Re: LF: RE: 8,97 kHz active antenna circuit and pictures

[Horst Stöcker <horst.stoecker@web.de>]

Hello Stefan,

TV Transformer, interesting. I think it should work well on lower distance. QRP on 9kHz, hi. I also had this idea after my first tests on 9kHz. I wanted to test it but my few TV transformers are DST and I think I will need a flyback. The flybacks are common in the first generations of tv sets up to the seventies but hard to get nowadays.

I am not sure if the hoizontal antenna is the best solution. As we know in theory there are more ground losses. But if this will be of any significant influence at this low frequencies?

I am looking foward to your tests again.

BTW I am waiting for more motivating weather conditions. I collected a few hundred meters of isolated military wire. After confectioning it I will have material for an earthbase of about 800 to 1000 m. This will be tested as soon as possible.

Horst

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Von: "Stefan Schäfer" <Stefan.Schaefer@iup.uni-heidelberg.de>
Gesendet: 10.05.2010 20:52:33
An: rsgb_lf_group@blacksheep.org
Betreff: Re: LF: RE: 8,97 kHz active antenna circuit and pictures

Hello Victor, LF,

It took a little bit to reply to your answer. You have been absolutely right! DLF(153kHz) is here just some 10km away and the strong french LF broadcast station on 162kHz has caused the nonlinear working of my first stage i assume. Yesterday i talked with Markus/DF6NM and he gave me the very useful hint to add a C between drain and gnd of the first stage (what forms a low pass with the drain R). Before some minutes i added a 100nF capacitor, so the edge frequency should be about 15kHz. Before that, i have looked on a second experimental active E field antenna how it influences the gain on the dreamers band (almost no difference). But see the S/N improvement NOW on my grabber (http://www.iup.uni-heidelberg.de/schaefer_vlf/DK7FC_VLF_Grabber.html)! What a big difference!!! :-)))))
So happy about that! :-)
Tnx to Markus and you, Victor!

73, Stefan/DK7FC

PS: I have built a small TX antenna at my new home QTH in Heidelberg. With a TV transformer and my 300W PA (running at 15W DC input) i apply about 2kV rms on a 10m horizontal wire, about 3m above gnd. The distance to the grabber here is 1,1km. Hopefully i can see something, at least in DFCW-600...




Am 28.04.2010 15:51, schrieb victor13@online.nl:

Hi Stefan,

 

looks nice but I suspect you  have some im problem in your first stage because off the strong line at 9 KHz,Maby it's better to use a filter at the input....

 

73

 

Victor

-----Oorspronkelijk bericht-----
Van: Stefan Schäfer [mailto:owner-rsgb_lf_group@blacksheep.org]Namens Stefan Schäfer
Verzonden: woensdag 28 april 2010 12:50
Aan: rsgb_lf_group@blacksheep.org
Onderwerp: VLF: 8,97 kHz active antenna circuit and pictures

Dear LF,

Daniele and others asked for the circuit of my active E field antenna that i am using for my grabber. Now i have created a pdf file where you can find the circuit and a picture of the arrangement and a spectrogram of the currently working circuit.

http://www.iup.uni-heidelberg.de/schaefer_vlf/8,97kHz%20active%20E%20field%20antenna%20by%20DK7FC.pdf

So, if you are interested or want to get some ideas for your own circuit, take a look on it. I hope the link works.

So, best 73 and maybe cu this evening there, dreamers.

Stefan/DK7FC

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