2 15 5 2 2 2 4 3 2 4;}
/* Style Definitions */
p.MsoNormal, li.MsoNormal, div.MsoNormal
{margin:0cm;
margin-bottom:.0001pt;
font-size:11.0pt;
font-family:"Calibri","sans-serif";
mso-fareast-language:EN-US;}
a:link, span.MsoHyperlink
{mso-style-priority:99;
color:blue;
text-decoration:underline;}
a:visited, span.MsoHyperlinkFollowed
{mso-style-priority:99;
color:purple;
text-decoration:underline;}
span.EstiloCorreioElectrnico17
{mso-style-type:personal-compose;
font-family:"Calibri","sans-serif";
color:windowtext;}
.MsoChpDefault
{mso-style-type:export-only;
font-family:"Calibri","sans-serif";
mso-fareast-language:EN-US;}
@page WordSection1
{size:612.0pt 792.0pt;
margin:70.85pt 3.0cm 70.85pt 3.0cm;}
div.WordSection1
{page:WordSection1;}
--></style><!--[if gte mso 9]><xml>
<o:shapedefaults v:ext="edit" spidmax="1026" />
</xml><![endif]--><!--[if gte mso 9]><xml>
<o:shapelayout v:ext="edit">
<o:idmap v:ext="edit" data="1" />
</o:shapelayout></xml><![endif]--></head><body lang=PT link=blue vlink=purple><div class=WordSection1><p class=MsoNormal><span lang=EN-US>VLF earth mode beacon TX schematic<o:p></o:p></span></p><p class=MsoNormal><span lang=EN-US><o:p> </o:p></span></p><p class=MsoNormal><span lang=EN-US>Roger G3XBM has made available the schematic of the 5W QRP VLF beacon transmitter used in his successful 6km 8.76kHz VLF earth mode (through the ground) tests.<o:p></o:p></span></p><p class=MsoNormal><span lang=EN-US><o:p> </o:p></span></p><p class=MsoNormal><span lang=EN-US>The keyer IC is from K1EL's website and gives 10wpm, QRSS3 and QRSS30 beacon messages. This keys the frequency stable 4060 crystal oscillator-divider that feeds the TDA2003 amplifier. The output of this is matched to the earth electrode pair using a tapped toroid transformer with a number of step-up taps between 10-160 ohms.<o:p></o:p></span></p><p class=MsoNormal><span lang=EN-US><o:p> </o:p></span></p><p class=MsoNormal><span lang=EN-US>Receiver is a pair of earth electrodes in the ground into a low input impedance tuned preamp feeding a PC running Spectrum Laboratory (free) software set at 11mHz bandwidth. The whole system is far from optimized.<o:p></o:p></span></p><p class=MsoNormal><span lang=EN-US><o:p> </o:p></span></p><p class=MsoNormal><span lang=EN-US>This week Roger hopes to repeat the test at 1.095kHz and possibly 0.547kHz. He expects stronger signals as he goes down in frequency as long as the mains hum is OK. Earlier tests suggest 0.838kHz signals were up to 6dB stronger than those at around 8.76kHz at 5km range.<o:p></o:p></span></p><p class=MsoNormal><span lang=EN-US><o:p> </o:p></span></p><p class=MsoNormal><span lang=EN-US>9 kHz Schematic at<o:p></o:p></span></p><p class=MsoNormal><span lang=EN-US>https://sites.google.com/site/sub9khz/earthmode/vlf-xbm-blog<o:p></o:p></span></p><p class=MsoNormal><span lang=EN-US><o:p> </o:p></span></p></div></body></html>