Message-ID: <4F7ED36C.206@iup.uni-heidelberg.de>
Date: Fri, 06 Apr 2012 13:28:44 +0200
From: =?ISO-8859-15?Q?Stefan_Sch=E4fer?= <Stefan.Schaefer@iup.uni-heidelberg.de>
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To: rsgb_lf_group@blacksheep.org
References: <4F7DAA67.1000404@iup.uni-heidelberg.de> <006b01cd13d1$2fbb5070$1502a8c0@Clemens04>
In-Reply-To: <006b01cd13d1$2fbb5070$1502a8c0@Clemens04>
Subject: Re: LF: Re: Audio transformer test
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Hi Clemens,

In my application i use it to decouple my 2 orthogonal VLF loops from=20
the soundcard and do some "matching" of the low output impedance of the=20
loop to the high input impedance of the soundcard. The levels absolute=20
signal levels rised arround 10 dB, so it is an improvement. However the=20
MSKs, especially DHO38 is 10 dB down now since the transformer does not=20
work on such a high frequency. Anyway, my focus is below 9 kHz and the=20
levels from 9...25 kHz are still fair.
There is however not really a S/N improvement and mains hum and all the=20
man made noise in the H field make the loops rather a game instead of a=20
system suitable to detect weak signals from Dreamers. Seems i have to=20
change the location of the loops. The old problem...

73, Stefan/DK7FC


Am 06.04.2012 10:42, schrieb Clemens Paul:
> Hi Stefan,
>
> I have measured exactly this transformer about a year ago for a friend.
> He tried it for a (meanwhile abandoned) soundcard based SDR- TRX projec=
t
> for HF and failed due to lack of sensitivity.
> I connected two of these XMFs back to back and measured in a 50 Ohm=20
> environment
> with a VNA from 5-20kHz.
> There was plenty of loss,IIRC something *around* 10dB per transformer.
> That's not surprising after you have measured the DC resistance (high!).
> This may or may not be of importance for your application depending on
> your AF level and type of matching (power matching versus voltage=20
> matching).
>
> 73
> Clemens
> DL4RAJ
>
>
> ----- Original Message ----- From: "Stefan Sch=E4fer"=20
> <Stefan.Schaefer@iup.uni-heidelberg.de>
> To: <rsgb_lf_group@blacksheep.org>
> Sent: Thursday, April 05, 2012 4:21 PM
> Subject: VLF: Audio transformer test
>
>
>> VLF,
>>
>> I just checked the amplitude and frequency respose of the audio=20
>> transformer i use to decouple my signals between soundcard and=20
>> antenna. Just a simple test. They are in use in various applications,=20
>> are cheep and small.
>> Type, Distributor and datasheet:=20
>> http://www.reichelt.de/Trenntrafos/NFU-1-4/index.html?;ACTION=3D3;LA=3D=
444;GROUP=3DC54;GROUPID=3D3320;ARTICLE=3D73039;START=3D0;SORT=3Dartnr;OFF=
SET=3D16;SID=3D32fRwi5qwQASAAACIkJWk502917f27b61570f9f85c5c030e3f831#av_t=
abdata=20
>>
>>
>> Looks they operate down to 5 Hz which is excellent:=20
>> http://dl.dropbox.com/u/19882028/VLF/Uebertragertest.png
>> Also the wide range looks fine up to 20 kHz:=20
>> http://dl.dropbox.com/u/19882028/VLF/Uebertragertest_wide.png
>>
>> In the pictures, the upper SL instance is a frequency generator=20
>> driving the headphone output of the soundcard. The lower instance=20
>> records signals coming from the Mic input.
>>
>> As a conclusion i found that the transformer is even suitable for=20
>> ZEVS receiving at 82 Hz.
>>
>> 73, Stefan/DK7FC
>>
>>
>