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Date: Wed, 04 May 2011 18:27:21 +0200
From: =?ISO-8859-2?Q?Stefan_Sch=E4fer?= <Stefan.Schaefer@iup.uni-heidelberg.de>
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Subject: Re: LF: G3ZJO grabber
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Hello Eddie,

Well, your noise floor below 5 kHz seems to look much better than here.=20
I started some ULF tests last year but have (temporarely!) stopped due=20
to the bad SNR and other more important projects. If you have some FETs=20
left, why not build a ELF probe? In a first thought, i would remove the=20
HPF and increase the C values of the LPF by a factor 30, to get a cut=20
off frequency of about 500 Hz. But there are existing designs which may=20
work better, no idea.

73 and tell us if you got ZEVS!

Stefan


Am 04.05.2011 15:06, schrieb qrss:
> Hello Stefan
>
> I was prompted to take a look 'down low' a couple of weeks ago when=20
> SM5LE said, look 'Schumann resonances'. You will be surprised that I=20
> am using your E-Probe, unmodified. I wasn't expecting to see much so I=
=20
> was surprised by the results.
> Have I seen Schumann resonances? I am not going to say, proof needs=20
> time of observation.
>
> Information about the signals and phenomena down there is scarce, I=20
> have heard mention of 90Hz for submarine comms so many thanks for the=20
> link I have removed my LPF and shifted the window up to take a look on=
=20
> 82Hz.
>
> EDIT
> Carrier at 80.2Hz, 75.2Hz and 64.24Hz which would seem to be a=20
> harmonic of the 32Hz and likewise the 16Hz a sub harmonic of 32Hz.
>
> My searches for information have certainly taken me to Renato's page,=20
> I was showing a link to his site as a 8.9kHz Grabber, since looking at=
=20
> his site I have moved him into a Link class of his own.
>
> There have been questions about the pulses of interference at ULF.=20
> When we look at our VLF Wide displays the Sferics seem to peter out=20
> around 3kHz, (your filter is doing its job). However I have used the=20
> 0....50Hz view to prove to my own satisfaction that Sferics are still=20
> going strong down to 0Hz. Probably removing the 3kHz cut of would=20
> cause havoc down there.
>
> There are several carriers of unknown origin, maybe due to my urban=20
> location which I can investigate. Any thoughts of what runs at 32Hz=20
> would be welcome, I am pretty sure it comes down from the antenna.=20
> Well, when there are no tests on 8.9kHz I can keep interested.
>
> 73 Eddie
>
> On 04/05/2011 12:14, Stefan Sch=E4fer wrote:
>> Hello Eddie, VLF,
>>
>> Your additional grabber windows are interesting. Remembers me to the=20
>> site of Renato Romero ;-)
>> What antenna do you use for displaying the range of 0...50 Hz? My=20
>> probe circuit has a high pass filter with an edge frequency of about=20
>> 3 kHz. So if your QRM below 3 kHz is not to strong, you may remove=20
>> that and get better signals on ELF. Have you ever received the ZEVS=20
>> at 82 Hz? http://www.vlf.it/zevs/zevs.htm
>>
>> 73, Stefan/DK7FC
>>
>>
>