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Date: Wed, 2 Dec 2009 19:33:05 +0000
Message-ID: <1f0624b90912021133v6a61a9dfkd07160d88b7d3a7e@mail.gmail.com>
From: Gary - G4WGT <g4wgt@tiscali.co.uk>
To: rsgb_lf_group@blacksheep.org
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Subject: Re: LF: Results of optimising an active antenna
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Alberto, LF,

I tried that arrangement with my PA0RDT Mini-Whip active antenna inside a
large baked beans can, the can being the antenna & the results were a lot
poorer than the small 30mm x 45mm of the original design, I have also trie=
d
adding a 500mm whip to the original with poorer results also. So now I use
the Mini-Whip as originally designed by Roelof. You can see the results on
my grabbers.

http://myweb.tiscali.co.uk/wgtaylor/grabber2.html

<http://myweb.tiscali.co.uk/wgtaylor/grabber2.html>73

Gary - G4WGT.

2009/12/2 Alberto di Bene <dibene@usa.net>

> Stefan Sch=E4fer wrote:
>
>>
>> My Conclusion: It seems that a short receiving antenna can bee seen as=
 a
>> capacitive divider out of the capacity between far field and antenna an=
d the
>> capacity between antenna and ground. If the wire length is to much, the
>> input stage becomes nonlinear/goes into saturation. If the height above
>> ground is increased the signal comes up, but not the signal/noise
>> ratio(surely there will be a benefit if such an antenna is placed in a
>> region with heavy local qrm. Then, the height should be increased and=
 the
>> wire length can be decreased). So, one cannot say =93the more the bette=
r=94
>> talking about the wire length!
>>
>
> It would be quite interesting if somebody could try to use, instead of=
 a
> wire, something
> with a greater capacity towards ground, e.g. a can of beer (after drinki=
ng
> the beer, of course...:-)
> One of half liter (slightly more than 1 pint) could do, I think...
>
> Maybe the increased capacity towards ground could make it more effective
> than a wire
>
> 73  Alberto  I2PHD
>
> P.S. And the entire active antenna circuitry could be placed inside the
> can...
>
>
>
>

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Alberto, LF,<div><br></div><div>I tried that arrangement with my PA0RDT Mi=
ni-Whip active antenna inside a large baked beans can, the can being the=
 antenna &amp; the results were a lot poorer than the small 30mm x 45mm of=
 the original design, I have also tried adding a 500mm whip to the origina=
l with poorer results also. So now I use the Mini-Whip as originally desig=
ned by Roelof. You can see the results on my grabbers.</div>
<div><br></div><div><a href=3D"http://myweb.tiscali.co.uk/wgtaylor/grabber=
2.html">http://myweb.tiscali.co.uk/wgtaylor/grabber2.html</a></div><div><b=
r></div><div><a href=3D"http://myweb.tiscali.co.uk/wgtaylor/grabber2.html"=
></a>73</div>
<div><br></div><div>Gary - G4WGT.<br><br><div class=3D"gmail_quote">2009/1=
2/2 Alberto di Bene <span dir=3D"ltr">&lt;<a href=3D"mailto:dibene@usa.net=
">dibene@usa.net</a>&gt;</span><br><blockquote class=3D"gmail_quote" style=
=3D"margin:0 0 0 .8ex;border-left:1px #ccc solid;padding-left:1ex;">
Stefan Sch=E4fer wrote:<br>
<blockquote class=3D"gmail_quote" style=3D"margin:0 0 0 .8ex;border-left:1=
px #ccc solid;padding-left:1ex">
<br>
My Conclusion: It seems that a short receiving antenna can bee seen as a=
 capacitive divider out of the capacity between far field and antenna and=
 the capacity between antenna and ground. If the wire length is to much,=
 the input stage becomes nonlinear/goes into saturation. If the height abo=
ve ground is increased the signal comes up, but not the signal/noise ratio=
(surely there will be a benefit if such an antenna is placed in a region=
 with heavy local qrm. Then, the height should be increased and the wire=
 length can be decreased). So, one cannot say =93the more the better=94 ta=
lking about the wire length!<br>

</blockquote>
<br>
It would be quite interesting if somebody could try to use, instead of a=
 wire, something<br>
with a greater capacity towards ground, e.g. a can of beer (after drinking=
 the beer, of course...:-)<br>
One of half liter (slightly more than 1 pint) could do, I think...<br>
<br>
Maybe the increased capacity towards ground could make it more effective=
 than a wire<br>
<br>
73 =A0Alberto =A0I2PHD<br>
<br>
P.S. And the entire active antenna circuitry could be placed inside the ca=
n...<br>
<br>
<br>
<br>
</blockquote></div><br></div>

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