Envelope-to: dave@picks.force9.co.uk
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From: "hamilton mal" <g3kev.ham@virgin.net>
To: rsgb_lf_group@blacksheep.org
References: <007001c62a34$97e808b0$2101a8c0@AUG2004> <007701c62a41$1414dbf0$8b1c0d54@traceydlqceh0p> <002601c62a73$2f204f10$2201a8c0@pcroelof>
Date: Sun, 5 Feb 2006 19:14:40 -0000
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Subject: LF: Re: Re: Active_antennas
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----- Original Message -----
From: "Roelof Bakker" <roelof@ndb.demon.nl>
To: <rsgb_lf_group@blacksheep.org>
Sent: Sunday, February 05, 2006 4:42 PM
Subject: LF: Re: Active_antennas


> Hello Walter, Tracey, Alan,
>
> It happens to be that I own a battery powered SPM-3 and I have often used
a
> (mini) whip without any connection to ground. As a whip is a monopole some
> counterpoise is necessary.

Watch the counterpoise effect because, if it is long this could become the
antenna. Try using the counterpoise itself as an antenna and the signal
could be stronger than via the actual antenna !!


 I gathered that this happened by capacitive
> coupling between the case of the SPM-3 and earth (the real thing). As the
> (mini) whips capacitance is small, the value of the capacitor to earth
need
> not be very large.
>
> This was confirmed when I lifted the SPM-3 from the plastic garden table
and
> put it on the ground: the signal level increased. If I remember correct it
> was in the order of 1 dB or so.
>
> Regarding Tracey's suggestion, when the weather is a bit more like it, I
> will hoist the contraption up a fiberglass pole. The only problem is that
> the capacitance of the SPM-3 to ground will be substantial larger than
from
> the (mini) whip.
>
> Best regards,
>
> Roelof Bakker, pa0rdt
>
>