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From: Roger Lapthorn <rogerlapthorn@gmail.com>
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Date: Fri, 18 Mar 2011 16:59:58 +0000
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Subject: Re: LF: Loop TX antennas at VLF?
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Many thanks Andy. I'll see what the numbers say.=20

Mal, you are right that real two way QSOs may need high power and ERP but=
 surely all forms of experimentation at VLF are valid.=20

I also wonder about the (very small) amount of power that may be radiated=
 when using utilities assisted earth mode with signals conducted along pip=
es for miles? Is there an easy way to estimate this radiated component?=20

73s
Roger G3XBM

Via my 2.4GHz handheld (iPod Touch 4g)

On 18 Mar 2011, at 14:24, Andy Talbot <andy.g4jnt@gmail.com> wrote:

> Here's an Excel S/S I did in the 73kHz days.   Other people have updated=
 versions now, but it serves to get you into a region to design from - or=
 know when to not bother
> =20
> http://www.g4jnt.com/DownLoad/MAGLOOP.XLS
> Andy
> www.g4jnt.com
>=20
> =20
> On 18 March 2011 14:09, Roger Lapthorn <rogerlapthorn@gmail.com> wrote:
> Just wondering if anyone has done the maths to work out what sort of ERP=
 could be expected at 8.97kHz with, say, 100W to a smallish loop antenna=
 in the garden?=20
>=20
> It would certainly avoid the need for very very large matching coils and=
 may be easier to engineer than a Marconi. Even an efficiency of -80dB wou=
ld allow 1uW ERP and, judging by results from G3XIZ with around 2uW, this=
 could be useful with long stable carrier transmissions of several hours.=
 Most of us could run a loop with an area of 100sq m. with thickish wire=
 in our gardens. A loop might also be more practical for portable operatio=
ns perhaps with a triangle with one high support.
>=20
> Certainly my own results with WSPR at 136 and 500kHz with just a few wat=
ts and quite thin wire and around 80sq m loop area were encouraging. Mind=
 you, 9kHz is very much lower than 136kHz, so the radiation resistance wou=
ld be tiny I assume.=20
>=20
> 73s
> Roger G3XBM
>=20
> --=20
> http://g3xbm-qrp.blogspot.com/
> http://www.g3xbm.co.uk
> http://www.youtube.com/user/g3xbm
> https://sites.google.com/site/sub9khz/
> G3XBM   GQRP 1678    ISWL G11088
>=20

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<html><body bgcolor="#FFFFFF"><div>Many thanks Andy. I'll see what the numbers say.&nbsp;</div><div><br></div><div>Mal, you are right that real two way QSOs may need high power and ERP but surely all forms of experimentation at VLF are valid.&nbsp;</div><div><br></div><div>I also wonder about the (very small) amount of power that may be radiated when using utilities assisted earth mode with signals conducted along pipes for miles? Is there an easy way to estimate this radiated component?&nbsp;</div><div><br></div><div>73s</div><div>Roger G3XBM</div><div><br>Via my 2.4GHz handheld (iPod Touch 4g)</div><div><br>On 18 Mar 2011, at 14:24, Andy Talbot &lt;<a href="mailto:andy.g4jnt@gmail.com">andy.g4jnt@gmail.com</a>&gt; wrote:<br><br></div><div></div><blockquote type="cite"><div><div>Here's an Excel S/S&nbsp;I did in the 73kHz days.&nbsp;&nbsp; Other people&nbsp;have updated versions now, but it serves to get you into a region to design from - or know when to not bother</div>
<div>&nbsp;</div>
<div><a href="http://www.g4jnt.com/DownLoad/MAGLOOP.XLS"><a href="http://www.g4jnt.com/DownLoad/MAGLOOP.XLS">http://www.g4jnt.com/DownLoad/MAGLOOP.XLS</a></a><br></div>
<div>Andy</div>
<div><a href="http://www.g4jnt.com/"><a href="http://www.g4jnt.com">www.g4jnt.com</a></a></div>
<div><br>&nbsp;</div>
<div class="gmail_quote">On 18 March 2011 14:09, Roger Lapthorn <span dir="ltr">&lt;<a href="mailto:rogerlapthorn@gmail.com"><a href="mailto:rogerlapthorn@gmail.com">rogerlapthorn@gmail.com</a></a>&gt;</span> wrote:<br>
<blockquote style="BORDER-LEFT: #ccc 1px solid; MARGIN: 0px 0px 0px 0.8ex; PADDING-LEFT: 1ex" class="gmail_quote">Just wondering if anyone has done the maths to work out what sort of ERP could be expected at 8.97kHz with, say, 100W to a smallish loop antenna in the garden? <br>
<br>It would certainly avoid the need for very very large matching coils and may be easier to engineer than a Marconi. Even an efficiency of -80dB would allow 1uW ERP and, judging by results from G3XIZ with around 2uW, this could be useful with long stable carrier transmissions of several hours. Most of us could run a loop with an area of 100sq m. with thickish wire in our gardens. A loop might also be more practical for portable operations perhaps with a triangle with one high support.<br>
<br>Certainly my own results with WSPR at 136 and 500kHz with just a few watts and quite thin wire and around 80sq m loop area were encouraging. Mind you, 9kHz is very much lower than 136kHz, so the radiation resistance would be tiny I assume. <br>
<br>73s<br>Roger G3XBM<br clear="all"><font color="#888888"><br>-- <br><a href="http://g3xbm-qrp.blogspot.com/" target="_blank"><a href="http://g3xbm-qrp.blogspot.com/">http://g3xbm-qrp.blogspot.com/</a></a><br><a href="http://www.g3xbm.co.uk/" target="_blank"><a href="http://www.g3xbm.co.uk">http://www.g3xbm.co.uk</a></a><br>
<a href="http://www.youtube.com/user/g3xbm" target="_blank"><a href="http://www.youtube.com/user/g3xbm">http://www.youtube.com/user/g3xbm</a></a><br><a href="https://sites.google.com/site/sub9khz/" target="_blank"><a href="https://sites.google.com/site/sub9khz/">https://sites.google.com/site/sub9khz/</a></a><br><a href="http://vlf_grabber/" target="_blank"></a>G3XBM&nbsp;&nbsp; GQRP 1678&nbsp;&nbsp;&nbsp; ISWL G11088<br>
</font></blockquote></div><br>
</div></blockquote></body></html>

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