Dear all, Mal in special,
if the cable to the rx would really be the antenna for the active
aerial, only local qrm would be received! The screen of the cable has to
be grounded bfore entering the house, as Roelof has stated, but avoid
any additional grounding within the house.
Especially at VLF an 1:1 isolation or separation transformer having an
inductivity of 10 mH or higher is needed for active aerials before the
receiver to break currents in the screen which the cable has picked up
from the environment. And on an ordinary toroid the polarization of the
transformer has to be optimized for real noise-free performance.
Just by this method I got rid of qrm from a nearby solar panel
installation and its 300 Hz spectrum up to 20 kHz which has plagued me
since autumn 2010. For my inductive aerials, this interfering field ist
still existing. But copy of SAQ last Friday using the active aerial (in
my case using an LT1252 as amplifier just needing 10 mA) has been ufb
again.
73 Ha-Jo, DJ1ZB
"mal hamilton" <[email protected]> schrieb:
> Minto
> Get rid of fluorescent strip lights from your house, only QRM generators for
> radio amateurs.
> It seems MINIWHIP antennas work better the higher they are installed above
> ground which makes me think that the cable connecting the probe to the RX is
> in fact the REAL antenna. !!!!!!!!!!!!!!!
> A probe antenna should work equally well at ground level in the clear as in
> an elevated position.
> G3KEV
>
>
> ----- Original Message -----
> From: "Minto Witteveen" <[email protected]>
> To: <[email protected]>
> Sent: Tuesday, August 09, 2011 8:44 PM
> Subject: Re: LF: HB9ASB...
>
>
> > .. And he is even visible on my grabber!
> > I raised the miniwhip from +4 to +11 meters (large fishing rod in the
> > backyard).
> > Signal levels increased by 15 dB. Noise level was raised too, but the QRM
> > from my fluorescent lights in the house no longer show up. so there must
> be
> > some improvement.
> > Tomorrow I will again measure de DCF39 to noise ratio.
> >
> > 73's
> > Minto pa3bca
> >
> >
> >
> > --------------------------------------------------------------------------
> > Ceterum censeo Carthaginem delendam esse
> > -----Original Message-----
> > From: Stefan Schäfer
> > Sent: Tuesday, August 09, 2011 21:10
> > To: [email protected]
> > Subject: LF: HB9ASB...
> >
> > ...now joins in at 137.695! 25 dB SNR here.
> >
> > Looking forward to a opening band tonite...
> >
> > 73, Stefan
> >
> >
>
>
>
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