Message-ID: <001501cda635$eeda16c0$0501a8c0@xphd97xgq27nyf>
From: "mal hamilton" <g3kevmal@talktalk.net>
To: <rsgb_lf_group@blacksheep.org>
References: <50731B6C.2060506@iup.uni-heidelberg.de> <50732867.7070201@telia.com> <5074294B.80807@iup.uni-heidelberg.de> <op.wlwzelqpyzqh0k@pc-roelof> <50743561.9060504@iup.uni-heidelberg.de>
Date: Tue, 9 Oct 2012 15:51:22 -0000
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Subject: Re: LF: active antenna output termination?
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Stefan
I am not convinced that these type of Active probe antennas are suitable in
an environment where there is a strong noise source or other strong adjacent
signals present on the same band.
A better idea is a passive type antenna as large as possibe without preamps
and suitable attenuation if required and a good Receiver
Even a modest sized loaded vertical gives enough signal capture, has hi-Q on
the frequncy of interest when resonated followed by a good well designed
sensitive RX
This is my approach and it works well although my radio environment is
Quiet. A uProbe might work for me but I do not need one!!
gl de mal/g3kev



----- Original Message -----
From: "Stefan Schäfer" <Stefan.Schaefer@iup.uni-heidelberg.de>
To: <rsgb_lf_group@blacksheep.org>
Sent: Tuesday, October 09, 2012 2:32 PM
Subject: Re: LF: active antenna output termination?


> Hi Roelof,
>
> In the moment it's just in my mind, not on the paper. I thought it is no
> good idea to publish anything as long as the problems are not solved.
>
> Of course all the problems are not only coming from the circuit design
> but also depend on the local situation. The AFN signal is a good
> example. I still don't know why it took so long until i discovered this
> strong signal. Another issue is the grounding situation, cable length
> and also the frequency response of the input impedance of a receiver.
> All this may let a circuit design appear as a nearly perfect solution in
> the one location but appers as complete rubbish in the other location...
>
> Just found another bug: The IM coming a few seconds after adding the 50
> Ohm termination load are coming from a 0.1 A poly switch fuse which is
> in the supply path of the RX, which feeds the probe. I should have
> switched 1 uF in series to the 50 Ohm, not to apply DC, of course. First
> i remembered the fuse but thought that this can't be the problem because
> there are still signals shown on the MF RX. The fuse does not lower the
> voltage to 0V but to 2V which seems to be enough to produce some signals
> for the MF RX, which has its own supply voltage.
>
> I'm going to make a drawing...
>
> 73, Stefan
>
> Am 09.10.2012 15:50, schrieb Roelof Bakker:
> > Hello Stefan,
> >
> > Where can I find the circuit diagram of your probe and also of the
> > "Fernspeiseweiche"?
> >
> > 73,
> > Roelof, pa0rdt
>